From owner-freebsd-hackers Tue Nov 14 12:21:03 1995 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id MAA09552 for hackers-outgoing; Tue, 14 Nov 1995 12:21:03 -0800 Received: from brasil.moneng.mei.com (brasil.moneng.mei.com [151.186.20.4]) by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id MAA09535 for ; Tue, 14 Nov 1995 12:20:56 -0800 Received: (from jgreco@localhost) by brasil.moneng.mei.com (8.7.Beta.1/8.7.Beta.1) id OAA29269; Tue, 14 Nov 1995 14:18:45 -0600 From: Joe Greco Message-Id: <199511142018.OAA29269@brasil.moneng.mei.com> Subject: Re: Multiple http servers - howto ? To: rashid@rk.ios.com (Rashid Karimov) Date: Tue, 14 Nov 1995 14:18:44 -0600 (CST) Cc: terry@lambert.org, luigi@labinfo.iet.unipi.it, hackers@FreeBSD.org In-Reply-To: <199511141907.OAA02701@rk.ios.com> from "Rashid Karimov" at Nov 14, 95 02:07:10 pm X-Mailer: ELM [version 2.4 PL24] Content-Type: text Sender: owner-hackers@FreeBSD.org Precedence: bulk > > > 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