Subject: Re: [Sip] I-D: Preventing Fragmentation for Client Initiated Connections in the Session Initiation Protocol (SIP)

From: "Alan Bergmin" <[email-masked]>
Date: Sun, 7 Jan 2007 08:38:38 +0100

> The TCP connections are temporary, not permanent.
>
> I think that we can compare this to a HTTP server.  Even if I am
> constantly logged in slashdot.org, there is no permanent TCP connection
> between my browser and slashdot.org's HTTP server.  This is because it
> is more efficient to close the connection at the end of the transaction,
> and to open a new one when I click on reload.

Looking at most of exising web sites, I agree most of TCP connections
are temporary (ie: limited to the life of the HTTP transaction).
However for "dynamic" web sites like Gmail, there is a permanent TCP
connection reused for many HTTP transactions.

> So there is 3 possible combinations of transports for SIP; UDP alone,
> permanent TCP and UDP + temporary TCP.

As SIP is definitely closer to "dynamic web sites", I would rather
limit TCP cases to the "permanent TCP" case only and remove the "UDP +
temporary TCP" case.

Alan

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: Marc Petit-Huguenin <[email-masked]>
Date: Sun, 7 Jan 2007 09:09:30 +0100

> connection reused for many HTTP transactions.

Yes, an AJAX pattern tries to use a permanent connection to the server
and to use streaming to do not have to reload the data periodically.
This is explained here:

http://ajaxpatterns.org/HTTP_Streaming

This is the concerns in this document about the ability of a server to
manage a lot of permanent TCP connections that make me rethink the
assumption that permanent TCP connections for SIP was the definitive
solution.  After some prototyping and load testing, I concluded that it
was possible to use the hybrid TCP-UDP transport with an endpoint behind
a NAT, and that this solution was more scalable than the TCP-only solution.

-- 
Marc Petit-Huguenin
Home: [email-masked]
Work: [email-masked]

---

From: Cullen Jennings <[email-masked]>
Date: Sun, 14 Jan 2007 23:03:08 -0800

> connection reused for many HTTP transactions.

I'm running Safari to gmail and that does not seem to be true. It had  
a bunch of connections but they all seemed to close fairly quickly.  
Check it out and see if you get the same thing.

(I do agree with your meta point that AJAX is going to cause longer  
lived TCP connections).