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IETF RFC 8545
Last modified on Tuesday, March 12th, 2019
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Internet Engineering Task Force (IETF) A. Morton, Ed.
Request for Comments: 8545 AT&T Labs
Updates: 4656, 5357 G. Mirsky, Ed.
Category: Standards Track ZTE Corp.
ISSN: 2070-1721 March 2019
Well-Known Port Assignments for
the One-Way Active Measurement Protocol (OWAMP) and
the Two-Way Active Measurement Protocol (TWAMP)
 Abstract
This memo explains the motivation and describes the reassignment of
well-known ports for the One-Way Active Measurement Protocol (OWAMP)
and the Two-Way Active Measurement Protocol (TWAMP) for control and
measurement. It also clarifies the meaning and composition of these
Standards Track protocol names for the industry.
This memo updates RFCs 4656 and 5357, in terms of the UDP well-known
port assignments, and it clarifies the complete OWAMP and TWAMP
protocol composition for the industry.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/RFC 8545.
Morton & Mirsky Standards Track PAGE 1 
RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Requirements Language ...........................................3
3. Scope ...........................................................3
4. Definitions and Background ......................................3
5. New Well-Known Ports ............................................5
5.1. Impact on TWAMP-Control Protocol ...........................5
5.2. Impact on OWAMP-Control Protocol ...........................6
5.3. Impact on OWAMP-Test/TWAMP-Test Protocols ..................6
6. Security Considerations .........................................7
7. IANA Considerations .............................................8
8. References ......................................................8
8.1. Normative References .......................................8
8.2. Informative References .....................................9
Appendix A. Background on TWAMP Light .............................10
Acknowledgements ..................................................11
Contributors ......................................................11
Authors' Addresses ................................................11
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RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
1. Introduction
The IETF IP Performance Metrics (IPPM) Working Group first developed
the One-Way Active Measurement Protocol (OWAMP), as specified in
[RFC 4656]. Further protocol development to support testing resulted
in the Two-Way Active Measurement Protocol (TWAMP), as specified in
[RFC 5357].
Both OWAMP and TWAMP require the implementation of a control and mode
negotiation protocol (OWAMP-Control and TWAMP-Control) that employs
the reliable transport services of TCP (including security
configuration and key derivation). The control protocols arrange for
the configuration and management of test sessions using the
associated test protocol (OWAMP-Test or TWAMP-Test) on UDP transport.
The IETF recognizes the value of assigning a well-known UDP port to
the OWAMP-Test and TWAMP-Test protocols and also recognizes that this
goal can be easily arranged through port reassignments.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC 2119] [RFC 8174] when, and only when, they appear in all
capitals, as shown here.
3. Scope
The scope of this memo is twofold: (1) to reallocate the well-known
ports for the UDP test protocols that compose necessary parts of
their respective Standards Track protocols (OWAMP and TWAMP) and
(2) to clarify the meaning and composition of these Standards Track
protocol names for the industry.
This memo updates [RFC 4656] and [RFC 5357], in terms of the UDP
well-known port assignments.
4. Definitions and Background
This section defines key terms and clarifies the required composition
of the OWAMP and TWAMP Standards Track protocols.
"OWAMP-Control" is the protocol defined in Section 3 of [RFC 4656].
"OWAMP-Test" is the protocol defined in Section 4 of [RFC 4656].
Morton & Mirsky Standards Track PAGE 3
RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
OWAMP is described in this direct quote from Section 1.1 of
[RFC 4656]: "OWAMP actually consists of two inter-related protocols:
OWAMP-Control and OWAMP-Test." A similar sentence appears in
Section 2 of [RFC 4656]. For avoidance of doubt, the implementation
of both OWAMP-Control and OWAMP-Test is REQUIRED for Standards Track
OWAMP as specified in [RFC 4656] (applying the consensus of many
dictionary definitions of "consist").
"TWAMP-Control" is the protocol defined in Section 3 of [RFC 5357].
"TWAMP-Test" is the protocol defined in Section 4 of [RFC 5357].
TWAMP is described in this direct quote from Section 1.1 of
[RFC 5357]: "Similar to OWAMP [RFC 4656], TWAMP consists of two
inter-related protocols: TWAMP-Control and TWAMP-Test." For
avoidance of doubt, the implementation of both TWAMP-Control and
TWAMP-Test is REQUIRED for Standards Track TWAMP as specified in
[RFC 5357] (applying the consensus of many dictionary definitions of
"consist").
"TWAMP Light" is an idea described in Appendix I ("TWAMP Light
(Informative)") of [RFC 5357]; TWAMP Light includes an unspecified
control protocol combined with the TWAMP-Test protocol. In
[RFC 5357], the TWAMP Light idea was relegated to Appendix I because
TWAMP Light failed to meet the requirements for IETF protocols (there
are no specifications for negotiating this form of operation and no
specifications for mandatory-to-implement security features), as
described in Appendix A of this memo. See also [LarsAD] and
[TimDISCUSS].
Since the idea of TWAMP Light clearly includes the TWAMP-Test
component of TWAMP, it is considered reasonable for future systems to
use the TWAMP-Test well-known UDP port (whose reallocated assignment
is specified in this document). Clearly, the TWAMP Light idea
envisions many components and communication capabilities beyond
TWAMP-Test (implementing the security requirements, for example);
otherwise, Appendix I of [RFC 5357] would be one sentence long
(equating TWAMP Light with TWAMP-Test only).
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RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
5. New Well-Known Ports
Originally, both TCP and UDP well-known ports were assigned to the
control protocols that are essential components of Standards Track
OWAMP and TWAMP.
Since OWAMP-Control and TWAMP-Control require TCP transport, they
cannot make use of the UDP ports that were originally assigned.
However, test sessions using OWAMP-Test or TWAMP-Test operate on UDP
transport.
Per this memo, IANA has reassigned the UDP well-known port from the
control protocol to the test protocol (see Section 7 ("IANA
Considerations")). The use of this UDP port is OPTIONAL in Standards
Track OWAMP and TWAMP. It may simplify some operations to have a
well-known port available for the test protocols or for future
specifications involving TWAMP-Test to use this port as a default
port. For example, [TR-390] is a specification for testing at the
customer edge of IP networks, and conforming implementations will
benefit from reallocation of the well-known UDP port to the test
protocol.
5.1. Impact on TWAMP-Control Protocol
Section 3.5 of [RFC 5357] describes the detailed process of
negotiating the Receiver Port number, on which the TWAMP
Session-Reflector will send and receive TWAMP-Test packets; see the
quoted text below. The Control-Client, acting on behalf of the
Session-Sender, proposes the Receiver Port number from the Dynamic
Ports range [RFC 6335]:
The Receiver Port is the desired UDP port to which TWAMP-Test
packets will be sent by the Session-Sender (the port where the
Session-Reflector is asked to receive test packets). The Receiver
Port is also the UDP port from which TWAMP-Test packets will be
sent by the Session-Reflector (the Session-Reflector will use the
same UDP port to send and receive packets).
It is possible that the proposed Receiver Port may not be available,
e.g., the port is in use by another test session or another
application. In this case, we update the last paragraph of
Section 3.5 of [RFC 5357] per Erratum ID 1587 (see
<https://www.rfc-editor.org/errata/eid1587>) as follows:
... the Server at the Session-Reflector MAY suggest an alternate
and available port for this session in the Port field. The
Control-Client either accepts the alternate port or composes a new
Session-Request message with suitable parameters. Otherwise, the
Morton & Mirsky Standards Track PAGE 5
RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
Server uses the Accept field to convey other forms of session
rejection or failure to the Control-Client and MUST NOT suggest an
alternate port; in this case, the Port field MUST be set to zero.
A Control-Client that supports the use of the allocated TWAMP-Test
Receiver Port (Section 7) MAY request to use that port number in the
Request-TW-Session command. If the Server does not support the
allocated TWAMP-Test Receiver Port, then it sends an alternate port
number in the Accept-Session message with Accept field = 0. Thus,
the deployment of the allocated TWAMP Receiver Port number is
backward compatible with existing TWAMP-Control solutions that are
based on [RFC 5357]. Of course, using a UDP port number chosen from
the Dynamic Ports range [RFC 6335] will help avoid the situation where
the Control-Client or Server finds that the proposed port is already
in use.
5.2. Impact on OWAMP-Control Protocol
As described above, an OWAMP-Control client that supports the use of
the allocated OWAMP-Test Receiver Port (Section 7) MAY request to use
that port number in the Request-Session command. If the Server does
not support the allocated OWAMP-Test Receiver Port (or does not have
the port available), then it sends an alternate port number in the
Accept-Session message with Accept field = 0. Further exchanges
proceed as already specified.
5.3. Impact on OWAMP-Test/TWAMP-Test Protocols
OWAMP-Test/TWAMP-Test may be used to measure IP performance metrics
in an Equal-Cost Multipath (ECMP) environment. Though algorithms to
balance IP flows among available paths have not been standardized,
the most common is the five-tuple that uses destination IP address,
source IP address, protocol type, destination port number, and source
port number. When attempting to monitor different paths in an ECMP
network, it is sufficient to vary only one of five parameters, e.g.,
the source port number. Thus, there will be no negative impact on
the ability to arrange concurrent OWAMP/TWAMP test sessions between
the same test points to monitor different paths in the ECMP network
when using the reallocated UDP port number as the Receiver Port, as
using the port is optional.
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RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
6. Security Considerations
The security considerations that apply to any active measurement of
live paths are relevant here as well (see [RFC 4656] and [RFC 5357]).
When considering the privacy of those involved in measurement or
those whose traffic is measured, the sensitive information available
to potential observers is greatly reduced when using active
techniques that are within this scope of work. Passive observations
of user traffic for measurement purposes raise many privacy issues.
We refer the reader to the security and privacy considerations
described in the Large-Scale Measurement of Broadband Performance
(LMAP) framework [RFC 7594], which covers both active and passive
techniques.
The registered UDP port as the Receiver Port for OWAMP-Test/
TWAMP-Test could become a target of denial of service (DoS) or could
be used to aid man-in-the-middle (MITM) attacks. To improve
protection against DoS, the following methods are recommended:
o filtering access to the OWAMP/TWAMP Receiver Port via an
access list.
o using a non-globally routable IP address for the OWAMP/TWAMP
Session-Reflector address.
A MITM attacker may try to modify the contents of the OWAMP-Test/
TWAMP-Test packets in order to alter the measurement results.
However, an implementation can use authenticated mode to detect
modification of data. In addition, an implementation can use
encrypted mode to prevent eavesdropping and undetected modification
of the OWAMP-Test/TWAMP-Test packets.
There is also the risk of a network under test giving special
treatment to flows involving the well-known UDP port, with or without
knowing source and destination addresses of measurement systems, and
thus biasing the results through preferential or detrimental
processing.
Morton & Mirsky Standards Track PAGE 7
RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
7. IANA Considerations
IANA has reallocated two UDP port numbers from the System Ports range
of the "Service Name and Transport Protocol Port Number Registry"
[RFC 6335]. Specifically, IANA has reallocated UDP ports 861 and 862
as shown below, leaving the TCP port assignments as is. IANA has
also updated the Assignee and Contact for these ports (both UDP and
TCP) to be the IESG and the IETF Chair, respectively.
+---------------+--------+-----------+------------------+-----------+
| Service | Port | Transport | Description | Reference |
| Name | Number | Protocol | | |
+---------------+--------+-----------+------------------+-----------+
| owamp-control | 861 | tcp | OWAMP-Control | RFC 4656 |
| owamp-test | 861 | udp | OWAMP-Test | RFC 8545 |
| | | | Receiver Port | |
| | | | | |
| twamp-control | 862 | tcp | TWAMP-Control | RFC 5357 |
| twamp-test | 862 | udp | TWAMP-Test | RFC 8545 |
| | | | Receiver Port | |
+---------------+--------+-----------+------------------+-----------+
8. References
8.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<https://www.rfc-editor.org/info/RFC 2119>.
[RFC 4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and
M. Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC 4656, September 2006,
<https://www.rfc-editor.org/info/RFC 4656>.
[RFC 5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and
J. Babiarz, "A Two-Way Active Measurement Protocol
(TWAMP)", RFC 5357, DOI 10.17487/RFC 5357, October 2008,
<https://www.rfc-editor.org/info/RFC 5357>.
[RFC 6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and
S. Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC 6335, August 2011,
<https://www.rfc-editor.org/info/RFC 6335>.
Morton & Mirsky Standards Track PAGE 8
RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
[RFC 7594] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
Aitken, P., and A. Akhter, "A Framework for Large-Scale
Measurement of Broadband Performance (LMAP)", RFC 7594,
DOI 10.17487/RFC 7594, September 2015,
<https://www.rfc-editor.org/info/RFC 7594>.
[RFC 8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC 8174,
DOI 10.17487/RFC 8174, May 2017,
<https://www.rfc-editor.org/info/RFC 8174>.
8.2. Informative References
[IPPM-TWAMP-06]
Hedayat, K., Krzanowski, R., Yum, K., Morton, A., and
J. Babiarz, "A Two-way Active Measurement Protocol
(TWAMP)", Work in Progress, draft-ietf-ippm-twamp-06,
December 2007.
[LarsAD] Eggert, L., "Subject: [ippm] AD review:
draft-ietf-ippm-twamp-06.txt", message to the ippm mailing
list, April 2008, <https://mailarchive.ietf.org/
rch/msg/ippm/LzcTPYhPhWhbb5-ncR046XKpnzo>.
[TimDISCUSS]
"Tim Polk's Ballot discuss", July 2008,
<https://datatracker.ietf.org/doc/RFC 5357/history>.
[TR-390] Broadband Forum, "TR-390: Performance Measurement from IP
Edge to Customer Equipment using TWAMP Light", Issue: 1,
May 2017, <https://www.broadband-forum.org/technical/
download/TR-390.pdf>.
Morton & Mirsky Standards Track PAGE 9
RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
Appendix A. Background on TWAMP Light
This informative appendix provides the background on the decision to
move the TWAMP Light idea to an informative appendix in [RFC 5357].
As also noted in Section 4, the TWAMP Light idea was relegated to
Appendix I of [RFC 5357] because it failed to meet the requirements
for IETF protocols (there are no specifications for negotiating this
form of operation and no specifications for mandatory-to-implement
security features), as described in the references cited below:
o Lars Eggert's Area Director review [LarsAD], where he pointed out
that having two variants of TWAMP (TWAMP Light and Complete TWAMP)
requires a protocol mechanism to negotiate which variant will be
used. Note that "Complete TWAMP" is called "Standards Track
TWAMP" in this document. See Lars's "Section 5.2, paragraph 0"
comment on [LarsAD], which refers to a section in [IPPM-TWAMP-06].
The working group consensus was to place the TWAMP Light
description in Appendix I and to refer to that appendix only as an
"incremental path to adopting TWAMP, by implementing the
TWAMP-Test protocol first."
o Tim Polk's "Ballot discuss" of 2008-07-16 [TimDISCUSS], which
points out that TWAMP Light was an incomplete specification
because the key required for authenticated and encrypted modes
depended on the TWAMP-Control Session key. Additional requirement
statements were added in Appendix I to address Tim's Ballot
discuss (see the last three paragraphs of Appendix I in
[RFC 5357]).
Since the idea of TWAMP Light clearly includes the TWAMP-Test
protocol and other undefined facilities, Appendix I of [RFC 5357]
simply describes ideas for how TWAMP-Test might be used outside of
the context of Standards Track TWAMP.
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RFC 8545 OWAMP/TWAMP Well-Known Ports March 2019
Acknowledgements
The authors thank the IPPM Working Group for their rapid review;
thanks also to Muthu Arul Mozhi Perumal and Luay Jalil for their
participation and suggestions.
Contributors
Richard Foote and Luis M. Contreras made notable contributions on
this topic.
Authors' Addresses
Al Morton (editor)
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
United States of America
Phone: +1 732 420 1571
Fax: +1 732 368 1192
Email: acmorton@att.com
Greg Mirsky (editor)
ZTE Corp.
Email: gregimirsky@gmail.com
Morton & Mirsky Standards Track PAGE 11
RFC TOTAL SIZE: 22389 bytes
PUBLICATION DATE: Tuesday, March 12th, 2019
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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