Hi, >I still have some difficult in using IETF and cannot find the whole sorted comments about this draft, so i have some doubt about this draft. > > 1. "If a forking proxy receives a reliably sent 199 response for a dialog, for which the proxy has previously generated and sent a 199 response, the proxy MUST forward the 199 response." > > Does it describe the case below? Although P1 have sent a 199 response, P1 havs to forword the send reliably 199 too.Or is the first 199 mistaked for 18x? > > UAC P1 UAS_2 > --- INVITE ------> > --- INVITE (leg 2) -> > <-- 199(leg 2) -- > <-- 199 (leg 2) ----- > <-- 199(leg 2) --
>I think it shall be 199, as currently written. > >[Eric]: If this is 199, then Is there a special purpose to send two 199 in the same dialog? >I think that one 199 is enough. >And the first 199 may be reliable too, that will make it a little difficult to send the second 199. The second 199 could include information which is to be forwarded to the UAC. >2. "10. Usage with 100rel > > When a 199 Early Dialog Terminated provisional response is sent by a UAS, since the provisional response is only used for information purpose, the UAS SHOULD send it unreliably even if the 100rel > option tag [RFC3262] is present in the Require header of the associated request." > > >I have seen a comment on this question,but still not understood about >it. If the INVITE has a Require tag "Require: 100rel",does the UAS still >use unreliable 199 response? > >That is the recommendation, yes. The reasons is that we want to keep 199 >as "lightweight" as possible, without requireing re-transmissions and >PRACKs. > >[Eric]: But reliable 199 have more advantage, and It is worth to use the reliable 199,I think. I don't know what that advantage would be, compared to having to send PRACKs etc. This has been discussed quite much, so I would really need some good justification to change it now. Also, the draft doesn't forbid you to send the 199 reliably. It's only a SHOULD. >If 199 is reliable, there is one more advantage. If the 199 arrives >before the first 18x response, UAC can discard the first 199 and process >it until UAC receives the first 18x response that has the same >to-tag as 199, as the reliable 199 should be re-transmited until >received PRACK. > >If the INVITE contains "Require: 100rel", the first 18x must also be >sent reliably. And, I don't think the UAS is allowed to send another >reliable response until the first one is acknowledged, so I don't think >a reliable 199 would reach the UAC before the first reliable 18x. > >[Eric]: Surely the UAS is allowed to send another reliable response until the first one is acknowledged, If I remember correctly, the FIRST reliable response must be acknowleded before the next reliable response is sent. But, we can double check in the PRACK spec. >but reliable 199 will be useful if the first 18x is unreliable, or the first 18x has been acknwledged. It's another case different from the above one whose INVITE contains "require: 100rel". If 100rel is required the 18x cannot be unreliable. Regards, Christer _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [email protected] for questions on current sip Use [email protected] for new developments on the application of sip
