[MMUSIC] trickle-ice review
Peter Saint-Andre - &yet <peter@andyet.net> Tue, 07 July 2015 04:16 UTC
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Date: Mon, 06 Jul 2015 22:01:06 -0600
From: Peter Saint-Andre - &yet <peter@andyet.net>
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Subject: [MMUSIC] trickle-ice review
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Because I'll probably be on a plane (not to Prague!) during the MMUSIC session on July 22, I figured it might be helpful to post some comments to the list. Abstract... OLD The above mechanism is also referred to as "trickle ICE". NEW This mechanism is called "trickle ICE". Rationale: the mechanism is never referred to as anything other than trickle ICE. Section 1... A typo: OLD describes mechanisms for gathering, candidates, prioritizing them, NEW describes mechanisms for gathering candidates, prioritizing them, [I found some other typos here and there but haven't noted them - our friends on the RFC Editor team can help later on.] Section 4... This sounds a bit strange, as if RFC 5245 talks about support for trickle: According to [RFC5245] every time an agent supporting trickle ICE generates an offer or an answer, it MUST include the "trickle" token in the ice-options attribute. I suggest: According to [RFC5245], supported features MUST be advertised in the ice-options attribute. Therefore an agent supporting trickle ICE MUST include a token of "trickle" in the ice-options attribute every time it generates an offer or an answer. Section 5... I question this statement: For optimal performance, it is RECOMMENDED that an initial offer contains host candidates only. This would allow both agents to start gathering server reflexive, relayed and other non-host candidates simultaneously, and it would also enable them to begin connectivity checks. As we have discovered recently (see the research the Philipp Hancke has been performing on deployed WebRTC audio/video services), the best call setup time and thus user experience is found by sending only relayed candidates first. Recommending that user agents send only host candidates in the initial offer will only perpetuate slow call setup times. Section 6.1... An agent can respond to an initial offer at any point while gathering candidates. The answer can again contain any set of candidates including none or all of them. Unless it is protecting host addresses for privacy reasons, the agent would typically construct this initial answer including only them, thus allowing the remote party to also start forming checklists and performing connectivity checks. By "them" I assume you mean host candidates. If so, see above on the "host-only-first" policy. Section 8... For the most part, trickle ICE agents perform connectivity checks following vanilla ICE procedures. Of course, the asynchronous nature of candidate harvesting in trickle ICE would impose a number of changes described here. Actually I think it is not just harvesting but communication. Section 9.3... Once an agent sends the end-of-candidates event, it will update the state of the corresponding check list as explained in section Section 8.1. Past that point agents MUST NOT send any new candidates. Once an agent has received an end-of-candidates indication, it MUST also ignore any newly received candidates for that media stream. Adding new candidates to the negotiation is hence only possible through an ICE restart. The second sentence is somewhat at odds with the last sentence. I suggest saying something like "Past that point agents MUST NOT send any new candidates within this ICE session" or some such. I have not yet formed an opinion on the open issues described in Appendix A, nor have I yet had a chance to check that the XMPP Jingle use of trickled candidates (which dates from 2005!) is fully consistent with draft-ietf-mmusic-trickle-ice. I will try to complete those tasks before the Prague meeting. Peter -- Peter Saint-Andre https://andyet.com/
- [MMUSIC] trickle-ice review Peter Saint-Andre - &yet
- Re: [MMUSIC] trickle-ice review Bernard Aboba
- Re: [MMUSIC] trickle-ice review Peter Saint-Andre - &yet
- Re: [MMUSIC] trickle-ice review Emil Ivov