- A. CSMA/CD
- B. IGMP
- C. port security
- D. split horizon
Ethernet began as a local area network technology that provided a half-duplex shared channel for stations connected to coaxial cable segments linked with signal repeaters. In this appendix, we take a detailed look at the half-duplex shared- channel mode of operation, and at the CSMA/CD mechanism that makes it work. In the original half-duplex mode, the CSMA/CD protocol allows a set of stations to compete for access to a shared Ethernet channel in a fair and equitable manner.
The protocol’s rules determine the behavior of Ethernet stations, including when they are allowed to transmit a frame onto a shared Ethernet channel, and what to do when a collision occurs. Today, virtually all devices are connected to Ethernet switch ports over full-duplex media, such as twisted-pair cables. On this type of connection, assuming that both devices can support the full-duplex mode of operation and that Auto-Negotiation (AN) is enabled, the AN protocol will automatically select the highest-performance mode of operation supported by the devices at each end of the link. That will result in full-duplex mode for the vast majority of
Ethernet connections with modern interfaces that support full duplex and AN.