Re: [rtcweb] Meaning of SHOULD support/use interleaving

Harald Alvestrand <harald@alvestrand.no> Mon, 27 October 2014 18:27 UTC

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Date: Mon, 27 Oct 2014 11:23:14 -0700
From: Harald Alvestrand <harald@alvestrand.no>
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Subject: Re: [rtcweb] Meaning of SHOULD support/use interleaving
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On 10/27/2014 07:19 AM, Christer Holmberg wrote:
> Hi,
>
>>> Within the CLUE WG, we had a discussion regarding the following statement in section 6.1 of draft-ietf-rtcweb-data-channel-12.txt:
>>>  
>>> "The support for message interleaving as defined in
>>>                 [I-D.ietf-tsvwg-sctp-ndata] SHOULD be used."
>>>  
>>> First, it is a little unclear what "the support SHOULD be used" means.
>> My understanding is that SCTP implementations supporting the extension will use it.
>> This is negotiated during the setup of the SCTP association.
> If it's done on SCTP level, why do we need to talk about it in the data channel draft? 
>
> Is there a reason why it is important to use it for data channels? If so, does it apply to data channels in general? 

NDATA was added in order to avoid head-of-line blocking on the transport
(if I understand this correctly, until this was added, sending a huge
message would block the delivery of small messages on all channels until
the huge message was fully delivered).

Unlike Michael, I see no reason to make this a SHOULD; I think it should
be a MUST, and the older implementations in browsers should just be
called out as non-conformant.

That said, I think that data channels ought to interoperate successfully
with implementations that don't support the extension - but data channel
implementations in WebRTC endpoints should be under a "MUST implement,
MUST offer" ruleset.



>
> Regards,
>
> Christer
>
>
>
> Whether messages are interleaved or not depends on the stream scheduler. This is a sender side only decision. The receiver has to deal with it.
> It is not a MUST, since there are implementations now in use which don't support the extension.
>
> Best regards
> Michael
>>  
>> Second, does it mean that any data channel protocol (e.g CLUE) SHOULD use interleaving, even if the characteristics of the protocol wouldn't require it?
>>  
>> Regards,
>>  
>> Christer
>> _______________________________________________
>> rtcweb mailing list
>> rtcweb@ietf.org
>> https://www.ietf.org/mailman/listinfo/rtcweb
> _______________________________________________
> rtcweb mailing list
> rtcweb@ietf.org
> https://www.ietf.org/mailman/listinfo/rtcweb


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