Open-plan Local-number Identifier Values for Enterprises (OLIVE)

draft-kaplan-martini-with-olive-02Hadriel Kaplan

The Problem

• Draft-gin handles E.164• So how do we handle Local Numbers?

sip:1234;phone-context=+12125551212@ssp.com

“Local Numbers”• Technically RFC 3966 defines “Local Numbers”

– The phone-context param defines the scope of the user portion, and the users and any other params are only known to the authority of that context

• In practice, things aren’t that simple– the Local-Number syntax is only followed in specific cases; e.g.,

only within the SSP– the “dial-plan” and knowledge of params is not consistently nor

fully in one spot– the scoping model of RFC 3966 creates two tiers of scoping:

URI-user and URI level

Two ways to handle it• How would this “work” if the IP-PBX sent

separate, explicit REGISTERs?– In Martini we only care about IP-PBX case– We need a way to REGISTER for a Local-Number

• Two ways it could have explicitly REGISTERed for a Local-Number:1. It REGISTERed to a specific Domain: e.g.,

sip:enterprise.com or sip:enterprise.priv.ssp.com2. It REGISTERed the AoR: e.g.,

sip:1234;phone-context=pbx.com@ssp.com

So…• The first way (Register to an explicit domain)

doesn’t need a new draft– Just have the IP-PBX REGISTER to that domain,

separately from “public” numbers– IP-PBX uses a contact param to segregate inbound

requests, if that’s an issue• The second way (Register the AoR) is what

draft-olive describes – It can just re-use the draft-gin REGISTER, because

there’s no name collision or confusion, so long as the whole user portion remains intact to the IP-PBX

What this means…• The Request-URI reaching the PBX, and

presumably any coming from it for a private plan, would be expressed as a rfc3966 Local-Numbersip:1234;phone-context=pbx.com@192.1.2.3

• Is that reasonable?– I think so – it has to be distinguished somehow– It could be done with yet-another-header, but what

would we set the Request-URI to anyway?

Example

• PBX does a draft-gin REGISTER• SSP has provisioning for *;phone-

context=+5 goes to pbx123

Originator SSP PBX

INVITEsip:789;ph=+5@ssp.com

INVITEsip:789;ph=+5@192.1.2.3

REGISTER sip:ssp.comTo: <sip:pbx123@ssp.com>Contact: <sip:192.1.2.3;bnc>

Open Issues

Non-context Local Numbers• But what if the PBX doesn’t know about

this “phone-context” stuff?– It’s as if the PBX registered

“sip:123@ssp.com” – it’s just a username to it– But not really, because 123@ssp.com may

overlap with other Enterprises• Possible solutions:

– Describe it as a transformation step, to remove phone-context

– Or require registering to a unique domain name (e.g., enterprise.ssp.com)

Other Open Issues• Vermouth handling (how to check the list of

AoRs on the Registrar)– Can’t have a simple syntax, because names aren’t

fully known by registrar– Answer: use wildcarding

• What to do about Local-Number user parameters– Some are processed by SSP, some by PBX– In theory only the authority of the phone-context

knows what to do with them, but who is that authority??