[ On Tuesday, October 12, 1999 at 17:52:27 (+0100), Ian Jackson wrote: ]
> Subject: Re: [Exim] Delivery optimization tips for large lists ?
>
> A friend of mine works for an ISP. One of their big mail servers was
> configured to (a) run nscd and (b) do reverse lookup on all incoming
> SMTP connections. But, nscd is crap[tm] and serialises all its DNS
> queries, giving rather unhelpful behaviour: you didn't get 220 until
> everyone in the queue in front of you had had their crap nameservers
> timed out on. nscd could in principle not serialise requests, and use
> the DNS TTL values, but that's probably too much hard work for Sun.
While nscd could presumably be used to safely relieve the load on a
NIS(+) server even for host information requests since NIS servers are
(as far as I understand) always authoritative, I don't believe it or
anything like it has any place whatsoever in a network using DNS.
BIND's named does its own caching, and properly of course. Trying to
out-smart it with a dumb cache daemon is stupid and will always cause
problems. Trying to out-smart it with a new implementation of a DNS
server would be OK, but trying to put a full DNS caching server
implementation in nscd would be, if not outright stupid, at least a
waste of programming effort (some folks might contend that since nscd is
supposedly thread safe and most DNS resolvers are not that there would
be some advantage, but...).
> (Plug: fed up with libresolv ? Try my resolver library, currently in
> alpha. http://www.chiark.greenend.org.uk/~ian/adns/ )
I keep meaning to have a closer look at your code -- thanks for the
reminder!
--
Greg A. Woods
+1 416 218-0098 VE3TCP <gwoods@???> <robohack!woods>
Planix, Inc. <woods@???>; Secrets of the Weird <woods@???>
