Hello Paul, > I guess it depends on what you mean by interoperability. None of the > directionality stuff was in 2543, so you can't expect something > operating by 2543 rules to do that.
The definition of interoperability I had in mind in the context of SIP was just something like this: Two UAs are interoperable if they are able to operate together successfully in the most important scenarios, e.g. establishing a call, ending a call, putting an established call on hold. As far as I know, 3261 was specified in a way such that 3261 and 2543 UAs are interoperable, at least when only the basic SIP signalling scenarios are considered. So I expected that this would also be the case for the SDP and Offer/Answer related aspects. > ... > I don't believe a strategy for this is written anywhere. > > To make this work, UA1 needs to recognize that the absence of any > explicit directionality in the answer is a hint that UA2 doesn't support > this. > > In that case UA1 need to go the extra mile and do its hold according to > 2543 rules - using c=0.0.0.0 in another offer. This is what I was afraid of. So we really have to resort to hints or guesses and add extra complexity to a UA based on 3261 in order to be interoperable with a 2354 based UA? At least it seems to me as if there would have been some options to avoid this, e.g. by using a different version number or maybe just by avoiding the "since sendrecv is the default" clause in 3264. Do you know whether most 3261 based UAs really do something similar to what you suggested or do you rather think that most 3261 UAs don't try to be interoperable with 2543 UAs (at all)? Thanks in advance for any further help! Regards, Peter _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
