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Some resources on proxies (may include caches and nat, also at least initially).

The reason I came back to this page is to try to deal with a specific problem -- how do I set up a TWiki to use mod-perl. See ModPerl (which I probably need to add some things to) -- EdgarBrown said "I have a different mod_perl installation on my server (Apache under Linux Mandrake), which requires proxiing to the perl port on local host" and he sent me some additional information via a private email (some of which I want to add here or on the ModPerl page).

I tried what he suggested, and although TWiki works with what I've done, I believe I am still using "standard Apache" and not mod-perl based on the performance. (Need to explain exactly what I did.)

Anyway, part of my problem comes down to understanding exactly what a proxy is -- hence this page.

I think, from past knowledge / experience, I have a half baked idea of what a proxy is -- now I need to deal with some details.

Trying to be more specific, to make TWiki work in mod-perl, must I use a different URL? Or, how does TWiki (or the Apache running TWiki) know to serve some things via mod-perl and other things directly (as both the standard Apache and mod-perl variation run at the same time, and I have not deleted all the configuration information for TWiki from the standard httpd.conf (Apache configuration) file.

more later -- duty calls

See AboutThesePages.



Collecting some definitions:

What is a Proxy Gateway?

A proxy gateway allows Mosaic to pass on a network request (in the form of a URL) to an outside agent which will perform the request for Mosaic, and return the results to Mosaic. The intended effect of this is to allow Mosaic clients that are sealed off from the internet to pass their network requests off to a trusted agent that can access the internet for Mosaic. A user of a Mosaic client using a proxy gateway should feel as if they were directly connected to the internet.


An interface-specific object that provides the parameter marshaling and communication required for a client to call an application object that is running in a different execution environment, such as on a different thread or in another process. The proxy is located with the client and communicates with a corresponding stub that is located with the application object that is being called.

A server that sits between a client application, such as a Web browser, and a real server. It intercepts all requests to the real server to see if it can fulfill the requests itself. If not, it forwards the request to the real server.

Proxy servers have two main purposes:

proxy server

In an enterprise that uses the Internet, a proxy server is a server that acts as an intermediary between a workstation user and the Internet so that the enterprise can ensure security, administrative control, and caching service. A proxy server is associated with or part of a gateway server that separates the enterprise network from the outside network and a firewall server that protects the enterprise network from outside intrusion. A proxy server receives a request for an Internet service (such as a Web page request) from a user. If it passes filtering requirements, the proxy server, assuming it is also a cache server, looks in its local cache of previously downloaded Web pages. If it finds the page, it returns it to the user without needing to forward the request to the Internet. If the page is not in the cache, the proxy server, acting as a client on behalf of the user, uses one of its own IP addresses to request the page from the server out on the Internet. When the page is returned, the proxy server relates it to the original request and forwards it on to the user.

To the user, the proxy server is invisible; all Internet requests and returned responses appear to be directly with the addressed Internet server. (The proxy is not quite invisible; its IP address has to be specified as a configuration option to the browser or other protocol program.)

An advantage of a proxy server is that its cache can serve all users. If one or more Internet sites are frequently requested, these are likely to be in the proxy's cache, which will improve user response time. In fact, there are special servers called cache servers. A proxy can also do logging.

The functions of proxy, firewall, and caching can be in separate server programs or combined in a single package. Different server programs can be in different computers. For example, a proxy server may in the same machine with a firewall server or it may be on a separate server and forward requests through the firewall.

There is another kind of proxy that hasn't been discussed. Actually there are a number, but I'm only mentioning the one.

This is where the main server works as EdgarBrown mentioned and is the standard for Mandrake Linux 8.0 and later. The main server recognises calls to perl scripts and hands them off to a proxy that has mod_perl built in. Thus there is non of the normal overhead. In effect the main server is the proxy in that it sits in-between the application and the server that executes the perl. You might call this configuration something like a _"hand-off proxy".

At Mod_Perl_Proxied I've written up the configuration for the Advanced Extranet Server. (http://www.advx.com). As I said, this is the default install on Mandrake Linux 8.0 and later.

-- AntonAylward - 07 Jan 2003


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  • () RandyKramer - 12 Jun 2002
  • <If you edit this page: add your name here; move this to the next line; and include your comment marker (initials), if you have created one, in parenthesis before your WikiName.>

[[Main.RandyKramer#12 Jun 2002][]]

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