Subject: [PCN] Architecture draft - PCN & ECN

From: <[email-masked]>
Date: Wed, 30 Jan 2008 11:49:40 -0000

Currently updating the architecture draft to reflect comments received.

In Section 3.5,other assumptions, currently says:

The following two assumptions apply if the PCN WG decides to encode
   PCN-marking in the ECN-field.
 
   o  It is assumed that PCN-nodes do not perform ECN, [RFC3168], on
      PCN-packets.
 
   o  If a packet that is part of a PCN-flow arrives at a PCN-ingress-
      node with its CE (Congestion experienced) codepoint set, then we
      assume that the PCN-ingress-node drops the packet.  After its
      initial Charter is complete, the WG may decide to work on a
      mechanism (such as through a signalling extension) that enables
      ECN-marking to be carried transparently across the PCN-domain.
 
There was some unresolved discussion about the 2nd bullet (downgrading
to best effort class was mentioned as another possibility), and more
generally the relationship of ECN & PCN. the issue also depends heavily
on the PCN encoding issue - I believe an update of that draft is about
to appear (today??)
 
So I'm proposing to replace the second bullet:
   o  If a packet that is part of a PCN-flow arrives at a PCN-ingress-
      node with its CE (Congestion experienced) codepoint set, then a
number of possibilities have been mentioned. The PCN-ingress-node could
drop the packet, or downgrade it to best effort, or it could encapsulate
the packet. Encapsulation would enable the ECN-marking to be carried
transparently across the PCN-domain, but may require an additional
mechanism (such as a signalling extension).
 
Hopefully the issue will get more discussion, but I think that's best
done in the context of the encoding draft.
 
phil 

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