El 04/08/2011 21:09, "Romel Khan" <[email protected]> escribió: > > So it is useful if one of UAS or UAC requires it, but it does not have to be mandatory. Some comments: > -- RFC3261 mentions early dialog without mentioning RFC3262. Then it seems logical to me that it needs to be made clear in this RFC3261 that early dialog must mean Contact and Record-Route (if Record-Route was received in INVITE) headers is mandatory in 1xx without reference to 100rel. > > -- A UAS could always send 1xx with headers that are required for early dialog but it doesn't have to enforce 100rel (eg because the origination or UAS side itself may not support reliable provisional response handling, or reliable provisioning not really required for its operation). UAS could send "support:100rel" if it supports it, or it would not send it if it doesn't support this. In my opinion, if UAC hasn't sent 100rel required, it should be up to the UAS to decide whether to enforce 100rel (with "required:100rel") if its application really requires SIP requests before call answer. If the origination side (UAC) side has a need to send early requests, like UPDATE, then the UAC should require 100rel from the termination side (UAS) by sending this yin INVITE. In a VoIP service provider world, these kind of capabilities are configured during interconnect turn up. > > -- I notice that some vendors gateway implementations, even if gateway is the termination side, require 100rel for the gateway to receive pre-answer requests such as UPDATE. This really didn't have to be this way. I have always seen these gateways, when it is the termination side, respond back SIP 183 with the headers that create early dialog. So if the origination side received the SIP 183 response, then there is no reason for the origination side to now not be able to send UPDATE request. Also, no reason for the termination gateways to not accept the SIP UPDATE without requiring PRACK.
I entirely agree with it. And I also think that the fact that a 1xx response without 100rel is not reliable does not mean that it does not create a dialog so Contact and RR are required.
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