Cabletron Systems MMAC-5FNB, Networking Manual

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Backbone Planning 4-13
Network Design
Backbone Planning
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 utilize 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 the technologies used by
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.