[dns-operations] forward compression pointers?

[Mark Andrews]

In message <20090830205935.GA10311 at mycre.ws>, Robert Edmonds writes:
> are there any DNS responders that generate forward compression pointers,
> or DNS initiators that reject them?

No and yes in that order.  Compression pointer are required to point
backwards by RFC 1035.  Note the word "prior" in the description.

4.1.4. Message compression

In order to reduce the size of messages, the domain system utilizes a
compression scheme which eliminates the repetition of domain names in a
message.  In this scheme, an entire domain name or a list of labels at
the end of a domain name is replaced with a pointer to a prior occurance
of the same name.

Mark
 
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org