Pseudowire Congestion Considerations
RFC 7893

Approval announcement
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From: The IESG <>
To: "IETF-Announce" <>
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Subject: Document Action: 'Pseudowire Congestion Considerations' to Informational RFC (draft-ietf-pals-congcons-02.txt)

The IESG has approved the following document:
- 'Pseudowire Congestion Considerations'
  (draft-ietf-pals-congcons-02.txt) as Informational RFC

This document is the product of the Pseudowire And LDP-enabled Services
Working Group.

The IESG contact persons are Alvaro Retana, Alia Atlas and Deborah

A URL of this Internet Draft is:

Technical Summary

 Pseudowires (PWs) have become a common mechanism for tunneling
traffic, and may be found in unmanaged scenarios competing for network
resources both with other PWs and with non-PW traffic, such as TCP/IP
flows. It is thus worthwhile specifying under what conditions such
competition is acceptable, i.e., the PW traffic does not significantly
harm other traffic or contribute more than it should to congestion. We
conclude that PWs transporting responsive traffic behave as desired
without the need for additional mechanisms. For inelastic PWs (such as
TDM PWs) we derive a bound under which such PWs consume no more
network capacity than a TCP flow. For TDM PWs, we find that the level
of congestion at which the PW can no longer deliver acceptable TDM
service is never significantly greater than this bound, and typically
much lower. Therefore, as long as the PW is shut down when it can no
longer deliver acceptable TDM service, it will never do significantly
more harm than even a single TCP flow. We propose employing a
transport circuit breaker to shut down a TDM PW that persistently
fails to comply with acceptable TDM service criteria.

Working Group Summary

 This draft was the result of one of the chartered work items in the
PWE3 WG, "Publish document outlining PW-specific congestion avoidance
and response guidelines." The process has been slow due to the
challenge of finding a set of authors that were both qualified and
willing to undertake the work in a thorough manner, and once they
volunteered, competing demands for their time and changes in thei
employment. The great majority of the work was done during the
lifetime of the PWE3 WG. It received a good set of comments during WG
LC, which have been included in the draft, and it is now ready for

Note that due to the use of modeling, simulations, and resulting color
graphs, the PDF version of this draft is the canonical version. 

Document Quality

This is informational, so there are no implementations. The draft
received a thorough set of reviews from both WG chairs during WG LC,
and I did another shepherd's review following WG LC comment resolution.

   Who is the Document Shepherd for this document?  Who is the 
   Responsible Area Director?  If the document requires IANA
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Andy Malis, Deborah Brungard