One document matched: draft-ietf-ips-iser-00.txt
INTERNET DRAFT Mike Ko
draft-ietf-ips-iser-00.txt John Hufferd
IBM Corporation
Mallikarjun Chadalapaka
Hewlett-Packard Company
Uri Elzur
Broadcom Corporation
Hemal Shah
Intel Corporation
Patricia Thaler
Agilent Technologies, Inc.
Expires: March, 2005
iSCSI Extensions for RDMA Specification
Status of this Memo
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Abstract
iSCSI Extensions for RDMA provides the RDMA data transfer capability
to iSCSI [iSCSI] by layering iSCSI on top of the Remote Direct
Memory Access Protocol (RDMAP). The iWARP protocol suite provides
RDMA Read and Write services, which enable data to be transferred
directly into SCSI I/O Buffers without intermediate data copies.
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This document describes the extensions to the iSCSI protocol to
support RDMA services as defined by the iWARP protocol suite.
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Table of Contents
1 Definitions and Acronyms....................................6
1.1 Definitions.................................................6
1.2 Acronyms...................................................11
2 Introduction...............................................14
2.1 Motivation.................................................14
2.2 Architectural Goals........................................15
2.3 Protocol Overview..........................................16
2.4 RDMA services and iSER.....................................17
2.4.1 STag......................................................17
2.4.2 Send......................................................18
2.4.3 RDMA Write................................................18
2.4.4 RDMA Read.................................................18
2.5 SCSI Read Overview.........................................19
2.6 SCSI Write Overview........................................19
2.7 iSCSI/iSER Layering........................................19
3 Upper Layer Interface Requirements.........................21
3.1 Operational Primitives offered by iSER.....................21
3.1.1 Send_Control..............................................21
3.1.2 Put_Data..................................................22
3.1.3 Get_Data..................................................22
3.1.4 Allocate_Connection_Resources.............................22
3.1.5 Deallocate_Connection_Resources...........................23
3.1.6 Enable_Datamover..........................................23
3.1.7 Connection_Terminate......................................24
3.1.8 Notice_Key_Values.........................................24
3.1.9 Deallocate_Task_Resources.................................24
3.2 Operational Primitives used by iSER........................24
3.2.1 Control_Notify............................................25
3.2.2 Data_Completion_Notify....................................25
3.2.3 Data_ACK_Notify...........................................25
3.2.4 Connection_Terminate_Notify...............................26
3.3 iSCSI Protocol Usage Requirements..........................26
4 Lower Layer Interface Requirements.........................28
4.1 Interactions with the iWARP Layer..........................28
4.2 Interactions with the Transport Layer......................29
5 Connection Setup and Termination...........................30
5.1 iSCSI/iSER Connection Setup................................30
5.1.1 Initiator Behavior........................................31
5.1.2 Target Behavior...........................................33
5.1.3 iSER Hello Exchange.......................................35
5.2 iSCSI/iSER Connection Termination..........................36
5.2.1 Normal Connection Termination at the Initiator............36
5.2.2 Normal Connection Termination at the Target...............36
5.2.3 Termination without Logout Request/Response PDUs..........37
6 Login/Text Operational Keys................................39
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6.1 HeaderDigest and DataDigest................................39
6.2 MaxRecvDataSegmentLength...................................39
6.3 RDMAExtensions.............................................39
6.4 TargetRecvDataSegmentLength................................40
6.5 InitiatorRecvDataSegmentLength.............................41
6.6 OFMarker and IFMarker......................................41
7 iSCSI PDU Considerations...................................43
7.1 iSCSI Data-Type PDU........................................43
7.2 iSCSI Control-Type PDU.....................................44
7.3 iSCSI PDUs.................................................44
7.3.1 SCSI Command..............................................44
7.3.2 SCSI Response.............................................46
7.3.3 Task Management Function Request/Response.................47
7.3.4 SCSI Data-out.............................................49
7.3.5 SCSI Data-in..............................................49
7.3.6 Ready To Transfer (R2T)...................................52
7.3.7 Asynchronous Message......................................54
7.3.8 Text Request & Text Response..............................54
7.3.9 Login Request & Login Response............................54
7.3.10 Logout Request & Logout Response........................55
7.3.11 SNACK Request...........................................55
7.3.12 Reject..................................................55
7.3.13 NOP-Out & NOP-In........................................56
8 Flow Control and STag Management...........................57
8.1 Flow Control for RDMA Send Message Types...................57
8.2 Flow Control for RDMA Read Resources.......................57
8.3 STag Management............................................58
8.3.1 Allocation of STags.......................................58
8.3.2 Invalidation of STags.....................................58
9 iSER Control and Data Transfer.............................60
9.1 iSER Header Format.........................................60
9.2 iSER Header Format for iSCSI Control-Type PDU..............60
9.3 iSER Header Format for iSER Hello Message..................62
9.4 iSER Header Format for iSER HelloReply Message.............63
9.5 SCSI Data Transfer Operations..............................64
9.5.1 SCSI Write Operation......................................64
9.5.2 SCSI Read Operation.......................................65
9.5.3 Bidirectional Operation...................................65
10 iSER Error Handling and Recovery...........................66
10.1 Error Handling............................................66
10.1.1 Errors in the Transport Layer...........................66
10.1.2 Errors in the iWARP protocol suite......................67
10.1.3 Errors in the iSER Layer................................67
10.1.4 Errors in the iSCSI Layer...............................69
10.2 Error Recovery............................................71
10.2.1 SNACK Handling and PDU Recovery.........................71
10.2.2 Connection Recovery.....................................72
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11 Security Considerations....................................73
12 IANA Considerations........................................74
13 References.................................................75
13.1 Normative References......................................75
13.2 Informative References....................................75
14 Appendix...................................................76
14.1 iWARP Message Format for iSER.............................76
14.1.1 iWARP Message Format for iSER Hello Message.............76
14.1.2 iWARP Message Format for iSER HelloReply Message........77
14.1.3 iWARP Message Format for SCSI Read Command PDU..........78
14.1.4 iWARP Message Format for SCSI Read Data.................79
14.1.5 iWARP Message Format for SCSI Write Command PDU.........80
14.1.6 iWARP Message Format for RDMA Read Request..............81
14.1.7 iWARP Message Format for Solicited SCSI Write Data......82
14.1.8 iWARP Message Format for SCSI Response PDU..............83
15 AuthorĘs Address...........................................84
16 Acknowledgments............................................85
17 Full Copyright Statement...................................87
Table of Figures
Figure 1 Example of iSCSI/iSER Layering in Full Feature Mode........20
Figure 2 iSER Header Format.........................................60
Figure 3 iSER Header Format for iSCSI Control-Type PDU..............61
Figure 4 iSER Header Format for iSER Hello Message..................62
Figure 5 iSER Header Format for iSER HelloReply Message.............63
Figure 6 SendSE Message containing an iSER Hello Message............76
Figure 7 SendSE Message containing an iSER HelloReply Message.......77
Figure 8 SendSE Message containing a SCSI Read Command PDU..........78
Figure 9 RDMA Write Message containing SCSI Read Data...............79
Figure 10 SendSE Message containing a SCSI Write Command PDU........80
Figure 11 RDMA Read Request Message.................................81
Figure 12 RDMA Read Response Message containing SCSI Write Data.....82
Figure 13 SendInvSE Message containing SCSI Response PDU............83
.
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1 Definitions and Acronyms
Some of the following definitions are taken from [RDMAP]. In those
definitions, the term ULP refers to the iSER Layer.
1.1 Definitions
Advertisement (Advertised, Advertise, Advertisements, Advertises) -
The act of informing a Remote Peer that a local nodeĘs buffer is
available to it. A Node makes a buffer available for incoming
RDMA Read Request Message or incoming RDMA Write Message access
by informing its RDMA/DDP peer of the Tagged Buffer identifiers
(STag, TO, and buffer length). This Advertisement of Tagged
Buffer information is not defined by RDMA/DDP and is left to the
ULP. A typical method would be for the Local Peer to embed the
Tagged Buffer's STag, TO, and buffer length in a Send Message
destined for the Remote Peer.
Completion (Completed, Complete, Completes) - Completion is defined
as the process by the iWARP layer to inform the ULP, in this
case the iSER Layer, that a particular RDMA Operation has
performed all functions specified for the RDMA Operation.
Connection - A connection is a logical circuit between the initiator
and the target, e.g., a TCP connection. Communication between
the initiator and the target occurs over one or more
connections. The connections carry control messages, SCSI
commands, parameters, and data within iSCSI Protocol Data Units
(iSCSI PDUs).
Connection Handle - An information element that identifies the
particular iSCSI connection and is unique for a given iSCSI-iSER
pair. Every invocation of an Operational Primitive MUST be
qualified with the Connection Handle.
Data Sink - The peer receiving a data payload. Note that the Data
Sink can be required to both send and receive RDMAP Messages to
transfer a data payload.
Data Source - The peer sending a data payload. Note that the Data
Source can be required to both send and receive RDMAP Messages
to transfer a data payload.
Datamover Interface (DI) - The interface between the iSCSI Layer and
the Datamover Layer as described in [DA].
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Datamover Layer - A layer that is directly below the iSCSI Layer and
above the underlying transport layers. This layer exposes and
uses a set of transport independent Operational Primitives for
the communication between the iSCSI Layer and itself. The
Datamover layer, operating in conjunction with the transport
layers, moves the control and data information on the iSCSI
connection. In this specification, the iSER Layer is the
Datamover layer.
Datamover Protocol - A Datamover protocol is the wire-protocol that
is defined to realize the Datamover layer functionality. In
this specification, the iSER protocol is the Datamover protocol.
Event - An indication provided by the RDMAP Layer to the ULP to
indicate a Completion or other condition requiring immediate
attention.
Inbound RDMA Read Queue Depth (IRD) - The maximum number of incoming
outstanding RDMA Read Requests that the RNIC can handle on a
particular RDMAP Stream at the Data Source.
Invalidate STag - A mechanism used to prevent the Remote Peer from
reusing a previous explicitly Advertised STag, until the Local
Peer makes it available through a subsequent explicit
Advertisement.
I/O Buffer - A buffer that is used in a SCSI Read or Write operation
so SCSI data may be sent from or received into that buffer.
iSCSI - The iSCSI protocol is a mapping of the SCSI remote procedure
model of SAM-2 over the TCP, and the protocol itself is defined
in [iSCSI].
iSCSI control-type PDU - Any iSCSI PDU that is not an iSCSI data-
type PDU and also not a SCSI Data-out PDU carrying solicited
data is defined as an iSCSI control-type PDU. Specifically, it
is to be noted that SCSI Data-out PDUs for unsolicited data are
defined as iSCSI control-type PDUs.
iSCSI data-type PDU - An iSCSI data-type PDU is defined as an iSCSI
PDU that causes data transfer, transparent to the remote iSCSI
Layer, to take place between the peer iSCSI nodes on a full
feature phase iSCSI connection. An iSCSI data-type PDU, when
requested for transmission by the sender iSCSI Layer, results in
the associated data transfer without the participation of the
remote iSCSI Layer, i.e. the PDU itself is not delivered as-is
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to the remote iSCSI Layer. The following iSCSI PDUs constitute
the set of iSCSI data-type PDUs - SCSI Data-In PDU and R2T PDU.
iSCSI Layer - A layer in the protocol stack implementation within an
end node that implements the iSCSI protocol and interfaces with
the iSER Layer via the Datamover Interface.
iSCSI PDU (iSCSI Protocol Data Unit) - The iSCSI Layer at the
initiator and the iSCSI Layer at the target divide their
communications into messages. The term "iSCSI protocol data
unit" (iSCSI PDU) is used for these messages.
iSCSI/iSER Connection - An iSER-assisted iSCSI connection.
iSCSI/iSER Session - An iSER-assisted iSCSI session.
iSCSI-iSER Pair - The iSCSI Layer and the underlying iSER Layer.
iSER - iSCSI Extensions for RDMA, the protocol defined in this
document.
iSER-assisted - A term generally used to describe the operation of
iSCSI when the iSER functionality is also enabled below the
iSCSI Layer for the specific iSCSI/iSER connection in question.
iSER-IRD - This variable represents the maximum number of incoming
outstanding RDMA Read Requests that the iSER Layer at the
initiator declares on a particular RDMAP Stream.
iSER-ORD - This variable represents the maximum number of
outstanding RDMA Read Requests that the iSER Layer can initiate
on a particular RDMAP Stream. This variable is maintained only
by the iSER Layer at the target.
iSER Layer - The layer that implements the iSCSI Extensions for RDMA
(iSER) protocol.
iWARP - A suite of wire protocols comprising of [RDMAP], [DDP], and
[MPA] when layered above [TCP]. [RDMAP] and [DDP] may be
layered above SCTP or other transport protocols.
Local Peer - The RDMAP implementation on the local end of the
connection. Used to refer to the local entity when describing
protocol exchanges or other interactions between two Nodes.
Node - A computing device attached to one or more links of a
network. A Node in this context does not refer to a specific
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application or protocol instantiation running on the computer.
A Node may consist of one or more RNICs installed in a host
computer.
Operational Primitive - An Operational Primitive is an abstract
functional interface procedure that requests another layer to
perform a specific action on the requestorĘs behalf or notifies
the other layer of some event. The Datamover Interface between
an iSCSI Layer and a Datamover layer within an iSCSI end node
uses a set of Operational Primitives to define the functional
interface between the two layers. Note that not every
invocation of an Operational Primitive may elicit a response
from the requested layer. A full discussion of the Operational
Primitive types and request-response semantics available to
iSCSI and iSER can be found in [DA].
Outbound RDMA Read Queue Depth (ORD) - The maximum number of
outstanding RDMA Read Requests that the RNIC can initiate on a
particular RDMAP Stream at the Data Sink.
RDMA-enabled Network Interface Controller (RNIC) - A network I/O
adapter or embedded controller with iWARP functionality.
RDMA Operation - A sequence of RDMAP Messages, including control
Messages, to transfer data from a Data Source to a Data Sink.
The following RDMA Operations are defined - RDMA Write
Operation, RDMA Read Operation, Send Operation, Send with
Invalidate Operation, Send with Solicited Event Operation, Send
with Solicited Event and Invalidate Operation, and Terminate
Operation.
RDMA Protocol (RDMAP) - A wire protocol that supports RDMA
Operations to transfer ULP data between a Local Peer and the
Remote Peer as described in [RDMAP].
RDMA Read Operation - An RDMA Operation used by the Data Sink to
transfer the contents of a Data Source buffer from the Remote
Peer to a Data Sink buffer at the Local Peer. An RDMA Read
operation consists of a single RDMA Read Request Message and a
single RDMA Read Response Message.
RDMA Read Request - An RDMAP Message used by the Data Sink to
request the Data Source to transfer the contents of a buffer.
The RDMA Read Request Message describes both the Data Source and
the Data Sink buffers.
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RDMA Read Response - An RDMAP Message used by the Data Source to
transfer the contents of a buffer to the Data Sink, in response
to an RDMA Read Request. The RDMA Read Response Message only
describes the Data Sink buffer.
RDMA Write Operation - An RDMA Operation used by the Data Source to
transfer the contents of a Data Source buffer from the Local
Peer to a Data Sink buffer at the Remote Peer. The RDMA Write
Message only describes the Data Sink buffer.
RDMAP Message - The sequence of RDMAP packets which represent a
single RDMA operation or a part of RDMA Read Operation.
RDMAP Stream - A single bidirectional association between the peer
RDMAP layers on two Nodes over a single transport-level stream.
For iSER, the association is created when the iSCSI connection
transitions to iSER-assisted mode following a successful iSCSI
Login Phase during which iSER support is negotiated.
Remote Direct Memory Access (RDMA) - A method of accessing memory on
a remote system in which the local system specifies the remote
location of the data to be transferred. Employing an RNIC in the
remote system allows the access to take place without
interrupting the processing of the CPU(s) on the system.
Remote Peer - The RDMAP implementation on the opposite end of the
connection. Used to refer to the remote entity when describing
protocol exchanges or other interactions between two Nodes.
SCSI Layer - This layer builds/receives SCSI CDBs (Command
Descriptor Blocks) and sends/receives them with the remaining
command execute [SAM2] parameters to/from the iSCSI Layer.
Send - An RDMA Operation that transfers the contents of a ULP Buffer
from the Local Peer to a Buffer at the Remote Peer.
Send Message Type - A Send Message, Send with Invalidate Message,
Send with Solicited Event Message, or Send with Solicited Event
and Invalidate Message.
SendInvSE Message - A Send with Solicited Event and Invalidate
Message.
SendSE Message - A Send with Solicited Event Message
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Sequence Number (SN) - DataSN for a SCSI Data-in PDU and R2TSN for
an R2T PDU. The semantics for both types of sequence numbers
are as defined in [iSCSI].
Session, iSCSI Session - The group of Connections that link an
initiator SCSI port with a target SCSI port form an iSCSI
session (equivalent to a SCSI I-T nexus). Connections can be
added to and removed from a session even while the I-T nexus is
intact. Across all connections within a session, an initiator
sees one and the same target.
Solicited Event (SE) - A facility by which an RDMA Operation sender
may cause an Event to be generated at the recipient, if the
recipient is configured to generate such an Event, when a Send
with Solicited Event or Send with Solicited Event and Invalidate
Message is received.
Steering Tag (STag) - An identifier of a Tagged Buffer on a Node as
defined in [RDMAP] and [DDP].
Tagged Buffer - A buffer that is explicitly Advertised to a Remote
Peer through exchange of an STag, Tagged Offset, and length.
Tagged Offset (TO) - The offset within a Tagged Buffer.
Traditional iSCSI - Refers to the iSCSI protocol defined by [iSCSI]
(i.e. without the iSER enhancements).
Untagged Buffer - A buffer that is not explicitly Advertised to the
Remote Peer.
1.2 Acronyms
Acronym Definition
--------------------------------------------------------------
AHS Additional Header Segment
BHS Basic Header Segment
CO Connection Only
CRC Cyclic Redundancy Check
DDP Direct Data Placement Protocol
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DI Datamover Interface
IANA Internet Assigned Numbers Authority
IETF Internet Engineering Task Force
I/O Input - Output
IO Initialize Only
IP Internet Protocol
IPsec Internet Protocol Security
iSER iSCSI Extensions for RDMA
ITT Initiator Task Tag
LO Leading Only
MPA Marker PDU Aligned Framing for TCP
NOP No Operation
NSG Next Stage (during the iSCSI Login Phase)
OS Operating System
PDU Protocol Data Unit
R2T Ready To Transfer
R2TSN Ready To Transfer Sequence Number
RDMA Remote Direct Memory Access
RDMAP Remote Direct Memory Access Protocol
RFC Request For Comments
RNIC RDMA-enabled Network Interface Controller
SAM2 SCSI Architecture Model - 2
SCSI Small Computer Systems Interface
SNACK Selective Negative Acknowledgment - also
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Sequence Number Acknowledgement for data
STag Steering Tag
SW Session Wide
TCP Transmission Control Protocol
TMF Task Management Function
TO Tagged Offset
ULP Upper Level Protocol
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2 Introduction
2.1 Motivation
The iSCSI protocol ([iSCSI]) is a mapping of the SCSI remote
procedure invocation model (see [SAM2]) over the TCP protocol. SCSI
commands are carried by iSCSI requests and SCSI responses and status
are carried by iSCSI responses. Other iSCSI protocol exchanges and
SCSI Data are also transported in iSCSI PDUs.
Out-of-order TCP segments in the traditional iSCSI model have to be
stored and reassembled before the iSCSI protocol layer within an end
node can place the data in the iSCSI buffers. This reassembly is
required because not every TCP segment is likely to contain an iSCSI
header to enable its placement and TCP itself does not have a built-
in mechanism for signaling ULP message boundaries to aid placement
of out-of-order segments. This TCP reassembly at high network
speeds is quite counter-productive for the following reasons: wasted
memory bandwidth in data copying, need for reassembly memory, wasted
CPU cycles in data copying, and the general store-and-forward
latency from an application perspective. [iSCSI] itself recognized
that TCP reassembly could be a serious issue and had introduced the
notion of a "sync and steering layer" that is optional to implement
and use. [iSCSI] further defined one specific sync and steering
layer - called "markers" - an application-level way of framing iSCSI
PDUs within the TCP data stream even when the TCP segments are not
yet reassembled to be in-order.
With these [iSCSI] defined techniques, a Network Interface
Controller customized for iSCSI (SNIC) could offload the TCP/IP
processing and support direct data placement.
Supporting direct data placement is the main function of the iWARP
protocol suite. A NIC enhanced with the RDMAP/DDP functions (RNIC)
can be used by any application that has been extended to support
RDMA.
With the availability of RNICs within a host system, which does not
have SNICs, it is appropriate for iSCSI to be able to exploit the
direct data placement function of the RNIC like other applications.
iSCSI Extensions for RDMA (iSER) is designed precisely to take
advantage of generic RDMA technologies - iSERĘs goal is to permit
iSCSI to employ direct data placement and RDMA capabilities using a
generic RNIC. In summary, iSCSI/iSER protocol stack is designed to
enable scaling to high speeds by relying on a generic data placement
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process and RDMA technologies and products, which enable direct data
placement of both in-order and out-of-order data.
This document describes iSER as a protocol extension to iSCSI, both
for convenience of description and also because it is true in a very
strict protocol sense. However, it is to be noted that iSER is in
reality extending the connectivity of the iSCSI protocol defined in
[iSCSI], and the name iSER reflects this reality.
When the iSCSI protocol defined by [iSCSI] (i.e. without the iSER
enhancements) is intended in the rest of the document, the term
"traditional iSCSI" is used to make the intention clear.
2.2 Architectural Goals
This section summarizes the architectural goals that guided the
design of iSER.
1. Provide iWARP-based data transfer model for iSCSI that enables
direct in order or out of order data placement of SCSI data into
pre-allocated SCSI buffers while maintaining in order data
delivery.
2. Not require any major changes to SCSI Architecture Model (SAM/SAM-
2/SAM-3) and SCSI command set standards.
3. Utilize existing traditional iSCSI infrastructure (sometimes
referred to as "iSCSI ecosystem") including but not limited to
MIB, bootstrapping, negotiation, naming & discovery, and security.
4. Not require iSCSI full feature phase interoperability between an
end node operating in traditional iSCSI mode, and an end node
operating in iSER-assisted mode.
5. Allow initiator and target implementations that utilize generic
RNICs and implement iSCSI and iSER in software (not require iSCSI
or iSER specific assists in the iWARP protocol suite or RNIC).
6. Require full and only generic iWARP functionality at both the
initiator and the target.
7. Require a session to operate in the traditional iSCSI data
transfer mode if iSER is not supported by either the initiator or
the target.
8. Implement a light weight Datamover protocol for iSCSI with minimal
state maintenance.
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2.3 Protocol Overview
Consistent with the architectural goals stated in section 2.2, the
iSER protocol does not require changes in the iSCSI ecosystem or any
related SCSI specifications. iSER protocol defines the mapping of
iSCSI PDUs to RDMAP Messages in such a way that it is entirely
feasible to realize iSCSI/iSER implementations that are based on
generic RNICS. The iSER protocol layer requires minimal state
maintenance to assist an iSCSI full feature phase connection,
besides being oblivious to the notion of an iSCSI session. The
crucial protocol aspects of iSER may be summarized thus:
1. iSER-assisted mode is negotiated during the iSCSI login for each
session, and an entire iSCSI session MUST operate in one mode
(i.e. one connection in the session cannot operate in iSER-
assisted mode while a different connection of the same session is
already in full feature mode in the traditional iSCSI mode).
2. Once in iSER-assisted mode, all iSCSI interactions on that
connection use RDMAP Messages.
3. A Send Message Type is used for carrying an iSCSI control-type
PDU preceded by an iSER header. See section 7.2 for more details
on iSCSI control-type PDUs.
4. RDMA Write, RDMA Read Request, and RDMA Read Response Messages
are used for carrying control and all data information associated
with the iSCSI data-type PDUs. See section 7.1 for more details
on iSCSI data-type PDUs.
5. Target drives all data transfer (with the exception of iSCSI
unsolicited data) for SCSI writes and SCSI reads, by issuing RDMA
Read Requests and RDMA Writes respectively.
6. The iWARP protocol suite guarantees data integrity. (For TCP,
iWARP uses a CRC-enhanced framing layer on TCP). For this
reason, iSCSI header and data digests are negotiated to "None"
for iSCSI/iSER sessions.
7. The iSCSI error recovery hierarchy defined by [iSCSI] is fully
supported by iSER.
8. iSER requires no changes to iSCSI authentication, security, and
text mode negotiation mechanisms.
Note that traditional iSCSI implementations may have to be adapted
to employ iSER. It is expected that the adaptation when required is
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likely to be centered around the upper layer interface requirements
of iSER (section 3).
2.4 RDMA services and iSER
iSER is designed to work with software and/or hardware protocol
stacks providing the protocol services defined in [RDMAP]. The
following subsections describe the key protocol elements of RDMAP
that iSER relies on.
2.4.1 STag
An STag is the RNIC-unique identifier of an I/O Buffer that the iSER
Layer Advertises to the remote iSCSI/iSER node in order to complete
a SCSI I/O.
In iSER, Advertisement is the act of informing the target by the
initiator that an I/O Buffer is available at the initiator for RDMA
Read or RDMA Write access by the target. The initiator Advertises
the I/O Buffer by including the STag in the header of an iSER
Message containing the SCSI Command PDU to the target. The base
Tagged Offset is not explicitly specified, but the target must
always assume it as zero. The buffer length is as specified in the
SCSI Command PDU.
The iSER Layer at the initiator Advertises the STag for the I/O
Buffer of each SCSI I/O to the iSER Layer at the target in the iSER
header of the SendSE Message containing the SCSI Command PDU, unless
the I/O can be completely satisfied by unsolicited data alone.
The iSER Layer at the target provides the STag for the I/O Buffer
that is the Data Sink of an RDMA Read Operation (section 2.4.4) to
the RDMAP layer on the initiator node - i.e. this is completely
transparent to the iSER Layer at the initiator.
The iSER protocol is defined so that the Advertised STag is
automatically invalidated upon a normal completion of the associated
task. This automatic invalidation is realized via the SendInvSE
Message carrying the SCSI Response PDU. There are two exceptions to
this automatic invalidation - bidirectional commands, and abnormal
completion of a command. The iSER Layer at the initiator is
required to explicitly invalidate the STag in these cases, in
addition to sanity checking the automatic invalidation even when
that does happen.
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2.4.2 Send
Send is the RDMA Operation that is not addressed to an Advertised
buffer by the sending side, and thus uses Untagged buffers on the
receiving side.
The iSER Layer at the initiator uses the Send Operation to transmit
any iSCSI control-type PDU to the target. As an example, the
initiator uses Send Operations to transfer iSER Messages containing
SCSI Command PDUs to the iSER Layer at the target.
An iSER layer at the target uses the Send Operation to transmit any
iSCSI control-type PDU to the initiator. As an example, the target
uses Send Operations to transfer iSER Messages containing SCSI
Response PDUs to the iSER Layer at the initiator.
2.4.3 RDMA Write
RDMA Write is the RDMA Operation that is used to place data into an
Advertised buffer on the receiving side. The sending side addresses
the Message using an STag and a Tagged Offset that are valid on the
Data Sink.
The iSER Layer at the target uses the RDMA Write Operation to
transfer the contents of a local I/O Buffer to an Advertised I/O
Buffer at the initiator. The iSER Layer at the target uses the RDMA
Write to transfer whole or part of the data required to complete a
SCSI Read command.
The iSER Layer at the initiator does not employ RDMA Writes.
2.4.4 RDMA Read
RDMA Read is the RDMA Operation that is used to retrieve data from
an Advertised buffer on a remote node. The sending side of the RDMA
Read Request addresses the Message using an STag and a Tagged Offset
that are valid on the Data Source in addition to providing a valid
local STag and Tagged Offset that identify the Data Sink.
The iSER Layer at the target uses the RDMA Read Operation to
transfer the contents of an Advertised I/O Buffer at the initiator
to a local I/O Buffer at the target. The iSER Layer at the target
uses the RDMA Read to fetch whole or part of the data required to
complete a SCSI Write.
The iSER Layer at the initiator does not employ RDMA Reads.
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2.5 SCSI Read Overview
The iSER Layer at the initiator receives the SCSI Command PDU from
the iSCSI Layer. The iSER Layer at the initiator generates an STag
for the I/O Buffer of the SCSI Read and Advertises the buffer by
including the STag as part of the iSER header for the PDU. The iSER
Message is transferred to the target using a SendSE Message.
The iSER Layer at the target uses one or more RDMA Writes to
transfer the data required to complete the SCSI Read.
The iSER Layer at the target uses a SendInvSE Message to transfer
the SCSI Response PDU back to the iSER Layer at the initiator. The
iSER Layer at the initiator notifies the iSCSI Layer of the
availability of the SCSI Response PDU.
2.6 SCSI Write Overview
The iSER Layer at the initiator receives the SCSI Command PDU from
the iSCSI Layer. If solicited data transfer is involved, the iSER
Layer at the initiator generates an STag for the I/O Buffer of the
SCSI Write and Advertises the buffer by including the STag as part
of the iSER header for the PDU. The iSER Message is transferred to
the target using a SendSE Message.
The iSER Layer at the initiator may optionally send one or more non-
immediate unsolicited data PDUs to the target using Send Message
Types.
If solicited data transfer is involved, the iSER Layer at the target
uses one or more RDMA Reads to transfer the data required to
complete the SCSI Write.
The iSER Layer at the target uses a SendInvSE Message to transfer
the SCSI Response PDU back to the iSER Layer at the initiator. The
iSER Layer at the initiator notifies the iSCSI Layer of the
availability of the SCSI Response PDU.
2.7 iSCSI/iSER Layering
iSCSI Extensions for RDMA (iSER) is layered between the iSCSI layer
and the RDMAP layer. Figure 1 shows an example of the relationship
between SCSI, iSCSI, iSER, RDMAP, and the rest of the iWARP stack
when the transport layer is TCP.
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+-------------------------------------+
| SCSI |
+-------------------------------------+
| iSCSI |
DI ------> +-------------------------------------+
| iSER |
+-------------------------------------+
| RDMAP |
+-------------------------------------+
| DDP |
+-------------------------------------+
| MPA |
+-------------------------------------+
| TCP |
+-------------------------------------+
Figure 1 Example of iSCSI/iSER Layering in Full Feature Mode
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3 Upper Layer Interface Requirements
This section discusses the upper layer interface requirements in the
form of an abstract model of the required interactions between the
iSCSI Layer and the iSER Layer. The abstract model used here is
derived from the architectural model described in [DA].
The interface requirements are specified by Operational Primitives.
An Operational Primitive is an abstract functional interface
procedure between the iSCSI Layer and the iSER Layer that requests
one layer to perform a specific action on behalf of the other layer
or notifies the other layer of some event. Whenever an Operational
Primitive in invoked, the Connection_Handle qualifier is used to
identify a particular iSCSI connection. For some Operational
Primitives, a Data_Descriptor is used to identify the iSCSI/SCSI
data buffer associated with the requested or completed operation.
The abstract model and Operational Primitives defined in this
section are for the ease of description of iSER protocol. In the
rest of the iSER specification, the compliance statements related to
the use of these Operational Primitives are only for the purpose of
the required interactions between the iSCSI Layer and the iSER
Layer. Note that the compliance statements related to Operational
Primitives in the rest of this specification only mandate functional
equivalence on implementations, but do not put any requirements on
the implementation specifics of the interface between the iSCSI
Layer and the iSER Layer.
3.1 Operational Primitives offered by iSER
The iSER protocol layer MUST support the following Operational
Primitives to be used by the iSCSI protocol layer.
3.1.1 Send_Control
Input qualifiers: Connection_Handle, BHS and AHS (if any) of
the iSCSI PDU, iSCSI PDU specific qualifiers
Return results: Not specified
This is used by the iSCSI Layers at the initiator and the target to
request the outbound transfer of an iSCSI control-type PDU (see
section 7.2). For details on iSCSI PDU specific qualifiers, see
section 7.3. The iSCSI Layer can only invoke the Send_Control
Operational Primitive when the connection is in iSER-assisted mode.
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3.1.2 Put_Data
Input qualifiers: Connection_Handle, content of a SCSI Data-in
PDU header, Data_Descriptor, Notify_Enable
Return results: Not specified
This is used by the iSCSI Layer at the target to request the
outbound transfer of data for a SCSI Data-in PDU from the buffer
identified by the Data_Descriptor qualifier. The iSCSI Layer can
only invoke the Put_Data Operational Primitive when the connection
is in iSER-assisted mode.
The Notify_Enable qualifier is used to indicate to the iSER Layer
whether or not it should generate an eventual local completion
notification to the iSCSI Layer. See section 3.2.2 on
Data_Completion_Notify for details.
3.1.3 Get_Data
Input qualifiers: Connection_Handle, content of an R2T PDU,
Data_Descriptor, Notify_Enable
Return results: Not specified
This used by the iSCSI Layer at the target to request the inbound
transfer of solicited data requested by an R2T PDU into the buffer
identified by the Data_Descriptor qualifier. The iSCSI Layer can
only invoke the Get_Data Operational Primitive when the connection
is in iSER-assisted mode.
The Notify_Enable qualifier is used to indicate to the iSER Layer
whether or not it should generate the eventual local completion
notification to the iSCSI Layer. See section 3.2.2 on
Data_Completion_Notify for details.
3.1.4 Allocate_Connection_Resources
Input qualifiers: Connection_Handle, Resource_Descriptor
(optional)
Return results: Status
This is used by the iSCSI Layers at the initiator and the target to
request the allocation of all connection resources necessary to
support iWARP for an operational iSCSI/iSER connection. The iSCSI
Layer may optionally specify the implementation-specific resource
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requirements for the iSCSI connection using the Resource_Descriptor
qualifier.
A return result of Status=success means the invocation succeeded,
and a return result of Status=failure means that the invocation
failed. If the invocation is for a Connection_Handle for which an
earlier invocation succeeded, the request will be ignored by the
iSER Layer and the result of Status=success will be returned. Only
one Allocate_Connection_Resources Operational Primitive invocation
can be outstanding for a given Connection_Handle at any time.
3.1.5 Deallocate_Connection_Resources
Input qualifiers: Connection_Handle
Return results: Not specified
This is used by the iSCSI Layers at the initiator and the target to
request the deallocation of all connection resources that were
allocated earlier as a result of a successful invocation of the
Allocate_Connection_Resources Operational Primitive.
3.1.6 Enable_Datamover
Input qualifiers: Connection_Handle,
Transport_Connection_Descriptor, Final Login_Response_PDU
(optional)
Return results: Not specified
This is used by the iSCSI Layers at the initiator and the target to
request that a specified iSCSI connection be transitioned to iSER-
assisted mode. The Transport_Connection_Descriptor qualifier is
used to identify the specific connection associated with the
Connection_Handle. The iSCSI layer can only invoke the
Enable_Datamover Operational Primitive when there was a
corresponding prior resource allocation.
The Final_Login_Response_PDU input qualifier is applicable only for
a target, and contains the final Login Response PDU that concludes
the iSCSI Login phase and which must be sent as a byte stream as
expected by the iSCSI Layer at the initiator. When this qualifier
is used, the iSER Layer at the target MUST transmit this final Login
Response PDU before transitioning to iSER-assisted mode.
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3.1.7 Connection_Terminate
Input qualifiers: Connection_Handle
Return results: Not specified
This is used by the iSCSI Layers at the initiator and the target to
request that a specified iSCSI/iSER connection be terminated and all
associated connection and task resources be freed. When this
Operational Primitive invocation returns to the iSCSI layer, the
iSCSI layer may assume full ownership of all iSCSI-level resources,
e.g. I/O Buffers, associated with the connection.
3.1.8 Notice_Key_Values
Input qualifiers: Connection_Handle, number of keys, list of
Key-Value pairs
Return results: Not specified
This is used by the iSCSI Layers at the initiator and the target to
request the iSER Layer to take note of the specified Key-Value pairs
which were negotiated by the iSCSI peers for the connection.
3.1.9 Deallocate_Task_Resources
Input qualifiers: Connection_Handle, ITT
Return results: Not specified
This is used by the iSCSI Layers at the initiator and the target to
request the deallocation of all iWARP-specific resources allocated
by the iSER Layer for the task identified by the ITT qualifier.
This Operational Primitive is only used for tasks that did not
conclude with a SCSI Response PDU, and is not used when a SCSI
Response PDU normally concludes a task. iWARP-specific task
resources are deallocated by the iSER Layer when a SCSI Response PDU
normally concludes a task, even if the SCSI Status was not success.
3.2 Operational Primitives used by iSER
The iSER layer MUST use the following Operational Primitives offered
by the iSCSI protocol layer when the connection is in iSER-assisted
mode.
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3.2.1 Control_Notify
Input qualifiers: Connection_Handle, an iSCSI control-type PDU
Return results: Not specified
This is used by the iSER Layers at the initiator and the target to
notify the iSCSI Layer of the availability of an inbound iSCSI
control-type PDU. A PDU is described as "available" to the iSCSI
Layer when the iSER Layer notifies the iSCSI Layer of the reception
of that inbound PDU, along with an implementation-specific
indication as to where the received PDU is.
3.2.2 Data_Completion_Notify
Input qualifiers: Connection_Handle, ITT, SN
Return results: Not specified
This is used by the iSER Layer to notify the iSCSI Layer of the
completion of outbound data transfer that was requested by the iSCSI
Layer only if the invocation of the Put_Data Operational Primitive
(see section 3.1.2) was qualified with Notify_Enable set. SN refers
to the DataSN associated with the SCSI Data-In PDU.
This is used by the iSER Layer to notify the iSCSI Layer of the
completion of inbound data transfer that was requested by the iSCSI
Layer only if the invocation of the Get_Data Operational Primitive
(see section 3.1.3) was qualified with Notify_Enable set. SN refers
to the R2TSN associated with the R2T PDU.
3.2.3 Data_ACK_Notify
Input qualifier: Connection_Handle, ITT, DataSN
Return results: Not specified
This is used by the iSER Layer at the target to notify the iSCSI
Layer of the arrival of the data acknowledgement (as defined in
[iSCSI]) requested earlier by the iSCSI Layer for the outbound data
transfer via an invocation of the Put_Data Operational Primitive
where the A-bit in the SCSI Data-in PDU is set to 1. See section
7.3.5. DataSN refers to the expected DataSN of the next SCSI Data-
in PDU which immediately follows the SCSI Data-in PDU with the A-bit
set to which this notification corresponds, with semantics as
defined in [iSCSI].
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3.2.4 Connection_Terminate_Notify
Input qualifiers: Connection_Handle
Return results: Not specified
This is used by the iSER Layers at the initiator and the target to
notify the iSCSI Layer of the unsolicited termination or failure of
an iSCSI/iSER connection. The iSER Layer MUST deallocate the
connection and task resources associated with the terminated
connection before the invocation of this Operational Primitive.
Note that the Connection_Terminate_Notify Operational Primitive is
not invoked when the termination of the connection was earlier
requested by the local iSCSI Layer.
3.3 iSCSI Protocol Usage Requirements
An iSER-assisted iSCSI protocol layer should satisfy the following
protocol usage requirements from the iSER protocol:
1. The iSCSI Layers at both the initiator and the target MUST
negotiate the RDMAExtensions key (see section 6.3) to "Yes" on
the leading connection. If the invocation of the
Allocate_Connection_Resources Operational Primitive to the iSER
layer fails after this key is negotiated to "Yes", the iSCSI
layer MUST fail the iSCSI Login process or terminate the
connection as appropriate. See section 10.1.3.1 and 10.1.3.2
for details.
2. The iSCSI Layer at the initiator MUST set ExpDataSN = 0 in Task
Management Function Requests for Task Allegiance Reassignment
for read/bidirectional commands, so as to cause the target to
send all unacknowledged read data.
3. The iSCSI Layer at the target MUST always return the SCSI status
in a separate SCSI Response PDU for read commands, i.e., there
MUST NOT be a "phase collapse" in concluding a SCSI Read
Command.
4. The iSCSI Layers at both the initiator and the target MUST
successfully negotiate the InitiatorRecvDataSegmentLength key
(see section 6.5) for each iSER-assisted connection, and follow
its defined semantics.
5. The iSCSI Layer at both the initiator and the target MUST
successfully negotiate the TargetRecvDataSegmentLength key (see
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section 6.4) for each iSER-assisted connection, and follow its
defined semantics.
6. The iSCSI Layer at the initiator SHOULD NOT issue proactive
(based on time-outs) SNACKs for PDUs that it presumes are lost.
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4 Lower Layer Interface Requirements
4.1 Interactions with the iWARP Layer
The iSER protocol layer is layered on top of the iWARP protocol
stack (see Figure 1) and the following are the key features that are
assumed to be supported by iWARP:
* The RDMAP layer supports all basic RDMAP operations, including
RDMA Write Operation, RDMA Read Operation, Send Operation, Send
with Invalidate Operation, Send with Solicited Event Operation,
Send with Solicited Event & Invalidate Operation, and Terminate
Operation.
* The RDMAP/DDP layers provide reliable, in-order message delivery
and direct data placement.
* The RDMAP layer encapsulates a single iSER Message into a single
RDMAP message on the Data Source side. The RDMAP layer
decapsulates the iSER Message before delivering it to the iSER
Layer on the Data Sink side.
* When the iSER Layer provides the STag to be remotely invalidated
to the RDMAP layer for a SendInvSE Message, the RDMAP layer uses
this STag as the STag to be invalidated in the SendInvSE Message.
* The RDMAP layer uses the STag and Tagged Offset provided by the
iSER Layer for the RDMA Write and RDMA Read Request Messages.
* When the RDMAP layer delivers the content of an RDMA Send Message
Type to the iSER Layer, the RDMAP layer provides the length of
the RDMA Send message. This ensures that the iSER Layer does not
have to carry a length field in the iSER header.
* When the RDMAP layer delivers the SendSE or SendInvSE Message to
the iSER Layer, it notifies the iSER Layer with the mechanism
provided on that interface.
* When the RDMAP layer delivers a SendInvSE Message to the iSER
Layer, it passes the value of the STag that was invalidated.
* The RDMAP layer propagates all status and error indications to
the iSER Layer.
* The iWARP implementation supports the enabling of the iWARP mode
after Connection establishment.
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* Whenever the iSER Layer terminates the RDMAP Stream, the RDMAP
layer terminates the associated Connection.
4.2 Interactions with the Transport Layer
The iSER Layer does not interface with the transport layer (e.g.,
TCP) directly. During Connection setup, the iSCSI Layer is
responsible for setting up the Connection. If the login is
successful, the iSCSI Layer invokes the Enable_Datamover Operational
Primitive to request the iSER Layer to transition to the iSER-
assisted mode for that iSCSI connection. See section 5.1 on
iSCSI/iSER Connection Setup. After transitioning to iSER-assisted
mode, the iWARP layer is responsible for maintaining the Connection
and reports to the iSER Layer of any Connection failures.
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5 Connection Setup and Termination
5.1 iSCSI/iSER Connection Setup
During connection setup, the iSCSI Layer at the initiator is
responsible for establishing a connection with the target. After
the connection is established, the iSCSI Layers at the initiator and
the target enter the Login Phase using the same rules as outlined in
[iSCSI]. Transition to iSER-assisted mode occurs when the
connection transitions into the iSCSI full feature phase following a
successful login negotiation between the initiator and the target in
which iSER-assisted mode is negotiated and the connection resources
necessary to support iWARP have been allocated at both the initiator
and the target.
iSER-assisted mode MUST be enabled only if it is negotiated on the
leading connection during the LoginOperationalNegotiation Stage of
the iSCSI Login Phase. iSER-assisted mode is negotiated using the
RDMAExtensions=<boolean-value> key. Both the initiator and the
target MUST exchange the RDMAExtensions key with the value set to
"Yes" to enable iSER-assisted mode. If both the initiator and the
target fail to negotiate the RDMAExtensions key set to "Yes", then
the connection MUST continue with the login semantics as defined in
[iSCSI].
iSER-assisted mode is defined for a Normal session only and the
RDMAExtensions key MUST NOT be negotiated for a Discovery session.
An iSER enabled node is not required to initiate the RDMAExtensions
key exchange if its preference is for the traditional iSCSI mode.
The RDMAExtensions key, if offered, MUST be sent in the first
available Login Response or Login Request PDU in the
LoginOperationalNegotiation stage. This is due to the fact that the
value of some login parameters might depend on whether iSER-assisted
mode is enabled or not.
iSER-assisted mode is a session-wide attribute. If both the
initiator and the target negotiated RDMAExtensions="Yes" on the
leading connection of a session, then all subsequent connections of
the same session MUST enable iSER-assisted mode without having to
exchange RDMAExtensions key during the iSCSI Login Phase.
Conversely, if both the initiator and the target failed to negotiate
RDMAExtensions to "Yes" on the leading connection of a session, then
the RDMAExtensions key MUST NOT be negotiated further on any
additional subsequent connection of the session.
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When the RDMAExtensions key is negotiated to "Yes", the HeaderDigest
and the DataDigest keys MUST be negotiated to "None" on all
iSCSI/iSER connections participating in that iSCSI session. This is
because, for an iSCSI/iSER connection, the iWARP protocol suite
provides a CRC32c-based error detection for all iWARP Messages.
Furthermore, all SCSI Read data are sent using RDMA Write Messages
instead of the SCSI Data-in PDUs, and all solicited SCSI write data
are sent using RDMA Read Response Messages instead of the SCSI Data-
out PDUs. HeaderDigest and DataDigest which apply to iSCSI PDUs
would not be appropriate for RDMA Read and RDMA Write operations
used with iSER.
5.1.1 Initiator Behavior
If the outcome of the iSCSI negotiation is to enable iSER-assisted
mode, then on the initiator side, prior to sending the Login Request
with the T (Transit) bit set to 1 and the NSG (Next Stage) field set
to FullFeaturePhase, the iSCSI Layer MUST invoke the
Allocate_Connection_Resources Operational Primitive to request the
iSER Layer to allocate the connection resources necessary to support
iWARP. The connection resources required are defined by
implementation and are outside the scope of this specification. The
iSCSI Layer may invoke the Notice_Key_Values Operational Primitive
before invoking the Allocate_Connection_Resources Operational
Primitive to request the iSER Layer to take note of the negotiated
values of the iSCSI keys for the Connection. The specific keys to
be passed in as input qualifiers are implementation dependent.
These may include, but not limited to, MaxOutstandingR2T,
ErrorRecoveryLevel, etc.
Among the connection resources allocated at the initiator is the
Inbound RDMA Read Queue Depth (IRD). As described in section 9.5.1,
R2Ts are transformed by the target into RDMA Read operations. IRD
limits the maximum number of simultaneously incoming outstanding
RDMA Read Requests per an RDMAP Stream from the target to the
initiator. The required value of IRD is outside the scope of the
iSER specification. The iSER Layer at the initiator MUST set IRD to
1 or higher if R2Ts are to be used in the connection. However, the
iSER Layer at the initiator MAY set IRD to 0 based on implementation
configuration which indicates that no R2Ts will be used on that
connection. Initially, the iSER-IRD value at the initiator SHOULD
be set to the IRD value at the initiator and MUST NOT be more than
the IRD value.
On the other hand, the Outbound RDMA Read Queue Depth (ORD) MAY be
set to 0 since the iSER Layer at the initiator does not issue RDMA
Read Requests to the target.
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If the iSCSI Layer invokes the Allocate_Connection_Resources
Operational Primitive after the connection resources necessary to
support iWARP are known through iSCSI negotiation, then only the
connection resources required are allocated. However, failure to
allocate the requested connection resources locally results in a
login failure and its handling is described in section 10.1.3.1.
If the iSCSI Layer invokes the Allocate_Connection_Resources
Operational Primitive before the iSCSI Login Phase, it avoids the
potential login failure due to failure to allocate the requested
connection resources. However, since the connection resources
necessary to support iWARP are not yet known, the connection
resources to be allocated must equal or exceed whatever is required
as determined in the later iSCSI negotiation. As a result,
resources are allocated but unused if the connection resources
required are less than the allocated ones unless the iSCSI Layer
frees up the unused resources. In the event that the iSCSI login
fails, or if the connection is to remain in traditional iSCSI mode,
the connection resources to support iWARP MUST be deallocated as
described in section 10.1.4.6.
If the iSER Layer at the initiator is successful in allocating the
connection resources necessary to support iWARP, the following
events MUST occur in the specified sequence:
1. The iSER Layer MUST return a success status to the iSCSI Layer
in response to the Allocate_Connection_Resources Operational
Primitive.
2. After the target returns the Login Response with the T bit set
to 1 and the NSG field set to FullFeaturePhase, and a status
class of 0 (Success), the iSCSI Layer MUST invoke the
Enable_Datamover Operational Primitive with the following
qualifiers to request the iSER Layer to transition to iSER-
assisted mode (See section 10.1.4.6 for the case when the status
class is not Success.):
a. Connection_Handle that identifies the iSCSI connection.
b. Transport_Connection_Descriptor which identifies the
specific transport connection associated with the
Connection_Handle.
3. The iSER Layer MUST enable iWARP and transition the connection
to iSER-assisted mode.
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4. The iSER Layer MUST send the iSER Hello Message as the first
RDMAP message. See Section 5.1.3 on iSER Hello Exchange.
If an iSCSI implementation wants to ensure that the resources
necessary to support iWARP are allocated and therefore invokes the
Allocate_Connection_Resources Operational Primitive prior to
initiating the iSCSI negotiation, then it is responsible for
managing the resource deallocation if the iSCSI login fails or if
the negotiated values of the iSCSI keys are different than the
allocated value.
5.1.2 Target Behavior
If the outcome of the iSCSI negotiation is to enable iSER-assisted
mode, then on the target side, prior to sending the Login Response
with the T (Transit) bit set to 1 and the NSG (Next Stage) field set
to FullFeaturePhase, the iSCSI Layer MUST invoke the
Allocate_Connection_Resources Operational Primitive to request the
iSER Layer to allocate the resources necessary to support iWARP.
The connection resources required are defined by implementation and
are outside the scope of this specification. Optionally, the iSCSI
Layer may invoke the Notice_Key_Values Operational Primitive before
invoking the Allocate_Connection_Resources Operational Primitive to
request the iSER Layer to take note of the negotiated values of the
iSCSI keys for the Connection. The specific keys to be passed in as
input qualifiers are implementation dependent. These may include,
but not limited to, MaxOutstandingR2T, ErrorRecoveryLevel, etc.
Among the connection resources allocated at the target is the
Outbound RDMA Read Queue Depth (ORD). As described in section
9.5.1, R2Ts are transformed by the target into RDMA Read operations.
The ORD limits the maximum number of simultaneously outstanding RDMA
Read Requests per RDMAP Stream from the target to the initiator.
Initially, the iSER-ORD value at the target SHOULD be set to the ORD
value at the target.
On the other hand, the IRD at the target MAY be set to 0 since the
iSER Layer at the target does not expect RDMA Read Requests to be
issued by the initiator.
If the iSCSI Layer invokes the Allocate_Connection_Resources
Operational Primitive after the connection resources necessary to
support iWARP are known through iSCSI negotiation, then only the
connection resources required are allocated. However, failure to
allocate the requested connection resources locally results in a
login failure and its handling is described in section 10.1.3.1.
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If the iSCSI Layer invokes the Allocate_Connection_Resources
Operational Primitive before the iSCSI Login Phase, it avoids the
potential login failure due to failure to allocate the requested
connection resources. However, since the connection resources
necessary to support iWARP are not yet known, the connection
resources to be allocated must equal or exceed whatever is required
as determined in the later iSCSI negotiation. As a result,
resources are allocated but unused if the connection resources
required are less than the allocated ones unless the iSCSI Layer
frees up the unused resources. In the event that the iSCSI login
fails, or if the connection is to remain in traditional iSCSI mode,
the connection resources to support iWARP MUST be deallocated as
described in section 10.1.4.6.
If the iSER Layer at the target is successful in allocating the
connection resources necessary to support iWARP, the following
events MUST occur in the specified sequence:
1. The iSER Layer MUST return a success status to the iSCSI Layer
in response to the Allocate_Connection_Resources Operational
Primitive.
2. The iSCSI Layer MUST invoke the Enable_Datamover Operational
Primitive with the following qualifiers to request the iSER
Layer to transition to iSER-assisted mode:
a. Connection_Handle that identifies the iSCSI connection.
b. Transport_Connection_Descriptor which identifies the
specific transport connection associated with the
Connection_Handle.
c. The final transport layer (e.g. TCP) message containing the
Login Response with the T bit set to 1 and the NSG field set
to FullFeaturePhase
3. The iSER Layer MUST send the final SCSI Login Response PDU in
byte stream mode to conclude the iSCSI Login Phase.
4. After sending the final SCSI Login Response PDU in byte stream
mode, the iSER Layer MUST enable iWARP and transition the
connection to iSER-assisted mode.
5. After receiving the iSER Hello Message from the initiator, the
iSER Layer MUST respond with the iSER HelloReply Message to be
sent as the first RDMAP Message. See section 5.1.3 on iSER
Hello Exchange for more details.
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Note: In the above sequence, the operations as described in the
bullets 3 and 4 must be performed atomically. Failure to do this
may result in race conditions.
5.1.3 iSER Hello Exchange
After the connection transitions into the iSER-assisted mode, the
first RDMAP Message sent by the iSER Layer at the initiator to the
target MUST be the iSER Hello Message. The iSER Hello Message is
used by the iSER Layer at the initiator to declare iSER parameters
to the target. See section 9.3 on iSER Header Format for iSER Hello
Message.
In response to the iSER Hello Message, the iSER Layer at the target
MUST return the iSER HelloReply Message as the first RDMAP Message
sent by the target. The iSER HelloReply Message is used by the iSER
Layer at the target to declare iSER parameters to the initiator.
See section 9.4 on iSER Header Format for iSER HelloReply Message.
In the iSER Hello Message, the iSER Layer at the initiator declares
the iSER-IRD value to the target.
Upon receiving the iSER Hello Message, the iSER Layer at the target
MUST set the iSER-ORD value to the minimum of the iSER-ORD value at
the target and the iSER-IRD value declared by the initiator. The
iSER Layer at the target MAY adjust (lower) its ORD value to match
the iSER-ORD value if the iSER-ORD value is smaller than the ORD
value at the target in order to free up the unused resources.
In the iSER HelloReply Message, the iSER Layer at the target
declares the iSER-ORD value to the initiator.
Upon receiving the iSER HelloReply Message, the iSER Layer at the
initiator MAY adjust (lower) its IRD value to match the iSER-ORD
value in order to free up the unused resources, if the iSER-ORD
value declared by the target is smaller than the iSER-IRD value
declared by the initiator.
It is an iSER level negotiation failure if the iSER parameters
declared in the iSER Hello Message by the initiator is unacceptable
to the target. See section 10.1.3.3 on the handling of the error
situation.
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5.2 iSCSI/iSER Connection Termination
5.2.1 Normal Connection Termination at the Initiator
The iSCSI Layer at the initiator terminates an iSCSI/iSER connection
normally by invoking the Send_Control Operational Primitive
qualified with the Logout Request PDU. The iSER Layer at the
initiator MUST use a SendSE Message to send the Logout Request PDU
to the target. After the iSER Layer at the initiator receives the
SendSE Message containing the Logout Response PDU from the target,
it MUST notify the iSCSI Layer by invoking the Control_Notify
Operational Primitive qualified with the Logout Response PDU.
After the iSCSI logout process is complete, the iSCSI layer at the
target is responsible for closing the iSCSI/iSER connection as
described in Section 5.2.2. After the RDMAP layer at the initiator
reports that the Connection has been closed, the iSER Layer at the
initiator MUST deallocate all connection resources, deallocate all
task resources (if any) associated with the connection, invalidate
the local mapping(s) (if any) that associate the ITT(s) used on that
connection to the local STag(s), and then invoke the
Connection_Terminate_Notify Operational Primitive to notify the
iSCSI Layer.
5.2.2 Normal Connection Termination at the Target
Upon receiving the SendSE Message containing the Logout Request PDU,
the iSER Layer at the target MUST notify the iSCSI Layer at the
target by invoking the Control_Notify Operational Primitive
qualified with the Logout Request PDU. The iSCSI Layer completes
the logout process by invoking the Send_Control Operational
Primitive qualified with the Logout Response PDU. The iSER Layer at
the target MUST use a SendSE Message to send the Logout Response PDU
to the initiator. After the iSCSI logout process is complete, the
iSCSI Layer at the target MUST invoke the Connection_Terminate
Operational Primitive to request the iSER Layer at the target to
terminate the RDMAP Stream.
As part of the termination process, the RDMAP layer MUST close the
Connection. When the RDMAP layer notifies the iSER Layer after the
RDMAP stream and the associated Connection are terminated, the iSER
Layer MUST deallocate all connection resources, deallocate all task
resources (if any) associated with the connection, and invalidate
the local and remote mapping(s) (if any) that associate the ITT(s)
used on that connection to the local STag(s) and the Advertised
STag(s) respectively.
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5.2.3 Termination without Logout Request/Response PDUs
5.2.3.1 Connection Termination Initiated by the iSCSI Layer
The Connection_Terminate Operational Primitive MAY be invoked by the
iSCSI Layer to request the iSER Layer to terminate the RDMAP Stream
without having previously exchanged the Logout Request and Logout
Response PDUs between the two iSCSI/iSER nodes. As part of the
termination process, the RDMAP layer will close the Connection.
When the RDMAP layer notifies the iSER Layer after the RDMAP stream
and the associated Connection are terminated, the iSER Layer MUST
perform the following actions.
If the Connection_Terminate Operational Primitive is invoked by the
iSCSI Layer at the target, then the iSER Layer at the target MUST
deallocate all connection resources, deallocate all task resources
(if any) associated with the connection, and invalidate the local
and remote mappings (if any) that associate the ITT(s) used on the
connection to the local STag(s) and the Advertised STag(s)
respectively.
If the Connection_Terminate Operational Primitive is invoked by the
iSCSI Layer at the initiator, then the iSER Layer at the initiator
MUST deallocate all connection resources, deallocate all task
resources (if any) associated with the connection, and invalidate
the local mapping(s) (if any) that associate the ITT(s) used on the
connection to the local STag(s).
5.2.3.2 Connection Termination Notification to the iSCSI Layer
If the iSCSI/iSER connection is terminated without the invocation of
Connection_Terminate from the iSCSI Layer, the iSER Layer MUST
invoke the Connection_Terminate_Notify Operational Primitive to
notify the iSCSI Layer that the iSCSI/iSER connection has been
terminated.
Prior to invoking Connection_Terminate_Notify, the iSER Layer at the
target MUST deallocate all connection resources, deallocate all task
resources (if any) associated with the connection, and invalidate
the local and remote mappings (if any) that associate the ITT(s)
used on the connection to the local STag(s) and the Advertised
STag(s) respectively.
Prior to invoking Connection_Terminate_Notify, the iSER Layer at the
initiator MUST deallocate all connection resources, deallocate all
task resources (if any) associated with the connection, and
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invalidate the local mappings (if any) that associate the ITT(s)
used on the connection to the local STag(s).
If the remote iSCSI/iSER node initiated the closing of the
Connection (e.g., by sending a TCP FIN or TCP RST), the iSER Layer
MUST invoke the Connection_Terminate_Notify Operational Primitive to
notify the iSCSI Layer after the RDMAP layer reports that the
Connection is closed.
Another example of a Connection termination without a preceding
logout is when the iSCSI Layer at the initiator does an implicit
logout (connection reinstatement).
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6 Login/Text Operational Keys
Certain iSCSI login/text operational keys have restricted usage in
iSER, and additional keys are used to support the iSER protocol
functionality. All other keys defined by [iSCSI] and not discussed
in this section may be used on iSCSI/iSER connections with the same
semantics.
6.1 HeaderDigest and DataDigest
Irrelevant when: RDMAExtensions=Yes
Negotiations resulting in RDMAExtensions=Yes for a session implies
HeaderDigest=None and DataDigest=None for all connections in that
session and overrides both the default and an explicit setting.
6.2 MaxRecvDataSegmentLength
For an iSCSI connection belonging to a session in which
RDMAExtensions=Yes was negotiated on the leading connection of the
session, MaxRecvDataSegmentLength need not be declared in the Login
Phase. Instead InitiatorRecvDataSegmentLength (as described in
section 6.5) and TargetRecvDataSegmentLength (as described in
section 6.4) keys are negotiated. The values of the local and
remote MaxRecvDataSegmentLength are derived from the
InitiatorRecvDataSegmentLength and TargetRecvDataSegmentLength keys
even if the MaxRecvDataSegmentLength was declared during the login
phase.
In the full feature phase, the initiator MUST consider the value of
its local MaxRecvDataSegmentLength (that it would have declared to
the target) as having the value of InitiatorRecvDataSegmentLength,
and the value of the remote MaxRecvDataSegmentLength (that would
have been declared by the target) as having the value of
TargetRecvDataSegmentLength. Similarly, the target MUST consider
the value of its local MaxRecvDataSegmentLength (that it would have
declared to the initiator) as having the value of
TargetRecvDataSegmentLength, and the value of the remote
MaxRecvDataSegmentLength (that would have been declared by the
initiator) as having the value of InitiatorRecvDataSegmentLength.
The MaxRecvDataSegmentLength key is applicable only for iSCSI
control-type PDUs.
6.3 RDMAExtensions
Use: LO (leading only)
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Senders: Initiator and Target
Scope: SW (session-wide)
RDMAExtensions=<boolean-value>
Irrelevant when: SessionType=Discovery
Default is No
Result function is AND
This key is used by the initiator and the target to negotiate the
support for iSER-assisted mode. To enable the use of iSER-assisted
mode, both the initiator and the target MUST exchange
RDMAExtensions=Yes. iSER-assisted mode MUST NOT be used if either
the initiator or the target offers RDMAExtensions=No.
An iSER-enabled node is not required to initiate the RDMAExtensions
key exchange if it prefers to operate in the traditional iSCSI mode.
However, if the RDMAExtensions key is to be negotiated, an initiator
MUST offer the key in the first Login Request PDU in the
LoginOperationalNegotiation stage of the leading connection, and a
target MUST offer the key in the first Login Response PDU with which
it is allowed to do so (i.e., the first Login Response PDU issued
after the first Login Request PDU with the C bit set to 0) in the
LoginOperationalNegotiation stage of the leading connection. In
response to the offered key=value pair of RDMAExtensions=yes, an
initiator MUST respond in the next Login Request PDU with which it
is allowed to do so, and a target MUST respond in the next Login
Response PDU with which it is allowed to do so.
Negotiating the RDMAExtensions key first enables a node to negotiate
the optimal value for other keys. Certain iSCSI keys such as
MaxBurstLength, MaxOutstandingR2T, ErrorRecoveryLevel, InitialR2T,
ImmediateData, etc., may be negotiated differently depending on
whether connection is in traditional iSCSI mode or iSER-assisted
mode.
6.4 TargetRecvDataSegmentLength
Use: IO (Initialize only)
Senders: Initiator and Target
Scope: CO (connection-only)
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Irrelevant when: RDMAExtensions=No
TargetRecvDataSegmentLength=<numerical-value-512-to-(2**24-1)>
Default is 8192 bytes
Result function is minimum
This key is relevant only for the iSCSI connection of an iSCSI
session if RDMAExtensions=Yes was negotiated on the leading
connection of the session. It is used by the initiator and the
target to negotiate the maximum size of the data segment that an
initiator may send to the target in an iSCSI control-type PDU. For
SCSI Command PDUs and SCSI Data-out PDUs containing non-immediate
unsolicited data to be sent by the initiator, the initiator MUST
send all non-Final PDUs with a data segment size of exactly
TargetRecvDataSegmentLength whenever the PDUs constitute a data
sequence whose size is larger than TargetRecvDataSegmentLength.
6.5 InitiatorRecvDataSegmentLength
Use: IO (Initialize only)
Senders: Initiator and Target
Scope: CO (connection-only)
Irrelevant when: RDMAExtensions=No
InitiatorRecvDataSegmentLength=<numerical-value-512-to-(2**24-1)>
Default is 8192 bytes
Result function is minimum
This key is relevant only for the iSCSI connection of an iSCSI
session if RDMAExtensions=Yes was negotiated on the leading
connection of the session. It is used by the initiator and the
target to negotiate the maximum size of the data segment that a
target may send to the initiator in an iSCSI control-type PDU.
6.6 OFMarker and IFMarker
Irrelevant when: RDMAExtensions=Yes
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Negotiations resulting in RDMAExtensions=Yes for a session implies
OFMarker=No and IFMarker=No for all connections in that session and
overrides both the default and an explicit setting.
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7 iSCSI PDU Considerations
When a connection is in the iSER-assisted mode, two types of message
transfers are allowed between the iSCSI Layer at the initiator and
the iSCSI Layer at the target. These are known as the iSCSI data-
type PDUs and the iSCSI control-type PDUs and these terms are
described in the following sections.
7.1 iSCSI Data-Type PDU
An iSCSI data-type PDU is defined as an iSCSI PDU that causes data
transfer, transparent to the remote iSCSI layer, to take place
between the peer iSCSI nodes in the full feature phase of an
iSCSI/iSER connection. An iSCSI data-type PDU, when requested for
transmission by the iSCSI Layer in the sending node, results in the
data being transferred without the participation of the iSCSI Layers
at the sending and the receiving nodes. This is due to the fact
that the PDU itself is not delivered as-is to the iSCSI Layer in the
receiving node. Instead, the data transfer operations are
transformed into the appropriate RDMA operations which are handled
by the RNIC. The set of iSCSI data-type PDUs consists of SCSI Data-
in PDUs and R2T PDUs.
If the invocation of the Operational Primitive by the iSCSI Layer to
request the iSER Layer to process an iSCSI data-type PDU is
qualified with Notify_Enable set, then upon completing the RDMA
operation, the iSER Layer at the target MUST notify the iSCSI Layer
at the target by invoking the Data_Completion_Notify Operational
Primitive qualified with ITT and SN. There is no data completion
notification at the initiator since the RDMA operations are
completely handled by the RNIC at the initiator and the iSER Layer
at the initiator is not involved with the data transfer associated
with iSCSI data-type PDUs.
If the invocation of the Operational Primitive by the iSCSI Layer to
request the iSER Layer to process an iSCSI data-type PDU is
qualified with Notify_Enable cleared, then upon completing the RDMA
operation, the iSER Layer at the target MUST NOT notify the iSCSI
Layer at the target and MUST NOT invoke the Data_Completion_Notify
Operational Primitive.
If an operation associated with an iSCSI data-type PDU fails for any
reason, the contents of the Data Sink buffers associated with the
operation are considered indeterminate.
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7.2 iSCSI Control-Type PDU
Any iSCSI PDU that is not an iSCSI data-type PDU and also not a SCSI
Data-out PDU carrying solicited data is defined as an iSCSI control-
type PDU. The iSCSI Layer invokes the Send_Control Operational
Primitive to request the iSER Layer to process an iSCSI control-type
PDU. iSCSI control-type PDUs are transferred using RDMAP Send
Message Types. Specifically, it is to be noted that SCSI Data-Out
PDUs carrying unsolicited data are defined as iSCSI control-type
PDUs. See section 7.3.4 on the treatment of SCSI Data-out PDUs.
When the iSER Layer receives an iSCSI control-type PDU, it MUST
notify the iSCSI Layer by invoking the Control_Notify Operational
Primitive qualified with the iSCSI control-type PDU.
7.3 iSCSI PDUs
This section describes the handling of each of the iSCSI PDU types
by the iSER Layer. The iSCSI Layer requests the iSER Layer to
process the iSCSI PDU by invoking the appropriate Operational
Primitive. A Connection_Handle MUST qualify each of these
invocations. In addition, BHS and the optional AHS of the iSCSI PDU
as defined in [iSCSI] MUST qualify each of the invocations. The
qualifying Connection_Handle, the BHS and the AHS are not explicitly
listed in the subsequent sections.
7.3.1 SCSI Command
Type: control-type PDU
PDU-specific qualifiers (for SCSI Write or bidirectional
command): ImmediateDataSize, UnsolicitedDataSize,
DataDescriptorOut
PDU-specific qualifiers (for SCSI Read or bidirectional
command): DataDescriptorIn
The iSER Layer at the initiator MUST send the SCSI command in a
SendSE Message to the target.
For a SCSI Write or bidirectional command, the iSCSI Layer at the
initiator MUST invoke the Send_Control Operational Primitive as
follows:
* If there is immediate data to be transferred for the SCSI write
or bidirectional command, the qualifier ImmediateDataSize MUST be
used to define the number of bytes of immediate unsolicited data
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to be sent with the write or bidirectional command, and the
qualifier DataDescriptorOut MUST be used to define the
initiator's I/O Buffer containing the SCSI Write data.
* If there is unsolicited data to be transferred for the SCSI Write
or bidirectional command, the qualifier UnsolicitedDataSize MUST
be used to define the number of bytes of immediate and non-
immediate unsolicited data for the command. The iSCSI Layer will
issue one or more SCSI Data-out PDUs for the non-immediate
unsolicited data. See Section 7.3.4 on SCSI Data-out.
* If there is solicited data to be transferred for the SCSI Write
or bidirectional command, as indicated by the Expected Data
Transfer Length in the SCSI Command PDU exceeding the value of
UnsolicitedDataSize, the iSER Layer at the initiator MUST do the
following:
a. It MUST allocate a Write STag for the I/O Buffer defined by
the qualifier DataDescriptorOut. DataDescriptorOut
describes the I/O buffer starting with the immediate
unsolicited data (if any), followed by the non-immediate
unsolicited data (if any) and solicited data. This means
that the BufferOffset for the SCSI Data-out for this command
is equal to the TO. This implies zero TO for this STag
points to the beginning of this I/O Buffer.
b. It MUST establish a local mapping that associates the
Initiator Task Tag (ITT) to the Write STag.
c. It MUST Advertise the Write STag to the target by sending it
as the Write STag in the iSER header of the iSER Message
(the payload of the RDMAP SendSE Message) containing the
SCSI Write or bidirectional command PDU. See section 9.2 on
iSER Header Format for iSCSI Control-Type PDU.
For a SCSI Read or bidirectional command, the iSCSI Layer at the
initiator MUST invoke the Send_Control Operational Primitive
qualified with DataDescriptorIn which defines the initiatorĘs I/O
Buffer for receiving the SCSI Read data. The iSER Layer at the
initiator MUST do the following:
a. It MUST allocate a Read STag for the I/O Buffer.
b. It MUST establish a local mapping that associates the
Initiator Task Tag (ITT) to the Read STag.
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c. It MUST Advertise the Read STag to the target by sending it
as the Read STag in the iSER header of the iSER Message (the
payload of the RDMAP SendSE Message) containing the SCSI
Read or bidirectional command PDU. See section 9.2 on iSER
Header Format for iSCSI Control-Type PDU.
If the amount of unsolicited data to be transferred in a SCSI
Command exceeds TargetRecvDataSegmentLength, then the iSCSI Layer at
the initiator MUST segment the data into multiple iSCSI control-type
PDUs, with the data segment length in all PDUs generated except the
last one having exactly the size TargetRecvDataSegmentLength. The
data segment length of the last iSCSI control-type PDU carrying the
unsolicited data can be up to TargetRecvDataSegmentLength.
When the iSER Layer at the target receives the SCSI Command, it MUST
establish a remote mapping that associates the ITT to the Advertised
Write STag and the Read STag if present in the iSER header. The
Write STag is used by the iSER Layer at the target in handling the
data transfer associated with the R2T PDU(s) as described in section
7.3.6. The Read STag is used in handling the SCSI Data-in PDU(s)
from the iSCSI Layer at the target as described in section 7.3.5.
7.3.2 SCSI Response
Type: control-type PDU
PDU-specific qualifiers: DataDescriptorStatus
The iSCSI Layer at the target MUST invoke the Send_Control
Operational Primitive qualified with DataDescriptorStatus which
defines the buffer containing the sense and response information.
The iSCSI Layer at the target MUST always return the SCSI status for
a SCSI command in a separate SCSI Response PDU. "Phase collapse"
for transferring SCSI status in a SCSI Data-in PDU MUST NOT be used.
The iSER Layer at the target sends the SCSI Response PDU according
to the following rules:
* If no STags were Advertised by the initiator in the iSER Message
containing the SCSI command PDU, then the iSER Layer at the
target MUST send a SendSE Message containing the SCSI Response
PDU.
* If the initiator Advertised a Read STag in the iSER Message
containing the SCSI Command PDU, then the iSER Layer at the
target MUST send a SendInvSE Message containing the SCSI Response
PDU. The RDMAP header of the SendInvSE Message MUST carry the
Read STag to be invalidated at the initiator.
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* If the initiator Advertised only the Write STag in the iSER
Message containing the SCSI command PDU, then the iSER Layer at
the target MUST send a SendInvSE Message containing the SCSI
Response PDU. The RDMAP header of the SendInvSE Message MUST
carry the Write STag to be invalidated at the initiator.
When the iSCSI Layer at the target invokes the Send_Control
Operational Primitive to send the SCSI Response PDU, the iSER Layer
at the target MUST invalidate the remote mapping that associates the
ITT to the Advertised STag(s) before transferring the SCSI Response
PDU to the initiator.
Upon receiving the SendInvSE Message containing the SCSI Response
PDU from the target, the RDMAP layer at the initiator will
invalidate the STag specified in the RDMAP header. The iSER
Layer at the initiator MUST ensure that the correct STag is
invalidated. If both the Read and the Write STags were Advertised
earlier by the initiator, then the iSER Layer at the initiator MUST
explicitly invalidate the Write STag upon receiving the SendInvSE
Message because the RDMAP header of the SendInvSE Message can only
carry one STag (in this case the Read STag) to be invalidated.
The iSER Layer at the initiator MUST ensure the invalidation of the
STag(s) used in a command before invoking the Control_Notify
Operational Primitive qualified with the SCSI Response to notify the
iSCSI Layer at the initiator. This precludes the possibility of
using the STag(s) after the completion of the command thereby
causing data corruption.
When the iSER Layer at the initiator receives the SendSE or the
SendInvSE Message containing the SCSI Response PDU, it SHOULD
invalidate the local mapping that associates the ITT to the local
STag(s). The iSER Layer MUST ensure that all local STag(s)
associated with the ITT are invalidated before invoking the
Control_Notify Operational Primitive to notify the iSCSI Layer of
the SCSI Response PDU.
7.3.3 Task Management Function Request/Response
Type: control-type PDUs
PDU-specific qualifiers (for TMF Request): DataDescriptorOut,
DataDescriptorIn
The iSER Layer MUST use a SendSE Message to send the Task Management
Function Request/Response PDU.
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For the Task Management Function Request with the TASK REASSIGN
function, the iSER Layer at the initiator MUST do the following:
* It MUST use the ITT as specified in the Referenced Task Tag from
the Task Management Function Request PDU to locate the existing
STag(s), if any, in the local mapping(s) that associates the ITT
to the local STag(s).
* It MUST invalidate the existing STag(s), if any, and the local
mapping(s) that associates the ITT to the local STag(s).
* It MUST allocate a Read STag for the I/O Buffer as defined by the
qualifier DataDescriptorIn if the Send_Control Operational
Primitive invocation is qualified with DataDescriptorIn.
* It MUST allocate a Write STag for the I/O Buffer as defined by
the qualifier DataDescriptorOut if the Send_Control Operational
Primitive invocation is qualified with DataDescriptorOut.
* If STags are allocated, it MUST establish new local mapping(s)
that associate the ITT to the allocated STag(s).
* It MUST Advertise the STags, if allocated, to the target in the
iSER header of the SendSE Message carrying the iSCSI PDU, as
described in section 9.2.
For the Task Management Function Request with the TASK REASSIGN
function for a SCSI Read or bidirectional command, the iSCSI Layer
at the initiator MUST set ExpDataSN to 0 since the data transfer and
acknowledgements happen transparently to the iSCSI Layer at the
initiator. This provides the flexibility to the iSCSI Layer at the
target to request transmission of only the unacknowledged data as
specified in [iSCSI].
When the iSER Layer at the target receives the Task Management
Function Request with the TASK REASSIGN function, it MUST do the
following:
* It MUST use the ITT as specified in the Referenced Task Tag from
the Task Management Function Request PDU to locate the mappings
that associate the ITT to the Advertised STag(s) and the local
STag(s), if any.
* It MUST invalidate the local STaq(s), if any, associated with the
ITT.
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* It MUST replace the Advertised STag(s) in the remote mapping that
associates the ITT to the Advertised STag(s) with the Write STag
and the Read STag if present in the iSER header. The Write STag
is used in the handling of the R2T PDU(s) from the iSCSI Layer at
the target as described in section 7.3.6. The Read STag is used
in the handling of the SCSI Data-in PDU(s) from the iSCSI Layer
at the target as described in section 7.3.5.
7.3.4 SCSI Data-out
Type: control-type PDU
PDU-specific qualifiers: DataDescriptorOut
The iSCSI Layer at the initiator MUST invoke the Send_Control
Operational Primitive qualified with DataDescriptorOut which defines
the initiatorĘs I/O Buffer containing unsolicited SCSI Write data.
If the amount of unsolicited data to be transferred as SCSI Data-out
exceeds TargetRecvDataSegmentLength, then the iSCSI Layer at the
initiator MUST segment the data into multiple iSCSI control-type
PDUs, with the DataSegmentLength having the value of
TargetRecvDataSegmentLength in all PDUs generated except the last
one. The DataSegmentLength of the last iSCSI control-type PDU
carrying the unsolicited data can be up to
TargetRecvDataSegmentLength. The iSCSI Layer at the target MUST
perform the reassembly function for the unsolicited data.
For unsolicited data, if the F bit is set to 0 in a SCSI Data-out
PDU, the iSER Layer at the initiator MUST use a Send Message to send
the SCSI Data-out PDU. If the F bit set to 1, the iSER Layer at the
initiator MUST use a SendSE Message to send the SCSI Data-out PDU.
Solicited SCSI Write Data are handled using the R2T mechanism as
described in section 7.3.6. Therefore SCSI Data-out PDUs for
solicited data should never be requested for transmission by the
iSCSI Layer at the initiator. However, if a solicited SCSI Data-out
PDU is inadvertently requested (i.e. TTT!=0xffffffff) for
transmission by the iSCSI Layer at the initiator, the iSER Layer at
the initiator is not required to distinguish it as such. The iSER
Layer at the initiator in such a case MAY treat it as an iSCSI
control-type PDU and handle it as unsolicited data.
7.3.5 SCSI Data-in
Type: data-type PDU
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PDU-specific qualifiers: DataDescriptorIn
When the iSCSI Layer at the target is ready to return the SCSI Read
data to the initiator, it MUST invoke the Put_Data Operational
Primitive qualified with DataDescriptorIn which defines the SCSI
Data-in buffer. See section 7.1 on the general requirement on the
handling of iSCSI data-type PDUs. SCSI Data-in PDU(s) are used in
SCSI Read data transfer as described in section 9.5.2.
The iSER Layer at the target MUST do the following for each
invocation of the Put_Data Operational Primitive:
1. It MUST use the ITT in the SCSI Data-in PDU to locate the remote
Read STag in the remote mapping that associates the ITT to
Advertised STag(s). The remote mapping was established earlier
by the iSER Layer at the target when the SCSI Read Command was
received from the initiator.
2. It MUST generate and send an RDMA Write Message containing the
read data to the initiator.
a. It MUST use the remote Read STag as the Data Sink STag of
the RDMA Write Message.
b. It MUST use the Buffer Offset from the SCSI Data-in PDU as
the Data Sink Tagged Offset of the RDMA Write Message.
c. It MUST use DataSegmentLength from the SCSI Data-in PDU to
determine the amount of data to be sent in the RDMA Write
Message.
3. It MUST associate DataSN and ITT from the SCSI Data-in PDU with
the RDMA Write operation. If the Put_Data Operational Primitive
invocation was qualified with Notify_Enable set, then when the
iSER Layer at the target receives a completion from the RDMAP
layer for the RDMA Write Message, the iSER Layer at the target
MUST notify the iSCSI Layer by invoking the
Data_Completion_Notify Operational Primitive qualified with
DataSN and ITT. Conversely, if the Put_Data Operational
Primitive invocation was qualified with Notify_Enable cleared,
then the iSER Layer at the target MUST NOT notify the iSCSI
Layer on completion and MUST NOT invoke the
Data_Completion_Notify Operational Primitive.
When the A-bit is set to 1 in the SCSI Data-in PDU, the iSER Layer
at the target MUST notify the iSCSI Layer at the target when the
data transfer is complete at the initiator. To perform this
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additional function, the iSER Layer at the target can take advantage
of the operational ErrorRecoveryLevel if previously disclosed by the
iSCSI Layer via an earlier invocation of the Notice_Key_Values
Operational Primitive. There are two approaches that can be taken:
1. If the iSER Layer at the target knows that the operational
ErrorRecoveryLevel is 2, or if the iSER Layer at the target does
not know the operational ErrorRecoveryLevel, then the iSER Layer
at the target MUST issue a zero-length RDMA Read Message
following the RDMA Write Message. When the iSER Layer at the
target receives a completion for the RDMA Read Message from the
RDMAP layer, implying that the RNIC at the initiator has
completed processing the RDMA Write Message due to the
completion ordering semantics of RDMAP, the iSER Layer at the
target MUST invoke the Data_Ack_Notify Operational Primitive
qualified with ITT and DataSN (see section 3.2.3) to notify the
iSCSI Layer at the target.
2. If the iSER Layer at the target knows that the operational
ErrorRecoveryLevel is 1, then the iSER Layer at the target MUST
do one of the following:
a. It MUST invoke the Data_Ack_Notify Operational Primitive
qualified with ITT and DataSN (see section 3.2.3) when it
receives the local completion from the RDMAP layer for the
RDMA Write Message. This is allowed since digest errors do
not occur in iSER (see section 10.1.4.2) and a CRC error
will cause the connection to be terminated and the task to
be terminated anyway. The local RDMA Write completion from
the RDMAP layer guarantees that the RDMAP layer will not
access the I/O Buffer again to transfer the data associated
with that RDMA Write operation.
b. Alternatively, it MUST use the same procedure for handling
the data transfer completion at the initiator as for
ErrorRecoveryLevel 2.
It should be noted that the iSCSI Layer at the target cannot set the
A-bit to 1 if the ErrorRecoveryLevel=0.
SCSI status MUST always be returned in a separate SCSI Response PDU.
The S bit in the SCSI Data-in PDU MUST always be set to 0. There
MUST NOT be a "phase collapse" in the SCSI Data-in PDU.
Since the RDMA Write Message only transfers the data portion of the
SCSI Data-in PDU but not the control information in the header, such
as ExpCmdSN, if timely updates of such information is crucial, the
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iSCSI Layer at the initiator MAY issue NOP-out PDUs to request the
iSCSI Layer at the target to respond with the information using NOP-
in PDUs.
7.3.6 Ready To Transfer (R2T)
Type: data-type PDU
PDU-specific qualifiers: DataDescriptorOut
In order to send an R2T PDU, the iSCSI Layer at the target MUST
invoke the Get_Data Operational Primitive qualified with
DataDescriptorOut which defines the I/O Buffer for receiving the
SCSI Write data from the initiator. See section 7.1 on the general
requirements on the handling of iSCSI data-type PDUs.
The iSER Layer at the target MUST do the following for each
invocation of the Get_Data Operational Primitive:
1. It MUST ensure a valid local STag for the I/O Buffer and a valid
local mapping that associates the Initiator Task Tag (ITT) to
the local STag. This may involve allocating a valid local STag
and establishing a local mapping.
2. It MUST use the ITT in the R2T to locate the remote Write STag
in the remote mapping that associates the ITT to Advertised
STag(s). The remote mapping was established earlier by the iSER
Layer at the target when the iSER Message containing the
Advertised Write STag and the SCSI Command PDU for a SCSI Write
or bidirectional command was received from the initiator.
3. If the iSER-ORD value at the target is set to 0, the iSER Layer
at the target MUST terminate the connection and free up the
resources associated with the connection (as described in 5.2.3)
if it received the R2T PDU from the iSCSI Layer at the target.
Upon termination of the connection, the iSER Layer at the target
MUST notify the iSCSI Layer at the target using the
Connection_Terminate_Notify Operational Primitive.
4. If the iSER-ORD value at the target is set to greater than 0,
the iSER Layer at the target MUST transform the R2T PDU into an
RDMA Read Request Message. While transforming the R2T PDU, the
iSER Layer at the target MUST ensure that the number of
outstanding RDMA Read Request Messages does not exceed iSER-ORD
value. To transform the R2T PDU, the iSER Layer at the target:
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a. MUST derive the local STag and local Tagged Offset from the
DataDescriptorOut that qualified the Get_Data invocation.
b. MUST use the local STag as the Data Sink STag of the RDMA
Read Request Message.
c. MUST use the local Tagged Offset as the Data Sink Tagged
Offset of the RDMA Read Request Message.
d. MUST use the Desired Data Transfer Length from the R2T PDU
as the RDMA Read Message Size of the RDMA Read Request
Message.
e. MUST use the remote Write STag as the Data Source STag of
the RDMA Read Request Message.
f. MUST use the Buffer Offset from the R2T PDU as the Data
Source Tagged Offset of the RDMA Read Request Message.
5. It MUST associate R2TSN and ITT from the R2T PDU with the RDMA
Read operation. If the Get_Data Operational Primitive
invocation was qualified with Notify_Enable set, then when the
iSER Layer at the target receives a completion from the RDMAP
layer for the RDMA Read operation, the iSER Layer at the target
MUST notify the iSCSI Layer by invoking the
Data_Completion_Notify Operational Primitive qualified with
R2TSN and ITT. Conversely, if the Get_Data Operational
Primitive invocation was qualified with Notify_Enable cleared,
then the iSER Layer at the target MUST NOT notify the iSCSI
Layer on completion and MUST NOT invoke the
Data_Completion_Notify Operational Primitive.
When the RDMAP layer at the initiator receives a valid RDMA Read
Request Message, it will return an RDMA Read Response Message
containing the solicited write data to the target. When the RDMAP
layer at target receives the RDMA Read Response Message from the
initiator, it will place the solicited data in the I/O Buffer
referenced by the Data Sink STag in the RDMA Read Response Message.
Since the RDMA Read Request Message from the target does not
transfer the control information in the R2T PDU such as ExpCmdSN, if
timely updates of such information is crucial, the iSCSI Layer at
the initiator MAY issue NOP-out PDUs to request the iSCSI Layer at
the target to respond with the information using NOP-in PDUs.
Similarly, since the RDMA Read Response Message from the initiator
only transfers the data but not the control information normally
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found in the SCSI Data-out PDU, such as ExpStatSN, if timely updates
of such information is crucial, the iSCSI Layer at the target MAY
issue NOP-in PDUs to request the iSCSI Layer at the initiator to
respond with the information using NOP-out PDUs.
7.3.7 Asynchronous Message
Type: control-type PDU
PDU-specific qualifiers: DataDescriptorSense
The iSCSI Layer MUST invoke the Send_Control Operational Primitive
qualified with DataDescriptorSense which defines the buffer
containing the sense and iSCSI Event information. The iSER Layer
MUST use a SendSE Message to send the Asynchronous Message PDU.
7.3.8 Text Request & Text Response
Type: control-type PDU
PDU-specific qualifiers: DataDescriptorTextOut (for Text
Request), DataDescriptorIn (for Text Response)
The iSCSI Layer MUST invoke the Send_Control Operational Primitive
qualified with DataDescriptorTextOut (or DataDescriptorIn) which
defines the Text Request (or Text Response) buffer. The iSER Layer
MUST use SendSE Messages to send the Text Request and Text Response
PDUs.
7.3.9 Login Request & Login Response
Type: control-type PDU
PDU-specific qualifiers: DataDescriptorLoginReqeuest (for Login
Request), DataDescriptorLoginResponse (for Login Response)
The Login Request PDUs and the Login Response PDUs are exchanged
when the connection between the initiator and the target is still in
the byte stream mode. During the login negotiation, the iSCSI Layer
interacts with the transport layer directly and the iSER Layer is
not involved. See section 5.1 on iSCSI/iSER Connection Setup.
If the iSCSI Layer attempts to send a Login Request (or a Login
Response) PDU during the full feature phase, it MUST invoke the
Send_Control Operational Primitive qualified with
DataDescriptorLoginRequest (or DataDescriptorLoginResponse) which
defines the Login Request (or Login Response) buffer. The iSER
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Layer MUST handle it as an iSCSI control-type PDU as described in
section 7.2, and use SendSE Messages to send the Login Request and
Login Response PDUs.
7.3.10 Logout Request & Logout Response
Type: control-type PDU
PDU-specific qualifiers: None
The iSER Layer MUST use a SendSE Message to send the Logout Request
or Logout Response PDU. Section 5.2.1 and 5.2.2 describe the
handling of the Logout Request and the Logout Response at the
initiator and the target and the interactions between the initiator
and the target to terminate a connection.
7.3.11 SNACK Request
Type: control-type PDU
PDU-specific qualifiers: None
Since HeaderDigest and DataDigest must be negotiated to "None",
there are no digest errors when the connection is in iSER-assisted
mode. Also since RDMAP delivers all messages in the order they were
sent, there are no sequence errors when the connection is in iSER-
assisted mode. Therefore the iSCSI Layer SHOULD NOT send SNACK
Request PDUs. In particular, the Proactive (Time out) SNACK SHOULD
NOT be issued. If the iSCSI Layer invokes the Send_Control
Operational Primitive to request the iSER Layer to send a SNACK
Request, the iSER Layer MUST handle it as an iSCSI control-type PDU
as described in section 7.2, and use a SendSE Message to send the
SNACK Request PDU. Upon receiving the iSER Message containing the
SNACK PDU, the iSER Layer notifies the iSCSI Layer using the
Control_Notify Operational Primitive.
7.3.12 Reject
Type: control-type PDU
PDU-specific qualifiers: DataDescriptorReject
The iSCSI Layer MUST invoke the Send_Control Operational Primitive
qualified with DataDescriptorReject which defines the Rejct buffer.
The iSER Layer MUST use a SendSE Message to send the Reject PDU.
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7.3.13 NOP-Out & NOP-In
Type: control-type PDU
PDU-specific qualifiers: DataDescriptorNOPOut (for NOP-Out),
DataDescriptorNOPIn (for NOP-In)
The iSCSI Layer MUST invoke the Send_Control Operational Primitive
qualified with DataDescriptorNOPOut (or DataDescriptorNOPIn) which
defines the Ping (or Return Ping) data buffer. The iSER Layer MUST
use SendSE Messages to send the NOP-Out (or NOP-In) PDU.
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8 Flow Control and STag Management
8.1 Flow Control for RDMA Send Message Types
RDMAP Send Message Types are used by the iSER Layer to transfer
iSCSI control-type PDUs. Each RDMAP Send Message Type consumes an
Untagged Buffer at the Data Sink. However, neither the RDMAP layer
nor the iSER Layer provides an explicit flow control mechanism for
the RDMAP Send Message Types. Therefore, the iSER Layer SHOULD
provision enough Untagged buffers for handling incoming RDMAP Send
Message Types to prevent a buffer underrun condition at the RDMAP
layer. If a buffer underrun happens, it may result in the
termination of the connection. An implementation may choose to
satisfy this requirement by using a common buffer pool shared across
multiple connections, with usage limits on a per connection basis
and usage limits on the buffer pool itself. In such an
implementation, exceeding the buffer usage limit for a connection or
the buffer pool itself may trigger interventions from the iSER Layer
to replenish the buffer pool and/or to isolate the connection
causing the problem.
8.2 Flow Control for RDMA Read Resources
The total number of RDMA Read operations that can be active
simultaneously on an iSCSI/iSER connection depends on the amount of
resources allocated as declared in the iSER Hello exchange described
in section 5.1.3. Exceeding the number of RDMA Read operations
allowed on a connection will result in the connection being
terminated by the RDMAP layer. The iSER Layer at the target
maintains the iSER-ORD to keep track of the maximum number of RDMA
Read Requests that can be issued by the iSER Layer on a particular
RDMAP Stream.
During connection setup (see section 5.1), iSER-IRD is known at the
initiator and iSER-ORD is known at the target after the iSER Layers
at the initiator and the target have respectively allocated the
connection resources necessary to support iWARP, as directed by the
Allocate_Connection_Resources Operational Primitive from the iSCSI
Layer before the end of the iSCSI Login Phase. In the full feature
phase, the first message sent by the initiator is the iSER Hello
Message (see section 9.3) which contains the value of iSER-IRD. In
response to the iSER Hello Message, the target sends the iSER
HelloReply Message (see section 9.4) which contains the value of
iSER-ORD. The iSER Layer at both the initiator and the target MAY
adjust (lower) the resources associated with iSER-IRD and iSER-ORD
respectively to match the iSER-ORD value declared in the HelloReply
Message. The iSER Layer at the target MUST flow control the RDMA
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Read Request Messages to not exceed the iSER-ORD value at the
target.
8.3 STag Management
An STag, as defined in [RDMAP], is an identifier of a Tagged Buffer
used in an RDMA operation. The allocation and the subsequent
invalidation of the STags are specified in this document if the
STags are exposed on the wire by being Advertised in the iSER header
or declared in the RDMAP header of an iWARP Message.
8.3.1 Allocation of STags
When the iSCSI Layer at the initiator invokes the Send_Control
Operational Primitive to request the iSER Layer at the initiator to
process a SCSI Command, zero, one, or two STags may be allocated by
the iSER Layer. See section 7.3.1 for details. The number of STags
allocated depends on whether the command is unidirectional or
bidirectional and whether solicited write data transfer is involved
or not.
When the iSCSI Layer at the initiator invokes the Send_Control
Operational Primitive to request the iSER Layer at the initiator to
process a Task Management Function Request with the TASK REASSIGN
function, besides allocating zero, one, or two STags, the iSER Layer
MUST invalidate the existing STags, if any, associated with the ITT.
See section 7.3.3 for details.
The iSER Layer at the target allocates a local Data Sink STag when
the iSCSI Layer at the target invokes the Get_Data Operational
Primitive to request the iSER Layer to process an R2T PDU. See
section 7.3.6 for details.
8.3.2 Invalidation of STags
The invalidation of the STags at the initiator at the completion of
a unidirectional or bidirectional command when the associated SCSI
Response PDU is sent by the target is described in section 7.3.2.
When a unidirectional or bidirectional command concludes without the
associated SCSI Response PDU being sent by the target, the iSCSI
Layer at the initiator MUST invoke the Deallocate_Task_Resources
Operational Primitive qualified with ITT. In response, the iSER
Layer at the initiator MUST locate the STag(s) (if any) in the local
mapping that associates the ITT to the local STag(s). The iSER
Layer at the initiator MUST invalidate the STag(s) (if any) and the
local mapping.
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For an RDMA Read operation used to realize a SCSI Write data
transfer, the iSER Layer at the target SHOULD invalidate the Data
Sink STag at the conclusion of the RDMA Read operation referencing
the Data Sink STag (to permit the immediate reuse of buffer
resources).
For an RDMA Write operation used to realize a SCSI Read data
transfer, the Data Source STag at the target is not declared to the
initiator and is not exposed on the wire. Invalidation of the STag
is thus not specified.
When a unidirectional or bidirectional command concludes without the
associated SCSI Response PDU being sent by the target, the iSCSI
Layer at the target MUST invoke the Deallocate_Task_Resources
Operational Primitive qualified with ITT. In response, the iSER
Layer at the target MUST locate the local STag(s) (if any) in the
local mapping that associates the ITT to the local STag(s). The
iSER Layer at the target MUST invalidate the local STag(s) (if any)
and the mapping.
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9 iSER Control and Data Transfer
For iSCSI data-type PDUs (see section 7.1), the iSER Layer uses RDMA
Read and RDMA Write operations to transfer the solicited data. For
iSCSI control-type PDUs (see section 7.2), the iSER Layer uses RDMAP
Send Message Types.
9.1 iSER Header Format
An iSER header MUST be present in every RDMAP Send Message Type.
The iSER header is located in the first 12 bytes of the message
payload of the RDMAP Send Message Type, as shown in Figure 2.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode| Opcode Specific Fields |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode Specific Fields |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode Specific Fields |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 iSER Header Format
Opcode - Operation Code: 4 bits
The Opcode field identifies the type of iSER Messages:
0001b = iSCSI control-type PDU
0010b = iSER Hello Message
0011b = iSER HelloReply Message
All other opcodes are reserved.
9.2 iSER Header Format for iSCSI Control-Type PDU
The iSER Layer uses RDMAP Send Message Types to transfer iSCSI
control-type PDUs (see section 7.2). The message payload of each of
the RDMAP Send Message Types used for transferring an iSER Message
contains an iSER Header followed by an iSCSI control-type PDU.
The iSER header in an RDMAP Send Message Type carrying an iSCSI
control-type PDU MUST have the format as described in Figure 3.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |W|R| |
| 0001b |S|S| Reserved |
| |V|V| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Write STag (or N/A) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Read STag (or N/A) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 iSER Header Format for iSCSI Control-Type PDU
WSV - Write STag Valid flag: 1 bit
This flag indicates the validity of the Write STag field of the
iSER Header. If set to one, the Write STag field in this iSER
Header is valid. If set to zero, the Write STag field in this
iSER Header MUST be ignored at the receiver. The Write STag
Valid flag is set to one when there is solicited data to be
transferred for a SCSI Write or bidirectional command, or when
there are non-immediate unsolicited and solicited data to be
transferred for the referenced task specified in a Task
Management Function Request with the TASK REASSIGN function.
RSV - Read STag Valid flag: 1 bit
This flag indicates the validity of the Read STag field of the
iSER Header. If set to one, the Read STag field in this iSER
Header is valid. If set to zero, the Read STag field in this
iSER Header MUST be ignored at the receiver. The Read STag
Valid flag is set to one for a SCSI Read or bidirectional
command, or a Task Management Function Request with the TASK
REASSIGN function.
Write STag - Write Steering Tag: 32 bits
This field contains the Write STag when the Write STag Valid
flag is set to one. For a SCSI Write or bidirectional command,
the Write STag is used to Advertise the initiatorĘs I/O Buffer
containing the solicited data. For a Task Management Function
Request with the TASK REASSIGN function, the Write STag is used
to Advertise the initiator's I/O Buffer containing the non-
immediate unsolicited data and solicited data. This Write STag
is used as the Data Source STag in the resultant RDMA Read
operation(s). When the Write STag Valid flag is set to zero,
this field MUST be set to zero.
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Read STag - Read Steering Tag: 32 bits
This field contains the Read STag when the Read STag Valid flag
is set to one. The Read STag is used to Advertise the
initiatorĘs Read I/O Buffer of a SCSI Read or bidirectional
command, or a Task Management Function Request with the TASK
REASSIGN function. This Read STag is used as the Data Sink
STag in the resultant RDMA Write operation(s). When the Read
STag Valid flag is zero, this field MUST be set to zero.
Reserved:
Reserved fields MUST be set to zero on transmit and MUST be
ignored on receive.
9.3 iSER Header Format for iSER Hello Message
An iSER Hello Message MUST only contain the iSER header which MUST
have the format as described in Figure 4. iSER Hello Message is the
first RDMAP Message sent on the RDMAP Stream from the iSER Layer at
the initiator to the iSER Layer at the target.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | | | |
| 0010b | Rsvd | MaxVer| MinVer| iSER-IRD |
| | | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4 iSER Header Format for iSER Hello Message
MaxVer - Maximum Version: 4 bits
This field specifies the maximum version of the iSER protocol
supported. It MUST be set to 1 to indicate the version of the
specification described in this document.
MinVer - Minimum Version: 4 bits
This field specifies the minimum version of the iSER protocol
supported. It MUST be set to 1 to indicate the version of the
specification described in this document.
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iSER-IRD: 16 bits
This field contains the value of the iSER-IRD at the initiator.
Reserved (Rsvd):
Reserved fields MUST be set to zero on transmit, and MUST be
ignored on receive.
9.4 iSER Header Format for iSER HelloReply Message
An iSER HelloReply Message MUST only contain the iSER header which
MUST have the format as described in Figure 5. The iSER HelloReply
Message is the first RDMAP Message sent on the RDMAP Stream from the
iSER Layer at the target to the iSER Layer at the initiator.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |R| | | |
| 0011b |Rsvd |E| MaxVer| CurVer| iSER-ORD |
| | |J| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5 iSER Header Format for iSER HelloReply Message
REJ - Reject flag: 1 bit
This flag indicates whether the target is rejecting this
connection. If set to one, the target is rejecting the
connection.
MaxVer - Maximum Version: 4 bits
This field specifies the maximum version of the iSER protocol
supported. It MUST be set to 1 to indicate the version of the
specification described in this document.
CurVer - Current Version: 4 bits
This field specifies the current version of the iSER protocol
supported. It MUST be set to 1 to indicate the version of the
specification described in this document.
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iSER-ORD: 16 bits
This field contains the value of the iSER-ORD at the target.
Reserved (Rsvd):
Reserved fields MUST be set to zero on transmit, and MUST be
ignored on receive.
9.5 SCSI Data Transfer Operations
The iSER Layer at the initiator and the iSER Layer at the target
handle each SCSI Write, SCSI Read, and bidirectional operation as
described below.
9.5.1 SCSI Write Operation
The iSCSI Layer at the initiator MUST invoke the Send_Control
Operational Primitive to request the iSER Layer at the initiator to
send the SCSI Write Command. The iSER Layer at the initiator MUST
request the RDMAP layer to transmit a SendSE Message with the
message payload consisting of the iSER header followed by the SCSI
Command PDU and immediate data (if any). If there is solicited
data, the iSER Layer MUST Advertise the Write STag in the iSER
header of the SendSE Message, as described in section 9.2. Upon
receiving the SendSE Message, the iSER Layer at the target MUST
notify the iSCSI Layer at the target by invoking the Control_Notify
Operational Primitive qualified with the SCSI Command PDU. See
section 7.3.1 for details on the handling of the SCSI Write Command.
For the non-immediate unsolicited data, the iSCSI Layer at the
initiator MUST invoke a Send_Control Operational Primitive qualified
with the SCSI Data-out PDU. Upon receiving each Send or SendSE
Message containing the non-immediate unsolicited data, the iSER
Layer at the target MUST notify the iSCSI Layer at the target by
invoking the Control_Notify Operational Primitive qualified with the
SCSI Data-out PDU. See section 7.3.4 for details on the handling of
the SCSI Data-out PDU.
For the solicited data, when the iSCSI Layer at the target has an
I/O Buffer available, it MUST invoke the Get_Data Operational
Primitive qualified with the R2T PDU. See section 7.3.6 for details
on the handling of the R2T PDU.
When the data transfer associated with this SCSI Write operation is
complete, the iSCSI Layer at the target MUST invoke the Send_Control
Operational Primitive when it is ready to send the SCSI Response
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PDU. Upon receiving a SendSE or SendInvSE Message containing the
SCSI Response PDU, the iSER Layer at the initiator MUST notify the
iSCSI Layer at the initiator by invoking the Control_Notify
Operational Primitive qualified with the SCSI Response PDU. See
section 7.3.2 for details on the handling of the SCSI Response PDU.
9.5.2 SCSI Read Operation
The iSCSI Layer at the initiator MUST invoke the Send_Control
Operational Primitive to request the iSER Layer at the initiator to
send the SCSI Read Command. The iSER Layer at the initiator MUST
request the RDMAP layer to transmit a SendSE Message with the
message payload consisting of the iSER header followed by the SCSI
Command PDU. The iSER Layer at the initiator MUST Advertise the
Read STag in the iSER header of the SendSE Message, as described in
section 9.2. Upon receiving the SendSE Message, the iSER Layer at
the target MUST notify the iSCSI Layer at the target by invoking the
Control_Notify Operational Primitive qualified with the SCSI Command
PDU. See section 7.3.1 for details on the handling of the SCSI Read
Command.
When the requested SCSI data is available in the I/O Buffer, the
iSCSI Layer at the target MUST invoke the Put_Data Operational
Primitive qualified with the SCSI Data-in PDU. See section 7.3.5
for details on the handling of the SCSI Data-in PDU.
When the data transfer associated with this SCSI Read operation is
complete, the iSCSI Layer at the target MUST invoke the Send_Control
Operational Primitive when it is ready to send the SCSI Response
PDU. Upon receiving the SendInvSE Message containing the SCSI
Response PDU, the iSER Layer at the initiator MUST notify the iSCSI
Layer at the initiator by invoking the Control_Notify Operational
Primitive qualified with the SCSI Response PDU. See section 7.3.2
for details on the handling of the SCSI Response PDU.
9.5.3 Bidirectional Operation
The initiator and the target handle the SCSI Write and the SCSI Read
portions of this bidirectional operation in a similar manner as
described in Section 9.5.1 and Section 9.5.2 respectively.
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10 iSER Error Handling and Recovery
[RDMAP] and the protocols below it provide the iSER Layer with
reliable in-order delivery. Therefore, the error management needs
of an iSCSI/iSER connection are somewhat different than those of
traditional iSCSI running directly over TCP.
10.1 Error Handling
iSER error handling is described in the following sections,
classified loosely based on the sources of errors:
1. Those originating at the transport layer (e.g., TCP).
2. Those originating at the RDMAP layer.
3. Those originating at the iSER Layer.
4. Those originating at the iSCSI Layer.
10.1.1 Errors in the Transport Layer
If the transport layer is TCP, then TCP packets with errors are
silently dropped by the TCP layer and result in retransmission at
the TCP layer. This has no impact on the iSER Layer. However,
connection loss (e.g., link failure) and unexpected termination
(e.g., TCP graceful or abnormal close without the iSCSI Logout
exchanges) at the transport layer will cause the iSCSI/iSER
connection to be terminated as well.
10.1.1.1 Failure in the Transport Layer Before iWARP is Enabled
If the Connection is lost or terminated before the iSCSI Layer
invokes the Allocate_Connection_Resources Operational Primitive, the
login process is terminated and no further action is required.
If the Connection is lost or terminated after the iSCSI Layer has
invoked the Allocate_Connection_Resources Operational Primitive,
then the iSCSI Layer MUST invoke the Deallocate_Connection_Resources
Operational Primitive to request the iSER Layer to deallocate all
connection resources.
10.1.1.2 Failure in the Transport Layer After iWARP is Enabled
If the Connection is lost or terminated after the iSCSI Layer has
invoked the Enable_Datamover Operational Primitive, the iSER Layer
MUST notify the iSCSI Layer of the connection loss by invoking the
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Connection_Terminate_Notify Operational Primitive. Prior to
invoking the Connection_Terminate_Notify Operational Primitive, the
iSER layer MUST perform the actions described in Section 5.2.3.2.
10.1.2 Errors in the iWARP protocol suite
The RDMAP layer does not have error recovery operations built in.
If errors are detected at the RDMAP layer, the RDMAP layer will
terminate the RDMAP Stream and the associated Connection.
10.1.2.1 Errors Detected in the Local RDMAP Layer
If an error is encountered at the local RDMAP layer, the RDMAP layer
MAY send a Terminate Message to the Remote Peer to report the error
if possible. (See [RDMAP] for the list of errors where a Terminate
Message is sent.) The RDMAP layer is responsible for terminating
the Connection. After the RDMAP layer notifies the iSER Layer that
the Connection is terminated, the iSER Layer MUST notify the iSCSI
Layer by invoking the Connection_Terminate_Notify Operational
Primitive. Prior to invoking the Connection_Terminate_Notify
Operational Primitive, the iSER layer MUST perform the actions
described in Section 5.2.3.2.
10.1.2.2 Errors Detected in the RDMAP Layer at the Remote Peer
If an error is encountered at the RDMAP layer at the Remote Peer,
the RDMAP layer at the Remote Peer may send a Terminate Message to
report the error if possible. If it is unable to send the Terminate
Message, the Connection is terminated. This is treated similar to a
failure in the transport layer after iWARP is enabled as described
in section 10.1.1.2.
If an error is encountered at the RDMAP layer at the Remote Peer and
it is able to send a Terminate Message, the RDMAP layer at the
Remote Peer is responsible for terminating the connection. After
the local RDMAP layer notifies the iSER Layer that the Connection is
terminated, the iSER Layer MUST notify the iSCSI Layer by invoking
the Connection_Terminate_Notify Operational Primitive. Prior to
invoking the Connection_Terminate_Notify Operational Primitive, the
iSER layer MUST perform the actions described in Section 5.2.3.2.
10.1.3 Errors in the iSER Layer
The error handling due to errors at the iSER Layer is described in
the following sections.
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10.1.3.1 Insufficient Connection Resources to Support iWARP at the
Initiator at Connection Setup
After the iSCSI Layer at the initiator invokes the
Allocate_Connection_Resources Operational Primitive during the iSCSI
login negotiation phase, if the iSER Layer at the initiator fails to
allocate the connection resources necessary to support iWARP, it
MUST return a status of failure to the iSCSI Layer at the initiator.
The iSCSI Layer at the initiator MUST terminate the Connection as
described in Section 5.2.3.1.
10.1.3.2 Insufficient Connection Resources to Support iWARP at the
Target at Connection Setup
After the iSCSI Layer at the target invokes the
Allocate_Connection_Resources Operational Primitive during the iSCSI
login negotiation phase, if the iSER Layer at the target fails to
allocate the connection resources necessary to support iWARP, it
MUST return a status of failure to the iSCSI Layer at the target.
The iSCSI Layer at the target MUST send a Login Response with a
status class of 3 (Target Error), and a status code of "0302" (Out
of Resources). The iSCSI Layers at the initiator and the target
MUST terminate the Connection as described in Section 5.2.3.1.
10.1.3.3 iSER Negotiation Failures
If the iWARP or iSER related parameters declared by the initiator in
the iSER Hello Message is unacceptable to the iSER Layer at the
target, the iSER Layer at the target MUST set the Reject (REJ) flag,
as described in section 9.4, in the iSER HelloReply Message. The
following are the cases when the iSER Layer MUST set the REJ flag to
1 in the HelloReply Message:
* The initiator-declared iSER-IRD value is greater than 0 and the
target-declared iSER-ORD value is 0.
* The initiator-supported and the target-supported iSER protocol
versions do not overlap.
After requesting the RDMAP layer to send the iSER HelloReply
Message, the handling of the error situation is similar to that for
iSER format errors, as described in section 10.1.3.4.
10.1.3.4 iSER Format Errors
The following types of errors in an iSER header are considered
format errors:
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* Illegal contents of any iSER header field
* Inconsistent field contents in an iSER header
* Length error for an iSER Hello or HelloReply Message (see section
9.3 and 9.4)
When a format error is detected, the following events MUST occur in
the specified sequence:
1. The iSER Layer MUST request the RDMAP layer to terminate the
RDMAP Stream. The RDMAP layer MUST terminate the associated
Connection.
2. The iSER Layer MUST notify the iSCSI Layer by invoking the
Connection_Terminate_Notify Operational Primitive. Prior to
invoking the Connection_Terminate_Notify Operational Primitive,
the iSER layer MUST perform the actions described in Section
5.2.3.2.
10.1.3.5 iSER Protocol Errors
The first iSER Message sent by the iSER Layer at the initiator after
transitioning into iSER-assisted mode MUST be the iSER Hello Message
(see section 9.3). Likewise, the first iSER Message sent by the
iSER Layer at the target after transitioning into iSER-assisted mode
MUST be the iSER HelloReply Message (see section 9.4). Failure to
send the iSER Hello or HelloReply Message, as indicated by the wrong
Opcode in the iSER header, is a protocol error.
The handling of an iSER protocol error is similar to that for iSER
format errors, as described in section 10.1.3.4.
10.1.4 Errors in the iSCSI Layer
The error handling due to errors at the iSCSI Layer is described in
the following sections. For error recovery, see section 10.2.
10.1.4.1 iSCSI Format Errors
When an iSCSI format error is detected, the iSCSI Layer MUST invoke
the Connection_Terminate Operational Primitive to request the iSER
Layer to terminate the RDMAP Stream. For more details on the
connection termination, see Section 5.2.3.1.
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10.1.4.2 iSCSI Digest Errors
In the iSER-assisted mode, the iSCSI Layer will not see any digest
error because both the HeaderDigest and the DataDigest keys are
negotiated to "None".
10.1.4.3 iSCSI Sequence Errors
For traditional iSCSI, sequence errors are caused by dropped PDUs
due to header or data digest errors. Since digests are not used in
iSER-assisted mode and the RDMAP layer will deliver all messages in
the order they were sent, sequence errors will not occur in iSER-
assisted mode.
10.1.4.4 iSCSI Protocol Error
When the iSCSI Layer handles certain protocol errors by dropping the
connection, the error handling is similar to that for iSCSI format
errors as described in section 10.1.4.1
When the iSCSI Layer uses the iSCSI Reject PDU and response codes to
handle certain other protocol errors, no special handling at the
iSER Layer is required.
10.1.4.5 SCSI Timeouts and Session Errors
This is handled at the iSCSI Layer and no special handling at the
iSER Layer is required.
10.1.4.6 iSCSI Negotiation Failures
For negotiation failures that happen during the Login Phase at the
initiator after the iSCSI Layer has invoked the
Allocate_Connection_Resources Operational Primitive and before the
Enable_Datamover Operational Primitive has been invoked, the iSCSI
Layer MUST invoke the Deallocate_Connection_Resources Operational
Primitive to request the iSER Layer to deallocate all connection
resources. The iSCSI Layer at the initiator MUST terminate the
Connection.
For negotiation failures during the Login Phase at the target, the
iSCSI Layer can use a Login Response with a status class other than
0 (success) to terminate the Login Phase. If the iSCSI Layer has
invoked the Allocate_Connection_Resources Operational Primitive and
before the Enable_Datamover Operational Primitive has been invoked,
the iSCSI Layer at the target MUST invoke the
Deallocate_Connection_Resources Operational Primitive to request the
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iSER Layer at the target to deallocate all connection resources.
The iSCSI Layer at both the initiator and the target MUST terminate
the Connection.
During the iSCSI Login Phase, if the iSCSI Layer at the initiator
receives a Login Response from the target with a status class other
than 0 (Success) after the iSCSI Layer at the initiator has invoked
the Allocate_Connection_Resources Operational Primitive, the iSCSI
Layer MUST invoke the Deallocate_Connection_Resources Operational
Primitive to request the iSER Layer to deallocate all connection
resources. The iSCSI Layer MUST terminate the Connection in this
case.
For negotiation failures during the full feature phase, the error
handling is left to the iSCSI Layer and no special handling at the
iSER Layer is required.
10.2 Error Recovery
Error recovery requirements of iSCSI/iSER are the same as that of
traditional iSCSI. All three ErrorRecoveryLevels as defined in
[iSCSI] are supported in iSCSI/iSER.
* For ErrorRecoveryLevel 0, session recovery is handled by iSCSI
and no special handling by the iSER Layer is required.
* For ErrorRecoveryLevel 1, see section 10.2.1 on SNACK Handling
and PDU Recovery.
* For ErrorRecoveryLevel 2, see section 10.2.2 on Connection
Recovery.
The iSCSI Layer may invoke the Notice_Key_Values Operational
Primitive during connection setup to request the iSER Layer to take
note of the value of the operational ErrorRecoveryLevel, as
described in sections 5.1.1 and 5.1.2.
10.2.1 SNACK Handling and PDU Recovery
As described in sections 10.1.4.2 and 10.1.4.3, digest and sequence
errors will not occur in the iSER-assisted mode. If the RDMAP layer
detects an error, it will close the iSCSI/iSER connection, as
described in section 10.1.2. Therefore, PDU recovery is not useful
in the iSER-assisted mode.
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The iSCSI Layer at the initiator SHOULD disable timeout-driven
proactive SNACKs. If the iSCSI Layer at the target receives a
SNACK, it MUST respond to it as required by [iSCSI].
The iSCSI Layer at the initiator SHOULD disable iSCSI timeout-driven
PDU retransmissions.
10.2.2 Connection Recovery
The iSCSI Layer at the initiator MAY reassign connection allegiance
for non-immediate commands which are still in progress and are
associated with the failed connection by using a Task Management
Function Request with the TASK REASSIGN function. See section 7.3.3
for more details.
When the iSCSI Layer at the initiator does a task reassignment for a
SCSI Write command, it MUST qualify the Send_Control Operational
Primitive invocation with DataDescriptorOut which defines the I/O
Buffer for both the non-immediate unsolicited data and the solicited
data. This allows the iSCSI Layer at the target to use recovery
R2Ts to request for data originally sent as unsolicited and
solicited from the initiator.
When the iSCSI Layer at the target accepts a reassignment request
for a SCSI Read command, it MUST invoke the Put_Data Operational
Primitive to request the iSER Layer to process SCSI Data-in for all
unacknowledged data. See section 7.3.5 on the handling of SCSI
Data-in.
When the iSCSI Layer at the target accepts a reassignment request
for a SCSI Write command, it MUST invoke the Get_Data Operational
Primitive to request the iSER Layer to process a recovery R2T for
any non-immediate unsolicited data and any solicited data sequences
that have not been received. See section 7.3.6 on the handling of
Ready To Transfer (R2T).
The iSCSI Layer at the target MUST NOT issue recovery R2Ts on an
iSCSI/iSER connection for a task for which the connection allegiance
was never reassigned. The iSER Layer at the target MAY reject such
a recovery R2T received via the Get_Data Operational Primitive
invocation from the iSCSI Layer at the target, with an appropriate
error code.
The iSER Layer at the target will process the requests invoked by
the Put_Data and Get_Data Operational Primitives for a reassigned
task in the same way as for the original commands.
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11 Security Considerations
Since iSER is layered on top of the iWARP layer and provides the
RDMA extensions to the iSCSI protocol, the security considerations
of iSER are similar to that of the underlying RDMAP layer as
described in [RDMAP].
All the security protocol mechanisms described in [iSCSI] MAY be
deployed for an iSCSI/iSER connection. If the IPsec mechanism is
used, then it MUST be established before the connection transitions
from the traditional iSCSI mode to the iSER-assisted mode.
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12 IANA Considerations
The login operational keys RDMAExtensions,
InitiatorRecvDataSegmentLength, and TargetRecvDataSegmentLength will
be registered with IANA before this draft is approved to become an
RFC.
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13 References
13.1 Normative References
[iSCSI] J. Satran et al., "iSCSI", RFC 3720, April 2004
[RDMAP] R. Recio et al., "An RDMA Protocol Specification", IETF
Internet-draft draft-ietf-rddp-rdmap-01.txt (work in progress),
October 2003
[DDP] H. Shah et al., "Direct Data Placement over Reliable
Transports", IETF Internet-draft draft-ietf-rddp-ddp-03.txt
(work in progress), August 2004
[MPA] P. Culley et al., "Marker PDU Aligned Framing for TCP
Specification", IETF Internet-draft draft-ietf-rddp-mpa-01.txt
(work in progress), July 2004
[TCP] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981
13.2 Informative References
[SAM2] T10/1157D, SCSI Architecture Model - 2 (SAM-2)
[DA] M. Chadalapaka et al., "Datamover Architecture for iSCSI", IETF
Internet-draft, draft-ietf-ips-da-00.txt (work in progress),
September 2004
[VERBS] J. Hilland et al., "RDMA Protocol Verbs Specification",
RDMAC Consortium Draft Specification draft-hilland-iwarp-verbs-
v1.0-RDMAC, April 2003
[IPSEC] S. Kent et al., "Security Architecture for the Internet
Protocol", RFC 2401, November 1998
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14 Appendix
14.1 iWARP Message Format for iSER
This section is for information only and is NOT part of the
standard. It simply depicts the iWARP Message format for the
various iSER Messages when the transport layer is TCP.
14.1.1 iWARP Message Format for iSER Hello Message
The following figure depicts an iSER Hello Message encapsulated in
an iWARP SendSE Message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0010b | Zeros | 0001b | 0001b | iSER-IRD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6 SendSE Message containing an iSER Hello Message
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14.1.2 iWARP Message Format for iSER HelloReply Message
The following figure depicts an iSER HelloReply Message encapsulated
in an iWARP SendSE Message. The Reject (REJ) flag is set to 0.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0011b |Zeros|0| 0001b | 0001b | iSER-ORD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7 SendSE Message containing an iSER HelloReply Message
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14.1.3 iWARP Message Format for SCSI Read Command PDU
The following figure depicts a SCSI Read Command PDU embedded in an
iSER Message encapsulated in an iWARP SendSE Message. For this
particular example, in the iSER header, the Write STag Valid flag is
set to zero, the Read STag Valid flag is set to one, the Write STag
field is set to all zeros, and the Read STag field contains a valid
Read STag.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0001b |0|1| All zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Read STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCSI Read Command PDU |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8 SendSE Message containing a SCSI Read Command PDU
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14.1.4 iWARP Message Format for SCSI Read Data
The following figure depicts an iWARP RDMA Write Message carrying
SCSI Read data in the payload:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink Tagged Offset |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCSI Read data |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9 RDMA Write Message containing SCSI Read Data
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14.1.5 iWARP Message Format for SCSI Write Command PDU
The following figure depicts a SCSI Write Command PDU embedded in an
iSER Message encapsulated in an iWARP SendSE Message. For this
particular example, in the iSER header, the Write STag Valid flag is
set to one, the Read STag Valid flag is set to zero, the Write STag
field contains a valid Write STag, and the Read STag field is set to
all zeros since it is not used.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0001b |1|0| All zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Write STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCSI Write Command PDU |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10 SendSE Message containing a SCSI Write Command PDU
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14.1.6 iWARP Message Format for RDMA Read Request
An iSCSI R2T is transformed into an iWARP RDMA Read Request Message.
The following figure depicts an iWARP RDMA Read Request Message:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Not Used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (RDMA Read Request) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (RDMA Read Request) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DDP (RDMA Read Request) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink STag (SinkSTag) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Data Sink Tagged Offset (SinkTO) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RDMA Read Message Size (RDMARDSZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Source STag (SrcSTag) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Data Source Tagged Offset (SrcTO) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11 RDMA Read Request Message
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14.1.7 iWARP Message Format for Solicited SCSI Write Data
The following figure depicts an iWARP RDMA Read Response Message
carrying the solicited SCSI Write data in the payload:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Sink Tagged Offset |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCSI Write Data |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12 RDMA Read Response Message containing SCSI Write Data
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14.1.8 iWARP Message Format for SCSI Response PDU
The following figure depicts a SCSI Response PDU embedded in an iSER
Message encapsulated in an iWARP SendInvSE Message:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA Header | DDP Control | RDMA Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Invalidate STag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Queue Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Send) Message Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0001b |0|0| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| All Zeros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SCSI Response PDU |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MPA CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13 SendInvSE Message containing SCSI Response PDU
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15 AuthorĘs Address
Mallikarjun Chadalapaka
Hewlett-Packard Company
8000 Foothills Blvd.
Roseville, CA 95747-5668, USA
Phone: +1-916-785-5621
Email: cbm@rose.hp.com
Uri Elzur
Broadcom Corporation
16215 Alton Parkway
Irvine, California 92619-7013, USA
Phone: +1-949-926-6432
Email: Uri@Broadcom.com
John Hufferd
IBM Corp.
5600 Cottle Rd.
San Jose, CA 95120, USA
Phone: +1-408-256-0403
Email: hufferd@us.ibm.com
Mike Ko
IBM Corp.
650 Harry Rd.
San Jose, CA 95120, USA
Phone: +1-408-927-2085
Email: mako@us.ibm.com
Hemal Shah
Intel Corporation
MS AN1-PTL1
1501 South Mopac Expressway, #400
Austin, Texas 78746, USA
Phone: +1-512-732-3963
Email: hemal.shah@intel.com
Patricia Thaler
Agilent Technologies, Inc.
1101 Creekside Ridge Drive, #100
M/S-RG10
Roseville, CA 95678, USA
Phone: +1-916-788-5662
email: pat_thaler@agilent.com
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16 Acknowledgments
Dwight Barron
Hewlett-Packard Company
20555 SH.249
Houston, TX 77070-2698, USA
Phone: +1-281-514-2769
Email: Dwight.Barron@Hp.com
John Carrier
Adaptec, Inc.
691 S. Milpitas Blvd.
Milpitas, CA 95035, USA
Phone: +1-360-378-8526
Email: john_carrier@adaptec.com
Ted Compton
EMC Corporation
Research Triangle Park, NC 27709, USA
Phone: +1-919-248-6075
Email: compton_ted@emc.com
Paul R. Culley
Hewlett-Packard Company
20555 SH 249
Houston, Tx. 77070-2698, USA
Phone: +1-281-514-5543
Email: paul.culley@hp.com
Jeff Hilland
Hewlett-Packard Company
20555 SH 249
Houston, Tx. 77070-2698, USA
Phone: +1-281-514-9489
Email: jeff.hilland@hp.com
Mike Krause
Hewlett-Packard Company
43LN
19410 Homestead Road
Cupertino, CA 95014, USA
Phone: +1-408-447-3191
Email: krause@cup.hp.com
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Jim Pinkerton
Microsoft, Inc.
One Microsoft Way
Redmond, WA, 98052, USA
Email: jpink@windows.microsoft.com
Renato J. Recio
IBM Corp.
11501 Burnett Road
Austin, TX 78758, USA
Phone: +1-512-838-3685
Email: recio@us.ibm.com
Julian Satran
IBM Corp.
Haifa Research Lab
Haifa University Campus - Mount Carmel
Haifa 31905, Israel
Phone: +972-4-829-6264
Email: Julian_Satran@il.ibm.com
Tom Talpey
Network Appliance
375 Totten Pond Road
Waltham, MA 02451, USA
Phone: +1-781-768-5329
EMail: thomas.talpey@netapp.com
Jim Wendt
Hewlett-Packard Company
8000 Foothills Boulevard MS 5668
Roseville, CA 95747-5668, USA
Phone: +1-916-785-5198
Email: jim_wendt@hp.com
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17 Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
This document and the information contained herein is provided on an
"AS IS" basis and ADAPTEC INC., AGILENT TECHNOLOGIES INC., BROADCOM
CORPORATION, CISCO SYSTEMS INC., DELL COMPUTER CORPORATION, EMC
CORPORATION, HEWLETT-PACKARD COMPANY, INTERNATIONAL BUSINESS
MACHINES CORPORATION, INTEL CORPORATION, MICROSOFT CORPORATION,
NETWORK APPLIANCE INC., THE INTERNET SOCIETY, AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
The IETF takes no position regarding the validity or scope of any
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to pertain to the implementation or use of the technology
described in this document or the extent to which any license
under such rights might or might not be available; nor does it
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Copies of IPR disclosures made to the IETF Secretariat and any
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The IETF invites any interested party to bring to its attention
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to implement this standard. Please address the information to the
IETF at ietf-ipr@ietf.org.
Ko et. al. Expires Narch 2005 87
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