One document matched: draft-morton-ippm-twamp-session-cntrl-00.txt
Network Working Group A. Morton
Internet-Draft AT&T Labs
Intended status: Standards Track July 6, 2008
Expires: January 7, 2009
Independent Session Control Feature for TWAMP
draft-morton-ippm-twamp-session-cntrl-00
Status of this Memo
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Abstract
The IETF is completing its work on TWAMP - the Two-Way Active
Measurement Protocol. This memo describes a proposed feature for
TWAMP, intended for discussion in the IP Performance Metrics WG. The
feature gives the sender the ability to start and stop one or more
test sessions using the Session Identifiers.
Requirements Language
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 RFC 2119 [RFC2119].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3
3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 4
3.1. Connection Setup with Individual Session Control . . . . . 4
3.2. Start-Sessions Command with Session Control . . . . . . . 5
3.3. Stop-Sessions Command with Session Control . . . . . . . . 6
3.4. SERVWAIT Timer Operation . . . . . . . . . . . . . . . . . 6
3.5. Additional considerations . . . . . . . . . . . . . . . . 7
4. TWAMP Test with Individual Session Control . . . . . . . . . . 7
4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 7
4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6.1. Registry Specification . . . . . . . . . . . . . . . . . . 8
6.2. Registry Management . . . . . . . . . . . . . . . . . . . 9
6.3. Experimental Numbers . . . . . . . . . . . . . . . . . . . 9
6.4. Registry Contents . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 12
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1. Introduction
The IETF is completing its work on TWAMP - the Two-Way Active
Measurement Protocol [I-D.ietf-ippm-twamp], which is an extension to
the One-way Active Measurement Protocol, OWAMP [RFC4656].
This memo describes a new proposed feature for TWAMP, so it can be
discussed and interest to take-up the feature assessed. TWAMP (and
OWAMP) start all previously requested and accepted test sessions at
once. This feature allows the Control-Client to control the test
sessions on the basis of their Session Identifier (SID). The feature
permits a short duration TWAMP test to start (and stop) during a
longer test. For example, this feature permits a specific diagnostic
test to begin if intermediate results indicate that the test is
warranted.
This feature requires a Mode bit position assignment and the
assignment of two new TWAMP command numbers (for the augmented Start
and Stop commands).
The relationship between this memo and TWAMP is intended to be an
update to the TWAMP RFC when published.
2. Purpose and Scope
The purpose of this memo is to describe an additional function and
feature for TWAMP [I-D.ietf-ippm-twamp]. The feature needs a clear
description so it can be discussed and (hopefully) adopted in the IP
Performance Metrics Charter.
The scope of the memo is currently limited to specifications of the
following features:
1. Extension of the modes of operation through assignment of a new
value in the Mode field to communicate feature capability and
use, the definition of augmented Start Session and Stop Session
commands, and the definition of related procedures for TWAMP
entities. The motivation for this added feature is the ability
to start and stop individual test sessions at will, using a
single TWAMP-control connection.
When new features are discussed and reach consensus, they may become
chartered work items in IETF IPPM (and may appear in a different
memo).
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3. TWAMP Control Extensions
TWAMP-Control protocol is a derivative of the OWAMP-Control protocol,
and provides two-way measurement capability. TWAMP
[I-D.ietf-ippm-twamp] uses the Mode field to identify and select
specific communication capabilities, and this field is a recognized
extension mechanism. The following sections describe one such
extension.
3.1. Connection Setup with Individual Session Control
TWAMP connection establishment follows the procedure defined in
section 3.1 of [RFC4656]. The Individual Session Control mode
requires one new bit position (and value) to identify the ability of
the Server/Session-Reflector to start and stop specific sessions
(according to their Session Identifier, or SID). This new feature
requires an additional TWAMP mode bit assignment as follows:
Value Description Reference/Explanation
0 Reserved
1 Unauthenticated RFC4656, Section 3.1
2 Authenticated RFC4656, Section 3.1
4 Encrypted RFC4656, Section 3.1
8 Unauth. TEST protocol, draft-...-more-twamp (3)
Auth. CONTROL
16 Unauth. TEST protocol, draft-...-more-twamp (4)
Encrypted CONTROL
32 Auth. TEST protocol, draft-...-more-twamp (5)
Encrypted CONTROL
--------------------------------------------------------
zzz Individual Session this memo, bit position (Z)
Control
In the original OWAMP mode field, setting bit positions 0, 1 or 2
indicated the security mode of the Control protocol, and the Test
protocol inherited the same mode (see section 4 of [RFC4656]). In
the [I-D.morton-ippm-more-twamp] proposal, bit positions (3, 4 or 5)
discontinue the inheritance of the security mode in the Test
protocol.
The Server sets the new bit position (possibly bit 8) in the Server
Greeting message to indicate its capabilities and willingness to
control sessions on an individual basis if desired.
If the Control-Client intends to control sessions on an individual
basis, it MUST set the mode bit corresponding to that mode in the
Setup Response message.
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3.2. Start-Sessions Command with Session Control
Having requested one or more test sessions and received affirmative
Accept-Session responses, an OWAMP client MAY start the execution of
the requested test sessions by sending a Start-Sessions message to
the server.
The format of this message is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7 | |
+-+-+-+-+-+-+-+-+ +
| MBZ (7 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Sessions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| First SID (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| remaining SIDs (16 octets each) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Number of sessions field indicates the count of sessions that
this Start command applies to. The SID is as defined in OWAMP (and
TWAMP) section 3.5 [RFC4656].
The Server MUST respond with a Start-Ack message (which SHOULD be
sent as quickly as possible). Start-Ack messages have the format
defined in section 3.7 of [RFC4656].
The Control Client MUST NOT send a subsequent Start Sessions command
until an outstanding message is acknowledged with a Start-Ack
message.
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3.3. Stop-Sessions Command with Session Control
The Stop-Sessions command can only be issued by the Control-Client.
The message MUST contain at least one SID. The message is terminated
with a single block HMAC, to complete the Stop-Sessions Command.
Thus, the TWAMP Stop-Sessions command for individual session control
is constructed as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 8 | Accept | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Sessions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| First SID (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| remaining SIDs (16 octets each) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Number of sessions field indicates the count of sessions that
this Stop command applies to. The SID is as defined in OWAMP (and
TWAMP) section 3.5 [RFC4656].
3.4. SERVWAIT Timer Operation
Section 3.1 of [I-D.ietf-ippm-twamp] describes the operation of the
optional SERVWAIT timer. In normal TWAMP operation, the Server
suspends monitoring the SERVWAIT timer while test sessions are in
progress. When the Individual Session Control feature is utilized,
this suspension is extended to cover the time when ANY test session
is in progress.
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Thus, the Server SHALL suspend monitoring control connection activity
after receiving any Start-Sessions command, and SHALL resume after
receiving a Stop-Sessions command for all corresponding SIDs (and no
test sessions are in-progress).
3.5. Additional considerations
The value of the Modes field sent by the Server (in the Server
Greeting message) is the bit-wise OR of the mode values that it is
willing to support during this session.
If this feature is adopted, the last seven bits of the Modes 32-bit
field are used. The first 25 bits MUST be zero. A client conforming
to this version of the specification MUST ignore the values in the
first 25 bits of the Modes value. (This way, the bits are available
for future protocol extensions.)
Other ways in which TWAMP extends OWAMP are described in
[I-D.ietf-ippm-twamp].
4. TWAMP Test with Individual Session Control
The TWAMP test protocol is similar to the OWAMP [RFC4656] test
protocol with the exception that the Session-Reflector transmits test
packets to the Session-Sender in response to each test packet it
receives. TWAMP [I-D.ietf-ippm-twamp] defines two different test
packet formats, one for packets transmitted by the Session-Sender and
one for packets transmitted by the Session-Reflector. As with OWAMP-
Test protocol there are three security modes: unauthenticated,
authenticated, and encrypted. Unauthenticated mode has one test
packet format, while authenticated and encrypted modes use another
(common) format.
4.1. Sender Behavior
The individual session control feature requires that the sender MUST
manage test sessions according to their SID. Otherwise, the sender
behavior is as describe in section 4.1 of [I-D.ietf-ippm-twamp].
4.2. Reflector Behavior
The TWAMP Reflector follows the procedures and guidelines in section
4.2 of [I-D.ietf-ippm-twamp], with the following additional functions
required by this feature:
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o The session reflector MUST manage test sessions according to their
SID.
o Packets for a specific session/SID not received within the Timeout
(following the Stop-Session command) MUST be ignored by the
Reflector. The Session-Reflector MUST NOT generate a test packet
to the Session-Sender for packets that are ignored.
o If the optional REFWAIT timer is implemented, it SHOULD be
enforced when any test session is in-progress (started and not
stopped).
5. Security Considerations
These extended modes of operation permit stronger integrity
protection on the TWAMP-Control protocol while simultaneously
emphasizing accuracy or efficiency on the TWAMP-Test protocol, thus
enhancing overall security when compared to the previous options.
The security considerations that apply to any active measurement of
live networks are relevant here as well. See the security
considerations in[RFC4656] and [I-D.ietf-ippm-twamp].
6. IANA Considerations
This memo requests assignment of one mode bit position/value to the
IANA registry for the TWAMP Mode field, and describes behavior when
the new mode is used. This field is a recognized extension mechanism
for TWAMP.
This memo also requests assignment of two command numbers in the
TWAMP-Control Command Number registry, and describes the use of the
new commands. The command number field is a recognized extension
mechanism for TWAMP.
6.1. Registry Specification
IANA has created a TWAMP-Modes registry (as requested in
[I-D.morton-ippm-more-twamp]). TWAMP-Modes are specified in TWAMP
Server Greeting messages and Set-up Response messages, as described
in section 3.1 of [I-D.ietf-ippm-twamp], consistent with section 3.1
of [RFC4656], and extended by this memo. Modes are indicated by
setting bits in the 32-bit Modes field. Thus, this registry can
contain a total of 32 possible values.
IANA has also created a TWAMP-Control Command Number registry.
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TWAMP-Control commands are specified by the first octet in TWAMP-
Control messages as specified in section 3.5 of
[I-D.ietf-ippm-twamp], and augmented by this memo. This registry may
contain sixteen possible values.
6.2. Registry Management
Because the TWAMP-Control Command Number registry can contain only
sixteen values, TWAMP-Modes can only contain thirty-two values, and
because TWAMP is an IETF protocol, these registries must be updated
only by "IETF Consensus" as specified in [RFC2434](an RFC documenting
registry use that is approved by the IESG). Management of these
registries is described in section 8.2 of [I-D.ietf-ippm-twamp] and
[I-D.morton-ippm-more-twamp].
This memo proposes assignment of values 7 and 8.
6.3. Experimental Numbers
One experimental value has been assigned in the TWAMP-Control Command
Number registry.
No additional experimental values are assigned in the TWAMP-Modes
registry.
6.4. Registry Contents
TWAMP-Control Command Number Registry
Value Description Semantics Definition
0 Reserved
1 Forbidden
2 Start-Sessions RFC4656, Section 3.7
3 Stop-Sessions RFC4656, Section 3.8
4 Reserved
5 Request-TW-Session draft-ietf-ippm-twamp, Section 3.5
6 Experimentation draft-ietf-ippm-twamp, Section 8.3
------------------------------------------------------------------
7 Start-Sessions with this memo, Section 3.2
Individ. Session Cntrl.
8 Stop-Sessions with this memo, Section 3.3
Individ. Session Cntrl.
TWAMP-Modes Registry
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Value Description Reference/Explanation
0 Reserved
1 Unauthenticated RFC4656, Section 3.1
2 Authenticated RFC4656, Section 3.1
4 Encrypted RFC4656, Section 3.1
8 Unauth. TEST protocol, draft-...-more-twamp (3)
Auth. CONTROL
16 Unauth. TEST protocol, draft-...-more-twamp (4)
Encrypted CONTROL
32 Auth. TEST protocol, draft-...-more-twamp (5)
Encrypted CONTROL
--------------------------------------------------------
zzz Individual Session this memo, Section 3.1
Control bit position (Z)
7. Acknowledgements
The author would like to thank Murtaza Chiba for suggesting this
feature.
8. References
8.1. Normative References
[I-D.ietf-ippm-twamp]
Babiarz, J., "A Two-way Active Measurement Protocol
(TWAMP)", draft-ietf-ippm-twamp-08 (work in progress),
June 2008.
[I-D.morton-ippm-more-twamp]
Morton, A. and K. Hedayat, "More Features for TWAMP",
draft-morton-ippm-more-twamp-00 (work in progress),
February 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
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8.2. Informative References
[x] "".
Author's Address
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown,, NJ 07748
USA
Phone: +1 732 420 1571
Fax: +1 732 368 1192
Email: acmorton@att.com
URI: http://home.comcast.net/~acmacm/
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