[Serusers] Is SER supposed to send ACK for 2xx response?

[C Y]

Hello,

My setup is for an INVITE session is:

UAC ----> SER -----> UAS

I am using SER is a stateful forwarder (using
t_relay). 
I find that when my UAS sends a "200 OK" to my UAC
(via SER), SER does not send an ACK to my UAS. 
The 200 message is forwarded correctly to my UAC, but
my UAC is taking quite some time to reply.
Therefore, there is timeout, and my UAS is re-sending
the 200 messages to SER (and SER just forward them on
to my UAC).

My question is, is this correct behaviour?
Or is SER supposed to ACK immediately a 200 message,
before forwarding it to my UAC?

Thanks for any pointers!

Chee


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