Which access method is used by Ethernet networks sharing a single collision domain?

• A. Token Ring
• B. CSMA/CD
• C. TDMA
• D. CSMA/CA

Answer: (B)

CSMA/CD governs access when Ethernet devices share a single collision domain. In this setup, each node listens before transmitting (carrier sense). If the channel is free, a node starts transmitting, but others may also transmit, causing a collision that all parties detect (collision detection). When a collision is detected, all transmitting nodes stop, wait for a random backoff period, and then try again. This approach works on a shared medium like coax or a hub where every device can hear every other device’s signal, creating one collision domain. Modern Ethernet tends to use switches to separate collision domains, so CSMA/CD isn’t needed on each link anymore. Other options don’t apply here: token passing is used by Token Ring, time-division multiple access assigns fixed time slots (TDMA), and CSMA/CA is used in wireless networks to avoid collisions rather than detect them on a wired shared medium.