Subject: RE: [Sip] Path to Working Group Item

From: "Mark Watson"<[email-masked]>
Date: Tue, 5 Mar 2002 17:06:39 -0000

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]
> Sent: 05 March 2002 14:14
> To: Watson, Mark [MDN05:EP10:EXCH]
> Cc: Dean Willis; [email-masked]
> Subject: RE: [Sip] Path to Working Group Item
> 
> 
>  > Minor point, but limiting the destinations to which users 
> can make calls
>  > *reduces* revenue, because users can make fewer calls and 
> the service takeup
>  > will be depressed due to the perceived deficiency.
> 
> mark,
> 
> by limiting freedom i didn't mean limiting the number of end 
> points that
> can be reached, but limiting the way how they can be reached.  when i
> make a call from a 3gpp phone, i should be able to choose 
> whether i want
> to route the invite to my home proxy or skip my home proxy 
> and just use
> the services of the visited network if the visited network 
> can give me a
> better deal that way. 
>

And indeed you can do this as I described in my earlier mail. There is
nothing to stop you establishing a data connection (PDP Context) with the
QoS that you want and sending your call over that, via whomever you want (if
your terminal supports it).

As far as the mobile network is concerned it is providing you with a
bit-pipe and they will charge you for that.

Mobile operators, however, have a desire to offer what they consider to be
an enhanced service by linking together the provision of the bit-pipe with
the provision of the application layer service itself - this is what the
3GPP architecture does. Having paid so much for their spectrum licences they
quite reasonably want the capability to be more than a bit-pipe.

This does not stop you from *using* them as a bit-pipe: whatever works for
you/whatever you're prepared to pay for.

> also, i should be able to equally choose to use call routing and
> gatewaying services of a third party that is not a mobile network
> operator at all and still get the same qos service over the wireless
> access link as i get when i use the services of the mobile network
> operator.
> 

Yes, and I still don't see what is stopping you from doing this. All that is
happening with the 3GPP SIP architecture/extensions is that the mobile
operators are defining how their own services will work - if they want to
make this more complex or different from accessing a SIP service over the
Internet it is their own lookout, but there are good reasons for the
architecture and extensions in terms of the service it enables them to offer
to their customers, including differing charging models.

> with this background you should understand why i don't at all like the
> idea of breaking the sip protocol architecture and making 
> registration a
> prerequisite for making calls and thus giving the mobile network
> operators yet another brick for their wall.
> 

Registration is a pre-requisite for accessing services of the 3GPP IP
Multimedia Subsystem. 3GPP is not (cannot) make registration a pre-requiste
for accessing other SIP-based networks over wireless access.

However, in the case of this particular extensions, I think enough examples
have been given to show its utility in applications other then the 3GPP IMS,
and so it warrents IETF standardisation. By contrast a number of other 3GPP
requirements have been judged to be entirely 3GPP-specific, and for these
the IETF has suggested that 3GPP define its own solutions.

> -- juha

---

From: [email-masked]
Date: Tue, 5 Mar 2002 21:46:22 +0200

> your terminal supports it).

sure, but does my home proxy the same capabilities to control the pdp
context as the proxy of the mobile operator has for the 3gpp context?
someone on this list mentioned earlier mentioned that that is not the
case.  in an open architecture, the operator 3gpp proxy would have no
advantage over my home proxy for setting up the pdp contexts and
controlling the calls.

by the way, you didn't answer my question about why a 3gpp ua can't
decide to make a 3gpp pdp context call directly from the visited network
without using its home proxy.

-- juha

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---

From: "Dean Willis" <[email-masked]>
Date: Tue, 5 Mar 2002 18:11:17 -0600

> without using its home proxy.

Because 3GPP provides value-added services in the home proxy. If you don't
traverse the home proxy on mobile-originated calls, you don't get the
value-added services.

I gave an example earlier in the day using speed-dialing as a
value-added-service. Other services might include simultaneous search (I
know Juha might be at home, or work, or on his mobile, so I want my proxy to
fork to all three destinations), transcription services, personal
assistants, in-network conferencing (do the mixing "over there", so I pay
only once for air time), automatic update of my presence status (dean is now
in a call), etc. You could probably make a call without any services, but
it's kindof of uninteresting from a business perspective so we don't talk
about it alot, and it's not worth replacing the circuit-switch network with
an IP network for.

--
Dean

---

From: [email-masked]
Date: Wed, 6 Mar 2002 08:10:44 +0200

> traverse the home proxy on mobile-originated calls, you don't get the

if i don't want to use any value added services from my home proxy, but
just want to make a cheaper call by just using the generic services of
the network that i'm visiting (like ordering a pizza from a shop next to
my hotel), 3gpp should allow me to do it.  also, 3gpp should allow me to
make that call without registering with my home proxy, because i don't
want myself to be reachable.  

if 3gpp doesn't allow me to do that, 3gpp architecture is something very
different from sip architecture and it doesn't make sense to pollute
ietf sip protocol specifications with 3gpp requirements.

-- juha