On 10/12/16 12:40 PM, Brett Tate wrote:

Since these are B2BUAs, there are *three* different
early dialogs here:

All the rules regarding route sets, etc. apply
separately to each.

I agree.  However, I just wanted to mention that the 3gpp specs appear to
be requiring B2BUA Application Servers to add Record-Route instead of
replacing a gruu Contact.  I'm not sure how well the 3gpp requirement will
work since nothing has been specified for building (record routing) routes
for use when sending a request to a gruu location.

It always seemed to me that you should't be a UA without putting in your own Contact URI. But I have scoured 3261 for support for that opinion and have not found it. So I have (reluctantly) accepted that B2BUAs using Record-Route to stay in the path while leaving the Contact URI unchanged are valid.

But Record-Route does cause problems with GRUU. If you aren't careful you can end up in sub-optimal routing spirals.

A long time ago I worked on some proposals for additions to IMS that made things work with GRUU. It was complex. And I don't know if that stuff was ever adopted.


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