[rtcweb] Feedback for draft-ietf-rtcweb-mdns-ice-candidates-03

Nils Ohlmeier <nohlmeier@mozilla.com> Thu, 04 July 2019 05:26 UTC

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From: Nils Ohlmeier <nohlmeier@mozilla.com>
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Date: Wed, 3 Jul 2019 22:26:40 -0700
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Subject: [rtcweb] Feedback for draft-ietf-rtcweb-mdns-ice-candidates-03
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Hello,

I have concerns regarding the current recommendations in draft-ietf-rtcweb-mdns-ice-candidates-03 regarding the handling of IP addresses in the “c=“ lines.

Section 3.1.2.3 recommends to use mDNS for the connection-address. I think we should reconsider this advice as some SPD parsers handle parsing failures differently depending on line type.
In case of Firefox a parsing failure for the connection line is treated as terminal failure. Where parsing failures for a= lines are expected, as these might contain unknown new features.

Section 4.3 mentions that hostnames in ICE candidates can result in ICE failures, but it does not cover backward compatibility in regards to the c= line.

My recommendation is to change the draft so that it recommends to always use a fixed value, for example IP6 ::1 in all c= lines, if mDNS is in use. Obviously it could also be recommended to use an IP4 address instead. The important point is only to use the same IP consistently in all c= lines and across all instances.
I think the advantage of this is better backwards compatibility, and it will not reveal any more details about the user agent compared to using mDNS names in c= lines.

Best regards
  Nils Ohlmeier