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Re: Implement SRV DNS

From: John Peacock <jpeacock_at_rowman.com>
Date: 2004-04-21 18:05:21 CEST

Pierre THIERRY wrote:

> Where did you see that? I never heard about problematic implementations
> of SRV.

That text I quoted points to a specific problematic implementation; the current
RFC2782 (Feb 2000) _prohibits compression_ of SRV records, RFC2052 (Oct 1996)
_mandated_ it, and some servers following that earlier specification are still
in use.

> And about the widelyness, I know Windows 2000 uses SRV records
> everytime it can...

OK, that's one then (and yes I was already aware of it). I also happen to
believe that M$loth's implementation of DNS records in this instance is an abuse
of the core protocol.

> The SRV implementation is also in the TODO list of
> projects like KDE and Mozilla, and there's already some SRV code in the

And that's zero more. There are plans, there are TODO entries, but there aren't
other large projects which support it today (some 8 years after the RFC was
ratified). It was a good idea which failed the test of actual usage in the wild.

For example, it would be ideal for a web client to support it, so that web
servers could be easily and automatically load balanced. That is not possible
now since there are /no/ browsers which support it, and I don't think that it
will be implemented anytime soon. It's not the way that the industry has moved
in any case (rather they have used distributed caching, ala Akamai).

> I don't see why /one/ implementation, limited because designed to be
> very simple, should prevent anyone to use SRV records...

My concerns don't merely come from my use of DJBDNS (which does support SRV
records if so required). They arise from my perception that this is not a
widely utilized feature (similar to LOC records).

In addition, the Subversion client would be required to link to a resolver
library to make use of this feature. Right now, the client merely requests the
IP address associated with a name, then opens a connection to the requested port
on that address. Implementing SRV would require yet another platform
independent library to resolve the chain of SRV records.


John Peacock
Director of Information Research and Technology
Rowman & Littlefield Publishing Group
4501 Forbes Boulevard
Suite H
Lanham, MD  20706
301-459-3366 x.5010
fax 301-429-5748
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Received on Wed Apr 21 18:05:22 2004

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