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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