[MMUSIC] Magnus Westerlund's Discuss on draft-ietf-mmusic-data-channel-sdpneg-25: (with DISCUSS and COMMENT)

Magnus Westerlund via Datatracker <noreply@ietf.org> Fri, 05 April 2019 12:04 UTC

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Subject: [MMUSIC] Magnus Westerlund's Discuss on draft-ietf-mmusic-data-channel-sdpneg-25: (with DISCUSS and COMMENT)
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Magnus Westerlund has entered the following ballot position for
draft-ietf-mmusic-data-channel-sdpneg-25: Discuss

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There might be a serious issue in label definition.

5.1.3.  Label Parameter

   The 'label' parameter indicates the name of the channel.  It
   represents a label that can be used to distinguish, in the context of
   the WebRTC API [WebRtcAPI], an RTCDataChannel object from other
   RTCDataChannel objects.  This parameter maps to the 'Label' parameter
   defined in [I-D.ietf-rtcweb-data-protocol].  The 'label' parameter is
   optional.  If it is not present, then its value defaults to the empty

  label-opt       = "label=" quoted-string
  quoted-string   = DQUOTE *(quoted-char / escaped-char) DQUOTE
  quoted-char     = SP / quoted-visible
  quoted-visible  = %x21 / %x23-24 / %x26-7E ; VCHAR without " or %
  escaped-char    = "%" HEXDIG HEXDIG

I interpret that as the intention is to enable the SDP Attribute to carry the
label as defined in W3C API. That value is in the current candidatate
specification an https://www.w3.org/TR/webrtc/ as an USVSsting
(https://heycam.github.io/webidl/#idl-USVString). And in the reference version
of the WebRTC API as an DOMstring. Both are not limited to ASCII and may
contain any Unicode characters. Thus the escaping mechanism defined appear to
be insufficient.

I think the "quoted-string" need a definition of what type of string this truly
are so that it is clear what a character in the string is.

In addition the specification of escaping is undersspecified. I would recommend
at least adding discussion of the need and how to escape DQUOTE and % that can
be relatively common operations.


Section 5.1.3:

Is it correct that there are no limiation on the lenght of the label? So it
will okay if I use the more than 450k words of J.R.R.R Tolkien's Lords of the
Ring as label?

Is it really the intention to point to the very old version of the API from
2015? The current candidate specification is available here:
https://www.w3.org/TR/webrtc/ and are from 2018.