Subject: [PCN] updated PCN draft charter and drafts

From: "Anna Charny \(acharny\)" <[email-masked]>
Date: Tue, 24 Oct 2006 15:19:05 -0400

Dear all,

Below is an updated proposed charter for the discussion at the PCN BOF
in San Diego.

Also,  a quick update on PCN-related draft activities:  the following
drafts related to PCN work have recently been updated and/or posted for
the first time:

draft-chan-pcn-problem-statement-01.txt  (this is PCN Problem Statement)
draft-briscoe-tsvwg-cl-architecture-04.txt (this is PCN architecture)
draft-briscoe-cl-phb-03 (this is PCN marking)
draft-babiarz-pcn-sip-cap-00 (this is Sip-controlled Admission and
Preepmtion)
draft-zhang-pcn-performance-evaluation-00.txt (this is PCN simulation
draft)
draft-charny-pcn-single-marking-00.txt (this is about using single
marking for PCN admission and pre-emption)

Comments on all of these are welcome!

Regards,
Anna
---------------------

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) SIP Controlled Admission and Preemption: routers within the
DiffServ region are PCN-capable and trusted SIP endpoints (gateway or
host) perform admission and flow pre-emption  
   (c) Pseudowire: PCN may be used as a congestion avoidance mechanism
for end-user deployed pseudowires (collaborate with the PWE3 WG)

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)

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 many flows on any bottleneck link in the
PCN-enabled region 

3. By focusing on the QoS assurance required by real time 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 precedence-aware but are DSCP aware. 

Subsequent re-chartering may investigate solutions for when some of
these 
restrictions are not in place. 

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. 

Milestones

Nov 2006          initial Problem statement
Nov 2006          initial deployment models
March 2007        initial router marking behavior (including encoding)
March 2007        initial flow admission control and pre-emption
mechanism (including edge node measurements)
March/July 2007   submit Problem statement
March/July 2007   submit deployment models
Nov 2007          submit router marking behavior
Nov 2007/Mar 2008 submit flow admission control and pre-emption
mechanism
Nov 2007          initial signaling analysis
Mar 2008          re-charter or close

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