Re: [rtcweb] Opening unordered data channel issue
Victor Pascual Avila <victor.pascual.avila@gmail.com> Fri, 23 August 2013 10:40 UTC
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Date: Fri, 23 Aug 2013 12:40:44 +0200
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From: Victor Pascual Avila <victor.pascual.avila@gmail.com>
To: "<rtcweb@ietf.org>" <rtcweb@ietf.org>
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Subject: Re: [rtcweb] Opening unordered data channel issue
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I agree -- +1 for b) On Thu, Aug 22, 2013 at 7:12 PM, Justin Uberti <juberti@google.com> wrote: > I agree that b) is the cleanest choice. While this makes the handshake > 2-way, it does not suffer from the performance issues that affected the > previous 2- and 3-way handshake proposals, since data can be sent > immediately without waiting for the ACK. > > > On Thu, Aug 22, 2013 at 8:52 AM, Michael Tuexen > <Michael.Tuexen@lurchi.franken.de> wrote: >> >> Dear all, >> >> at the last IETF in Berlin we discussed how to handle the opening of >> unordered data channels (no matter wether reliable or not). The problem >> to be handled is that it is possible that user messages arrive at the >> receiver before the DATA_CHANNEL_OPEN message is received. The result >> of the discussion at the meeting was that the best solution is that >> the sender sends user messages also ordered (on unordered channels) >> until there is an indication from the peer that the DATA_CHANNEL_OPEN >> has been processed. This makes sure that the DATA_CHANNEL_OPEN message >> is not received before user messages and therefore the above problem >> is solved. >> >> The open issue is, what the indication from the peer is. There were >> two options discussed at the meeting and it was decided that Randall >> Stewart and myself bring this to the list with the pros and cons >> of the alternatives. So here are the two options: >> >> (a) Use any user message sent from the peer as an indication. >> (b) Use a new ACK message. >> >> Arguments: >> * Using (b) introduces a 2-way handshake for unordered data channels. >> However, it also works for data channels being used unidirectional. >> * Using (a) stays with the 1-way handshake, but in case of >> data channels being used unidirectional you will not see the benefits >> of unordered delivery. >> >> We had some discussions offline and think that using (b) is the >> cleaner solution. Please note that this 2-way handshake is not >> similar to the one we had some time ago. The ACK does not contain >> any additional information and it does not introduce any delay. >> You can send user data right after opening the data channel. >> >> For consistency we would even propose to use this 2 way handshake >> for ordered channels. It doesn't have any drawback and would mean >> that we use the same handshake for all data channels. >> >> So the proposed procedure for opening an arbitrary data channel is: >> 1) The opener sends a DATA_CHANNEL_OPEN message ordered and reliable. >> 2) The opener can start sending user data immediately. >> It will always be sent ordered, no matter whether the data channel >> is ordered or not. >> 3) The peer will send a DATA_CHANNEL_ACK message ordered and reliable >> in response to the DATA_CHANNEL_OPEN message. >> 4) After reception of the DATA_CHANNEL_ACK message, >> the opener will sent user messages unordered, >> if the data channel is unordered and ordered, if the >> data channel is ordered. >> >> Any opinions? >> >> Best regards >> Michael >> >> _______________________________________________ >> rtcweb mailing list >> rtcweb@ietf.org >> https://www.ietf.org/mailman/listinfo/rtcweb
- [rtcweb] Opening unordered data channel issue Michael Tuexen
- Re: [rtcweb] Opening unordered data channel issue Justin Uberti
- Re: [rtcweb] Opening unordered data channel issue Cullen Jennings (fluffy)
- Re: [rtcweb] Opening unordered data channel issue Bernard Aboba
- Re: [rtcweb] Opening unordered data channel issue Matthew Kaufman (SKYPE)
- Re: [rtcweb] Opening unordered data channel issue Hadriel Kaplan
- Re: [rtcweb] Opening unordered data channel issue Victor Pascual Avila
- Re: [rtcweb] Opening unordered data channel issue Harald Alvestrand
- Re: [rtcweb] Opening unordered data channel issue Eric Rescorla