UAC
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... client would like to receive subsequent requests within the same
dialog in the UAS->UAC direction compressed, this client SHOULD add
the parameter comp=sigcomp ...
... UAC, and it supports SigComp. The
UAC is configured to send compressed traffic to P1, and therefore, it
compresses the INVITE ...
... traffic to P1, and therefore, it
compresses the INVITE (1). In addition, the UAC wants to receive
future requests and responses for this dialog compressed. Therefore,
it adds the comp=Sigcomp ...
... Route set for this dialog. For requests from the UAS towards the
UAC (the opposite direction than the first INVITE), the next hop will
...
... sigcomp
Since the UAC wants to receive compressed requests (Contact of the
INVITE), P2 assumes that the UAC ...
... UAC wants to receive compressed requests (Contact of the
INVITE), P2 assumes that the UAC would also like to send compressed
requests (Record-Route of the 200 OK). Therefore, P2 modifies its
...
... INVITE (3), P2 did not used the comp=sigcomp parameter. Now it adds
it in the 200 OK (5). This will allow the UAC sending compressed
requests within this dialog.
...
... UAS
P1 sends the 200 OK (6) compressed to the UAC because the Via header
field contained the comp=sigcomp parameter.
...