> From: John MccLain [mailto:[EMAIL PROTECTED]
> 1) for DNS Request Distribution - I dont understand. The
> browser sends a URL
> to the DNS, the DNS responds back with an IP address. But
> what if at that IP
> address, you have a web server listening on port 80?
The browser talks to that Web server.
> If
> Tomcat is at that
> address also, Tomcat would have to listen on another port. Can the DNS
> distribute back to the browser the IP Address AND the Tomcat
> port so the
> browser connects to Tomcat on a non port 80 port?
Only if your original URL uses the name:port notation - there is nothing
in this scheme to prevent that.
> Also, is there a way to
> setup the DNS to Round Robin or check server load on the
> servers in the
> Tomcat cluster so it knows which Tomcat server ip:port to
> send back.
No standard way afaik. Worse, downstream DNS servers may (often do)
cache the returned IPs for up to a day despite any cache expiry you put
on them. If (say) the AOL DNS servers all get the same IP address in
their cache, all your AOL visitors will visit the same IP address.
DNS is a very lumpy way of doing load balancing.
> OR does
> this whole thing imply that you have an IP for each web
> server (IIS)
IP address yes; IIS depends on whether you want IIS or Tomcat at the
business end of the cluster.
> and
> each web server is tied to each server in the Tomcat cluster via a jk2
> redirector?
If you wish to use that architecture, yes.
> 2)TCP NAT distribution - Does this mean that when the browser
> connects to
> the IP address, that that connection is intercepted and the request is
> distributed to a server in the Tomcat cluster?
Yes.
> If this is the case, then
> what does the interception?
Generically, a router that has this capability. It's that router that
also does the NATing. Many mid- to high-end hardware routers and some
software routing packages can do this.
> and how do you configure that thing to use a
> specific algorithm (server load, Round Robin, etc..) to
> choose which server
> to forward the request to?
That is router-specific. There is no standard (afaik) for the servers
to return load information, so you're stuck with proprietary solutions
*or* the router doesn't load-balance.
> can it forward to an IP:PORT or does it have to
> forward to an IP
That is router-specific. Given that the capability typically exists on
mid- to high-end routers, most will also have the capability to change
the internal port that is in use.
- Peter
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