CSMA reduces collisions but doesn’t handle them when they occur. Once a collision happens, devices keep transmitting garbage, wasting bandwidth until the packet finishes.
An extension of CSMA that detects collisions during transmission and immediately stops, then uses a backoff algorithm before retrying, minimizing wasted bandwidth.
- Device listens before transmitting (carrier sense)
- If idle, start transmitting AND continuously monitor for collision
- If collision detected (signal strength changes): stop transmitting immediately
- Send a jam signal to notify all devices of the collision
- Wait a random time (binary exponential backoff) before retrying
- Listens before AND during transmission
- Detects collisions quickly and stops transmission
- Uses binary exponential backoff to reduce retry collisions
- Standard for traditional wired Ethernet (10/100 Mbps)
- Built from: CSMA — adds collision detection to basic CSMA
- Built from: Jam Signal — notifies others of collision
- Built from: Binary Exponential Backoff — retry algorithm
- Related: Collision Detection — the key addition over CSMA
- Contrasts with: CA — detection vs avoidance
- Only works on wired networks (can’t detect collision in wireless due to hidden terminal)
- Not used in modern full-duplex Ethernet (switches eliminate collisions)
- Maximum network diameter limited by collision detection time (slot time)