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Re: [rtcweb] RTCWEB data channel protocol: Do both endpoints need to send DATA_CHANNEL_OPEN?

Salvatore Loreto <salvatore.loreto@ericsson.com> Tue, 28 January 2014 08:30 UTC

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From: Salvatore Loreto <salvatore.loreto@ericsson.com>
To: Christer Holmberg <christer.holmberg@ericsson.com>
Thread-Topic: [rtcweb] RTCWEB data channel protocol: Do both endpoints need to send DATA_CHANNEL_OPEN?
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Date: Tue, 28 Jan 2014 08:30:46 +0000
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Subject: Re: [rtcweb] RTCWEB data channel protocol: Do both endpoints need to send DATA_CHANNEL_OPEN?
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On Jan 28, 2014, at 10:16 AM, Christer Holmberg <christer.holmberg@ericsson.com<mailto:christer.holmberg@ericsson.com>>
 wrote:

Hi,

As defined in draft-ietf-rtcweb-data-channel-06, a data channel consists of two unidirectional SCTP streams.

exactly it is a pair of one ingoing and one outgoing stream


draft-ietf-rtcweb-data-protocol-01 says that, if one endpoint wants to open a data channel, it sends a DATA_CHANNEL_OPEN (using a SCTP stream ID value of its choice). Then, the other endpoints sends DATA_CHANNEL_ACK on the same SCTP stream (eventhough it is a unidirectional stream).

not exactly, it says with the same stream identifier


   If a DATA_CHANNEL_OPEN message is received on an unused stream, the
   stream identifier corresponds to the role of the peer and all
   parameters in the DATA_CHANNEL_OPEN message are valid, then a
   corresponding DATA_CHANNEL_ACK message is sent on the stream with the
   same stream identifier as the one the DATA_CHANNEL_OPEN message was
   received on.


that means that means that the outgoing stream should have the same stream identifier of the ingoing one.
I understand is not clear at first read, we will try to clarify better


Q1: Assuming that both endpoints want to use the data channel, do both endpoints need to send DATA_CHANNEL_OPEN (on separate SCTP streams)? Or, can one of the endpoints, if it has received DCO, start using the data channel (using a SCTP stream of its choice)?

sorry I don't understand the question.
Are you asking for both endpoints trying to open the same channel and how avoid glare in opening channels
or you are looking in the scenario where both endpoints want to open to different channels?

br
Salvatore


Regards,

Christer


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