Re: WG Review: Congestion and Pre-Congestion Notification (pcn)

On Feb 19, 2007, at 5:19 AM, Pekka Savola wrote:
> I'd like to see it explicitly stated that transporting congestion  
> information in the (metered) IP packets themselves is out of scope.  
> This should exclude designs such as adding IP options en-route,  
> defining new extension headers, or modifying the packets in any,  
> currently undefined way.  (I say this explicitly because based on a  
> very quick look at the mailing list archives I saw discussion  
> relating to IP header encoding and it unnerved me.)

I dunno, I think that horse is out of the barn. In the TCP arena, the  
XCP and RCP proposals and RFC 3168 could each be described in those  
terms, and the pre-congestion notification proposals on the table all  
encode congestion information in the IP packets, mostly in the ECN  
field. I'll agree that they should not attempt to insert things into  
the packet (add an option), but using space already set aside in the  
packet needs to be on the table.

I would like to see some crossover between the TCP/SCTP congestion  
control proposals and the real-time pre-congestion proposals. That's  
not a matter of declaring something out of scope as much as it is to  
encourage thoughtful (and not knee-jerk) consideration of whether and  
how the two types of needs can be met.

The drafts I know to be relevant (you'll note that some are in pwe) are:

http://tools.ietf.org/html/draft-babiarz-pcn-sip-cap
   "SIP Controlled Admission and Preemption", Jozef Babiarz, 16-Oct-06,
   <draft-babiarz-pcn-sip-cap-00.txt>

http://tools.ietf.org/html/draft-briscoe-tsvwg-cl-architecture
   "An edge-to-edge Deployment Model for Pre-Congestion Notification:  
Admission
   Control over a DiffServ Region", Bob Briscoe, 25-Oct-06,
   <draft-briscoe-tsvwg-cl-architecture-04.txt>

http://tools.ietf.org/html/draft-briscoe-tsvwg-cl-phb
   "Pre-Congestion Notification marking", Bob Briscoe, 22-Oct-06,
   <draft-briscoe-tsvwg-cl-phb-03.txt>

http://tools.ietf.org/html/draft-briscoe-tsvwg-re-ecn-tcp
   "Re-ECN: Adding Accountability for Causing Congestion to TCP/IP", Bob
   Briscoe, 26-Oct-06, <draft-briscoe-tsvwg-re-ecn-tcp-03.txt>

http://tools.ietf.org/html/draft-chan-pcn-problem-statement
   "Pre-Congestion Notification Problem Statement", Kwok Ho Chan, 25- 
Oct-06,
   <draft-chan-pcn-problem-statement-01.txt>

http://tools.ietf.org/html/draft-davie-ecn-mpls
   "Explicit Congestion Marking in MPLS", Bruce Davie, 19-Oct-06,
   <draft-davie-ecn-mpls-01.txt>

http://tools.ietf.org/html/draft-ietf-pwe3-congestion-frmwk
   "Pseudowire Congestion Control Framework", Stewart Bryant, 2-Feb-07,
   <draft-ietf-pwe3-congestion-frmwk-00.txt>

http://tools.ietf.org/html/draft-rosen-pwe3-congestion
   "Pseudowire Congestion Control Framework", Eric Rosen, 19-Oct-06,
   <draft-rosen-pwe3-congestion-04.txt>

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