Subject: [SPIRITS] Re: O_BCSM/T_BCSM

From: "Vijay K. Gurbani" <[email-masked]>
Date: Wed, 22 May 2002 13:11:29 -0500

Vijaya Venkatachalam wrote:
> Hi Vijay,
> 
> I have a basic question.
> When a SIP INVITE is received by a SIN Enabled SIP Entity,
> how do we know whether to trigger the O_BCSM or the
> T_BCSM.

Both the O_BCSM and T_BCSM state machines will be initialized in any
SIN entity (mirroring equivalent processing in the PSTN).  The
question is when to execute services based on these state machines.
For that, it all depends on the context.  If the SIN entity is serving
the role of a default outbound proxy, O_BCSM applies, for instance.
If on the other hand, a SIN entity gets an INVITE and the address-of-
record matches, then T_BCSM applies.

Thus, for example, take the well known SIP trapezoid:

          P1-----------------P2
          /                   \
         /                     \
        UAC                   UAS

with P1 and UAC being in domain A and P2 and UAS being in domain B.
Then, a request from UAC to P1 (INVITE UAS@B) will get O_BCSM services
from P1 and the same request will get T_BCSM services at P2 (since the
address-of-record matches).

BTW, SPIRITS is probably not the best place to ask SIN questions; the
SIN design team uses a mailing list for this purpose.  By all means,
send me private email on SIN questions, and I will answer them,
CC'ing the mailing list.  If you would like to contribute to other
SIN deliverables, please let me know as well (we really need people
here...).

Best regards,

- vijay
-- 
Vijay K. Gurbani  vkg@{lucent.com,research.bell-labs.com,acm.org}
Wireless Networks Group/Internet Software and Services
Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
Naperville, Illinois 60566     Voice: +1 630 224 0216

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