RE: [tsvwg] Last Call: <draft-ietf-tsvwg-rtcweb-qos-15.txt> (DSCP and other packet markings for WebRTC QoS) to Proposed Standard

"Black, David" <david.black@xxxxxxx> · Tue, 3 May 2016 16:21:25 +0000

>
As a process question, where does that note go and why would it be a note for the RFC editor vs. language for readers?

The note will go into the datatracker because the Web RTC RTP usage draft (draft-ietf-rtcweb-rtp-usage) is in the RFC Editor Queue:

https://datatracker.ietf.org/doc/draft-ietf-rtcweb-rtp-usage/
Sorry for not mentioning that draft status in my earlier email.

One of the ART ADs would submit the RFC Editor Note, after Cullen and the rtcweb WG come up with its text, including figuring out where in the RTP usage draft
 to insert these statements.

Thanks, --David

From: Paul E. Jones [mailto:paulej@xxxxxxxxxxxxxx]

Sent: Tuesday, May 03, 2016 10:44 AM

To: Black, David; Magnus Westerlund; Cullen Jennings

Cc: ietf@xxxxxxxx; tsvwg-chairs@xxxxxxxx; draft-ietf-tsvwg-rtcweb-qos@xxxxxxxx; tsvwg@xxxxxxxx

Subject: RE: [tsvwg] Last Call: <draft-ietf-tsvwg-rtcweb-qos-15.txt> (DSCP and other packet markings for WebRTC QoS) to Proposed Standard

David,

The text you proposed for the flow type I incorporated. Since everyone agreed with the language, I didn't present it here.

I'll wait for Cullen's reply on the note.

As a process question, where does that note go and why would it be a note for the RFC editor vs. language for readers? Or an I misinterpreting the intent?

Paul

From: "Black, David" <david.black@xxxxxxx>

Sent: May 3, 2016 11:29:15 AM EDT

To: "Paul E. Jones" <paulej@xxxxxxxxxxxxxx>, Magnus Westerlund <magnus.westerlund@xxxxxxxxxxxx>, Cullen Jennings <fluffy@xxxxxx>

Cc: "ietf@xxxxxxxx" <ietf@xxxxxxxx>, "tsvwg-chairs@xxxxxxxx" <tsvwg-chairs@xxxxxxxx>, "draft-ietf-tsvwg-rtcweb-qos@xxxxxxxx"
 <draft-ietf-tsvwg-rtcweb-qos@xxxxxxxx>, "tsvwg@xxxxxxxx" <tsvwg@xxxxxxxx>, "Black, David" <david.black@xxxxxxx>

Subject: RE: [tsvwg] Last Call: <draft-ietf-tsvwg-rtcweb-qos-15.txt> (DSCP and other packet markings for WebRTC QoS) to Proposed Standard

Paul,
 As I understand, we need this addition:

          Currently in WebRTC, media sent over RTP is assumed to be
          interactive <xref target="I-D.ietf-rtcweb-rtp-usage"/>
          while media streamed over HTTP <xref target="RFC7230"/>
          <xref target="RFC7540"/> is assumed not to be.  Future WebRTC
          extensions could allow streamed, non-interactive media over RTP.

 I modified is slightly by adding "non-interactive" near the end and
 inserting a reference near "interactive", though this is perhaps a
 redundant reference since it appears elsewhere in the draft.

That's item [2], please make sure that item [1] is also covered.

 That RTP usage reference does not speak to HTTP, so I don't have a
 reference to "prove" that sentence above.  Is there a better reference?

With careful reading, one can discern that the Web RTC RTP usage draft
(draft-ietf-rtcweb-rtp-usage) implies that all Web RTC usage is interactive,
but some subtlety is involved.  IMHO, relying on implementers to grasp
that sort of "do what I mean" rationale is problematic.

Cullen - would you be amenable to drafting a blunt RFC Editor note
for the RTP usage draft to state that all current Web RTC RTP usage is
for interactive media, and non-interactive Web RTC media flows currently
use HTTP (and would that be HTTP over the Web RTC data channel or
something else)?

Obviously, the rtcweb WG will have to sign off on that RFC Editor note,
but this looks like a relatively short path to addressing the problem.

Thanks,
--David (as draft shepherd)
 -----Original Message-----
 From: Paul E. Jones [mailto:paulej@xxxxxxxxxxxxxx]
 Sent: Monday, May 02, 2016 10:18 PM
 To: Magnus Westerlund; Black, David; Cullen Jennings
 Cc: ietf@xxxxxxxx; tsvwg-chairs@xxxxxxxx; draft-ietf-tsvwg-rtcweb-qos@xxxxxxxx;
 tsvwg@xxxxxxxx
 Subject: Re: [tsvwg] Last Call: <draft-ietf-tsvwg-rtcweb-qos-15.txt> (DSCP and
 other packet markings for WebRTC QoS) to Proposed Standard

 As I understand, we need this addition:

          Currently in WebRTC, media sent over RTP is assumed to be
          interactive <xref target="I-D.ietf-rtcweb-rtp-usage"/>
          while media streamed over HTTP <xref target="RFC7230"/>
          <xref target="RFC7540"/> is assumed not to be.  Future WebRTC

extensions could allow streamed, non-interactive media over RTP.

 I modified is slightly by adding "non-interactive" near the end and
 inserting a reference near "interactive", though this is perhaps a
 redundant reference since it appears elsewhere in the draft.

 That RTP usage reference does not speak to HTTP, so I don't have a
 reference to "prove" that sentence above.  Is there a better reference?

 Paul

 ------ Original Message ------
 From: "Magnus Westerlund" <magnus.westerlund@xxxxxxxxxxxx>
 To: "Black, David" <david.black@xxxxxxx>; "Cullen Jennings"
 <fluffy@xxxxxx>
 Cc: "ietf@xxxxxxxx" <ietf@xxxxxxxx>; "tsvwg-chairs@xxxxxxxx"
 <tsvwg-chairs@xxxxxxxx>; "draft-ietf-tsvwg-rtcweb-qos@xxxxxxxx"
 <draft-ietf-tsvwg-rtcweb-qos@xxxxxxxx>; "tsvwg@xxxxxxxx"
 <tsvwg@xxxxxxxx>
 Sent: 4/19/2016 4:46:53 AM
 Subject: Re: [tsvwg] Last !
 Call:
<draft-ietf-tsvwg-rtcweb-qos-15.txt>
 (DSCP and other packet markings for WebRTC QoS) to Proposed Standard

Den 2016-04-18 kl. 15:04, skrev Black, David:
So, summarizing Magnus's concerns with proposals:

[1] Flow Type in application-facing browser API:

Propose an additional sentence:
OLD
    o  Flow Type: The browser provides this input as it knows if the
flow
       is audio, interactive video with or without audio,
non-interactive
       video with or without audio, or data.
NEW
    o  Flow Type: The browser provides this input as it knows if the
flow
       is audio, interactive video with or without audio,
non-interactive
       video with or without audio, or data.  For audio that is
associated
       with a video flow, the flow type of the associated video MAY
       be used instead of the associated audio type.

Magnus - does that new text suffice?

Yes.

[2] What does "interactive" mean in an implementation?:

We could add something along lines of ..... Currently in WebRTC,
media sent over
RTP is assumed to be interactive while media streamed over HTTP is
assumed not
to be. Future WebRTC extensions could allow streamed media over RTP.

I believe the proposed additional sentence addresses the question of
how a browser
determines whether a video flow is interactive.  This proposed
sentence will need to
cite a WebRTC document that contains a statement to that effect, as I
don't think this
draft is the right place to be the primary reference for that
statement.

Magnus - would this approach be ok?

Yes.

/Magnus

Thanks, --David
-----Original Message-----
From: Cullen Jennings [mailto:fluffy@xxxxxx]
Sent: Friday, April 15, 2016 10:48 AM
To: Black, David
Cc: Magnus Westerlund; ietf@xxxxxxxx; tsvwg-chairs@xxxxxxxx;
draft-ietf-tsvwg-
rtcweb-qos@xxxxxxxx; tsvwg@xxxxxxxx
Subject: Re: [tsvwg] Last Call: <draft-ietf-tsvwg-rtcweb-qos-15.txt>
(DSCP and
other packet markings for WebRTC QoS) to Proposed Standard

On Apr 3, 2016, at 3:37 PM, Black, David <david.black@xxxxxxx>
wrote:

I see a couple of Magnus's points that appear to need additi!
 onal
text
in the draft:

[1] Flow Type in application-facing browser API:

o Flow Type: The browser provides this input as it knows if
the flow is audio, interactive video with or without audio,
non-interactive video with or without audio, or data.

[... snip ...]
The main issue here is that to me it was not clear that
"Interactive
Video with or without audio" allows for setting these DSCP values
also
for the RTP stream containing audio also. This, I do see a need for
clarification on.

Propose an additional sentence:
OLD
    o  Flow Type: The browser provides this input as it knows if the
flow
       is audio, interactive video with or without audio,
non-interactive
       video with or without audio, or data.
NEW
    o  Flow Type: The browser provides this input as it knows if the
flow
       is audio, interactive video with or without audio,
non-interactive
       video with or without audio, or data.  For audio that is
associated
       with a video flow, the flow type of the associated video MAY
       be used instead of the as!
 sociated
audio type.

I hesitate to say anything stronger than "MAY" here.

Looks good.

[2] What does "interactive" mean in an implementation?:

We could add something along lines of ..... Currently in WebRTC,
media sent over
RTP is assumed to be interactive while media streamed over HTTP is
assumed not
to be. Future WebRTC extensions could allow streamed media over RTP.

The issue is that this document is called: DSCP and other packet
markings for WebRTC QoS. Then this document define something that
is not
imme!
 diately
mappable onto what is being defined in the other WebRTC
specifications. That is why I am raising that there need to be more
clear coupling. If that coupling is to mostly happen in another
document, can we at least then have a proposal on the table for
that
change to ensure that the result is understandable.

Well, this TSVWG draft is definitely not the right place for a
discussion of
when a video flow is interactive or non-interactive - I hope we can
agree
on that.

Beyond that, as Cullen (Jennings) is both an author of this document
and
one of the chairs of the rtcweb WG, I'd suggest that he and/or the
rtcweb
WG propose an appropriate location for discussion of when a video
flow
is interactive or non-interactive.  This TSVWG draft would then have
an
additional sentence added, e.g.,

  See [TBD] for further discussion of how to determine
  whet!
 her a
video flow is interactive vs. non-interactive.

I believe that the added reference here ([TBD] above) would be
normative.

Cullen?

That discussion happened long ago for WebRTC and we decided we did
not need
a _javascript_ controls point in the WebRTC API to indicate if RTP was
interactive or
not. If people start doing streaming video over RTP we can come back
and revisit
this and trivially add an API to indicate that in the W3C WebRTC API.
Part of what
drove this decision is the likes of Netflix / ITunes / Youtube are
not asking the
browser vendors for streaming media over RTSP or RTP. They think HTTP
works
much better for this. Thus the browser vendors see no need for non
interactive
video over RTP. I agree with Magnus that this might change some day
in the
future but right now, I think it's close enough that everyone can
live with it.
I'm
not OK in treating it like some open issue that is still in
discussion that
somehow holds up this spec - it's not.

Thanks, --David (as document  shepherd)

--
Magnus Westerlund

Services, Media and Network features, Ericsson Research EAB/TXM

Ericsson AB                 | Phone  +46 10 7148287
Färögatan 6                 | Mobile +46 73 0949079
SE-164 80 Stockholm, Sweden | mailto: magnus.westerlund@xxxxxxxxxxxx