Department of Engineering

The World Wide Web and speed

There are many reasons why the WWW might appear to be slow or why a site might be uncontactable. This page provides background information to help you: correct any problems that are under your control; report other problems effectively.

Things you can do

• Read the background information below!
• If you can't contact a site, it's useful to know if others can. Try the down for everyone or just me site
• Check that your local machine is ok - run large non-network programs.
• Check that your local bit of the network is ok - try non-WWW network-based operations.
• Check to see whether only non-European or non-Cambridge University sites are affected
• Check your personal cache size. Try emptying your cache sometimes (how you do this depends on the browser you use).
• Check whether you're using the CUED cache (under the proxy configuration options)
• Check the CUED system announcements and the ucam.eng.network-info newsgroup for known system/network problems and repair times. Look at the Status of JANET's links to the Internet to see if there are hardware problems with international links.
• If you want to report a network problem, mail network-support@eng.cam.ac.uk. If you want to report a WWW problem, mail webadmin@eng.cam.ac.uk. To improve your chances of a quick response, include the following information
  • The machine, operating system, browser, and browser version that you were using
  • Your cache and proxy settings
  • The time when you experienced problems
  • The page or pages that exhibited problems
  • The extent of the delay, and whether the delay was in beginning
  to load the page or during the completion of loading the page.
  • Whether the page loaded in quickly the second time around.
  As a test, empty your personal cache and load the list of local source code (over 150k long) noting how long it takes to load. If local users experience a delay of more than 5 seconds, something might be wrong.
• Use the options menu to turn off the images (these slow down transfer).
• Use local (UK) copies of US sites (these "mirror" sites are usually well-advertised at the master sites).

Remember that webadmin@eng.cam.ac.uk can't do anything about distant machines that are broken or non-local pages that have disappeared.

Background Information

• Caches - Suppose there's a popular very big file in the States that people in CUED want. It would be wasteful for each person to copy the file over. So we've set up a CUED cache which stores copies of external files that people have requested. If you ask for a file that someone at CUED has already looked at, you get the local version straight away rather than having to wait for the version to be re-loaded from the States.

  You should use the CUED cache - it saves the department money and performance will usually be better. However, there is a downside - if you look at an external page that no-one at CUED has recently looked at, the cache introduces an extra stage that slows you down.

• Page Complexity - When WWW authors update pages they are keen to use the latest features, which can make pages much slower. If, for example, they use Java applets, pages will be slow to load.
• Congestion - The WWW is a victim of its increasing popularity. Sites can suddenly become congested. For instance, if a site is mentioned in a newspaper, access to it might be slow for a few days
• Hardware Problems - Machines and networks have been known to stop working. If a network connection is broken there's usually an alternative route, but that route will be slower.