The backbone network, also called network backbone is an important architectural element of a network that carries the bulk of the network traffic. It provides the highest-speed transmission paths and the longest distances for exchang of data by interconnecting different local area networks (LANs) or subnetworks. At the local level, a backbone ties together diverse LANs in offices, colledges or office buildings. When several LANs are being interconnected over a large scale, it is metropolitan area network (MAN) or other wide area network (WAN), or even the Internet. The first Internet backbone was made between UCLA and SLI on October 29, 1969. Today, in the United States, most of backbones are run by telecommunication companies such as AT&T, Bell South, Congent, Qwest, Level 3, MCI/Worldcom, Sprint, and Time Warner.
Backbones are primarily used in medium to large-sized networks, such as a building or a group of buildings on a campus. These backbones generally fall into two basic categories – distributed backbone and collapsed backbone. In addition, there are parallel backbone and serial backbone applied in some networks. These four type of backbone as following:
Distributed backbone – A distributed backbone has a core consisting of multiple switches or routers chained together, typically in a ring. It allows for simple expansion and limited capital outlay for growth, because more layers of devices can be added to existing layers.
Collapsed backbone – A collapsed backbone has a central device at the hub of a star network. In medium to large networks, this central device is a chassis switch. It greatly facilitates the provisioning of appropriate bandwidth to the connected nodes. Each connected distribution node has its own dedicated connection into the core.
Parallel backbone – A parallel backbone consists of using two cables routed between the routers and switches. While there are additional initial costs of installing a parallel backbone, the benefits can quickly outweigh these costs.
Serial backbone – A serial backbone is the simplest kind of backbone network which consists of two or more internet working devices connected to each other by a single cable in a daisy-chain fashion. A serial backbone topology could be used for enterprise-wide networks.