Servers

A server is a computer designed to process requests and deliver data to other (client) computers over a local network or the internet. Although any computer running special software can function as a server, the most typical use of the word references the very large, high-powered machines that function as the pumps pushing and pulling data across the internet.

Most computer networks support one or more servers that handle specialized tasks.
As a rule, the larger the network—in terms of clients that connect to it or the amount of data that it moves—the more likely it is that several servers play a role, each dedicated to a specific purpose.
Strictly speaking, the server is the software that handles a task. However, the powerful hardware that supports this software is also usually called a server because server software coordinating a network of hundreds or thousands of clients requires hardware much more robust than what you’d buy for ordinary consumer use.

Common Types of Servers

A large, general-purpose network supporting a medium-sized company will likely deploy several different types of servers:

• Web servers, to show pages and run apps in connecting Web browsers
• Email servers, to facilitate the sending and receiving of messages
• FTP servers, to support the moving of files through File Transfer Protocol tools
• Identity servers, to support logins and security roles for authorized users

Hundreds of different types of specialized server types support computer networks. Apart from the common corporate types, home users often interface with online game servers, chat servers and even streaming-audio services.

Network Server Types

Many networks on the internet employ a client-server networking model integrating websites and communication services.
An alternative model—peer-to-peer networking—allows all devices on a network to function as either a server or client as needed. Peer networks offer a greater degree of privacy because communication between computers is more targeted, but most implementations of peer-to-peer networking aren’t robust enough to support very large traffic spikes.

Server Clusters

The word cluster is used broadly in computer networking to refer to implementations of shared computing resources. Typically, a cluster integrates the resources of two or more computing devices that could otherwise function separately (often, workstation or server devices) together for some common purpose.

A Web server farm (a collection of networked Web servers, each with access to content on the same site) function as a cluster conceptually. However, purists debate the technical classification of a server farm as a cluster, depending on the details of the hardware and software configuration.