Subject: Handover between two SIP servers

From: Daniel Floreani <[email-masked]>
Date: Mon, 23 Aug 1999 16:05:18 +0930

I am working on the issue of integrating the SIP protocol architecture
into the Mobile IP architecture, with special interest in Mobile IP
for Radio Access networks. 

I have made the following assumptions:

1> there is a SIP server in every Local Serving Function (LSF). This
means
that a SIP server manages the calls for a certain number of Radio access
networks.

2> the SIP server and the MobileIP Serving Mobility Manager interact
closely 
to update and/or find the mobile IP users current location.

3> the SIP server acts in proxy mode, not redirection mode.

So far, I think I have been sucessful in creating procedures for
registration, 
registration update after mobile IP handover, and call maintenance
after MIP handover within the same LSF. I have struck problems with
maintaining
a call if the Mobile user wishes to handover to a new LSF, and hence a 
new SIP server.

So in summary, my question is - is there a mechanism within SIP to allow
a 
SIP server, acting as a proxy to hand over to another SIP server, while
keeping
the current SIP session active.

thanks
daniel floreani
Email:[email-masked]

---

From: Henning Schulzrinne <[email-masked]>
Date: Mon, 23 Aug 1999 20:32:40 -0400

> for Radio Access networks.

I'm not quite sure what you mean by a "SIP session" below. The proxy
server usually doesn't see a session, just transactions, so it can't
hand over a session. A SIP server could "lie" in a Record-Route to force
the next request to go to a different server, but I don't think it
accomplishes what you'd like to do.

You might also want to take a look at the WoWMoM paper on SIP mobility;
see http://www.cs.columbia.edu/~hgs/sip/papers.html for a somewhat
different solution.

-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs