Re: [sipcore] Draft new version:draft-holmberg-sipcore-proxy-feature

["Andrew Allen" <[e-mail]>]

John

I agree the indication needs to identify the features supported not just the presence of an entity.

Andrew

----- Original Message -----
From: Elwell, John [mailto:[e-mail]]
Sent: Monday, January 24, 2011 09:32 AM
To: Andrew Allen; Christer Holmberg <[e-mail]>; [e-mail] <[e-mail]>
Subject: RE: [sipcore] Draft new version:draft-holmberg-sipcore-proxy-feature

Just picking on one particular example from Andrew's post: 

> SIP PBXs may be present in a network and may provide call 
> features and other services on behalf of the UA. In some 
> cases the UA may need to address requests to the PBX to 
> invoke some features or services. Although presence of the 
> PBX could be indicated using configuration this isn't really 
> effective when there are mobile UAs moving between enterprise 
> networks that have PBXs and public networks that don't.  
[JRE] Although we all perhaps have a similar notion of what a PBX is, this is not a tightly defined term in the SIP context (the nearest we have is the MARTINI notion of SIP-PBX in the context of bulk registration, but I suspect that is not what you have in mind). A PBX could do all sorts of things differently from some other SIP entity (such as a Service Provider SIP proxy), but particular behaviour is very much dependent on the design of a PBX and how it is deployed. If proxy features are indeed to be indicated (I have not yet formed an opinion on this), they should be more precisely defined, i.e., at the level of particular features that the PBX can perform, rather than just the fact it is a PBX.

John

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