Computer Networking

Computer networking is the engineering discipline dealing with communication between computer systems. These networks are made up of at least two computers, which could be separated by a few inches (Bluetooth) or by thousands of miles (Internet).

Local Area Network (LAN)

Covering a small area is a local area network (LAN). LAN connections are typically used in homes, offices, small groups of buildings, and colleges. LANS are usually based on switched Ethernet or Wi-Fi that runs at 10, 100, or 10,000 Mbit/s. There are some specific attributes that separate a LAN from a WAN.

Characteristics of a LAN Network

• LANs have a much smaller geographical area, with a max of a few kilometers, as opposed to a WAN's geographical area
• LANs do not have leased telecommunication lines and "LAN" is not referring to data that runs over a local analog telephone line
• LAN Networks have a much higher data rate than WAN Networks

Switched Ethernet is currently the most common physical layer, but in the past many different options have been used to accomplish the same means. LAN's that are much larger, typically have redundant and overlapping links, routers, or switches that can use spanning tree protocal and other techniques which recover from failed links. Most LANs are connected to the large public network (the Internet), and also link to other LANs that are tunnelled across using VPN technologies.

Wide Area Network (WAN)

Just the opposite of a LAN, a WAN covers a wide geographical area, which can involve a large amount of computers. These differ siginificantly from personal area networks (PANs), metropolitan area networks (MANs), and local area networks (LANs); which are normally limited to a room, building, site, or campus. The Internet is the most well-known example of a wide area network (WAN).

One use of a WAN is to actually connect local area networks (LANs) together, so that users and computers that are in the same area can communicate. Many of the WANs that are built are done so for certain organizations and are private. Those that are built by Internet Service Providers give connections from an organization's LAN to the Internet. These are usually built using leased lines, and at each end of the leased line a router connects to the LAN on one end and a hub within the WAN on the other end. Network protocols, including TCP/IP deliver transport and addressing functions. Protocols including Packet over SONET/SDH, MPLS, ATM and Frame relay are used by service providers to deliver links that are used in WANs. X.25 was one of the first WAN protocols, and is referred to as the "grandfather" of Frame Relays. Many of the functions of this original Frame Relay are still in use today.