One document matched: draft-tuexen-tsvwg-sctp-sack-immediately-06.txt
Differences from draft-tuexen-tsvwg-sctp-sack-immediately-05.txt
Network Working Group M. Tuexen
Internet-Draft I. Ruengeler
Intended status: Standards Track Muenster Univ. of Appl. Sciences
Expires: January 6, 2012 R. Stewart
Adara Networks
July 5, 2011
SACK-IMMEDIATELY extension for the Stream Control Transmission Protocol
draft-tuexen-tsvwg-sctp-sack-immediately-06.txt
Abstract
This document defines a method for a sender of a DATA chunk to
indicate that the corresponding SACK chunk should be sent back
immediately.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 6, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The I-bit in the DATA Chunk Header . . . . . . . . . . . . . . 3
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Sender Side Considerations . . . . . . . . . . . . . . . . 4
4.2. Receiver Side Considerations . . . . . . . . . . . . . . . 4
5. Interoperability Considerations . . . . . . . . . . . . . . . . 4
6. Socket API Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
[RFC4960] states that an SCTP implementation should use delayed
SACKs. In combination with the Nagle algorithm, reduced congestion
windows after timeouts, the handling of the SHUTDOWN-PENDING state,
or other situations this might result in reduced performance of the
protocol.
This document describes a simple extension of the SCTP DATA chunk by
defining a new flag, the I-bit. The sender indicates by setting this
bit that the corresponding SACK chunk should be sent back without
delaying it.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. The I-bit in the DATA Chunk Header
The following Figure 1 shows the extended DATA chunk.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0 | Res |I|U|B|E| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TSN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Identifier | Stream Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Protocol Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ \
/ User Data /
\ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
The only difference between the DATA chunk in Figure 1 and the DATA
chunk defined in [RFC4960] is the addition of the I-bit in the flags
field of the chunk header.
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4. Procedures
4.1. Sender Side Considerations
Whenever the sender of a DATA chunk can benefit from the
corresponding SACK chunk being sent back without delay, the sender
MAY set the I-bit in the DATA chunk header.
Reasons for setting the I-bit include
o The sender has not enough queued user data to send the remaining
DATA chunks due to the Nagle algorithm.
o The sending of a DATA chunk fills the congestion or receiver
window.
o The sender is in the SHUTDOWN-PENDING state.
o The sender has reduced its RTO.Min such that a retransmission
timeout will occur if the receiver delays its SACK.
o The application requests to set the I-bit of the last DATA chunk
of a user message when providing the user message to the SCTP
implementation.
4.2. Receiver Side Considerations
On reception of an SCTP packet containing a DATA chunk with the I-bit
set, the receiver SHOULD NOT delay the sending of the corresponding
SACK chunk and SHOULD send it back immediately.
5. Interoperability Considerations
According to [RFC4960] a receiver of a DATA chunk with the I-bit set
should ignore this bit when it does not support the extension
described in this document. Since the sender of the DATA chunk is
able to handle this case, there is no requirement for negotiating the
feature described in this document.
6. Socket API Considerations
This section describes how the socket API defined in
[I-D.ietf-tsvwg-sctpsocket] is extended to provide a way for the
application to set the I-bit.
Please note that this section is informational only.
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A socket API implementation based on [I-D.ietf-tsvwg-sctpsocket] is
extended by supporting a flag called SCTP_SACK_IMMEDIATELY, which can
be set in the snd_flags field of the struct sctp_sndinfo structure or
the sinfo_flags field of the struct sctp_sndrcvinfo structure, which
is deprecated.
If the SCTP_SACK_IMMEDIATELY flag is set when sending a user message,
the I-bit of the last DATA chunk of the corresponding user message is
set.
7. IANA Considerations
[NOTE to RFC-Editor:
"RFCXXXX" is to be replaced by the RFC number you assign this
document.
]
Following the chunk flag registration procedure defined in [RFC6096]
IANA should register a new bit, the I-bit, for the DATA chunk. The
suggested value is 0x08. The reference for the new chunk flag in the
chunk flags table for the DATA chunk available at sctp-parameters [1]
should be RFCXXXX.
8. Security Considerations
This document does not add any additional security considerations in
addition to the ones given in [RFC4960].
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC6096] Tuexen, M. and R. Stewart, "Stream Control Transmission
Protocol (SCTP) Chunk Flags Registration", RFC 6096,
January 2011.
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9.2. Informative References
[I-D.ietf-tsvwg-sctpsocket]
Stewart, R., Tuexen, M., Poon, K., Lei, P., and V.
Yasevich, "Sockets API Extensions for Stream Control
Transmission Protocol (SCTP)",
draft-ietf-tsvwg-sctpsocket-30 (work in progress),
June 2011.
URIs
[1] <http://www.iana.org/assignments/sctp-parameters>
Authors' Addresses
Michael Tuexen
Muenster University of Applied Sciences
Stegerwaldstr. 39
48565 Steinfurt
Germany
Email: tuexen@fh-muenster.de
Irene Ruengeler
Muenster University of Applied Sciences
Stegerwaldstr. 39
48565 Steinfurt
Germany
Email: i.ruengeler@fh-muenster.de
Randall R. Stewart
Adara Networks
Chapin, SC 29036
USA
Email: randall@lakerest.net
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