A network is basically all of the components (hardware and software) involved in connecting computers across small and large distances. Networks are used to provide easy access to information, thus increasing productivity for users.
There are lots of advantages from build up a network, but the three big facts are-
From sharing files you can view, modify, and copy files stored on a different computer on the network just as easily as if they were stored on your computer.
Resources such as printers, fax machines, Storage Devices (HDD, FDD and CD Drives), Webcam, Scanners, Modem and many more devices can be shared.
Just as you can share files on a network, you can often also share program on a network. For example, if you have the right type of software license, you can have a shared copy of Microsoft Office, or some other program, and keep it on the network server, from where it is also run
Local area networks (LANs) are used to connect networking devices that are in a very close geographic area, such as a floor of a building, a building itself, or a campus environment.
Wide area networks (WANs) are used to connect LANs together. Typically, WANs are used when the LANs that must be connected are separated by a large distance.
A metropolitan area network (MAN) is a hybrid between a LAN and a WAN.
Storage area networks (SANs) provide a high-speed infrastructure to move data between storage devices and file servers.
Disadvantage of SANs is their cost.
Content networks (CNs) were developed to ease users' access to Internet resources.
Companies deploy basically two types of CNs:
An intranet is basically a network that is local to a company. In other words, users from within this company can find all of their resources without having to go outside of the company. An intranet can include LANs, private WANs and MANs,
An extranet is an extended intranet, where certain internal services are made available to known external users or external business partners at remote locations.
An internet is used when unknown external users need to access internal resources in your network. In other words, your company might have a web site that sells various products, and you want any external user to be able to access this service.
A virtual private network (VPN) is a special type of secured network. A VPN is used to provide a secure connection across a public network, such as an internet. Extranets typically use a VPN to provide a secure connection between a company and its known external users or offices.
Authentication is provided to validate the identities of the two peers.
Confidentiality provides encryption of the data to keep it private from prying eyes.
Integrity is used to ensure that the data sent between the two devices or sites has not been tampered with.