Cabletron Systems MMAC-5FNB, Сетевое руководство

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Backbone Planning 4-17
Network Design
The device collapsed backbone is the most expensive backbone choice, simply
due to adding the cost of sophisticated, high-performance hardware to the costs
of a collapsed backbone cabling layout. In many cases, the additional control and
functionality provided by the device collapsed backbone configuration are so
valuable that the cost is well worth it.
• Connectivity Requirements - The device collapsed backbone implementation
brings all cables of the backbone to a single device, which takes care of the
interconnection issues.
• Ease of Expandability - As all the workgroups of the network are connected
through the backbone device, the expandability of the network is limited by
the amount of expandability that the device is capable of. As with the design
of facility cabling, planning for future needs will go a long way toward
reducing future expenses and possibly avoiding a costly “forklift” upgrade.
• Simplified Troubleshooting - The device collapsed backbone, by connecting
the workgroups through a manageable device, provides not only simplified
troubleshooting, but the ability to detect some backbone faults before they
become network failures.
• Extensive Control - The device collapsed backbone provides the highest level
of network control. Workgroups and devices on the backbone can be included
or bypassed with the click of a mouse or through the use of a terminal session.
Physically adding workgroups to the network will still require the connection
of facility cabling and jumper cables, but, as with the standard collapsed
backbone, the usefulness of planning ahead cannot be over-emphasized.
One danger of the device collapsed backbone is the existence of a single point of
failure: the backbone device. If the backbone device fails, the backbone network
will not operate. For more information on single points of failure and avoiding
their creation in a network, refer to the Fault Aversion section of this chapter.
Choosing Backbone Technologies
The selection of a backbone technology is a similar process to the selection of
workgroup technologies. As with the selection of a workgroup technology, make
sure you are familiar with the operation of each type of technology, the strengths
and shortcomings of those technologies, and the special design considerations
that each technology imposes on the network. You may, again, wish to refer to the
training information of this Networking Guide for initial instruction.
The selection of a backbone technology requires a careful examination of the
needs of your facility and the ways that the various technologies and organization
styles can fit those needs. It is the job of the Network Manager or persons
designing the network to determine which factors of the network design are the
foremost requirements.