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

[Christer Holmberg <[e-mail]>]

Hi,


>>> 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.

The 8445 text does not talk about encoding of candidates on the wire. A candidate always has an IP address and port - and that is true no matter what you signal in the SDP on the wire.

> 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.

I raised this issue before, and I think the agreement was that, with ICE, mDNS would only result in ONE address (either IPv4 OR IPv6).

Regards,

Christer