Christer Holmberg wrote:
Hi,
Trying to register the "same UA" concurrently with two different
instance ids in an attempt to get parallel forked call attempts via
different networks is creative but a bit ugly. For one thing
its hard in general to guarantee that the two will be parallel forked.
And the UA will have to attempt to correlate the two in order to realize
they are the same and so process correctly. An
SBC between the forking proxy and the UA is likely to disturb the
CallID, the From, and the caller's Contact address. With those messed up
the correlation will get difficult.
IF there is a need to do parallell forking to the "same UA", I think
it's better to simply allow it in Outbound - instead of trying to find
hacks on how to get around the current restrictions.
However, parallell forking in outbound should not be the default
behavior, because I strongly think that in most cases people only want
to receive the initial request on a SINGLE flow - no matter if they use
one or more contacts.
Making this behavior "possible but not default" means that there must be
two options: "do it", and "don't do it". The choice of which to do would
need to be encoded somewhere. This matters a lot to the UA, so I think
this option would have to be encoded as part of the registration
request. Thus outbound would have to change to accommodate it.
In any case, changing the mechanism for requesting this behavior
wouldn't really change the issues I raised about detecting when the same
call is delivered via both paths.
Thanks,
Paul
Regards,
Christer
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