Specifications

Ethernet Features
2-2 Introduction
Ethernet Features
The Institute of Electrical and Electronic Engineers (IEEE) is a standards
organization that establishes standards for many different technical areas.
This broad standards responsibility includes computer networking. IEEE
project 802 is responsible for networking standards for all network access
methods while project 802.3 specifically defines the Carrier Sense Multiple
Access/Collision Detection (CSMA/CD) access method, or Ethernet.
The following sections detail specific features involved with the
CSMA/CD media access method.
Media Access Method
As mentioned above, Ethernet is a Carrier Sense Multiple
Access/Collision Detection (CSMA/CD) LAN technology. Stations on an
Ethernet LAN can access the network at any time. Before sending data,
Ethernet stations “listen” to the network to see if it is already in use. If so,
the station wishing to transmit waits. If the network is not in use, the
station transmits. A collision occurs when two stations listen for network
traffic, “hear” none, then transmit simultaneously. In this case, both
transmissions are damaged and the stations, sensing this collision, must
retransmit at some later time. Backoff algorithms determine when the
colliding stations retransmit.
Ethernet is a broadcast network. In other words, all stations see all frames,
regardless of whether they represent an intended destination. Each station
must examine received frames to determine if it is the destination. If so,
the frame is passed to a higher protocol layer for appropriate processing.
Bandwidth
Ethernet bandwidth is 10 megabits per second although later
developments have produced Fast-Ethernet bandwidths of 100 megabits
per second.