Welcome

On this page you will find information regarding the SURF-ACE / Desire Web caching project, setting up a local Web caching server, which software to use and how to configure it, which settings are needed for the Web browser, and how to register the Web caching server with SURFnet BV's National Top-level Web caching server. You will also find a representation of the present structure of the SURFnet Web caching mesh.

SURF-ACE / Desire Web caching

The SURFnet Web caching project is being developed and implemented by the Utrecht University computer centre within the framework of the SURF-ACE/Desire Web caching project.
The main aim of this project is

• Improving the response times for intensively used Web pages, both inside and outside of SURFnet.
• Reducing Web traffic via the SURFnet backbone, the network links to the other Internet Service Providers in the Netherlands, and relieving the international links.
• Reducing the load on the Web servers.

Among other things, an analysis was carried out in this project of "The functionality and effectiveness of Web caching servers", and "The requirements and recommendations of Web caching services". This has resulted in a report called "The Survey of caching requirements and specifications for prototype". Another report, "The evaluation of different caching strategies for national and international access", is in preparation.

Web caching software

The SURF-ACE/Desire Web caching project recommends the use of the Squid Internet Object Cache, for several reasons. First, this software is currently the more advanced. It is being developed and supported by a number of able developers. Furthermore, it is available in source code and runs on a vast number of systems.
The latest and most stable production version is squid-1.1.9-src.tar.gz. The use of Web caching software other than Squid is possible but is not recommended.

For the daily analysis of the Web caching logfiles squid-stats v1.4 is used. This software is derived from the NLANR Cache Logfile Analysis Scripts.

Configuration of local Web caching server

The configuration file of the Web caching server strongly determines the Cache's functionality and behavior. Among other things, in the configuration file it can be defined who has access to the caching server, and which other Web caching servers in a hierarchy of caching servers may be accessed.
In the Netherlands, a National Top-level Web caching server is operational, which can be used by SURFnet clients as a parent. The linked Web caching servers at the different institutes can engage in a sibling relation among themselves. One difference between a parent and a sibling is that a parent can retrieve documents from the network at the request of a hierarchically lower caching server (a child). After having stored the documents in its Cache, the parent will send them on to the child. A sibling, however, will send the documents to the child only if they are present in its own Cache without having to retrieve them from the network.

An example of a Squid configuration file of an institute's Web caching server is the one used by Universiteit Utrecht. The one used by Hogeschool van Amsterdam is an example of a Web caching server which is configured as an HTTP Accelerator.
At present, the Universiteit Utrecht Web Cache has two "siblings", the HvA [www.hva.nl] and the SURFnet office [surver.surfnet.nl], and one "parent", the National Top-level Web caching server [cache.nic.surfnet.nl].

Both the caching servers of Universiteit Utrecht and of the SURFnet office cache all documents with the exception of documents in its own domain. The caching server of Hogeschool van Amsterdam, as it is configured as an HTTP Accelerator, also caches documents in its own domain, allowing it to be used by other Web caching servers (such as that of Universiteit Utrecht) as "parent" for the pages in the hva.nl domain.

With the exception of pages generated by CGI-scripts, each document retrieved by the National Top-level Web caching server is stored in its Cache, allowing other Web caching servers to use it as "parent" for pages both within and outside of the NL-domain. A mutual "parent" relation has been established with the Top-level Web caching server in Norway for the purpose of exchanging Web Documents.

Sibling relations

To enhance the performance of the SURFnet Web caching mesh, so-called sibling relations can be established between the different Web caching servers. A description of how to determine the most efficient sibling relations within the Mesh and how to configure these relations can be found on the Web caching service page.

The SURFnet Web-caching mesh

The present situation (April 17, 1997) of the SURFnet Web caching mesh, with clickable items. In a hierachical model, a lower cache can request documents from one of its "siblings", from its "parent" or directly from the remote Web server.
If present, the local Web caching information pages are available behind the clickable icons.

Web browser settings

A Web browser needs to be specially configured to enable it to use a Web caching server. This can be done manually (cf. a.o. the on-line Netscape v2.0.2 handbook) or, with the Netscape navigator v2.0 and up, via an Automatic Proxy Configuration Script.

An example of an "Automatic Proxy Configuration" (APC) script is that developed by Universiteit Utrecht. The default extension of the file containing the script is "PAC". A special MIME content-type needs to be defined on the Web server containing this APC-script. For the Cern/W3C daemon the following should be added to the configuration file:

   AddType .pac application/x-ns-proxy-autoconfig 7bit

When the APC-facility is in use, failure of the first-named Web caching server in the APC-script will result in the Web browser automatically switching to the next in line. If the line is empty (none of the Web caching servers is available) the Web browser will request that the proxy servers, the Web caching servers here, be skipped and that the document be retrieved directly from the Web server.

An example of a user instruction Web page is that of the Universiteit Utrecht. It explains what a proxy server is, why it should be used, and which settings are needed for the Netscape Navigator.

Registering with the National Top-level Web caching Server

If you wish to register an institute's Web caching server for a link with the National Top-level Web caching server you can use the following registration form.
Please note that this does not concern the registration of individual Web browsers, for which you should contact your own institute.

For more information regarding Web caching and/or linking to the National Top-level Web caching server of SURFnet BV you can contact H.Bekker@cc.ruu.nl.

SNET-cache list

A mailing list, "SNET-CACHE", has been established for communication among the Web caching servers' managers and the SURF-ACE/Desire Web caching project. You can take a subscription by filling in the Snet-Cache registration form.

You will be sent a confirmation of registration, to which you are required to reply "OK" within 48 hours.

Last modified: 17 april 1997 / Henny Bekker