A Class I repeater transmit or repeats the incoming line signals on one port to the other ports by first translating them to digital signals and then retranslating them to line signals. The translations are necessary when connecting different physical media (media conforming to more than one physical layer specification) to the same segment.
A Class II repeater immediately transmits or repeats the incoming line signals on one port to the other ports; it does not perform any translations. This repeater type connects identical media to the same segment (i.e. TX to TX). At most, two Class II repeaters can exist within a single network segment. The cable used to cascade the two devices is called an unpopulated segment, or IRL (Inter-Repeater Link).
Both Class I and Class II repeaters have multiple shared ports; ports that are on the same network segment. Since they share a fixed bandwidth, nodes attached to these ports must operate at the same speed, either 10 Mbps or 100 Mbps.
Fast Ethernet adheres to the EIA/TIA 568 Commercial Building Telecommunications Wiring Standard. It supports the two most commonly installed UTP cable types, Category 3 and Category 5. Fast Ethernet also supports STP, so cable plants wired for Token Ring can be used without modification. This allows for a dramatic cost savings since new cable doesn't need to be installed and tested.
Since the MAC layer and the frame format are both identical to that of 10BASE-T, linking Fast Ethernet to traditional Ethernet does not require expensive routing or repacketizing. Fast Ethernet also uses the same applications and the same drivers used by traditional Ethernet. In addition, the cost of the selectable 10/100 Mbps products that can provide 10 times the performance is roughly only twice the cost of standard Ethernet.
Fast Ethernet also has broad multivendor support ensuring interoperability among products, increasing availability of new products , and decreasing prices of 100 BASE-T technology..
