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The Workgroup in the Larger Network
5-17
Network Design
What Is a Backbone?
A backbone is a network segment or cable which is used to provide for the 
interconnection of a number of smaller workgroups or self-contained networks. 
The outlying networks, workgroups, or hubs communicate with one another 
through the backbone network. 
The use of a dedicated network acting as a backbone, tying all the separate 
networks together, is of benefit for several reasons.
Using a single network to handle the extremely important connections 
between networks allows Network Designers to use highly reliable 
technologies and cables. These designs are frequently expensive, and using 
them, initially, in the backbone network provides the benefits of these 
technologies or media without requiring the expense of providing that level of 
service to all points of the network.
A backbone network can be migrated out to the workgroups as the 
facility-wide network grows. As more users are added, it is often much easier 
to attach a concentrator or hub to a small backbone network than to continue 
expanding workgroups that may be already quite congested. In addition, the 
backbone 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 becomes 
available.
Since the amount of communications passing between several workgroups or 
hubs in an entire facility or campus is often quite large, backbone networks 
often use higher-speed networking technologies than those of the workgroup 
networks. A very common workgroup and backbone scenario involves several 
Ethernet workgroups in a building or campus connected to an FDDI backbone. 
This offers the communications passing between the separate Ethernet 
networks, operating at under 10 Mbps, to access a highly reliable and available 
100 Mbps network for communications between workgroups.
Methods of Configuring Backbones
Backbone networks can be set up in a number of different ways. This Networking 
Guide presents three of the most common means of configuring backbone 
networks. Almost any backbone network implementation may be designed from 
the following basic backbone types:
Distributed Backbone
Collapsed Backbone
Device Collapsed Backbone