Re: [Gen-art] Review of draft-ietf-mmusic-sctp-sdp-22

Christer Holmberg <christer.holmberg@ericsson.com> Sun, 05 February 2017 14:14 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Brian Carpenter <brian.e.carpenter@gmail.com>, "gen-art@ietf.org" <gen-art@ietf.org>
Thread-Topic: Review of draft-ietf-mmusic-sctp-sdp-22
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Date: Sun, 05 Feb 2017 14:14:05 +0000
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Subject: Re: [Gen-art] Review of draft-ietf-mmusic-sctp-sdp-22
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Hi Brian,

Thanks for your review! Please see inline.

...

Comments:
---------

>Two points I noted in the writeup:
>"There are existing implementations of earlier versions of the document..."
>
>Excellent, but I wonder why we don't see Implementation Status sections under RFC 6982 in more Last Call drafts.

Perhaps a topic for an IETF chairs lunch presentation?

I have to admit that I did not know about 6982 (now obsoleted by 7942). My suggestion would to not collect that information for this draft at this point of time, as it could take some time.

>"IPv6 address examples are not necessary since IP version differences are immaterial to the purpose of the specification."
>
>It's just as easy to give an IPv6 example though, and more future proof.

I can modify the address in the example, from IPv4 to v6.


Minor issue: (almost a nit)
------------

1.  Introduction
...
>>   NOTE: Due to the characteristics of TCP, usage of 'TCP/DTLS/SCTP'
>>   will always force ordered and reliable delivery of the SCTP
>>   packets, which limits the usage of the SCTP options.  Therefore, it is
>>   RECOMMENDED that TCP is only used in situations where UDP traffic
>>   is blocked.
>
> Why would one choose 'TCP/DTLS/SCTP' rather than just 'TCP/TLS'? I don't object to it being specified, but since you 
> don't support multihoming or multiple associations, what is the use case, in a few words?

SCTP supports multiple SCTP streams over a single association, and you can still use that with 'TCP/DTLS/SCTP'. E.g, the WebRTC Data Channel protocol uses two streams to realize a data channel.

I could modify the first sentence as following:

        "NOTE: Due to the characteristics of TCP, while multiple SCTP streams
         can still be used, usage of 'TCP/DTLS/SCTP' will always force...."

Nits:
-----

>> 4.4.2.  SDP Media Description values
>>
>>      m= line parameter        parameter value(s)
>>     
>>------------------------------------------------------------------
>>      <media>:                 "application"
>>      <proto>:                 "UDP/DTLS/SCTP" or "TCP/DTLS/SCTP"
>>      <port>:                  UDP port number (for "UDP/DTLS/SCTP")
>>                                     TCP port number (for ""UDP/DTLS/SCTP")
>
> I think the last line should be: TCP port number (for "TCP/DTLS/SCTP")

Correct. Will be fixed.

>There is some inconsistency in the use of quotation marks: "UDP/DTLS/SCTP" or 'UDP/DTLS/SCTP'

I'll fix that. I will use single quotes.

Regards,

Christer