[DNSOP] Re: draft-ietf-dnsop-3901bis

[Mark Andrews <[e-mail]>]

Repeating so this gets tied to the draft name.

Guidelines for DNS Resolvers states:

  If a recursive DNS resolver runs in a network that uses XLAT
  [RFC6877], and the recursive DNS resolver is aware of the used PREF64
  [RFC6146], it SHOULD synthesize mapped IPv6 addresses for remote
  authoritative DNS servers directly for DNS resolution, instead of
  relying on the socket translation layer of the operating system. A
  recursive DNS resolver SHOULD prefer non-synthesized IPv6 addresses
  over synthesized IPv6 addresses based on a PREF64. Additionally, the
  PREF64 in use MAY also be statically configured for the DNS resolver.

I am going to be contrary here and say that DNS servers MUST NOT
synthesis IPv6 address records from the PREF64 option.  This is
the wrong level of the stack to perform this translation as the
DNS server is not an IP router and to do this properly the DNS
server would need to process the kernels routing table.  Just
use the IPv4AAS built into the operating system as it reached
via the routing table in the kernel.

The DNS is an application that deals with IP literals.  CLAT is
the correct mechanism to deal with this with XLAT as is B4 with
DS-Lite.

For anyone here at IETF that has an OS that supports IPv6 mostly,
connect the “ietf” network and fire up a DNS server and perform 
DNS lookups using that server.  You will see that they just work
regardless of whether the zones are served by IPv4 only, dual stack
or IPv6 only.

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: [phone]              INTERNET: [e-mail]