[dns-operations] Google's name servers compressing names in SRV records

[Peter Koch]

On Thu, Aug 13, 2009 at 10:07:32AM -0700, Matthew Dempsky wrote:

> Has there been any standards action permitting this, or are they
> violating the specification?  This is causing interoperability
> problems for caches that are SRV record agnostic.

strictly speaking it was an earlier (non-standards) action that
suggested the compression.  Here's what RFC 3597 says:

   To avoid such corruption, servers MUST NOT compress domain names
   embedded in the RDATA of types that are class-specific or not well-
   known.  This requirement was stated in [RFC1123] without defining the
   term "well-known"; it is hereby specified that only the RR types
   defined in [RFC1035] are to be considered "well-known".
[...]
   Receiving servers MUST decompress domain names in RRs of well-known
   type, and SHOULD also decompress RRs of type RP, AFSDB, RT, SIG, PX,
   NXT, NAPTR, and SRV (although the current specification of the SRV RR
   in [RFC2782] prohibits compression, [RFC2052] mandated it, and some
   servers following that earlier specification are still in use).

So the server you mentioned didn't follow the spec by the letter, but
resolvers better not be SRV agnostic.

-Peter