2 cissp ® Official Study Guide Eighth Edition

LAN Media Access
There are at least five LAN media access technologies that are used to avoid or prevent 
transmission collisions. These technologies define how multiple systems all within the same 
collision domain are to communicate. Some of these technologies actively prevent colli-
sions, while others respond to collisions.

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Chapter 11 
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Secure Network Architecture and Securing Network Components
Carrier-Sense Multiple Access (CSMA)

This is the LAN media access technology that 

performs communications using the following steps:
1.
The host listens to the LAN media to determine whether it is in use.
2.
If the LAN media is not being used, the host transmits its communication.
3.
The host waits for an acknowledgment.
4.
If no acknowledgment is received after a time-out period, the host starts over at step 1.
CSMA does not directly address collisions. If a collision occurs, the communication would 
not have been successful, and thus an acknowledgment would not be received. This causes 
the sending system to retransmit the data and perform the CSMA process again.
Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA)

This is the LAN 

media access technology that performs communications using the following steps:
1.
The host has two connections to the LAN media: inbound and outbound. The host 
listens on the inbound connection to determine whether the LAN media is in use.
2.
If the LAN media is not being used, the host requests permission to transmit.
3.
If permission is not granted after a time-out period, the host starts over at step 1.
4.
If permission is granted, the host transmits its communication over the outbound
connection.