Subject: RE: [Sipping] Service Identification in SIP

From: "Atle Monrad \(GR/ETO\)" <[email-masked]>
Date: Tue, 20 Feb 2007 16:05:56 +0100

Paul

by the way, it would be useful to get this discussion on the sipping
list.

As a service is defined in terminals and possibly in application
servers, the interoperability on the service level are between the
terminals and the ASs that have implemented the service while
interoperability on the protocol level is something very different.
Please tell me which interop that is your concern
 
I do not see any interoparability, if you do, it would be useful that
you share it. 

Terminals may have different services and may not be interoperable in
all aspects, but isn't this just facts that is hard to get around? A PoC
terminal can only talk PoC to other PoC terminals for the PoC service
but it can communicate with other terminals aswell, right?  

/atle

FYI, GSMA consists of 700 operators. When GSMA give their
recommendations, it would be useful to listen and at least give some
technical feeback and not this kind of political statement. 

-----Original Message-----
From: Paul Kyzivat [mailto:[email-masked]] 
Sent: 20. februar 2007 15:31
To: Atle Monrad (GR/ETO)
Cc: Gonzalo Camarillo (JO/LMF); sipping; Mary Barnes
Subject: Re: [Sipping] Service Identification in SIP

Atle Monrad (GR/ETO) wrote:

> On the interoperability, I would just like to add that during 
> discussions in 3GPP, interoperability has not been considered a 
> problem by the operators. On the contrary, the GSM Association has 
> asked 3GPP to finalise the work on communication service identifiers 
> and sort out the bits and pieces in the protocol ASAP.

Of course they don't find interoperability to be a problem! They
constitute an oligopoly that is only concerned with interop among
themselves. Interop with anyone else is presumably a non-goal.

The ietf has broader aspirations for interop.

	Paul

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From: Paul Kyzivat <[email-masked]>
Date: Tue, 20 Feb 2007 17:30:06 -0500

> by the way, it would be useful to get this discussion on the sipping

it is.

> Please tell me which interop that is your concern

I don't think it is specifically interop at the protocol level. But it 
is involved in the expected semantics involved in using sip. I don't 
know if that is the service level or what.

For instance somebody (I think Jonathan) already identified issues if 
PoC device called what turns out to be a vanilla sip audio UAS. At the 
protocol level everything is fine - the audio media stream has been 
accepted and anything else rejected. The callee expects an audio call. 
The calling PoC client, or maybe his PoC server, will explode or 
something I guess. This is an interoperability problem.

> all aspects, but isn't this just facts that is hard to get around?

Well, I'm not concerned if my attempted IM call to you fails because you 
only have audio devices.

But if I take my vanilla sip audio/video client and make an audio/video 
call to you, who I know have an audio/video UAS, and my call is rejected 
because my UA didn't include the service ID that your provider requires 
for video calls, then I think there is an interop problem. If we don't 
support any common codecs then I will understand.

> A PoC

As Henning and others have pointed out, this is a fact based on the 
current approach to implementing PoC. But it isn't a desirable 
situation. There are other ways it could have been done that would have 
led to a more graceful handling of interop.

I gather that after you have failed to complete a call to me using PoC 
on your phone that you will switch it to regular audio mode and try 
again. It would be much more pleasing if your phone simply noticed that 
the response was not compatible with PoC and just switched to regular 
voice. In that case, PoC-specific servers that have Record-Routed would 
have to get out of the way somehow.

	Paul