Subject: [Sipping] comments on draft-shen-sipping-load-control-event-package

From: Jonathan Rosenberg <[email-masked]>
Date: Sun, 27 Jul 2008 20:55:03 -0400

A few comments on this draft:

* a think a bit more discussion is needed on how this is different from 
the work being done by Volker and the overload team. Clearly there is 
amount of overlap, in that both mechanisms attempt to work to reduce 
overall network congestion during periods of load. The mechanism here is 
much more policy-centric, and targeting the specific case where load is 
directed to a particular number. However, with a sufficiently general 
policy, could this not be used as an alternative feedback mechanism 
between a proxy and its upstream neighbor, to reduce the load on all 
traffic?

On the other hand, a more complementary way of thinking about them, is 
that when the overload mechanism ala draft-hilt-* indicates to an 
upstream proxy, 'hey, I'm overloaded, please reduce by 20%', now that 
proxy needs to make a POLICY decision about which traffic to discard to 
achieve said goal. Though it could randomly throw away traffic to 
achieve it, another approach would be to selectively discard traffic 
based on priorities. draft-shen could be thought of as a way to 
distribute those policies, directing a proxy how to discard traffic when 
the overload mechanism suggests its needed. I don't think thats quite 
your formulation, but if it was done that way it would make them clearly 
complementary.

* The draft talks about each proxy needing to subscribe to the package 
from its neighbors. I don't see how this works when the topology is such 
that requests could loop around, so that a particular proxy can be both 
an upstream and downstream neighbor

* some more discussion of use cases would be good; defining the 
parameters of the xml doc would really depend on understanding what kind 
of things are useful to use to as criteria for determining which traffic 
to discard

Thanks,
Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   499 Thornall St.
Cisco Fellow                                   Edison, NJ 08837
Cisco, Voice Technology Group
[email-masked]
http://www.jdrosen.net                         PHONE: (408) 902-3084
http://www.cisco.com
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