Date: Tue, 14 Nov 1995 14:18:44 -0600 (CST) From: Joe Greco <jgreco@brasil.moneng.mei.com> To: rashid@rk.ios.com (Rashid Karimov) Cc: terry@lambert.org, luigi@labinfo.iet.unipi.it, hackers@FreeBSD.org Subject: Re: Multiple http servers - howto ? Message-ID: <199511142018.OAA29269@brasil.moneng.mei.com> In-Reply-To: <199511141907.OAA02701@rk.ios.com> from "Rashid Karimov" at Nov 14, 95 02:07:10 pm
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> > > I have read that some http servers (probably some machines at NCSA)
> > > are actually a cluster of servers attached to the same ethernet. Client
> > > transparently contact one of the servers. I would like to know how this
> > > is achieved, e.g.
> > >
> > > i) by supplying different IP translations for the same name;
> > > ii) by a clever use of ARP
> > > iii) by some other technique which I do not know
> >
> > #1. Via DNS. The requesting hosts are rotored through a list of the
> > addresses.
> >
> > It isn't a very good scheme, mostly because caching exists.
>
> It is importante that you provide 0 expiration times
> for the corresponding A records - so that (at least RFC compliant)
> DNS servers will not cache the record ....
Not necessarily something you WANT to do either, however.
> There are a few pitfalls in http ... namely lack of support
> for multiple WWW domains on the same computer(the URL gets
> stripped, so the server never sees the domain name in URL)
> and the mechanism for authentic redirection to the mirror Web site -
> in case when the first server is overloaded or/and is under maintenance.
Yes, although this can be done under an OS such as FreeBSD, with careful IP
aliasing.
www.xyz IN A 206.55.64.140
IN A 206.55.64.141
www.abc IN A 206.55.64.142
IN A 206.55.64.143
Where 206.55.64.{140,142} are on one box and 206.55.64.{141,143} are on
another. During maintenance of one machine you can even temporarily assign
the other machine's addresses to the first machine... not that I've tried
it.
> Would be great if this issues could be addressed in future
> implementation of the hhtp proto... will take some time tho
> to upgrade all the servers and browsers
It would make sense to provide a cleaner interface, yes. But it can be done
with today's technology.
... JG
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