Subject: [PCN] PCN modified charter and PCN BOF minutes uploaded

From: "Anna Charny \(acharny\)" <[email-masked]>
Date: Fri, 17 Nov 2006 13:19:31 -0500

Dear all, 

The draft PCN BOF minutes and the modified Draft Charter have now been
uploaded.  The modified draft charter is also attached below. 

The following is the summary of changes to the charter based on the
comments made during the PCN BOF and a later comment from Magnus about
manageability:

1) Replaced "SIP-controlled Admission and Preemption" by
"Application-controlled Admission and Pre-emption" where applicable.

2) Removed PWE3-related deployment model as the initial deployment model
of interest (this may be possibly revisited if a later re-chartering if
necessary)

3) Added the need for an applicability statement and related milestones

4) Replaced the assumption of "many flows on the bottleneck link" by
"sufficient flows on the bottleneck link"

5) Removed the explicit "real time traffic" assumption (leaving
"inelastic" only)

6) Added "MLPP" before "precedence-aware" for clarification of
Assumption 

7) Added the following clarification related to the trust assumption:

In particular, after re-chartering it's expected that the WG will cover
the case with multiple, non-trusting domains. However, even during the
initial standardization phase, this case needs to be kept in mind, as
the anti-cheating solution will have impact on e.g. the choice of
encoding.

8) Added an explicit statement that the WG will work with other groups
in the IETF and other standards bodies if appropriate

9) Added the need to work on/discuss manageability issues and related
milestones

10) made the milestones more specific (e.g. submit as an Informational
RFC rather that just "submit")

Please send your questions and comments!

Anna Charny and Scott Bradner
PCN BOF Chairs

-------------------------------------------------
PCN Draft Charter (Pre-Congestion Notification)
 
The PCN WG will tackle the problem of how to provide scalable, resilient

admission control and strong QoS assurance while using packet marking
techniques. 
Current attempts to deliver QoS using only packet marking (e.g.
DiffServ) are 
limited in the level of QoS assurance that can be provided without
substantial 
over-provisioning. To improve the QoS assurance, PCN will add flow
admission 
control and flow pre-emption. In normal circumstances admission control
should 
protect the QoS of previously admitted flows. In times of heavy
congestion 
(for example caused by route changes due to link or router failure)
pre-emption 
of some flows should preserve the QoS of remaining flows. While the WG
will 
address both admission and pre-emption, it is assumed that these
mechanisms can
be used independently of each other, and the use of one does not mandate
the
use of the other.  

The initial scope of the WG is the use of PCN within a single DiffServ
region. 
The overall approach will be based on a separation of functionality
between the 
interior routers and edge nodes of the DiffServ region. Interior routers
mark 
packet headers when their traffic is above a certain level, as an early
warning 
of incipient congestion ("pre-congestion"); this builds on concepts from

RFC 3168 "The Addition of Explicit Congestion Notification to IP". Edge
nodes 
of the DiffServ Region monitor the markings and that information is used
to 
make flow admission control and pre-emption decisions. The decisions
could be 
made by the edge nodes or by a centralized system (which is informed of
the 
edge nodes measurements). 

The WG will address the following specific problems and develop
standards 
track solutions to them:

1. When should an interior router mark a packet (i.e. at what traffic
level) 
   in order to give early warning of its own congestion?
2. How should such a mark be encoded in a packet (in the ECN and/or DSCP
fields)?
3. How should these markings (at packet granularity) be converted into 
   admission control and flow pre-emption decisions (at flow
granularity)?
 
To support this, the WG will work on the following Informational
documents:
1. a Problem Statement, to describe the problems the group is tackling 
   and the assumptions made
2. at least two deployment models, initially to help focus the problem
statement 
   and later to check that the solutions being developed satisfy the
deployment 
   scenario. Possible deployment models may be: 
   (a) IntServ over DiffServ (RFC2998): the DiffServ region is
PCN-enabled 
        and its edge nodes decide about admission and flow pre-emption
   (b) Application-controlled Admission and Pre-emption: routers within
       the DiffServ region are PCN-capable and trusted e.g. SIP
endpoints
       (gateway or host) perform admission and flow pre-emption.  
3. a generic analysis of the signaling extensions required to support
PCN. 
   Note that extensions/enhancements to specific signaling protocols 
   (e.g. RSVP, NSIS, SIP) will not be done in the PCN WG.
4. at least one example solution implementing the framework and its
performance 
   evaluation (e.g. simulation results), to provide evidence of the
viability 
   of the proposed standard in the proposed deployment models
5. an analysis of the tradeoffs of different encoding possibilities
(e.g. ECN 
   and DCSP marking)
6. an applicability statement (the decision on whether applicability
statement 
   will be delivered as a standalone document or will be incorporated
into other
   documents such as deployment models is TBD).
7. an analysis of the manageability issues of a PCN region
 
The initial scope of the WG will restrict the problem space in the
following ways:

1. By assuming the PCN-enabled Internet Region is a controlled
environment, 
   i.e. all the interior routers and edge nodes of the region run PCN
and 
   trust each other
2. By assuming there are sufficient flows on any relevant bottleneck
link in the 
   PCN-enabled region 
3. By focusing on the QoS assurance required by applications generating 
   inelastic traffic like voice and video requiring low delay, jitter
and 
   packet loss, i.e. as defined by the Controlled Load  Service
[RFC2211]. 
4. By keeping specific handling of emergency and other precedence (911,
GETS, 
   WPS, MLPP etc.) calls out of scope of the WG while (a) ensuring that
the edge
   nodes are not precluded from taking appropriate actions that may be
necessary
   for handling such calls and (b) assuming that PCN Internal Nodes may
not be
   MLPP precedence-aware but are DSCP aware.

Subsequent re-chartering may investigate solutions for when some of
these 
restrictions are not in place. 
In particular, after re-chartering it's expected that the WG will cover
the case with multiple, non-trusting domains. However, even during the
initial standardization phase, this case needs to be kept in mind, as
the anti-cheating solution will impact on e.g. the choice of encoding.
 
Topics out of scope for the WG include a general investigation of
admission 
control mechanisms. 

The WG will draw on the substantial prior academic and IETF work on 
measurement-based admission control.

The WG will work with relevant IETF WGs and, where appropriate, with
external groups.
 
Milestones:

Nov 2006          initial problem statement Internet Draft
Nov 2006          initial deployment models Internet Drafts
March 2007        initial router marking behavior (including encoding)
Internet Drafts
March 2007        initial flow admission control and pre-emption
mechanisms Internet Drafts
                  (including edge node measurements)
March 2007        initial applicability statement Internet Draft
March/July 2007   submit Problem statement to IESG for approval as
informational RFC
July 2007         submit deployment models to IESG for approval as
informational RFC
July 2007         submit applicability statement to IESG for approval as
informational RFC
                  (may be part of the deployment models)
July 2007         initial manageability issues document Internet Draft
Nov 2007          submit router marking behavior to IESG for approval as
standards track RFC
Nov 2007/Mar 2008 submit flow admission control and pre-emption
mechanism as standard track RFC
Nov 2007          initial signaling analysis Internet Draft 
Nov 2007          submit manageability issues document to IESG for
approval as informational RFC
Mar 2008          re-charter or close

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