Subject: SIP architecture for Roaming mobiles (was RE: [SIP] Minutes of SIP Security task force in Adelaide)

From: Giuseppe Ricagni <[email-masked]>
Date: Wed, 17 May 2000 17:33:41 +0200

Dear All,

I thought about generating a new thread as our discussion had completely
diverged from the purpose of the previous thread

Jörgen Björkner wrote:

>
> The home proxy always should be within the signaling path, even though
> you
> have roamed into another network. This is very important from a value
> added
> service perspective.

there are four kind of value added services:

   * a) those who require user profile information
   * b) those who don' t  require user profile information, but to some
     extent they are not supported by the visited domain
   * c) those who don' t  require user profile information and they are
     implemented by the visited domain.
   * d) null services: in other words, basic calls tha do not request
     any kind of value added service

Case a) and b) require some kind of interaction with the home network.

C) and d) don' t.

[...]

> The reason to have the home proxy within the signaling path is to be
> able to
> offer services that is invoked before the call is set up. One example
> is a
> speed dial dial service that translates one request URI to something
> else
> depending on a users preferences.

This is a type a) service. Yes, you need to execute it in the home
network, unless you download the user profile at registration time AND
the visited network has implemented that specific service.

With respect to the method used to classify service request within the
four cathegories, a possibility is that  the home domain, at
registration time, sends information to the visited domain on the
requirements to meet  to locally execute a given set of services for
that specific user. If the visited domain supports such requirements ==>
those services can be executed locally.

This mechanism can even  be extended to the full download of the user
profile.

[...]

> I have understood that some groups proposes a solution where the
> services is
> downloaded to the visited network. The solution with downloaded
> services has
> one severe problem, the fact that the execution environment must be
> homogenous between the operators.

The real problem I see here is a secuity one: PNOs will never allow 3rd
pty code to run on thei mission-critical machines.

> This is very limiting for a operator that
> want to distinguish himself and attract customers by providing
> creative
> services, which is very important on todays competitive market. A
> successful
> service might need to retrive information from an information system
> that
> the users service provider has access to. This means that althouh the
> code
> will be able to execute when it is downloaded to the visited network
> so will
> the information that is needed not be accessible.

> I don't think this would affect the call setup time in any significant
> way,
> and users is today used to longer call setup times when the roam into
> another operators network.

Please see my othe messages

Giuseppe

>
> /Jörgen
>
> -----Original Message-----
> From: James Kempf
> To: Michael Thomas; Giuseppe Ricagni
> Cc: [email-masked]; [email-masked]; James Kempf;
> Michael
> Thomas
> Sent: 2000-05-16 14:05
> Subject: Re: [SIP] Minutes of SIP Security task force in Adelaide
>
> >Giuseppe Ricagni writes:
> > >    * possible optimizations (e.g.: signalling for a basic call to
> an
> >Australian
> > >      fixed network number from an Italian mobile roaming to
> Australia could
> >be
> > >      processed locally, without any "tromboning")
> >
> >   If during call setup there needs to be a round
> >   trip to the home network, it pretty much negates
> >   any advantage of proxying the call locally.
> >
>
> When you take roaming into account, there is an advantage. Suppose the
>
> Italian now in Australia moves. If the home proxy is used, the network
>
> has to go back to the home to roam. If a local proxy is used, there is
>
> reduced latency. With a local proxy, you pay the round trip cost
> to the home network just once.
>
> In addition, some people have been talking about using SIP for other
> kinds of in-call signalling. If the mobile has to go all the way
> back to the home proxy, there is simply too much latency.
>
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--

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Giuseppe RICAGNI
System Architecture and Product Planning
Broadband Networks
Italtel
via Reiss Romoli - C10
20019 Castelletto di Settimo Milanese (MILANO)
ITALY

mailto:[email-masked]
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