Re: [rtcweb] [MMUSIC] What goes into c= line address when FQDN is used for the default candidate?

Justin Uberti <juberti@google.com> Thu, 07 February 2019 16:28 UTC

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From: Justin Uberti <juberti@google.com>
Date: Thu, 7 Feb 2019 08:28:06 -0800
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To: Harald Alvestrand <harald@alvestrand.no>
Cc: RTCWeb IETF <rtcweb@ietf.org>
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Subject: Re: [rtcweb] [MMUSIC] What goes into c= line address when FQDN is used for the default candidate?
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Note also that only host candidates will be mDNS; srflx and relay
candidates will continue to work as before.



On Thu, Feb 7, 2019 at 8:01 AM Harald Alvestrand <harald@alvestrand.no>
wrote:

> Den 05.02.2019 16:03, skrev Alan Ford:
> > If that update was to be made, this goes against the text
> > in draft-ietf-rtcweb-mdns-ice-candidates-02 which says:
> >
> >    An ICE agent that supports mDNS candidates MUST support the situation
> >    where the hostname resolution results in more than one IP address.
> >    In this case, the ICE agent MUST take exactly one of the resolved IP
> >    addresses and ignore the others.  The ICE agent SHOULD, if available,
> >    use the first IPv6 address resolved, otherwise the first IPv4
> >    address.
> >
> > But there’s a bigger problem here, which is how to cope with an FQDN is
> > not resolvable. So the intention, as I understand it, is that when these
> > host candidates leave the mDNS domain and are thus not resolvable, they
> > will be treated as peer reflexive candidates.
> >
> > But at that point there is no address family information available, so
> > how does an ICE agent know to do pairing with these candidates, which
> > requires the address family to be known?
>
> Peer reflective candidates are identified by means of an incoming packet.
> The address family is very obvious from the packet.
>
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