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Web Servers and Mirrors

Servers and Mirrors; a Short Technicial Explanation

What is a server?

A server is a computer, running special software, which is able to give answers to other computers/people. These computers "serve" information in various formats such as Hypertext(WWW), Gopher, Name-lookup, FTP, TELNET and lots of different services. In fact a UNIX server has a file named "services" that lists all the available packages that are located on it.

What are their building blocks?

  1. Computer - Servers are usually fast computers. Pentium 90 or better is best to use for a server. Computers include hard disks for storage of programs and web pages.
  2. Operating System - Unix and Linux are quite popular server operating systems. Microsoft's Windows NT is capable of becoming a server as well.
  3. Applications - WEB server is becoming quite popular these days, but with the next generation of the internet coming how does VSS(Virtual shopping server) sound?

What is a client?

A client is any other program asking for information from a server. An example of a client is your PC at home.

What is the relationship between clients and servers?

Clients request information from servers. Servers are usually more powerful and have large storage capacity to serve many clients at a time.

Why use a server?

To store information on one machine instead of keeping it on all the clients machines. This means that if information changes, the change can be made in the server and appear in all the clients without clients having to reconfigure their machines. It also allows clients to be made smaller and simpler, since a good deal of the resources are provided by the server.

What is a mirror?

A mirror is a server that looks like and serves an identicial piece of information to a client. These servers act the same but are at different URLs.

Why use mirrors?

There are several reasons for using mirror sites.
  1. Bandwidth - If a server can serve a 100 people, 10 servers can serve 1,000! Bandwidth or how much data can we send out at a time is a primary considerations especially when many clients are browsing.
  2. Speed - The closer you are physically to a mirror, the faster your connection can be to that mirror. The more distance between you and a mirror, the more data network routers and switches you have to go through before the data you requested can find its way to you!
  3. Reliability - Servers are pretty reliable, but sometimes a server may break down and not be reachable. If that's your only site, nobody can get to the information you want to show. If you have a bunch of mirror servers, a failure in one or two of them does not become a major problem. Clients just switch to another mirror and keep on surfing.

What are the challenges in coordination?

Having all these mirror sites presents a challenge in keeping all of them up to date with the latest revision of your web pages. Every time a page is changed, an update needs to be sent to all the mirrors or the sites will appear differently. Sometimes this takes a lot of time.

What is our concept?

We have multiple mirrors with complete copies of the site. We also have special camera image servers which send copies of our live webcast images to each mirror as well. This provides a more controlled load on any one server.

How does this better serve the viewer?

It allows for faster viewing of live feed pictures

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