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.
>
> What I meant was that 5245 explicitly states that all previously signalled candidates MUST be signalled in updated Offers, so candidate removal in the middle of ICE processing is not something that is defined for ICE.
>
> Also, non-signalled candidates, like peer reflexive, are not required to be signalled in update Offers, so their absence in an offer cannot in any way be construed as a request for their removal.

So, IF we can define the same for trickled candidates, then there might not be an issue.

We have to remember, though, that a trickled candidate is not a new candidate "type". The candidate types you trickle are the same types you send in Offer/Answer - tickle is simply an alternative candidate transport mechanism.

>> 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.
>
> Right, and I've already mentioned that I don't see any reason to consider them as part of the SDP state, just as you wouldn't consider peer-reflexive candidates to be part of it.

If a trickled candidate is eventually selected, doesn't a "clean up" SDP Offer have to be sent (as for any other non-default candidate), where the c- line is aligned with the candidate? In that case the candidate becomes part of the SDP state :)

Regards,

Christer