More Features for TWAMP
draft-morton-ippm-more-twamp-00

Status of this Memo

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Abstract

The IETF IP Performance Metrics Working Group is completing its work on TWAMP - the Two-Way Active Measurement Protocol. This memo describes additional features for TWAMP, such as 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 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].

Table of Contents

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

1.  Introduction

The IETF IP Performance Metrics (IPPM) Working Group is completing its work on TWAMP - the Two-Way Active Measurement Protocol [I‑D.ietf‑ippm‑twamp] (Babiarz, J., “A Two-way Active Measurement Protocol (TWAMP),” August 2008.), which is an extension to 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. Although it may appear that there are few prototype TWAMP implementations at present, this is a temporary situation (and this sentence will need revision very soon).

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 TBD. This could be an update to the TWAMP RFC when published, or the text could be expanded such that this is a complete replacement text.

2.  Purpose and Scope

The purpose of this memo is to specify additional functions and features for TWAMP [I‑D.ietf‑ippm‑twamp] (Babiarz, J., “A Two-way Active Measurement Protocol (TWAMP),” August 2008.). The features and extensions were vetted by the IPPM working group.

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] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.)), while retaining backward compatibility with TWAMP [I‑D.ietf‑ippm‑twamp] (Babiarz, J., “A Two-way Active Measurement Protocol (TWAMP),” August 2008.) 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] (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 [I‑D.ietf‑ippm‑twamp] (Babiarz, J., “A Two-way Active Measurement Protocol (TWAMP),” August 2008.), and in the following sections.

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] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.). 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

----------------------------------------------------
Protocol |     Permissible Mode Combinations
----------------------------------------------------
Control  |    Unauth.  |  Auth.   |  Encrypted
----------------------------------------------------
         |    Unauth.  |  Unauth. |   Unauth.
         -------------------------------------------
Test     |             |  Auth.   |    Auth.
         -------------------------------------------
         |             |          |  Encrypted
----------------------------------------------------

Other ways in which TWAMP extends OWAMP are described in [I‑D.ietf‑ippm‑twamp] (Babiarz, J., “A Two-way Active Measurement Protocol (TWAMP),” August 2008.).

4.  Extended TWAMP Test

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 [I‑D.ietf‑ippm‑twamp] (Babiarz, J., “A Two-way Active Measurement Protocol (TWAMP),” August 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. 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.

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] (Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, “A One-way Active Measurement Protocol (OWAMP),” September 2006.), with the following exceptions:

• the Send Schedule is not used, and
• 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] (Babiarz, J., “A Two-way Active Measurement Protocol (TWAMP),” August 2008.), with the following extensions:

• the support of additional security mode combinations defined in section 3.1 of this memo.

5.  Security Considerations

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 [I‑D.ietf‑ippm‑twamp] (Babiarz, J., “A Two-way Active Measurement Protocol (TWAMP),” August 2008.).

6.  IANA Considerations

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.

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] (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 values.

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] (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.

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

8.2. Informative References

Authors' Addresses

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