What is a Server?
A server is a powerful computer which provides services to devices on a network. These services may include:
- Log on access and security (like when you type in your username and password to access your school account)
- Website storage and access, so your browser can access web pages
- Email servers provide access to your email
- Storing files for all of the devices on the network. Any device on the network can access the files (as long as they have sufficient permission). For example, at school you can log on to any computer and still access your files.
There are lots of different types of server which provide lots of different services.
Networks which include a server are client-server networks. Networks which do not include a server are peer-to-peer networks.
Client-Server Networks
A computer network will include one or more servers. Each server will carry out a task for the devices (clients) on the network when requested.
Each server may have thousands of clients.
Example: A web server. The client computer's web browser will request web pages from the web server. The server will process their request, then send the web page files to the client computer to be displayed.
Pros and Cons of Client-Server Networks
Most of the benefits are due to all data being stored in one place — the server. This makes it easier to:
- Control files and who has access to them
- Back up data
- Install and update software
- Manage security (user access levels, anti-malware software)
- Servers can be expensive to buy, setup, and maintain
- Requires IT specialists
- The server is a single point of failure. If it stops working, or becomes overloaded, everyone loses access
Peer-to-Peer Networks
All devices are equal — there are no servers on the network.
Each device has its own resources, but shares them with other devices on the network.
Example 1: Scott's computer has a printer attached. Any device can send data to his computer to printed.
Example 2: Nahib has documents stored on her PC's hard disk drive. Anyone else on the network can access them from their own PC.
Misconception
Don't confuse a peer-to-peer network with a mesh topology. Client-server and peer-to-peer networks are logical connections whilst topologies show how devices are physically connected.
Pros and Cons of Peer-to-Peer Networks
- Easy to set up and maintain, so little need for expensive IT staff
- No dependence on a single device (a server)
- No expensive server to buy
- No centralised management, so difficult to maintain security, updates, and backups
- Difficult to maintain files as they may be scattered across several devices
- Data may be lost if the device storing it fails
- Devices may slow down if others are accessing them