Subject: RE: AW: [Sipping] 3G entities: Proxy or B2BUA?

From: "Roy, Radhika R, ALCTA" <[email-masked]>
Date: Fri, 26 Oct 2001 15:24:28 -0400

inline [RRR] ...

-----Original Message-----
From: Bert Culpepper [mailto:[email-masked]]
Sent: Friday, October 26, 2001 2:31 PM
To: Roy, Radhika R, ALCTA; [email-masked];

I see the discussion moving from a proxy sending a BYE to proxies
subscribing to and notifying each other, all to support a network
initiated termination requirement.

[RRR] Per SIP rule, a SIP Proxy cannot send BYE requests.

Just to be clear, as soon as a SIP proxy generates *any* SIP request it
is no longer a SIP proxy by definition.

[RRR] Not necessarily. For example, SUBSCRIBE/NOTIFY can be sent by UAs or
SIP Proxies equally.

So let the p-CSCF, s-CSCF, x-CSCF send a BYE when it wants to and be done
with it. 

[RRR] Again, per SIP rule, a proxy cannot send BYE requests.

It is only *not* a SIP proxy for that one SIP transaction.  

[RRR] So, it breaks the SIP rule as a proxy. It has to be a UA.

No changes to the SIP spec are required and this behavior breaks nothing in
the SIP network.

[RRR] A proxy does break the SIP rule, if it sends BYE requests. But a proxy
behaving as B2BUA can send the BYE request.

Maybe I'm missing something here and simplifying too much.  If so, I
apologize :(

Regards,
Bert

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---

From: "Miguel A. Garcia" <[email-masked]>
Date: Sat, 27 Oct 2001 13:12:23 +0300

Yeap, I agree with Radhika.

A SIP proxy cannot asynchronosly generate any message that belongs
to an existing call leg (sorry, dialog according to the new terminology).

When a proxy is sending a SUBSCRIBE or NOTIFY, the dialog is different,
and it is acting as a UA for that purpose.

/Miguel

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Miguel-Angel Garcia                     Oy LM Ericsson AB
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