Networking
Topologies
Networking |
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| The University of Findlay's College of Education | |
Connecting The Network
Hardware devices connected to the network make up the "physical network". This includes Network Interface Devices (NIC's) in each computer, the wire connecting the computers and the wire closet electronics.
One way of connecting computers in a network is a ring. The most popular type of ring was the Token Ring created by IBM. A "token" was sent around the network. As the token came by, each computer checked to see if a message was on board and addressed to the local machine. If a machine wanted to send a message, that message was placed on the token as it went by.
In the past ten years, the exact type of hardware used to create most networks has changed dramatically. Ten years ago, most networks were based on a bus topology.
With a bus topology, each computer is connected in a line. At the ends of the line, terminators ground the network signal so that it does not bounce back on the line and interfere with new signals. The bus topology was used because it was inexpensive compared with other network topologies. To connect a new computer to the network it was only necessary to purchase a NIC (no hubs or switches). The drawback to this topology was connectivity between each node. If something were to happen to any node, and a break in the network line were to occur, the entire network would go down.
As the price of hubs and switches came down, a shift towards the star topology began.
A star topology has every computer connecting directly to a hub or a switch. Because each computer connects directly to a hub, disconnecting one computer effects no other workstation's network connectivity.
At one time, the cost of an 8-port hub operating at 10 megabits (Mb) was more than $200. This put the cost of connecting to the network at $25 per computer plus wiring and NIC costs. Today the same 10 Mb hub is about $25, or less than $4 per computer. The star is the most popular connectivity model today because wire closet electronics have drastically decreased in price.