Hi, 

>I guess the problem arises when you want to do a single REGISTER
request for both instances. If I the use case correctly, the UA would
send two REGISTER requests (one on each interface) and 
>both REGISTERs would have the two Contacts (one for each instance-id).
Something like this:
>
>First REGISTER to Outbound-proxy #1
>
>   REGISTER sip:example.com SIP/2.0
>   Via: SIP/2.0/TCP 1.1.1.1;branch=z9hG4bKnashds7-1
>   From: Bob <sip:[EMAIL PROTECTED]>;tag=7F94778B653B-1
>   To: Bob <sip:[EMAIL PROTECTED]>
>   Call-ID: 16CB75F21C70-1
>   CSeq: 1 REGISTER
>   Supported: path, outbound
>   Route: <sip:ep1.example.com;lr>
>   Contact: <sip:[EMAIL PROTECTED];transport=tcp>;reg-id=1
>    ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
>   Contact: <sip:[EMAIL PROTECTED];transport=tcp>;reg-id=2
>    ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-BBCCDDEEFF00>"
>
>Second REGISTER to Outbound-proxy #2
>
>   REGISTER sip:example.com SIP/2.0
>   Via: SIP/2.0/TCP 2.2.2.2;branch=z9hG4bKnashds7-2
>   From: Bob <sip:[EMAIL PROTECTED]>;tag=7F94778B653B-2
>   To: Bob <sip:[EMAIL PROTECTED]>
>   Call-ID: 16CB75F21C70-2
>   CSeq: 1 REGISTER
>   Supported: path, outbound
>   Route: <sip:ep2.example.com;lr>
>   Contact: <sip:[EMAIL PROTECTED];transport=tcp>;reg-id=1
>    ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-BBCCDDEEFF00>"
>   Contact: <sip:[EMAIL PROTECTED];transport=tcp>;reg-id=2
>    ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
>
>Thus the UA could receive requests for either Contact on either of the
two outbound flows.
>
>Is having two UA instances in the same request legal with the current
text?

Isn't the edge proxy always going to send incoming request (towards the
UA) to the address/port where the REGISTER came from, in order for the
request to traverse the NAT? 

So, I don't think you can perform the kind of "third party registration"
which your example shows.

Regards,

Christer






-----Original Message-----
From: Elwell, John [mailto:[EMAIL PROTECTED]
Sent: Tuesday, October 14, 2008 11:02 AM
To: Bob Penfield; Christer Holmberg; Juha Heinanen; [email protected]; Paul
Kyzivat; Dean Willis
Subject: RE: [Sip] Dual registration without Outbound



> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of 
> Bob Penfield
> Sent: 14 October 2008 15:41
> To: Christer Holmberg; Juha Heinanen; [email protected]; Paul Kyzivat; Dean

> Willis
> Subject: Re: [Sip] Dual registration without Outbound
>
> For both GRUU and Outbound a given instance-id
> (+sip-instance) actually represents a single UA contact instance 
> rather than just a single User Agent. The basic idea behind GRUU is 
> that a request addressed to a GRUU is forwarded by the proxy to a 
> specific Contact address. The goal is the same with Outbound but it 
> adds multiple flows/paths to that UA Contact. This is reflected in the

> proxy procedures in both GRUU and Outbound.
>
> In both cases, the proxy does serial forking to Contacts with the same

> instance-id.
>
> For GRUU it starts with the most-recently registered binding 
> (according to section 6.1 of GRUU):
>
>        The proxy MUST select the most recently refreshed
>        contact.  As with draft-ietf-sip-outbound, if a request to this
>        target fails with a 408 (Request Timeout) or 430 (Flow Failed)
>        response, the proxy SHOULD retry with the next most recently
>        refreshed contact.  Furthermore, if the request fails with any
>        other response, the proxy MUST NOT retry on any other contacts
>        for this instance.
>
> For Outbound, it attempts the registered flows (according to section 7

> of Outbound):
>
>    When a proxy uses the location service to look up a registration
>    binding and then proxies a request to a particular contact, it
>    selects a contact to use normally, with a few additional rules:
>
>    o  The proxy MUST NOT populate the target set with more than one
>       contact with the same AOR and instance-id at a time.
>    o  If a request for a particular AOR and instance-id fails with a 
> 430
>       (Flow Failed) response, the proxy SHOULD replace the failed 
> branch
>       with another target (if one is available) with the same AOR and
>       instance-id, but a different reg-id.
>    o  If the proxy receives a final response from a branch other than 
> a
>       408 (Request Timeout) or a 430 (Flow Failed) response, the proxy
>       MUST NOT forward the same request to another target representing
>       the same AOR and instance-id.  The targeted instance has already
>       provided its response.
>
> Therefore, a User Agent that is registering multiple Contacts to allow

> the possibility of parallel forking would need to have a separate 
> instance-id for each Contact.
>
> For User Agent's that have multiple interfaces, it could use the MAC 
> address of each interface to create a unique UUID URN for each 
> contact.
>
> Thus, the following scenario is possible:
>
>   UA_Contact_wlan;+sip-instance=ID_1;reg-id=1 ----- OB_1 ----- REG_1
>   UA_Contact_wlan;+sip-instance=ID_1;reg-id=2 ----- OB_2 ----- REG_2
>   UA_Contact_3g;+sip-instance=ID_2;reg-id=1   ----- OB_1 ----- REG_1
>   UA_Contact_3g;+sip-instance=ID_2;reg-id=2   ----- OB_2 ----- REG_2
>
> Unfortunately, the current text in section 4.1 says that a UA has "an 
> Instance Identifier".
[JRE] In an earlier email I was trying to say roughly the same thing,
except the way I looked at it was that a device with multiple interfaces
would logically contain a UA for each interface, and each UA would than
have a single instance ID. In that case the text in section 4.1 still
works.

John
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