Re: [MMUSIC] UPDATE mechanism for Trickle ICE - Comment on draft-ivov-mmusic-trickle-ice-sip-01

[Christer Holmberg <[e-mail]>]

Hi,

>> First, I completely messed up with the candidate types. Sorry for the 
>> confusion :)
>>
>> Anyway, it doesn't really matter what type of candidates are trickled
>> - it's about whether trickled candidates can be affected by 
>> Offers/Answers.
>
> And by affected you really mean invalidated. OK, I think I understand now.
>
> I don't think there's anything in 5245 that defines semantics which would invalidate existing candidates.

Generally, in SDP Offer/Answer, when an SDP attribute is not present, it means that it's invalidated, or the default value (if such has been specified) is assumed.

You could of course argue that, if a candidate has never been carried in an SDP Offer/Answer to begin with, SDP Offer/Answers should have no impact on it.

But, that really depends on whether the candidates are considered part of the SDP state or not. IF so, trickled candidates would update that state, in the same way SDP Offers/Answers do.

My point is that these things need to be clearly clarified.

>>>> So, that would mean that if an Offer is received without the peer 
>>>> refexive candidates, the answerer would remove them.
>>>
>>> You lost me. How would an answerer remove candidates from an offer if 
>>> they weren't there in the first place? Did you mean to say something 
>>> else?
>>
>> I referred to the example below, where an Offer does not contain a 
>> candidate that was previously trickled, and whether the answerer will 
>> then assume that the candidate is no longer valid.
>
> Right. I don't think there's such a risk. 5245 explicitly forbids update Offers and Answers to remove candidates that have been announced previously and it allows (as in MAY, not SHOULD) that new candidates be added.
>
> The former should address your concern and I believe we could simply remove the latter as it is of little use, if any.

Well, then there is of course a risk that the receiver of the Answer will trigger an error, as the trickled candidate is not included in the Answer (as the Answer was sent before the candidate was trickled :)

Regards,

Christer