Network Working Group A. Morton
Internet-Draft AT&T Labs
Intended status: Standards Track K. Hedayat
Expires: January 7, 2009 Brix Networks
July 6, 2008
More Features for TWAMP
draft-morton-ippm-more-twamp-01
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Abstract
The IETF is completing its work on TWAMP - the Two-Way Active
Measurement Protocol. This memo describes additional features for
TWAMP, essentially the ability to use different security modes in the
TWAMP-Control and TWAMP-Test protocols.
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 . . . . . . . . . . . . . . . . . . . 3
3.1. Extended Connection Setup . . . . . . . . . . . . . . . . . 4
4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . . 5
4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 5
4.1.2. Packet Format and Content . . . . . . . . . . . . . . . 6
4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Registry Specification . . . . . . . . . . . . . . . . . . 6
6.2. Registry Management . . . . . . . . . . . . . . . . . . . . 7
6.3. Experimental Numbers . . . . . . . . . . . . . . . . . . . 7
6.4. Initial Registry Contents . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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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]. The TWAMP
specification gathered wide review as it approached completion, and
the by-products were several recommendations for new features in
TWAMP. There are a growing number TWAMP implementations at present,
and wide-spread usage is expected. There are even devices emerging
that test implementations for protocol compliance.
This memo describes additional features for TWAMP, such as the
ability to use different security modes in the TWAMP-Control and
TWAMP-Test protocols.
The relationship between this memo and the TWAMP is intended to be an
update to the TWAMP RFC when published.
2. Purpose and Scope
The purpose of this memo is to specify additional functions and
features for TWAMP [I-D.ietf-ippm-twamp]. The features and
extensions were vetted before adoption in this memo.
The scope of the memo is limited to specifications of the following
features:
1. Extension of the modes of operation through assignment of new
values in the Mode field (see section 3.1 of [RFC4656]), while
retaining backward compatibility with TWAMP [I-D.ietf-ippm-twamp]
implementations. These values add the ability to use different
security modes in the TWAMP-Control and TWAMP-Test protocols.
The motivation for this extension is to permit the low packet
rate TWAMP-Control protocol to utilize a stronger mode of
integrity protection than that used in the TWAMP-Test protocol.
(other items may be added)
3. TWAMP Control Extensions
TWAMP-Control protocol is a derivative of the OWAMP-Control protocol,
and provides two-way measurement capability. All TWAMP Control
messages are similar in format and follow similar guidelines to those
defined in section 3 of [RFC4656] with the exceptions described in
TWAMP [I-D.ietf-ippm-twamp], and in the following sections.
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All OWAMP-Control messages apply to TWAMP-Control, except for the
Fetch Session command.
3.1. Extended Connection Setup
TWAMP connection establishment follows the same procedure defined in
section 3.1 of [RFC4656]. The extended modes assign three new bit
positions (and values) to allow the Test protocol security mode to
differ from the Control protocol mode. With this extension, the
complete set of TWAMP values are 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, new bit position (3)
Auth. CONTROL
16 Unauth. TEST protocol, new bit position (4)
Encrypted CONTROL
32 Auth. TEST protocol, new bit position (5)
Encrypted 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
this extension to TWAMP, setting a higher mode field bit position (3,
4 or 5) SHALL discontinue the inheritance of the security mode in the
Test protocol, and each protocol's mode SHALL be specified
explicitly. When the desired TWAMP Test protocol mode is identical
to the Control Session mode, the corresponding mode bit (position 0,
1 or 2) SHALL be set. The table below gives the various combinations
that are now permissible in TWAMP, where the Test protocol may use
one of the modes in each column corresponding to a Control mode.
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----------------------------------------------------
Protocol | Permissible Mode Combinations
----------------------------------------------------
Control | Unauth. | Auth. | Encrypted
----------------------------------------------------
| Unauth. | Unauth. | Unauth.
-------------------------------------------
Test | | Auth. | Auth.
-------------------------------------------
| | | Encrypted
----------------------------------------------------
The value of the Modes field sent by the Server is the bit-wise OR of
the mode values that it is willing to support during this session.
Thus, the last six bits of the Modes 32-bit field are used. The
first 26 bits MUST be zero. A client conforming to this version of
the specification MUST ignore the values in the first 26 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. Extended TWAMP Test
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. The extension to TWAMP makes it
possible to specify these modes independently from the mode used in
the TWAMP-Control protocol.
4.1. Sender Behavior
This section describes extensions to the behavior of the TWAMP
Sender.
4.1.1. Packet Timings
The Send Schedule is not utilized in TWAMP, and there are no
extensions defined in this memo.
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4.1.2. Packet Format and Content
The Session Sender packet format and content follow the same
procedure and guidelines as defined in section 4.1.2 of [RFC4656],
with the following exceptions:
o the Send Schedule is not used, and
o the support of additional security mode combinations defined in
section 3.1 of this memo.
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 extensions:
o the support of additional security mode combinations defined in
section 3.1 of this memo.
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 [RFC4656] and
[I-D.ietf-ippm-twamp].
6. IANA Considerations
This memo adds three security mode combinations to the OWAMP-Control
specification[RFC4656], and describes behavior when the new modes are
used. This memo requests creation an IANA registry for the TWAMP
Mode field. This field is a recognized extension mechanism for
TWAMP.
6.1. Registry Specification
IANA is requested to create a TWAMP-Modes registry. TWAMP-Modes are
specified in TWAMP Server Greeting messages and Set-up Response
messages 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.
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6.2. Registry Management
Because the Modes registry can contain only thirty-two values, and
because TWAMP is an IETF protocol, this registry must be updated only
by "IETF Consensus" as specified in [RFC2434](an RFC documenting
registry use that is approved by the IESG). For the Modes registry,
we expect that new features will be assigned using monotonically
increasing bit positions and in the range [0-31] and the
corresponding values, unless there is a good reason to do otherwise.
6.3. Experimental Numbers
No experimental values are currently assigned for the Modes Registry.
6.4. Initial Registry Contents
TWAMP Modes Registry
Value Description Semantics Definition
0 Reserved
1 Unauthenticated RFC4656, Section 3.1
2 Authenticated RFC4656, Section 3.1
4 Encrypted RFC4656, Section 3.1
8 Unauth. TEST protocol, this document, Section 3.1
Auth. CONTROL
16 Unauth. TEST protocol, this document, Section 3.1
Encrypted CONTROL
32 Auth. TEST protocol, this document, Section 3.1
Encrypted CONTROL
7. Acknowledgements
The authors would like to thank Len Ciavattone for helpful review and
comments.
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),
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June 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.
8.2. Informative References
[x] "".
Authors' Addresses
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/
Kaynam Hedayat
Brix Networks
285 Mill Road
Chelmsford, MA 01824
USA
Phone: +1
Fax: +1
Email: khedayat@brixnet.com
URI: http://www.brixnet.com/
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