Subject: DNAME [4.9]: Name Compression in RDATA

From: Wouter Wijngaards <[email-masked]>
Date: Thu, 12 Oct 2006 12:25:04 +0200

Issue [4.9]:
   For old versions of servers only uncompressed is possible.  New
   version can still choose to use compressed or not.
   Clarify on compression proposal: Senders SHOULD NOT compress RDATA,
   receivers MUST be able to decompress, when the new version has been
   negotiated with the EDNS bits.

Best regards,
   Wouter

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From: Peter Koch <[email-masked]>
Date: Thu, 12 Oct 2006 14:49:05 +0200

>    negotiated with the EDNS bits.

For this we'd need a more detailed problem statement. Having a compression
pointer in the RDATA is most likely not very attractive, unless we'd find
'sibling' DNAMEs in long/deep names a lot:

      some.maybe.really.deep.example.	DNAME  other.maybe.really.deep.example.

If this were the case, it could be dealt with by local compression ;-)
The DNAME RDATA is probably more attractive as a compression target,
since an RRSet will follow with an owner that is a descendant of the DNAME's
target. Still I'm not sure it's worth the hassle of deploying yet another
hop-by-hop negotiation scheme. I'd suggest we stick with what RFC 3597
gave us: DNAME RDATA MUST NOT be compressed.

-Peter

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From: Edward Lewis <[email-masked]>
Date: Mon, 30 Oct 2006 10:21:41 -0500

>gave us: DNAME RDATA MUST NOT be compressed.

Don't look for more opportunities to compress data.  Compressing data 
is bad for the protocol.  It is why name servers cannot handle all 
types (other than SOA, NS, address records and DNSSEC records) as 
unknown types.

Without chasing down references myself, I am sure there's a document 
that says the only types to be compressed are the golden-oldies, 
i.e., mostly those in the first few RFCs.  (Ok, I did look it up - 
3597 section 4 - because Peter mentions it above.)
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Edward Lewis                                                +1-571-434-5468
NeuStar

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