CompTIA A+® Certification All-In-One For Dummies®, 2nd Edition

1.5. Examining Network Access Methods

Network access refers to the different methods that computers use to place data on the network. This section discusses these methods and identifies the advantages and disadvantages of each.

1.5.1. CSMA/CD

One of the most popular types of access methods is CSMA/CD (Carrier Sense Multiple Access/Collision Detection). Understanding this term is easier if you break it down into its individual parts and examine each part in detail:

• Carrier sense: All computers on the network are watching, or sensing, the network for network traffic. If the network has data already on the wire, a system will wait until the wire is free of traffic.

• Multiple access: All computers on the network have equal access to the network at any given time. In other words, anyone can place data on the network whenever he or she chooses. Note, however, that workstations on the network will try not to place data on the wire at the same time the wire is transmitting other data because the two pieces of data will collide, destroying the data. That's why it's so important for workstations to "sense" the wire.

  To summarize, carrier sense multiple access suggests that all workstations have access to the network and are watching the network to make sure it is clear of data before they send out their information.

• Collision detection: When two workstations send information at the same time, the data will collide and be damaged in transit. When two workstations have data that has been involved ...