[Sipping] Queries and comments on draft-hilt-sipping-overload-00.txt

["Darshan Bildikar" <[e-mail]>]

1) How does this document relate to
"draft-rosenberg-sipping-overload-reqs-01"? Does it take into cognisance the
requirements defined in this document? 

2) It is envisioned that overload information is exchanged through a header
in response messages. Why not a more EXPLICIT mechanism like
SUBSCRIBE/NOTIFY? Define an event package for overload and define a body
that can be used to indicate a rich set of overload parameters to the
upstream entity. 

3) The draft talks about overload w.r.t certain resources. If a sub/not
mechanism was used, it would allow overload control to be more "fine
grained". For example, the SUBSCRIBE message would indicate what resource
the requester is wants the overload throttling and statistics for. 

A use case that I can think of 

I have two applications on my box; CRBT and video conferencing. I might be
fast running out of ports for video conferencing but might still be able to
do CRBT at 100%. I should be able to control the load based on the REQUEST
URI. 

I'm thinking that the SUBSCRIBE shall indicate, "Give me overload statistics
as if I were sending you this REQUEST URI". I'm assuming that a request URI
maps to a "resource" but there could be a better way this could be done. 

This mechanism would help throttling based on SIP method, URI, host, port
etc and will be able to support REQ 18 defined in
draft-rosenberg-sipping-overload-reqs-01". 

Two things that I haven't really thought through.

1) Throttling based on codecs and media lines would be useful. For example,
I can support audio right now, but NOT video. 
2) Is it possible to make this mechanism more generic? It is after all a
throttling mechanism and could be applied to domains OTHER than overload
control. For example, Tele voting applications where an application server
indicates filtering to a switch i.e. "Notify every 100'th INVITE to me"

BR,
Darshan


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