[sipcore] RFC5626 and REGISTER with multiple contacts

[Ivo Sedlacek <[e-mail]>]

Hello,

can I please get experts' view on the issue below?

Use case:
- the UA contains several applications
- each application is associated with a unique contact
- all contacts of all the applications have the same IP address and port
- the UA registers all contacts of all the applications using a single REGISTER request, as due to the potentially large number of applications it is not feasible to register each contact individually

As long as outbound is NOT used, this works correctly.

Issue:

Once the UA would like to create several registration flows using outbound for reliability, the REGISTER request with multiple contacts sent by the UA can be rejected by the registrar since RFC5626 states:
---------------------------------
Therefore, if the Contact header field contains
   more than one header field value with a non-zero expiration and any
   of these header field values contain a "reg-id" Contact header field
   parameter, the entire registration SHOULD be rejected with a 400 (Bad
   Request) response.  The justification for recommending rejection
   versus making it mandatory is that the receiver is allowed by
   [RFC3261] to squelch (not respond to) excessively malformed or
   malicious messages.
---------------------------------

I can understand the reason for rejection where the contacts represent different UA instances, or have different IP addresses or ports.

However, the same sip.instance *and* the same IP address and port are used in each of the contact registered by the REGISTER request in the case above. I also assume that the reg-id would be the same for each contact associated with a given flow.

Is there a reason why REGISTER with multiple contacts, each having the same sip.instance, the same IP address and port and the same reg-id, should be rejected?

Thank you for clarification.

Kind regards

Ivo Sedlacek

Ericsson
GF Technology, Terminal Standardization
Sweden
Office: [phone]
[e-mail]
www.ericsson.com

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