I've received quite a few replies on this with some favoring doing
something with the Hosting Company DNS Servers but there is no agreement
if it can be done. Do the RFCs actually say it can be done, that is
assigning more than one IP address to a domain name and is this
something that a web hosting service which provides a virtual web server
to it's clients can set up for a client? We are talking a primary web
site on one ISP and an alternate web site on a differen't ISP and in a
different part of the country from each other.
Secondly, I've been told that ISPs and Web Hosting Companys are all
turning of pinging features. This does not make sense to me as pinging
in my mind is an essential networking capability. But this leads to a
second related question. How would a batch process written in perl, for
example, churn out a DNS request as I am told most browsers do. I
thought that a browser generated a ping and then a DNS request but I
have now been told differently.
Basically I'm looking for a solution that applies when a hosted web site
goes down in one part of the country (let's say because of some natural
or other disaster) and the alternative web site in another part of the
country takes over. Plus one web site can off load traffic to another.
I'm not looking at redundancy at a given site as some mistakenly
thought.
A DNS based solution obviates the need to do the processing in CGI and
therefore appears to be a more effective way to go about the solution,
but we have no consensus as to how that would be done. Doing it without
any initial CGI one could generate a HOME page from both the primary and
alternate web sites that had a URL or Java button that provided the
option of using either the primary or the alternate site however that
does not solve the problem of one site taking over the processing tasks
when another site is down or unresponsive to a ping or DNS request
(however that would be done).
Seems like a lot of people are interested in this solution, wish we had
one.
Bye-thanks_TED
The following is the original request:
Subject:
[CGI] Primary and Alternate Web Site
Date:
Thu, 09 Nov 2000 21:07:40 -0700
From:
Ted Hilts <[EMAIL PROTECTED]>
Organization:
MarketShare-PT
To:
[EMAIL PROTECTED], [EMAIL PROTECTED]
I'm not sure if this is really off topic or just something that does not
often come up. I was going to include the perl list but then I realized
that the code language was irrelevant it is a logistical problem.
I have a hosted web site and wish to set up an identical web site but as
an alternative. This way there is no single point of failure that can
take out both hosted web sites. This means one must be on a different
telco (ISP) than the other and neither can be tied to a server
installation that has the same power provider and that sort of thing.
Plus they probably should be in different parts of the country sort of
like mirrors in order to reduce internet traffic congestion. Of course
all this I can arrange by choosing 2 web hosting companies sufficiently
separated in this regard.
The problem is this. The primary host web site must be able to ping the
alternative and vice versa. This is a simple matter using a batch
process in both so each knows the other is up or one is down. Of course
if the primary is down the alternative assumes the role of primary until
the original primary is back up. Since the virtual web server cannot
make these kind of decisions, when to offload users, it must be done as
a CGI process and that process must check the up or down status of the
other. So already, I have introduced overhead at a CGI level of
operation just to determine whether a user should be offloaded to the
alternate site.
In order for this to even work it appears that the primary must have the
advertised domain name and the alternative must have an unadvertised
domain name and so is not directly accessible by users. They point
their browsers to the primary domain name and the CGI process at that
virtual server must somehow redirect if by some measure of activity it
deems that browser should be offloaded to the alternate site. The
easiest solution I can come up with to effect this kind of operation is
to have the CGI process generate the HOME page for the advertised
primary domain name but if off loading is required the URLs on that HOME
page point to the unadvertised domain name location.
This is all fine except when the primary hosted web site dies. Now no
browser can get to the unadvertised alternative domain name because it
is not known. So this is the dilemna. How does the alternative hosted
web site make itself look like the primarly hosted web site when the
primary web site is down?
Maybe someone has an entirely different approach to this kind of
coupling.
Sorry for a brain twister like this right in the middle of a difficult
election time for everyone.
Bye-thanks_TED
-----------------------------------------------------------------
Jann Linder wrote:
>
> Dan,
>
> Are you sure the browser tries one after another?
>
> My understanding was that in the situation you speak of, the DNS actually
> does a round-robin...giving one ip to the first requestor, then the second
> to the 2nd, then all the way through until no ips are left and it goes back
> to the first.
>
> I was under the impression that no element of TCP/IP allows for receiving
> more than one IP for a particular DNS lookup call.
>
> Jann
>
> on 11/9/00 2:53 PM, Daniel Macks at [EMAIL PROTECTED] wrote:
>
> > Ted Hilts said:
> > :
> > : I have a hosted web site and wish to set up an identical web site but as
> > : an alternative. This way there is no single point of failure that can
> > : take out both hosted web sites. This means one must be on a different
> > : telco (ISP) than the other and neither can be tied to a server
> > : installation that has the same power provider and that sort of thing.
> > : Plus they probably should be in different parts of the country sort of
> > : like mirrors in order to reduce internet traffic congestion. Of course
> > : all this I can arrange by choosing 2 web hosting companies sufficiently
> > : separated in this regard.
> >
> > This is a quite common task. Simply set up a DNS entry for "the
> > servers" and put in an A record for each IP. When a browser tries to
> > connect to a machine, it checks with DNS to translate the given name to
> > an IP. If there is more than one IP for a given name it tries one, and
> > then another, and then another, until it gets a response. DNS is explained
> > (in excruciating detail) in RFCs 1034 and 1035.
> >
> > dan
>
> --
> Mr. Jann Linder
> Director of Internet Development
> DinnerBroker/Pricing Dynamics, Inc.
> San Francisco, CA, US
> 1-415-641-5128 x235
>
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