Re: [Sipping] draft-mahy-iptel-cpc

["Ian Elz" <[e-mail]>]

Paul,

You are now stretching the requirements for CPC/OLI beyond what is now
supported in ISUP.

In current ISUP it would be possible to have as you correctly describe a
police cell phone but only a single value is included.

If you wish to allow multiple values then we raise an interworking
problem of which value is used when interworking with ISUP. We may need
to define one value as primary and others as secondary to allow correct
interworking.

Ian Elz

System Manager
DUCI LDC UK
(Lucid Duck)

Office: + 44 24 764 35256
gsm: [phone]
[e-mail]

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On
Behalf Of Paul Kyzivat
Sent: 28 March 2008 21:37
To: DOLLY, MARTIN C, sbcuid
Cc: [e-mail]; [e-mail]
Subject: Re: [Sipping] draft-mahy-iptel-cpc

As I recall from back when this was a topic of active discussion, there 
were significant issues about the semantics of the values.

I see that Rohan included semantics in the draft. But do they agree with

the ones that you are trying to interoperate with?

One thing I see is that the cpc can have only one value. But the list of

values does not seem to be mutually exclusive. For instance, I would 
think you could have a test call in combination with any of the others. 
And you you could have a police call from a cellular phone.

I suppose none of this is troubling if this is used only for calls 
sourced from the PSTN, since then the problem of classifying is up to 
the pstn side. But if a call originates for a sip client, there must be 
clear rules for how it is classified.

Also, how are the classifications authorized? It seems likely that the 
originating device will not be permitted to do it, but rather that some 
"trusted" middle box will have to do so.

And where do you expect this to be put? In P-A-I? If that is the only 
place where it makes sense, then perhaps a P-A-I header parameter would 
make more sense.

	Paul

DOLLY, MARTIN C, sbcuid wrote:
> Sumit,
>  
> For as long as the values are clear, this approach would be
acceptable.
>  
> Martin
> 
>
------------------------------------------------------------------------
> *From:* [e-mail] [mailto:[e-mail]] *On

> Behalf Of *Sumit Garg
> *Sent:* Friday, March 28, 2008 2:09 PM
> *To:* [e-mail]; [e-mail]
> *Subject:* Re: [Sipping] draft-mahy-iptel-cpc
> 
> I agree with Ian, we should avoid multiple parameters.
> 
> The way a lot of stuff is done in tel-uri might be useful....
> 
>  
> 
> We would only  need 1 parameter:  i.)  user-type=<cpc/oli-values>
> 
>                 Renamed /to user-type as we do not necessarily tie it
to 
> originating side.....we might find other needs in the future./
> 
>  
> 
> For the current scenario, the number itself would help the 
> implementation decide whether it is CPC/OLI.
> 
> A global number inherently has a country code which would help decide 
> the valid values (cpc/oli)
> 
> Otherwise the phone-context could be used to decide the same.
> 
>  
> 
> For implementations which use neither..i.e. for which context is 
> implicit...they would implicitly know whether  it is cpc/oli.
> 
>  
> 
> -Sumit
> 
>  
> 
>  
> 
> "The reasonable man adapts himself to the world; the unreasonable one 
> persists in trying to adapt the world to himself. Therefore all
progress 
> depends on the unreasonable man."
> -- George Bernard Shaw
> 
> *From:* Ian Elz [mailto:[e-mail]]
> *Sent:* Friday, March 28, 2008 12:10 PM
> *To:* DOLLY, MARTIN C, sbcuid; Sumit Garg; [e-mail];
[e-mail]
> *Subject:* RE: [Sipping] draft-mahy-iptel-cpc
> 
>  
> 
> Martin,
> 
>  
> 
> I saw you email with the list of values.
> 
>  
> 
> I was not proposing to remove the values but to combine them into an 
> extended list which encompassed both OLI and CPC. ANSI does not use
CPC 
> to any extent while ETSI/CCITT uses CPC for the same purpose as ANSI 
> uses OLI.
> 
>  
> 
> An expanded combined single parameter may be suitable for all the 
> required values.
> 
>  
> 
> If you look at what is proposed by 3GPP you will see that it is
proposed 
> to reduce the different CCITT operator CPC values by using 'language'
in 
> Accept-Contact. There may be options to use similar techniques to
enable 
> all the OLI values to be handled correctly.
> 
> /Ian Elz/
> 
> /System Manager/
> /DUCI LDC UK/
> /(Lucid Duck)/
> 
> /Office: + 44 24 764 35256/
> /gsm: [phone]/
> /[e-mail]/
> 
>
------------------------------------------------------------------------
> 
> 
>
------------------------------------------------------------------------
> 
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This list is for NEW development of the application of SIP
Use [e-mail] for questions on current sip
Use [e-mail] for new developments of core SIP