Packet Transport Mechanisms, continued

• interference detection.
  Each transceiver has an interference detector; a station can detect interference because what it is receiving is not what it is transmitting.
  Interference detection has three advantages:
  1. A station can detect collisions and re-schedule transmission (no need to wait for a lack of acknowledgement).

  2. Interference is detected within the propagation time (with Aloha a whole packet was transmitted and then examined for a collision).

  3. The frequency of collisions is immediately used to dynamically change the back-off times.

• truncated packet filtering.
  Interference detection and deference cause most collisions to result in truncated packets of only a few bits. To reduce the overhead of obviously damaged packets, the hardware is able to filter them out.

• collision consensus enforcement.
  Whenever a station detects a collision of its own transmission it deliberately jams the ether to ensure that other colliding stations hear the collision as quickly as possible and then to stop transmitting.