[SIPForum-techwg] Urgent questions on SIPconnect 1.1 registration mode

[Hadriel Kaplan]

Good catch.  The wording of "Main Public Identity" and such needs to be changed.

Based on the last change for how the Registration model works, the AoR being registered (the one in the To-URI of the REGISTER), is an AoR belonging to the SP, within the SP's domain and scope of authority/responsibility.  It is likely to be a private identity, and not publicly reachable/usable for anything else; however, if it is usable, any routing by the SP for the AoR would follow 3261 and replace the request-uri with the registered contact.

-hadriel

> -----Original Message-----
> From: techwg-bounces at sipforum.org [mailto:techwg-bounces at sipforum.org] On
> Behalf Of Elwell, John
> Sent: Thursday, July 09, 2009 6:11 AM
> To: techwg at sipforum.org
> Subject: [SIPForum-techwg] Urgent questions on SIPconnect 1.1 registration
> mode
> 
> Reading section 17 I now am totally confused about the role of the Main
> Public Identity. I need to have opinions on what we should be saying
> before I can propose text to address my concerns.
> 
> 1. The Main Public Identity is used for registration (i.e., in the To
> header field of the REGISTER request). It is unclear whether the SP or
> the Enterprise is responsible for this AOR in registration mode. For
> static mode, clearly the SIP-PBX has responsibility.
> 
> Section 5 seems to suggest SIP-PBX responsibility ("SIP PBX has
> responsibility for the AORs"), although it doesn't explicitly mention
> the Main Public Identity.
> 
> Section 10.1 also seems to suggest SIP-PBX responsibility ("Typically,
> calls sent to the Main Public Identity are terminated by an auto
> attendant or front desk operator on the SIP-PBX and then transferred
> within the enterprise to a private extension."). If the SIP-PBX is not
> responsible, calls to the auto attendant from within the SIP-PBX would
> need to be routed via the SP, which is not stated anywhere.
> 
> Section 17.1.1 seems to suggest SIP-PBX responsibility ("This document
> specifies support for only the first of the above models, where the
> SIP-PBX is responsible for providing services to the enterprise Public
> Identities" - this does not limit it to Alternative Public Identities,
> so presumably it includes the Main Public Identity).
> 
> But in 17.1.2 it states: "Note that the AoR used for the Registration is
> within the authoritative domain of the SP-SSE, and thus if that AoR
> itself is a publicly reachable AoR, the SP-SSE is responsible for
> providing services for it, rather than the IP-PBX."
> 
> Examples in 17.1.5 seem to suggest either can apply, which presumably
> means that it is a matter of agreement between the Enterprise and SP.
> But this is not stated anywhere else.
> 
> In the past we have talked about the SP using the Main Public Identifier
> as the default for populating the PAI header field for onward
> transmission within the SP network (although that is not written down,
> since it was considered outside scope). However, a Main Public
> Identifier of the form sip:xyz-corpsp at sp.net (as given in Example 1)
> would not be very suitable for this purpose. Do SP's indeed need to use
> the Main Public Identifier for default PAI purposes?
> 
> 
> 2. Related to this, how is an inbound request to the Main Public
> Identifier routed in registration mode. In 17.1.3 it states:
> "When the SP-SSE receives an out-of-dialog request containing a
> Request-URI that identifies either the Main or an Alternate Public
> Identity assigned to the SIP-PBX, it routes the request to the SIP-PBX
> using the location binding that was established when the SIP-PBX
> registered. The SP-SSE does this following the normal procedures for
> routing requests to registered SIP endpoints, except that it skips the
> request-retargeting step; i.e. based on locally configured data, the
> SP-SSE does not overwrite the enterprise Public Identity contained in
> the Request-URI with the SIP signaling address of the SIP-PBX. The Route
> header field, as described in Section 17.8, identifies the SIP-signaling
> address of the SIP-PBX in an out-of-dialog request"
> 
> In other words, Main Public Identifiers are treated the same as
> Alternate Public Identifiers.
> 
> Then in 17.8 it states:
> "When routing any out-of-dialog request to a registered SIP-PBX
> signaling address, the SP-SSE MUST include a Route header containing
> that registered address. A registered SIP-PBX signaling address is the
> Contact URI (including any associated URI parameters) that was bound to
> the called Main Public Identity when the SIP-PBX registered, as
> described in Section 17.5."
> 
> This does not allow for requests to the Main Public Identity to be
> treated any differently.
> 
> But in 17.1.2 it seems to contradict this:
> "Note that the AoR used for the Registration is within the authoritative
> domain of the SP-SSE, and thus if that AoR itself is a publicly
> reachable AoR, the SP-SSE is responsible for providing services for it,
> rather than the IP-PBX.  In such a case, the AoR is resolved and routed
> to the SIP-PBX using normal [RFC 3261 procedures], replacing the
> request-URI with the Registered Contact-URI instead of inserting a Route
> header, etc."
> 
> Opinions?
> 
> My opinion on both issues is that we have overloaded Main Public
> Identity to be both the default AoR (e.g., that of auto-attendant) and
> the AoR with which the PBX registers. For the first use, it seems it
> should be the responsibility of the SIP-PBX, and thus all inbound
> requests to that AoR would be treated the same as inbound requests to
> Alternate Public Identities. For the second use, it makes sense for the
> SP to be responsible. So I think we have 3 possible ways out of this:
> 
> 1. Decouple the two functions, so that we have a different AOR (not the
> Main Public Identity) for registration purposes. In that case, I would
> say that the AoR used for registration purposes is the responsibility of
> the SP.
> 
> 2. Be clear that the Main Public Identity is always the responsibility
> of the SIP-PBX (and eliminate any statements that suggest otherwise).
> 
> 3. Be clear that the Main Public Identity is always the responsibility
> of the SP. However, I don't like this option, because a) it does not
> make sense for static mode and b) it means internal requests within the
> SIP-PBX to the Main Public Identity have to go via the SP.
> 
> So I think we have to go with 1 or 2, and I tend to favour 1.
> 
> John
> 
> 
> 
> 
> 
> 
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