Re: [rtcweb] Is rtcweb the right place for draft-ietf-rtcweb-mdns-ice-candidates?

Bernard Aboba <> Thu, 04 July 2019 06:08 UTC

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From: Bernard Aboba <>
Date: Wed, 3 Jul 2019 23:08:38 -0700
Message-ID: <>
To: Nils Ohlmeier <>
Cc: Justin Uberti <>, "" <>
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Subject: Re: [rtcweb] Is rtcweb the right place for draft-ietf-rtcweb-mdns-ice-candidates?
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Nils said:

"assuming it includes using mDNS in the connection line, will break interop"

[BA]  Can someone provide a legacy citation relating to FQDNs in the
connection line?  I am struggling to find one.

<>  Section 5.7
only talks about IPv4 and IPv6 addresses.  I do not see mention of FQDNs.

draft-ietf-mmusic-ice-sip-sdp does not mention FQDNs in the "c=" line and
all examples show IPv4 or IPv6 addresses.

RFC 3264 does not mention FQDNs in c= lines in the text, although it uses
FQDNs within examples (such as Sections 10.1 and 10.2).

JSEP does not mention FQDNs in "c=" lines as far as I can tell.

Also in these documents, I do not see instructions on how a legacy
implementation should gracefully react to FQDNs in the connection line
(e.g. ignoring it).

On Wed, Jul 3, 2019 at 9:50 PM Nils Ohlmeier <> wrote:

> Probably not the ideal forum to point this out, but I hope the Chrome team
> is aware that rolling out this feature, assuming it includes using mDNS in
> the connection line, will break interop with Firefox.
> So I have to concur that rolling this out appears to be premature to me.
> Best
>   Nils Ohlmeier
> On 3Jul, 2019, at 17:58, Justin Uberti <
>> wrote:
> Hmm, that's unfortunate. I think this is a mistake, given that we are
> about to throw the switch to enable mDNS for 100% of Chrome endpoints;
> Chrome (and soon all browsers) will have to ignore ice-sip-sdp until this
> extension spec is written.
> ice-sip-sdp isn't published yet, so it seems an update to that document
> could still be a possibility. If that's not an option, putting forth #1 as
> a specific extension that allows FQDN candidates to be generated in certain
> situations seems like the right path.
> On Wed, Jul 3, 2019 at 5:40 PM Roman Shpount <> wrote:
>> Part of the problem is that mmusic have decided to punt on the FQDN
>> support. In the current mmusic-ice-sip-sdp the final language that was
>> included:
>> <connection-address>:  is taken from RFC 4566 [RFC4566].  It is the IP
>> address of the candidate, allowing for IPv4 addresses, IPv6 addresses, and
>> fully qualified domain names (FQDNs).  When parsing this field, an agent
>> can differentiate an IPv4 address and an IPv6 address by presence of a
>> colon in its value - the presence of a colon indicates IPv6.  *An agent
>> generating local candidates MUST NOT use FQDN addresses.  An agent
>> processing remote candidates MUST ignore candidate lines that include
>> candidates with FQDN *or IP address versions that are not supported or
>> recognized.  *The procedures for generation and handling of FQDN
>> candidates, as well as, how agents indicate support for such procedures,
>> need to be specified in an extension specification.*
>> So, at this point we have two options:
>> 1. draft-ietf-rtcweb-mdns-ice-candidates can update ice-sip-sdp and
>> define how FQDN candidates generated by mdns are handled
>> 2. write a new draft in mmusic which defines FQDN handling
>> In any case some sort of mmusic discussion is needed to reconcile this.
>> Best Regards,
>> _____________
>> Roman Shpount
>> On Wed, Jul 3, 2019 at 8:28 PM Justin Uberti <> wrote:
>>> The problem this draft is trying to solve is fairly RTCWEB-specific. If
>>> there are individual issues to resolve, we can send them out to mmusic for
>>> discussion, but AFAIK no changes to existing ICE specs are needed.
>>> On Wed, Jul 3, 2019 at 4:26 PM Roman Shpount <> wrote:
>>>> Hi All,
>>>> Is rtcweb the right place for draft-ietf-rtcweb-mdns-ice-candidates?
>>>> This entire draft seems to be ICE/SDP specific and not limited to rtcweb.
>>>> Also, there are significant interop implications for this draft
>>>> between browser and non-browser end points which probably warrant larger
>>>> discussion outside of rtcweb group. I would think mmusic would be a much
>>>> better place for this draft. I know there is an incentive to complete this
>>>> draft quickly but this has a potential to break a lot of things (it already
>>>> did break interop with almost every existing ICE implementation).
>>>> Regards,
>>>> _____________
>>>> Roman Shpount
>>>> _______________________________________________
>>>> rtcweb mailing list
>>> _______________________________________________
> rtcweb mailing list
> _______________________________________________
> rtcweb mailing list