Subject: RE: [Sipping] Q.931 and SIP-T

From: Juan Luis Esteban <[email-masked]>
Date: Tue, 29 Oct 2002 15:12:59 +0100

To follow up with the previous question:

1- Does the SIP community feel that a UNI protocol is not a SIP peer and
therefore interworking should not be addressed ? 
2- Is it necessary to address SIP-Q.931 taking into account that it could be
seen as 2 Interworking functions: SIP-ISUP/ISUP-Q931 ?.

Regards,

Is there any work in progress regarding Q.931-SIP Interworking ?.
Since ISUP-SIP interworking has been addressed, is there any reason for
which QSIG and DSS1 interworking has not been addressed ?.
I would think that since Q.931 is an asymmetrical protocol, its interworking
with SIP is not as straightforward as ISUP. Nevertheless, mapping at the
message level is still possible. At a first glance, messages such as Call
proceeding and Connect Ack could be generated locally, it would be
unnecessary to encapsulate them in SIP. Different behaviours should be also
taken into account depending on whether the PRI Gateway is User or
Network...

In practice, Tier 2 and 3 service providers have been deploying low density
PRI gateways where possible due to lower costs than SS7 Gateways, even in
associated signalling scenarios. 

Thanks,

Juan Luis Esteban
Capcom International

[email-masked]
Tel.: +34 91 217 00 04
Fax: +34 91 217 00 19

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Sipping mailing list  https://www1.ietf.org/mailman/listinfo/sipping
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Use [email-masked] for questions on current sip
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From: Rohan Mahy <[email-masked]>
Date: Wed, 30 Oct 2002 12:19:11 -0800

> therefore interworking should not be addressed ?

Personally I feel that the UNI/NNI distinction is irrelevant in the SIP 
world, so AFAIK that is not the reason for slow progress on the topic. 
Currently there are dozens of working, interoperable implementations of 
SIP to ISDN gateways.  The lack of a formal document describing this 
mapping has not been a hindrance thusfar, unlike the ISUP case where 
there were fundamental philosophical differences that needed to be 
addressed.  As I said on this list and in Yokohama (my comments 
were/are as an individual contributor), I do not feel that basic ISDN 
and QSIG is compelling because it is straightforward and lots of people 
have gotten it right without assistance; however, I think it would be 
*very* useful to describe interworking of QSIG supplementary services 
with SIP primitives such as REFER, Replaces, the message-summary 
package, the dialog event package, etc.

thanks,
-rohan

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From: Ranjith Mukundan <[email-masked]>
Date: Thu, 31 Oct 2002 10:10:45 +0530

> addressed.

[ranjith]
i dont think any of the 'interoperable implementations' address anything much
beyond the interworking of the basic setup, call proc, alerting and release.
also, i dont think any of these gateways are  deployed for end to end basic
call/service delivery for scenarios such as line - pri - sip - pri - line.
most deployments, i would assume, are just one-hop scenarios - i.e.,
line-pri-sip(ua). The end to end scenarios has its obvious deployment
advanatage - esp, to levarage the legacy access installed in enterprises
whilst using the company wan OR via VPNs to route the call "on-net" till a
far-end break out occurs back to PSTN.

> As I said on this list and in Yokohama (my comments
> have gotten it right without assistance;

[ranjith]
as i said, it would be only to a limited extent

> however, I think it would be

[ranjith]
that would be very useful indeed.