[SIP Beyond VoIP] Re-registration of number with Avaya IP office software

[Dan Pascu]

On 19 Jun 2019, at 11:20, Madis-Karli Koppel wrote:

> Hi
> 
> Is it possible to use python-sipsimple with Avaya IP office. 
> 
> I have managed to set it up a small system and everything else works perfectly except registration. When a registration refresh is sent mid-call the call drops (from Avaya side). 
> 
> I might be wrong, but according to my investigations the reason is mismatched FROM-tag in registration: registration uses _core.request that uses pjsip_endpt_create_request from sip_util.h that adds a new tag to the request and not the tag of old registration that Avaya would like. All of this means that Avaya treats the registration as a new registration and not refresh of old one.

Then Avaya is wrong. The REGISTER request doesn't establish a dialog. As a result it has no obligation to maintain the from/to tags from one request to the next. In fact it shouldn't exactly because REGISTER doesn't establish a dialog. The way the server identifies if it's a refreshed registration of a new one is by looking at the Contact header. If the contact associated with the AOR already exists on the server, then it's a refresh, else it's a new registration.

Section 10.2 of RFC3261 establishes only the following:

1. REGISTER doesn't establish a dialog (i.e. it shouldn't preserve from/to tags from one request to the next)
2. REGISTER requests sent from a UA to the same registrar should use the same Call-ID in order to allow the server to detect if a delayed REGISTER request came out of order

python-sipsimple honors both these requirements.

I also recommend reading section 10.3 which describes how the server should handle REGISTER requests. In neither 10.2 nor 10.3 is there any mention of from/to tags, except specifying that REGISTER doesn't establish a dialog which automatically implies that tags are not preserved.

> 
> Unfortunately enabling GRUU is not possible on Avaya side. 
> 
> Is there anything to do in this situation?

Ask Avaya to fix their device?

> 
> All the best
> Madis-Karli Koppel
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--
Dan