Network Working Group A. Morton
Internet-Draft AT&T Labs
Intended status: Standards Track K. Hedayat
Expires: April 22, 2009 Brix Networks
October 19, 2008
More Features for TWAMP
draft-ietf-ippm-more-twamp-00
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Abstract
The IETF has completed its work on TWAMP - the Two-Way Active
Measurement Protocol. This memo describes a simple extension to
TWAMP, the option 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 . . . . . . . . . . . . . . . 5
4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Registry Specification . . . . . . . . . . . . . . . . . . 6
6.2. Registry Management . . . . . . . . . . . . . . . . . . . . 6
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 has completed its work on the core specification of TWAMP -
the Two-Way Active Measurement Protocol [RFC5357]. TWAMP is an
extension of 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 that are designed to test
implementations for protocol compliance.
This memo describes a simple extension for TWAMP, the option to use
different security modes in the TWAMP-Control and TWAMP-Test
protocols.
The relationship between this memo and TWAMP is intended to be an
update to [RFC5357] when published.
2. Purpose and Scope
The purpose of this memo is to describe and specify an extension for
TWAMP [RFC5357]. The features and extensions were vetted before
adoption in this memo.
The scope of the memo is limited to specifications of the following:
o Extension of the modes of operation through assignment of one new
value in the Mode field (see section 3.1 of [RFC4656]), while
retaining backward compatibility with TWAMP [RFC5357]
implementations. This value adds the OPTIONAL 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.
3. TWAMP Control Extensions
TWAMP-Control protocol is a derivative of the OWAMP-Control protocol,
and coordinates a 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 [RFC5357], and in the following sections.
All OWAMP-Control messages apply to TWAMP-Control, except for the
Fetch Session command.
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3.1. Extended Connection Setup
TWAMP connection establishment follows the same procedure defined in
section 3.1 of [RFC4656]. This extended mode assigns one new bit
position (and value) to allow the Test protocol security mode to
operate in Unauthenticated mode, while the Control protocol operates
in Encrypted 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)
Encrypted CONTROL
In the original OWAMP Modes 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 Modes Field bit position 3 SHALL
discontinue the inheritance of the security mode in the Test
protocol, and each protocol's mode SHALL be as specified below. When
the desired TWAMP Test protocol mode is identical to the Control
Session mode, the corresponding Modes Field bit (position 0, 1 or 2)
SHALL be set. The table below gives the various combinations of
integrity protection that are permissible in TWAMP (with this
extension). The Test protocol SHALL use the mode in each column
corresponding to the Modes Field bit position.
--------------------------------------------------------
Protocol | Permissible Mode Combinations (Modes bit set)
--------------------------------------------------------
Control | Unauth.(0)| Auth. == Encrypted (1,2,3)
--------------------------------------------------------
| Unauth.(0)| Unauth. (3)
-----------------------------------------------
Test | | Auth.(1)
-----------------------------------------------
| | Encrypted (2)
--------------------------------------------------------
Note that the TWAMP-Control protocol security measures are identical
in the Authenticated and Encrypted Modes. Therefore, only one new
bit position (3) is needed to convey the single mixed security mode.
The value of the Modes Field sent by the Server in the Server-
Greeting message is the bit-wise OR of the modes (bit positions) that
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it is willing to support during this session. Thus, the last four
bits of the Modes 32-bit Field are used. The first 28 bits MUST be
zero. A client conforming to this extension of [RFC5357] MAY ignore
the values in the first 28 bits of the Modes Field, or it MAY support
other features that are communicated in these bit positions.
Other ways in which TWAMP extends OWAMP are described in [RFC5357].
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 [RFC5357] 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. This TWAMP extension makes it possible to use TWAMP-Test
Unauthenticated mode regardless of the mode used in the TWAMP-Control
protocol.
4.1. Sender Behavior
This section describes REQUIRED 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.
4.1.2. Packet Format and Content
The Session Sender packet format and content MUST follow the same
procedure and guidelines as defined in section 4.1.2 of [RFC4656] and
section 4.1.2 of [RFC5357], with the following exceptions:
o the Send Schedule is not used, and
o the Sessions-Sender MUST support the mixed security mode
(Unauthenticated TEST, Encrypted CONTROL,value 8, bit position 3)
defined in section 3.1 of this memo.
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4.2. Reflector Behavior
The TWAMP Reflector is REQUIRED to follow the procedures and
guidelines in section 4.2 of [RFC5357], with the following
extensions:
o the Sessions-Reflector MUST support the mixed security mode
(Unauthenticated TEST, Encrypted CONTROL,value 8, bit position 3)
defined in section 3.1 of this memo.
5. Security Considerations
The extended mixed-mode of operation permits stronger security/
integrity protection on the TWAMP-Control protocol while
simultaneously emphasizing accuracy or efficiency on the TWAMP-Test
protocol, thus making it possible to increase 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
[RFC5357].
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 bit
positions and corresponding values.
6.2. Registry Management
Because the TWAMP-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
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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
Encrypted CONTROL
7. Acknowledgements
The authors would like to thank Len Ciavattone for helpful review and
comments.
8. References
8.1. Normative References
[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.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
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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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