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

Roman Shpount <roman@telurix.com> Fri, 01 February 2019 20:09 UTC

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From: Roman Shpount <roman@telurix.com>
Date: Fri, 1 Feb 2019 15:09:05 -0500
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To: Christer Holmberg <christer.holmberg@ericsson.com>
Cc: Justin Uberti <juberti@google.com>, Simon Perreault <sperreault@jive.com>, "Dale R. Worley" <worley@ariadne.com>, RTCWeb IETF <rtcweb@ietf.org>, mmusic WG <mmusic@ietf.org>
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Subject: Re: [MMUSIC] [rtcweb] What goes into c= line address when FQDN is used for the default candidate?
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On Fri, Feb 1, 2019 at 2:58 PM Christer Holmberg <
christer.holmberg@ericsson.com> wrote:

> > Most likely mDNS draft will need to update RFC
> > 8445 to specify how ICE nomination procedures are
> > modified, when mDNS is used as candidate-
> > address.
>
> What part of 8445 would need to be updated?
>
>
Currently RFC 8445 specifies that candidates are only IP addresses and not an
FQDN:

   2.1.  Gathering Candidates

   In order to execute ICE, an ICE agent identifies and gathers one or
   more address candidates.  A candidate has a transport address -- a
   combination of IP address and port for a particular transport
   protocol (with only UDP specified here).  There are different types
   of candidates; some are derived from physical or logical network
   interfaces, and others are discoverable via STUN and TURN.

In case of mDNS, candidate is a FQDN name. So when gathering candidates,
DNS query will need to be performed and its result added to the candidate
list. Also, I am not 100% sure, but I think mDNS can resolve to either
IPv4/IPv6 or both addresses. So, single mDNS candidate can result in two
actual ICE candidates. All of this looks like RFC 8445 update.

Regards,
_____________
Roman Shpount