Re: INFO Framework: Tags

Dean Willis <[email protected]>
Newsgroups gmane.ietf.sip
Message-ID <[email protected]>
On Nov 20, 2008, at 10:45 PM, Elwell, John wrote:

> Dean,
>
>> -----Original Message-----
>> From: Dean Willis [mailto:[email protected]]
>> Sent: 20 November 2008 23:16
>> To: DRAGE, Keith (Keith)
>> Cc: Christer Holmberg; Paul Kyzivat; SIP List; Elwell, John
>> Subject: Re: [Sip] INFO Framework: Tags
>>
>>
>>
>> No, you use the options tag with a sip.extensions media feature tag
>> ala RFC 3840 in order to get a retargeting proxy to send the request
>> only to the subset of UAS that support the extension.
> [JRE] RFC 3841 does not compel a proxy to behave in this way, and in
> fact the proxy might not even support RFC 3841.

RFC 3840/3841 can insure such behavior, and (with Proxy-require) can  
assure that the proxy either supports the extension or  rejects the  
call.

> So you have to be
> prepared for your INVITE/Recv-Info to go to any UAS.

well, it MIGHT do so, and fail in a predictable way as a consequence  
due to the Require: info-package. That's not a bad thing.

> I don't in general
> see a need to specify this as part of the extension in general, but  
> if a
> particular package needs a feature tag, let it define one. Keep the
> extension simple.

Only standards-track RFCs can define SIP option tags under RFC 3427,  
and we have no plans to relax this requirement.

But we have a much looser policy for INFO packages; most will not be  
standards-track.

So, for those sorts of packages, an info-package option tag is  
potentially quite useful.

--
Dean

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