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Hub and switch differences

Chris:

I can't seem to get a definitive answer on the difference between a hub and a switch. What are the advantages to one over the other? By the way, did you get an answer for your plenum rated copper question? If not, call Metro Wire over in Hudson, MA. They carry cat3, cat5 and enhanced cat5 plenum rated copper.


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A Fibre hub uses the FC-AL protocol which is "loop" based, usually has either 8, 12, or in some cases 16 ports, and the 100MB per second bandwidth is "shared" through the device. Each server must wait its turn to "talk" on the loop.

A Fibre switch uses the FC-SW protocol, is "point-to-point" based, goes from 8 ports all the way up to the 128 port director class, and all hosts have the complete 100MB per second path to themselves. The solution is the same as in Ethernet networks. A Hub based network is always slower than a switched based network due to contention for the network resource. If you have an 8 port hub, only one system can "talk" at a time. With a switch, everyone can talk at the same time. The advantages are obvious.

As for the plenum rated cabling for networks, that is the industry standard, and should be able to be sourced from multiple vendors. Plenum rating means you can run your cables through air ducts, and if it catches fire, would not produce toxic fumes. The question to ask your supplier for cabling would be, "is it PVC coated?"? PVC emits toxic fumes when burned, so for plenum cables, use a non-PVC type of cable.

Chris


This was first published in July 2001

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