RFC 5357, "A Two-Way Active Measurement Protocol (TWAMP)", October 2008

Note: This RFC has been updated by RFC 5618, RFC 5938, RFC 6038, RFC 7717, RFC 7750, RFC 8545

Errata ID: 3511
Status: Rejected
Type: Editorial
Publication Format(s) : TEXT
Reported By: Steve Baillargeon
Date Reported: 2013-03-08
Rejected by: Martin Stiemerling
Date Rejected: 2015-07-16

Section Appendix says:

              controller                              responder
          +-----------------+                   +-------------------+
          |     Server      |<----------------->|                   |
          | Control-Client  |                   | Session-Reflector |
          | Session-Sender  |<--TWAMP-Test----->|                   |
          +-----------------+                   +-------------------+

   This example provides a simple architecture for responders where
   their role will be to simply act as light test points in the network.
   The controller establishes the test session with the Server through
   non-standard means.  After the session is established, the controller
   transmits test packets to the responder.  The responder follows the
   Session-Reflector behavior of TWAMP as described in section 4.2 with
   the following exceptions.

   In the case of TWAMP Light, the Session-Reflector does not
   necessarily have knowledge of the session state.  IF the Session-
   Reflector does not have knowledge of the session state, THEN the
   Session-Reflector MUST copy the Sequence Number of the received
   packet to the Sequence Number field of the reflected packet.  The
   controller receives the reflected test packets and collects two-way
   metrics.  This architecture allows for collection of two-way metrics.

It should say:

              controller                              responder
          +-----------------+                   +-------------------+
          |     Server      |                   |                   |
          | Control-Client  |                   | Session-Reflector |
          | Session-Sender  |<--TWAMP-Test----->|                   |
          +-----------------+                   +-------------------+

   This example provides a simple architecture for responders where
   their role will be to simply act as light test points in the network.
   The controller establishes the test session with the Server through
   non-standard means.  After the session is established, the controller
   transmits test packets to the responder. Other examples are also
   possible. For instance, the responder may include a light Server
   responsible to instantiate the test session states based on the
   received test packets. The responder follows the Session-Reflector
   behavior of TWAMP as described in section 4.2 with the following
   exceptions.

   In the case of TWAMP Light, the Session-Reflector does not
   necessarily have knowledge of the session state.  IF the Session-
   Reflector does not have knowledge of the session state, THEN the
   Session-Reflector MUST copy the Sequence Number of the received
   packet to the Sequence Number field of the reflected packet.  The
   controller receives the reflected test packets and collects two-way
   metrics. This architecture allows for collection of two-way metrics.
   Otherwise IF the Session- Reflector has knowledge of the session
   state (using inspection of the received test packets for instance),
   THEN the Session-Reflector MUST generate it is own sequence number
   for each reflected packet.  The controller receives the reflected
   test packets and collects two-way and one-way metrics.  This
   alternative allows for collection of two-way and one-way metrics with
   TWAMP Light.

Notes:

Many readers of the appendix don't understand the meaning of informative and try to interpret the TWAMP light description as a specification. To correct this problem, it is recommended to add a few more lines explaning other TWAMP light architectures are possible. The original text describes a single TWAMP light architecture and this is misleading.
--VERIFIER NOTES--
Erratas are not meant to be used to expand existing text beyond textual clarifications.

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