WebRTC MediaStream Identification in the Session Description Protocol
draft-ietf-mmusic-msid-17

No sure the following is useful information:

   This document is a work item of the MMUSIC WG, whose discussion list
   is mmusic@ietf.org.

First time I see this in an abstract.

Susan Hares <shares@ndzh.com> performed the opsdir review.

Copied here for completeness as it hasn't been addressed yet.

---

I have reviewed this document as part of the Operational directorate's

ongoing effort to review all IETF documents being processed by the IESG.  These

comments were written with the intent of improving the operational aspects of the

IETF drafts. Comments that are not addressed in last call may be included in AD reviews

during the IESG review.  Document editors and WG chairs should treat these comments

just like any other last call comments.

 

 

Status:  Almost ready to go, 2 minor concerns, NIT

 

General comment:  Document and concept are generally clear.  Thank you for providing a simple solution to this problem.  

 

Caveat:  My expertise is at lower end of the stack.  I cross referenced all the WebRTC documentation, but I’ve missed how implementations provide feedback that this protocols is up and working.  Therefore, I’ve indicated the operational issues as a set of questions for the authors to consider.

 

Minor concern:

1)      Error handling: Is it possible that the msid-value, msid-id, and msid-appdata can be inserted, and then received with values that are not valid  (1*64token-char]?

a.        If so, an error sequence is necessary. 

b.      If not, it is important to explain why not

Add section to 3.2

2)      Operational  issues:  A few questions for your to consider to provide the link to operational issues.

 

Normal operational:  How does the person who is utilizing this protocol in WebRTC situation check the status of the protocols?  Is it part of the WebRTC status information that the implementations provide?  If so, is there any common management parameters that you can suggest?  Is this in another document in IETF or W3C?

 

Error operations:  If you can have errors, how does the person who utilizes this protocol in WebRTC  find out the error rate.  Again, is it part of the WebRTC status information on errors?  Is it in another document W3C?  

 

 

Editorial NITS:

Page 7, section 3.1

 

Paragraph 2:  double “,” in the section highlighted makes this sentence’s meaning unclear.

Are these two sub-thoughts? If not two sub-thoughts, then perhaps the /new/ suggested text.

 

   When MSID is used, the only time this can happen is when, at a time

   subsequent to the initial negotiation, a negotiation is performed

   where the answerer adds a MediaStreamTrack to an already established

   connection and starts sending data before the answer is received by

   the offerer.  For initial negotiation, packets won't flow until the

   ICE candidates and fingerprints have been exchanged, so this is not

   an issue.

 

/new suggested/

When MSID is used, the only time this can happen is at a time

   subsequent to the initial negotiation,

/

 

Paragraph 3

 

Pagination makes the following text difficult.  Repagination in /new/ may help.  Or it may highlight where I was confused by your document.

 

/old/

The recipient of those packets will perform the following steps:

 

   o  When RTP packets are initially received, it will create an

      appropriate MediaStreamTrack based on the type of the media

      (carried in PayloadType), and use the MID RTP header extension

      [I-D.ietf-mmusic-sdp-bundle-negotiation] (if present) to associate

      the RTP packets with a specific media section.  If the connection

      is not in the RTCSignalingState "stable", it will wait at this

      point.

 

   o  When the connection is in the RTCSignalingState "stable", it will

      look at the relevant media section to find the msid attribute.

 

   o  If there is an msid attribute, it will use that attribute to

      populate the "id" field of the MediaStreamTrack and associated

      MediaStreams, as described above.

 

   o  If there is no msid attribute, the identifier of the

      MediaStreamTrack will be set to a randomly generated string, and

      it will be signalled as being part of a MediaStream with the

      WebIDL "label" attribute set to "Non-WebRTC stream".

 

   o  After deciding on the "id" field to be applied to the

      MediaStreamTrack, the track will be signalled to the user.

/

 

/new/

The recipient of those packets will perform the following steps:

 

   o  When RTP packets are initially received, it will create an

      appropriate MediaStreamTrack based on the type of the media

      (carried in PayloadType), and use the MID RTP header extension

      [I-D.ietf-mmusic-sdp-bundle-negotiation] (if present) to associate

      the RTP packets with a specific media section.  

-    If the connection is not in the RTCSignalingState "stable", it will wait at this point.

-    When the connection is in the RTCSignalingState "stable", it will look at the relevant media section to find the msid attribute.

 

·         Looking a Media section: 

o    If there is an msid attribute, it will use that attribute to populate the "id" field of the MediaStreamTrack and associated MediaStreams, as described above.

o    If there is no msid attribute, the identifier of the MediaStreamTrack will be set to a randomly generated string, and it will be signalled as being part of a MediaStream with the  WebIDL "label" attribute set to "Non-WebRTC stream".

 

   o  After deciding on the "id" field to be applied to the

      MediaStreamTrack, the track will be signalled to the user.

/


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My old discuss text was:

START 

I'm not sure that the answer to this question will require any
change to the document but wanted to check... 

I wondered about the privacy properties of these (and related)
WebRTC identifiers, esp. if they are being handled at various
different layers. Is there work somewhere in the WebRTC space
that's analysing that? For example, one concern might be that
msid-appdata could end up with some kind of privacy sensitive
value, but there's no guidance here about that and as the
examples use UUIDs it's not clear to me those represent nor what
typical values will be used. (Note: I'm not saying that I
believe this is a problem, I'm just checking if it's been
considered.)

I hope that there's no reason why these can't be very ephemeral
values that don't identify (or help re-identification of) people
or their preferences, locations etc., and I'd imagine there's
little reason to e.g. log them. If that's the case wouldn't it
be useful to add such guidance (somewhere, maybe not here)
to help developers to do the right thing?

END

Alissa suggested:

I wonder if adding a reference to https://www.w3.org/TR/mediacapture-streams/#dom-mediastream-id <https://www.w3.org/TR/mediacapture-streams/#dom-mediastream-id> or parroting that guidance would help.

And in response to a mail from Harald I then said:

Given that the W3C document has the details, I've cleared
the discuss. I do think it'd be good to at least have a
reference to that as Alissa suggested and perhaps to also
re-iterate a bit of the advice about avoiding fingerprinting
perhaps.