Re: [Sip] I-D on handling large UDP responses

["Jeroen van Bemmel" <jbemmel at zonnet.nl>]

Three initial comments:

1) I would expect the main source of large responses to be the UAS sending a 
large response body. A transport switch does not necessarily imply that a 
large response will follow, in general I think those 140 responses will 
often be a waste of bandwidth. You could instead consider sending it just 
before the proxy is about to forward a response >MTU (1500 if unknown) over 
UDP, and then preferrably only when no 140/141 response from some downstream 
node was forwarded already (only possible to detect this for stateful 
proxies).

2) The current draft can result in cases where both a 140 and a 141 response 
are sent, this seems wasteful. When the UAS sends a response >1500 bytes 
over non-UDP, it does not necessarily imply that there will be a response 
>1500 bytes using UDP at some point. So if the proxy forwarding rule is 
changed per (1)above, the UAS should only send a 141 when it is sending over 
UDP itself (i.e. no inspection of the via chain needed). If there is a 
transition to UDP in the path beyond, a proxy will send 140 instead. This 
avoids duplicate 140/141 responses

3) Given the above, it could probably be done with only 1 response code. 
Proxies should then set the to-tag to the to-tag of the large response

Regards,

Jeroen

----- Original Message ----- 
From: "Vijay K. Gurbani" <vkg at lucent.com>
To: "IETF SIP List" <sip at ietf.org>
Sent: Tuesday, October 03, 2006 8:45 PM
Subject: [Sip] I-D on handling large UDP responses


> Folks: An I-D on handling large UDP response has just been
> submitted to the I-D editor.  Until it appears in the archives, a
> copy can be obtained from:
>
> http://scm.sipfoundry.org/rep/ietf-drafts/gurbani/large-udp-response/draft-gurbani-sip-large-udp-response-00.txt
> http://scm.sipfoundry.org/rep/ietf-drafts/gurbani/large-udp-response/draft-gurbani-sip-large-udp-response-00.html
>
> The draft suggests the use of 1xx-class responses to solve this
> problem.
>
> Please look at the draft and provide comments and/or concerns.
>
> Thank you.
>
> - vijay
> --
> Vijay K. Gurbani  vkg at {lucent.com,research.bell-labs.com,acm.org}
> Bell Laboratories, Lucent Technologies, Inc.
> 2701 Lucent Lane, Rm. 9F-546, Lisle, Illinois 60532 (USA)
>
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