Subject: [SIP] Congestion control

From: Hidefumi Nakamura <[email-masked]>
Date: Fri, 22 Jun 2001 22:17:16 +0900

Hi. all,

I have a couple of questions about the suitable way to let the user agents/
proxy-servers know the congestion of sip-proxy(stateful) or location server, 
and the suitable action after the notification.

As long as I review the sip document (rfc2543bis-03), I think
the most suitable way is to return a "503 service unavailable" message
with "Retry-after" field.  Is is correct understanding?

The other question is of the case when the INVITE request comes via
several (stateful) proxy servers.  That is, INVITE comes through

UAa --> proxy A --> proxy B --> UAb

and proxy B is in congestion.

In this case, proxy B will return a "503" message to UserAgent-a (UAa)
via proxy A if my understanding of the first question is correct.   UAa
will postpone to send a message to proxy A, but what should "proxy A"
do if it receives other INVITE messages for proxyB, say, from UAc, within
the period indicated in "retry-after" field?
Should proxy-A send "503" to UAc or transfer the INVITE message
to proxy-B even if proxy-A already has the information that proxy-B
is in congestion?

Please let me know.

Thanks.

---
Hidefumi NAKAMURA
NTT Network Service Systems Laboratories
tel:+81 (422)59 3904; fax:+81 (422)60 4012
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From: Chandra Ravipati <[email-masked]>
Date: Fri, 29 Jun 2001 13:01:27 -0600

Hi,

I want to know how others are dealing with message segmentation for TCP. 

Do people use TPKT? or use Content-length: ?

Using "content-length" is very inefficient and very protocol specific. 
Why can't we use TPKT?

Thanks in advance for your participation in this discussion.
Chandra Ravipati.