[reSIProcate] DUM API question

[Robert Sparks <rjsparks@xxxxxxxxxxx>]

Derek asked me a question that I don't remember the answer to.

Consider the case where we issue an initial INVITE through
DUM. The request goes through one proxy and forks to two
endpoints. The first endpoint returns a 183. Sometime later,
the second endpoint returns a 603.

What is the flow through DUM when this 603 comes in? We've
got an existing dialog (with a usage/ early dialog state).
Should we create a second dialog with a usage for the 603?
(Dialog feels right, but usage doesn't.) How does the
usage with the 183 on it get told that it needs to come to
an end?

Variants of this to think through before answering are:
1) More than one branch returning provisionals that
   set up early dialogs.
2) Additional signaling activity on one of those
   branches (consider the original scenario but toss
   an UPDATE into the mix).

RjS