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

On 27 Oct 2014, at 19:23, Harald Alvestrand <harald@alvestrand.no> wrote:

> 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.
I personally also prefer a MUST, but the reason I gave was the one which
was used in the discussion resulting in a SHOULD. Since this is also brought
up by David, we possibly need to reconsider the issue and change it to a MUST.

Best regards
Michael
> 
> 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
> 
> 
> -- 
> Surveillance is pervasive. Go Dark.
> 
> _______________________________________________
> rtcweb mailing list
> rtcweb@ietf.org
> https://www.ietf.org/mailman/listinfo/rtcweb
> 