Subject: Re: [SPIRITS] INAP-SIP Interworking: Basic questions

From: [email-masked]
Date: Sat, 13 Apr 2002 15:57:54 +0530

>Hello,
>    In my understanding, the current focus of SPIRITS group is to provide
>the existing IN capabilities to
>SIP network.
>What about providing SIP services to existing SSPs.
>or hosting IN services in SIP environment (IP )?

>For the new implementations, I feel it is much easier to host services in
>SIP than installing new
>SCPs.  Is their any significant work being done in this direction.
>Is it wise to do so?
The Services provided in SCP are mainly network services providing the
number translation or controlling charging for the subscriber who
can be reached by anybody in the network. This (Number translation)
can be achieved using Redirect Server in SIP too. But there are some
services which are not request - response type. They typically require
the coordination between various entities in the network like Proxy Server
forking the INVITE request etc. Those are difficult to implement using SCP,
since it is mainly designed for Req-Resp services where resp is based on
data in database.

> One instance I found of such service is the Nortel-Telia implementation in
>the pre-spirits draft.
>In that example, the SIP server is being used as a Redirecting Server.
>However in case of providing support for mid call features, shouldn't a
>stateful SIP Proxy server is required?

Same as above

Regards
Dhiraj

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From: Igor Faynberg <[email-masked]>
Date: Sat, 13 Apr 2002 14:40:56 -0400

[email-masked] wrote:
>...
> services which are not request - response type.
>...

Precisely!  One example of such a service is network queing of calls
(something absolutely essential for the PSTN as it eliminates wasting of
circuits--and something that will, at certain point, become essential in
MPLS networks, for the same reason). 

Igor