Subject: Re: does anybody use additional/authority records on RD/RA replies

From: Bruce Campbell <[email-masked]>
Date: Sat, 11 Jan 2003 22:33:48 +0100 (CET)

On 11 Jan 2003, D. J. Bernstein wrote:

> Rob Austein writes:
> > Additional for sure: think about QTYPE=MX.
>
> One client---sendmail---tries to skip the A query by caching A records
> from the MX response. I'm amused by the ``save network traffic'' excuse
> for this complication. If you really care about DNS traffic, why aren't
> you running a real DNS cache on the same machine?

It is possible, especially with the example that you've posted, that the
design decision that lead to trying to obtain an 'A' from the additional
section of a 'MX' answer was made at a time when Internet links were
relatively expensive, and/or at a time when the memory footprint of a DNS
cache was not available on every machine.

Of course nowadays, the design of a new piece of software doesn't have to
take into account costs incurred by the entity running their software as
bandwidth/memory/cpu is so cheap, mores the pity.

--==--
Bruce.

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---

From: "D. J. Bernstein" <[email-masked]>
Date: 16 Jan 2003 01:12:13 -0000

Bruce Campbell writes:
> the memory footprint of a DNS cache

You think that it's better use of memory to have separate caches---plus
separate caching code---in every application?

Bad design decisions like this are responsible for most of the bloat in
programs like sendmail and named. It's particularly sad when one bloated
program uses the size of another bloated program as an excuse to add
even more bloat to the first instead of reusing the second.

---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago