100BASE-TX Fast Ethernet Standards


  • Fast Ethernet standard uses same CSMA/CD protocol as 10BASE-T, but:
    • with higher frequency signaling
    • improved encoding
    • 100BASE-TX refers to Fast Ethernet over Cat5 (or better) twisted pair copper cable
    • maximum link 100 m (328 ft)
  • supports hubs and switches
    • each switch port is its own collision domain
    • eliminates effect of contention
    • allows for full-duplex
      • each node can transmit and receive simultaneously
      • each node can use the full 100 Mbps bandwidth of the cable link
  • Compatible with hosts with 10 Mbps Ethernet interfaces
    • Fast Ethernet uses an autonegotiation protocol
      • allows a host to choose the highest supported connection
        • 10 or 100 Mbps
        • half or full duplex
      • 10BASE-T requires a node transmit regular electrical pulses to confirm viability of a link
        • Fast Ethernet codes a 16-bit data packet into this signal, advertising its capabilities
          • called Fast Link Pulse
      • node that does not support autonegotiation can be detected by one that does
        • will be sent an ordinary link integrity test signal instead
          • called Normal Link Pulses
  • Fast Ethernet is not deployed on new networks, but may be maintained on legacy networks