Subject: [sipcore] SIP Push: Wrong usage of "registrar" terminology and clarification of location of push proxy

From: Christer Holmberg <[email-masked]>
Date: Thu, 9 Aug 2018 19:02:43 +0000

Hi,

Ben and Robert raised on issue regarding the usage of "registrar", and that the location of the push proxy needs to clarification.

Regarding usage of "registrar", in some places the text indicates that the registrar forwards SIP requests towards the UA, and that the push proxy may in the registrar.

Now, that is not true. A registrar only processes REGISTER request. It does not forward SIP requests.

Instead, the text should talk about "the proxy responsible for the UA's domain" (terminology used in RFCC 3261), i.e., the proxy that replaces the AOR of an incoming request with the registered contact (including the pn- URI parameters). Sometimes that is called "home proxy", "S-CSCF" (IMS) etc. That proxy fetches the registered contact from the registrar - or from wherever the registrar has stored the contact information.

Regarding the location of the push proxy, it needs to be more clear that it must to be located between the UA and the "home proxy" (or in the home proxy). Otherwise the request will not contain the pn- URI paramters.

Regards,

Christer