Two hundred students open one video
A teacher says: "Open this video." Two hundred students press the link in the same minute.
Without help, the college link fetches the same video 200 times. With a cache (a store of copies), it fetches it once and hands out 199 copies. A proxy can also check the page is safe before anyone sees it.
Key words
| Word | What it means |
|---|---|
| Client-server network | a network where client devices ask a central server for services |
| Web server | a server that sends web pages to browsers |
| HTTP | the rules a browser and a web server use to talk |
| Proxy server | a server that makes web requests on behalf of the users behind it |
| Bandwidth | the most data a link can carry each second |
| Cache server | a server that keeps copies of pages it has fetched, to reuse them |
| Hit | a request that the cache can answer from its stored copy |
| Miss | a request that the cache has to fetch again from the real server |
| Mail server | a server that sends, receives and stores email |
| SMTP | the rules for sending email from one server to another |
| IMAP | the rules a mail program uses to read email kept on a server |
| Mailbox | the space on a mail server that holds one person's messages |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can say what web, proxy, cache and mail servers do and how each helps a college.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
The web server
A web server stores a website and sends its pages. Your browser asks using HTTP. The server answers with the page and a status, such as 200 for "found".
The college web server holds the public website. Another may hold the student portal.
The proxy server: a go-between
A proxy server sits between the users and the internet. Users ask the proxy. The proxy asks the website for them.
This gives the college a place to filter pages, block unsafe sites and keep a log. It also hides the pupils' own addresses from the website.
Quick check
Have a go
Quick check
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.