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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.
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 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].
1.
Introduction
2.
Purpose and Scope
3.
TWAMP Control Extensions
3.1.
Extended Connection Setup
4.
Extended TWAMP Test
4.1.
Sender Behavior
4.1.1.
Packet Timings
4.1.2.
Packet Format and Content
4.2.
Reflector Behavior
5.
Security Considerations
6.
IANA Considerations
6.1.
Registry Specification
6.2.
Registry Management
6.3.
Experimental Numbers
6.4.
Initial Registry Contents
7.
Acknowledgements
8.
References
8.1.
Normative References
8.2.
Informative References
§
Authors' Addresses
§
Intellectual Property and Copyright Statements
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The IETF has completed its work on the core specification of TWAMP - the Two-Way Active Measurement Protocol [RFC5357] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.). TWAMP is an extension of the One-way Active Measurement Protocol, OWAMP [RFC4656] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.). 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] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.) when published.
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The purpose of this memo is to describe and specify an extension for TWAMP [RFC5357] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.). The features and extensions were vetted before adoption in this memo.
The scope of the memo is limited to specifications of the following:
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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] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.) with the exceptions described in TWAMP [RFC5357] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.), and in the following sections.
All OWAMP-Control messages apply to TWAMP-Control, except for the Fetch Session command.
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TWAMP connection establishment follows the same procedure defined in section 3.1 of [RFC4656] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.). 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] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.)). 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 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] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.) 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] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.).
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The TWAMP test protocol is similar to the OWAMP [RFC4656] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.) 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] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.) 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.
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This section describes REQUIRED extensions to the behavior of the TWAMP Sender.
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The Send Schedule is not utilized in TWAMP, and there are no extensions defined in this memo.
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The Session Sender packet format and content MUST follow the same procedure and guidelines as defined in section 4.1.2 of [RFC4656] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.) and section 4.1.2 of [RFC5357] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.), with the following exceptions:
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The TWAMP Reflector is REQUIRED to follow the procedures and guidelines in section 4.2 of [RFC5357] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.), with the following extensions:
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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] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.) and [RFC5357] (Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” October 2008.).
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This memo adds three security mode combinations to the OWAMP-Control specification[RFC4656] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.), 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.
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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] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.), 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.
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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] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” October 1998.)(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.
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No experimental values are currently assigned for the Modes Registry.
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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
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The authors would like to thank Len Ciavattone for helpful review and comments.
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| [RFC2119] | Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML). |
| [RFC2434] | Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” BCP 26, RFC 2434, October 1998 (TXT, HTML, XML). |
| [RFC4656] | Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” RFC 4656, September 2006 (TXT). |
| [RFC5357] | Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, “A Two-Way Active Measurement Protocol (TWAMP),” RFC 5357, October 2008 (TXT). |
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| [x] | “.” |
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| 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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