Subject: Re: [sipcore] [dispatch] Comments on draft-allen-dispatch-routing-out-of-dialog-request-00

From: [email-masked] (Dale R. Worley)
Date: Fri, 21 Mar 2014 15:05:10 -0400

[moved from Dispatch]

> From: Hadriel Kaplan <[email-masked]>
>
> On Mar 16, 2014, at 8:54 PM, Andrew Allen <[email-masked]> wrote:
> > Having B2BUAs only include feature tags they understand to my view
> means no innovation and no new services. B2BUAs have then become the
> switches of old needing all to be updated or reconfigured to support
> any new services.
> 
> Yup, and that's exactly the right thing to happen.  It's what most
> IMS operators actually should *want* to happen as well.

> It's really not a bad thing to want service stability.

You can do it whichever way you prefer.  The B2BUA can copy all of the
feature tags if it is also transparent (proxy-like) enough that it
isn't goint to hinder any new features.  But if the B2BUA wants to
enforce stability, and goes to the effort to edit the SIP/SDP in
detail, then it should perform the corresponding editing of the
feature tags.

Dale

---

From: [email-masked] (Dale R. Worley)
Date: Fri, 21 Mar 2014 15:09:04 -0400

[moved from Dispatch]

> From: Andrew Allen <[email-masked]>
> 
> In addition as I state in my draft modifying the Contact header
> field means either the media feature tags of the remote UA are lost
> or the B2BUA is saying if you send a request to this address
> (including potentially after this session has ended) you can expect
> that this feature is supported.

Yes, but ...  The Contact URI that the B2BUA uses is really a stand-in
for the "real" Contact URI.  That is, the B2BUA has to use *different*
Contact URIs depending for each original Contact URI.

But it has to be doing that already if out-of-dialog requests are
going to work at all.  If the B2BUA receives an OOD REFER, it has to
know which destination "on the other side" to send the REFER to, and
it has only the request-URI to tell it that.

But if you are using different Contact URIs for each actual
destination, then it isn't confusing to provide different media
feature tags for diffent Contact URIs.

Dale