Subject: RE: [Sipping] Loose Routing Proposal

From: "Roy, Radhika R, ALCTA" <[email-masked]>
Date: Fri, 14 Sep 2001 10:10:32 -0400

[MAG] The call signaling flows, for users 1 and 2, both roaming, will
comprise the following segments:

1. Visited network 1 -> Home network 1
2. Home network 1 -> Home network 2
3. Home network 2 -> Visited network 2

[RRR] Miquel's call flows (1, 2, 3) are straight forward. Can we have a
generalized solution in SIP for these flows?

[RRR] I guess that there may be an alternative to above flows as well. The
functions of the home network(s) are not the same as those of the visited
networks. That is, the home network(s) will need to supply all information
to the visited network(s) and will not remain in the call signaling path
once its function is completed.

My guess is that visited networks 1 and 2 need to have association so that
they can work directly for call signaling once the function of the home
networks are completed. For example, address resolution, authentication,
authorization, service association, etc. may need to be done in the home
network(s) and the said may need to be passed to the visited network 1 for
establishment of the call.

Will not the call flows look like this as follows?

1. Visited network 1 -> Home network 1 -> Home Network 2 

2. Home Network 2 -> Home Network 1 -> Visited Network 1 

3. Home network 2 -> Visited Network 2

Items 2 and 3 can go on in parallel.

(Now the visited network 1 has all the information [e.g., address resolution
and others] to complete the call directly with visited network 2)

4. Visited network 1 <-> Visited Network 2 (call signaling using SIP)

5. Media directly between Visited network 1 and Visited Network 2

If we agree that the call flows will be like above, items 1 2, and 3 may be
addressed by a separate protocol other than SIP.

Best regards,
Radhika R. Roy
[email-masked]

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From: "Miguel A. Garcia" <[email-masked]>
Date: Sun, 16 Sep 2001 17:23:31 +0300

> generalized solution in SIP for these flows?

[MAG] SIP offers a general solution for 2 and 3 above. However, to my
knowledge, SIP does not offer a solution for 1. I personally call 1 
"routing or caller", because proxy severs use the caller to route the
call to the caller's home network.

> once its function is completed.

No, home networks don't need to suply any informationt to the visited.
Particularly, services are executed in the home network. You don't need to
transfer any logic from home to visited. This is the main reason whay we
are doing all this staff.

On the other hand, there might be other reasons why the visited network
wants to stay in the path for future requests, for instace, if the visited
network is controlling the cost of the call by time or something similar, 
it may realy on the reception of a BYE. There might be other reasons as well.

> establishment of the call.

[MAG] Yes, these activities are done in the home network. To my knowledge, there
is not reason to pass any other information to the visited network.

> addressed by a separate protocol other than SIP.

[MAG] I am lost here. I thought my sentences in my previous e-mail summarized 
the call flows.

/Miguel

-- 
Miguel-Angel Garcia                     Oy LM Ericsson AB
                                        Jorvas, Finland
mailto:[email-masked]     Phone:  +358 9 299 3553
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