[MMUSIC] FQDN Support Final Vote

[Suhas Nandakumar <[e-mail]>]

Hi All

  Below i have included 4 flavors of suggested text for FQDN support in
ice-sip-sdp.  Let's agree on one and go with it (even it doesn't make us
entirely happy).


*RFC5245 Version *
"<connection-address>: is taken from RFC 4566
<https://tools.ietf.org/html/rfc4566> [RFC4566
<https://tools.ietf.org/html/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 MUST ignore candidate lines that include
candidates with IP address versions that are not supported or
recognized.  An IP address SHOULD be used, but an FQDN MAY be used in
place of an IP address.  In that case, when receiving an offer or
answer containing an FQDN in an a=candidate attribute, the FQDN is
looked up in the DNS first using an AAAA record (assuming the agent
supports IPv6), and if no result is found or the agent only supports
IPv4, using an A.  If the DNS query returns more than one IP address,
one is chosen, and then used for the remainder of ICE processing.


*ice-sip-sdp pre-22 version1*


<connection-address>:  is taken from RFC 4566 [RFC4566].  It is the IP
address of the candidate.  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
MUST ignore candidate lines that include candidates with IP address
versions that are not supported or recognized.  An IP address SHOULD
be used, but an FQDN MAY be used in place of an IP address.  In that
case, when receiving an offer or answer containing an FQDN in an
a=candidate attribute, the FQDN is looked up in the DNS first using an
AAAA record (assuming the agent supports IPv6), and if no result is
found or the agent only supports IPv4, using an A record.  The rules
from section 6 of [RFC6724] is followed by fixing the source address
to be one from the candidate pair to be matched against destination
addresses

reported by FQDN, in cases where the DNS query returns more than one IP address.


*ice-sip-sdp current version*

<connection-address>:  is taken from RFC 4566 [RFC4566].  It is the
      IP address of the candidate.  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 MUST ignore candidate lines that include candidates with
      IP address versions that are not supported or recognized.  An IP
      address SHOULD be used, but an FQDN MAY be used in place of an IP
      address.  In that case, when receiving an offer or answer
      containing an FQDN in an a=candidate attribute, the FQDN is looked
      up in the DNS first using an AAAA record (assuming the agent
      supports IPv6), and if no result is found or the agent only
      supports IPv4, using an A record.  If a FQDN returns multiple IP
      addresses an agent MUST only use one of them throughout the
      duration of the ICE session.  Since an agent does not know whether
      the peer listens to the chosen IP address and port, it is
      RECOMMENDED to not use FQDNs that will resolve into multiple IP
      addresses.


*Roman-Christer Version *

<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 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 handling FQDN candidates, and for agents*

*to indicate support of such procedures, need to be specified in an
extension specification.* If candidate with FQDN <connection-address> is the

default destination/candidate, the "c=" address type MUST be set the IP
address family for the FQDN DNS resolution result and the "c=" connection

address MUST be set to FQDN. Differences in the "c=" line address family
and type with FQDN resolution result MUST not cause ICE support
verification failure.




*My vote is on current version since it is backward compatible with a
warning that using FQDN is not recommended since it MAY lead to failure.*