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[802SEC] FW: [New-work] WG Review: Congestion and Pre-Congestion Notification(pcn)

WG Chairs, 

The following announcement from the IETF may be of interest to your WG


-----Original Message-----
From: IESG Secretary [] 
Sent: Tuesday, February 13, 2007 3:50 PM
Subject: [New-work] WG Review: Congestion and Pre-Congestion

A new IETF working group has been proposed in the Transport Area.  
The IESG has not made any determination as yet.  The following draft
charter was submitted, and is provided for informational purposes only.
Please send your comments to the IESG mailing list ( by
February 19th.


Congestion and Pre-Congestion Notification (pcn)

Current Status: Proposed Wroking Group


Transport Area Director(s):
Magnus Westerlund <> Lars Eggert

Transport Area Advisor:
Lars Eggert <>

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General Discussion:
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In Body: (un)subscribe Archive:

Description of Working Group:

The Congestion and Pre-Congestion Notification (PCN) working group
develops mechanisms to protect the quality-of-service of established
inelastic flows within a DiffServ domain when congestion is imminent
or existing. These mechanisms operate at the domain boundary, based
on aggregated congestion and pre-congestion information from within
the domain. The focus of the WG is on developing standards for the
marking behavior of the interior nodes and the encoding and transport
of the congestion information. To allow for future extensions to
the mechanisms and their application to new deployment scenarios,
they are logically separated into several components, namely,
encoding and transport along forward path from marker to egress,
metering of congestion information at the egress, and transport of
congestion information back to the controlling ingress. Reaction
mechanisms at the boundary consist of flow admission and flow
termination. Although designed to work together, flow admission and
flow termination are independent mechanisms, and the use of one
does not require or prevent the use of the other. The WG may produce
a small number of informational documents that describe how specific
quality-of-service policies for a domain can be implemented using
these two mechanisms.

The PCN WG will specify the following components to protect the
quality-of-service of flows within a DiffServ domain:

(1) a general architecture for flow admission and termination
based on aggregated (pre-)congestion information

(2) a specification of conditions under which interior nodes
generate (pre-)congestion information

(3) encoding and transport of (pre-)congestion information
between the interior and domain egress

(4) metering of (pre-)congestion information at the domain egress

(5) encoding and transport of (pre-)congestion information
between the egress and the controlling domain ingress

(6) ingress node control mechanisms for flow admission or
termination, based on aggregated (pre-)congestion information

The WG focuses on the overall architecture, and specifically on the
marking behavior and encoding and transport mechanisms needed to
realize it. Standards-track protocols and mechanisms are only
developed where necessary for interoperability. For other components
of the architecture, the WG may document examples or provide
recommended solutions in informational documents. The architecture
document will be comprehensive, and include security, manageability
and operational considerations. If this WG requires extensions or
modifications to protocols that are products of other WGs, it may
motivate their need and describe requirements in informational
documents; design of such extensions and modifications will take
place in the appropriate WGs.

The initial scope of the PCN WG is restricted by the following

(A) these components are deployed in a single DiffServ domain,
where all boundary and interior nodes are PCN-enabled and
mutually trust each other

(B) all flows handled by these mechanisms are inelastic and
constrained to a known maximum rate through policing or

(C) the number of flows across any potential aggregation bottleneck
is sufficiently large for stateless, statistical mechanisms
to be effective

(D) flows may have different precedence, but the applicability
of the PCN mechanisms for emergency use (911, GETS, WPS,
MLPP, etc.) is out of scope

After completion of the initial phase, the PCN WG may re-charter
to develop solutions for scenarios where some of these restrictions
are not in place. It may also re-charter to consider applying the
PCN mechanisms to additional deployment scenarios (operation over
concatenated DiffServ domains, PCN-aware application mechanisms,
etc.). The WG may also consider to investigate additional response
mechanisms that act on (pre-)congestion information. One example
could be flow-rate adaptation (rather than flow admission/termination)
during times of congestion. The details of these work items are
outside the scope of the initial phase; but the WG may consider
their requirements to design components that are sufficiently general
to support such extensions in the future.

Goals and Milestones:

Nov 2007 Flow Admission and Termination Architecture (Informational)

Nov 2007 Survey of Encoding and Transport Choices of (Pre-)Congestion
Information within a DiffServ Domain (Informational)

Mar 2008 Flow Admission and Termination within a DiffServ Domain

Mar 2008 (Pre-)Congestion Detection within a DiffServ Domain
(Proposed Standard)

Mar 2008 Requirements for Signaling of (Pre-)Congestion Information
from Egress to Ingress in a DiffServ Domain (Informational)

Jul 2008 Encoding and Transport of (Pre-)Congestion Information
from within a DiffServ Domain to the Egress (Proposed

Nov 2008 Encoding and Transport of (Pre-)Congestion Information
from the Domain Egress to the Ingress (Proposed Standard)

Jul 2008 Suggested Flow Admission and Termination Boundary
Mechanisms (Informational)

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