Subject: [Sip] SIP Congestion Control

From: [email-masked]
Date: Wed, 31 Jul 2002 16:34:51 +0100

Hi,

Does SIP support congestion/flow control methods during application level
processing overload? (e.g. something equivalent to ISUP's ACC)

This is typically for scenarios where there could be a burst of calls (possibly
due to some media stimulated event) and hence a burst of SIP messages. The
target of these messages could either be a proxy server, voicemail server or
some other media server.

I am assuming there are sufficient resources in the IP network and no packets
will be dropped.

From going through RFC3261 SIP seems to rely on the congestion controls of the
transport protocols.
draft-willis-sip-congestsafe-00.txt also seems to address the case where a
transport network protocols like TCP and SCTP provide feedback control.

Thanks,
Amish

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---

From: "Naidu, Venkata" <[email-masked]>
Date: Wed, 31 Jul 2002 12:27:49 -0400

Amish,

-> I am assuming there are sufficient resources in the IP 
-> network and no packets will be dropped.

  Then where is the congestion in the network?
 
-> From going through RFC3261 SIP seems to rely on the 
-> congestion controls of the
-> transport protocols.
-> draft-willis-sip-congestsafe-00.txt also seems to address 
-> the case where a
-> transport network protocols like TCP and SCTP provide 
-> feedback control.

  I don't think congestion control, flow control methods
  are required in session/application level protocols
  when they depend on well tested, extensively reserached
  transport protocols (like TCP and respective extensions).

  Looks like every higher layer protocols are trying to
  solve their own congetion/flow control. Yes! I agree
  that there must be some corner cases where you can
  optimize/improve protocols (like SIP, BGP etc) when there 
  is much stress. But the problems you are trying to solve
  are very corner cases when you implement congestion/flow
  control in SIP, BGP etc

  I feel that this is duplicate work unless SIP is going
  achieve good preformance improvement with it's own
  congestion/flow control mechanisms when compared to
  best TCP extension(s).

--
Venkata.

---

From: [email-masked]
Date: Wed, 31 Jul 2002 13:05:15 -0400

Wouldn't this sort of load shedding or load balancing issue be best dealt
with at the application and not the protocol layer.

[email-masked]@ietf.org on 07/31/2002 11:34:51 AM

Sent by:  [email-masked]

To:   [email-masked]
cc:
Subject:  [Sip] SIP Congestion Control

Hi,

This is typically for scenarios where there could be a burst of calls
(possibly
due to some media stimulated event) and hence a burst of SIP messages. The
target of these messages could either be a proxy server, voicemail server
or
some other media server.

I am assuming there are sufficient resources in the IP network and no
packets
will be dropped.

From going through RFC3261 SIP seems to rely on the congestion controls of
the
transport protocols.
draft-willis-sip-congestsafe-00.txt also seems to address the case where a
transport network protocols like TCP and SCTP provide feedback control.

Thanks,
Amish

Important.
Confidentiality: This communication is intended for the above-named person
and
may be confidential and/or legally privileged. Any opinions expressed in
this
communication are not necessarily those of the company. If it has come to
you
in error you must take no action based on it, nor must you copy or show it
to
anyone; please delete/destroy and inform the sender immediately.

Monitoring/Viruses
Orange may monitor all incoming and outgoing emails in line with current
legislation.  Although we have taken steps to ensure that this email and
attachments are free from any virus, we advise that in keeping with good
computing practice the recipient should ensure they are actually virus
free.

Orange PCS Limited is a subsidiary of Orange SA and is registered in
England No
2178917, with its address at St James Court, Great Park Road, Almondsbury
Park,
Bradley Stoke, Bristol BS32 4QJ.
*******************************************************************************