Subject: guaranteed delay & reshaping/policing

From: [email-masked] (John Krawczyk)
Date: Wed, 28 Feb 96 16:28:57 EST

A few comments/questions on the reshaping/policing aspects of
Guaranteed:

   reshaping points (reshaping points are defined below)

The text says this twice, but there is never any formal definition of
a reshaping point.  It also never says when or why a particular node
would designate itself as a reshaping point.  Does this just map to
the policing points?

   Inside the network, this approach does not produce the desired
   results, because queueing effects will occasionally cause a flow's
   traffic that entered the network as conformant to be no longer
   conformant at some downstream network element.  Therefore, inside the
   network, service elements must reshape traffic before applying the
   token bucket test.  Reshaping entails delaying packets until they are
   within conformance of the TSpec.

I think this confirms that policing nodes and reshaping nodes are one
and the same.  If so, we should explicitly say that.

   regulator should start with its token bucket full of tokens).  Under
   guaranteed service, the amount of buffering required to reshape any
   conforming traffic back to its original token bucket shape is
   b+Csum+(Dsum*r), where Csum and Dsum are the sums of the parameters C
   and D between the last reshaping point and the current reshaping
   point.

This only addresses the distinct reservation scenario (one sender, one
reservation).  We need some text here to say what happens if this is a
shared reservation and the router is at a source branch point (i.e.,
when you have to take multiple Tspecs into account, and the sum of the
Tspec rates may be less than the clearing rate).

-jj