Support for Bursty Traffic

• Local Area Networks generally use a communication link shared by all computers connected to it.
• Example: In the original Ethernet implementation, the network consisted of a coaxial cable that computers would tap into.
• Hence, LANs use a broadcast communication medium.
• We had considered earlier, methods for sharing a broadcast channel.
• The methods we had identified were TDMA and FDMA.
• TDMA and FDMA are well suited to support synchronous traffic.
• If TDMA were used for LANs with bursty data traffic:
  • many time slots would go idle when computers do not have data to transmit,
  • When a computer has data to transmit, it has to wait its turn and transmission of the message is delayed.
• Hence, TDMA is not well suited for bursty data traffic as it uses the channel inefficiently and it induces considerable delays.
• A similar argument can be constructed to show that FDMA is inappropriate for data traffic.
• Question: Are there alternatives for accessing a shared broadcast channel that avoid the drawbacks of fixed-assignment multiple-access methods?