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From: lwj@cs.kun.nl (Luc Rooijakkers)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Compression in new DNS RR's
Keywords: new DNS RR compression
Message-ID: <2296@wn1.sci.kun.nl>
Date: 16 Oct 90 09:12:25 GMT
Sender: root@sci.kun.nl
Distribution: comp
Lines: 35

Several new RR types introduced in RFC 1183 include domain names. The
relevant types are AFSDB (18), RP (17), RT (21). Should name servers
compress the domain names in these RR types ? From RFC 1123,
Requirements For Internet Hosts, section 6.1.3.5 Extensibility:

                 Compression relies on knowledge of the format of data
                 inside a particular RR.  Hence compression must only be
                 used for the contents of well-known, class-independent
                 RRs, and must never be used for class-specific RRs or
                 RR types that are not well-known.  The owner name of an
                 RR is always eligible for compression.

So, are the new RR types to be considered well-known ? If so, this
creates a problem when resolvers and secondary name servers receive
these RR's but do not know that they contain compressed domain names.
This is also hinted at in RFC 1123:

                 A name server may acquire, via zone transfer, RRs that
                 the server doesn't know how to convert to printable
                 format.  A resolver can receive similar information as
                 the result of queries.  For proper operation, this data
                 must be preserved, and hence the implication is that
                 DNS software cannot use textual formats for internal
                 storage.

For secondary nameservers this should not be a problem, I think, since
these can be updated when needed. But caching resolvers are more
difficult to deal with.

Comments or answers, anyone ?

--
Luc Rooijakkers                                 Internet: lwj@cs.kun.nl
Faculty of Mathematics and Computer Science     UUCP: uunet!cs.kun.nl!lwj
University of Nijmegen, the Netherlands         tel. +3180652271