> Hi, if a UAC sends a SUBSCRIBE and the proxy does parallel forking to
> two servers, it could occur that both servers reply a 200.
> 
> Should the proxy relay the second 200 to the UAC? or should it absorb
> it?

It should be consumed instead of relayed by the proxy.

RFC 3261:

"This step, combined with the next, ensures that a stateful
 proxy will forward exactly one final response to a non-INVITE
 request, and either exactly one non-2xx response or one or more
 2xx responses to an INVITE request."

RFC 6026:

"When receiving any SIP response, a transaction-stateful proxy MUST
 compare the transaction identifier in that response against its
 existing transaction state machines.  The proxy MUST NOT forward the
 response if there is no matching transaction state machine." 

> Anyhow I do know that the UAC must be ready to receive an in-dialog
> NOTIFY with an unknown Totag (the NOTIFY generated by the second
> server) so the UAC should generate a second subscription dialog then
> and should manage it (as RFC 6665 mandates).


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