Backbone Planning4-13Network DesignBackbone PlanningWhat Is a Backbone?A backbone is a network segment or cable which is used to provide for theinterconnection of a number of smaller workgroups or self-contained networks.The outlying networks, workgroups, or hubs communicate with one anotherthrough the backbone network.The use of a dedicated network acting as a backbone, tying all the separatenetworks together, is of benefit for several reasons.• Using a single network to handle the extremely important connectionsbetween networks allows Network Designers to utilize highly reliabletechnologies and cables. These designs are frequently expensive, and usingthem, initially, in the backbone network provides the benefits of thesetechnologies or media without requiring the expense of providing that level ofservice to all points of the network.• A backbone network can be migrated out to the workgroups as thefacility-wide network grows. As more users are added, it is often much easierto attach a concentrator or hub to a small backbone network than to continueexpanding workgroups that may be already quite congested. In addition, thebackbone can provide a point from which a higher-speed technology can be‘painted out’ to the rest of the network as needs dictate and as money becomesavailable.• Since the amount of communications passing between several workgroups orhubs in an entire facility or campus is often quite large, backbone networksoften use higher-speed networking technologies than the technologies used bythe workgroup networks. A very common workgroup and backbone scenarioinvolves several Ethernet workgroups in a building or campus connected to anFDDI backbone. This offers the communications passing between the separateEthernet networks, operating at under 10 Mbps, to access a highly reliable andavailable 100 Mbps network for communications between workgroups.
