2 cissp ® Official Study Guide Eighth Edition

LAN Technologies
There are three main types of LAN technologies: Ethernet, Token Ring, and FDDI. A 
handful of other LAN technologies are available, but they are not as widely used. Only the 
main three are addressed on the CISSP exam. Most of the differences between LAN tech-
nologies exist at and below the Data Link layer.
Ethernet
Ethernet
is a shared-media LAN technology (also known as a broadcast technology). That 
means it allows numerous devices to communicate over the same medium but requires that 
the devices take turns communicating and performing collision detection and avoidance. 
Ethernet employs broadcast and collision domains. A broadcast domain is a physical group-
ing of systems in which all the systems in the group receive a broadcast sent by a single sys-
tem in the group. A broadcast is a message transmitted to a specific address that indicates 
that all systems are the intended recipients.
A collision domain consists of groupings of systems within which a data collision occurs 
if two systems transmit simultaneously. A data collision takes place when two transmitted 
messages attempt to use the network medium at the same time. It causes one or both of the 
messages to be corrupted.
Ethernet can support full-duplex communications (in other words, full two-way) and 
usually employs twisted-pair cabling. (Coaxial cabling was originally used.) Ethernet 
is most often deployed on star or bus topologies. Ethernet is based on the IEEE 802.3 
standard. Individual units of Ethernet data are called frames. Fast Ethernet supports 100 
Mbps throughput. Gigabit Ethernet supports 1,000 Mbps (1 Gbps) throughput. 10 Gigabit 
Ethernet support 10,000 Mbps (10 Gbps) throughput.
Token Ring
Token Ring
employs a token-passing mechanism to control which systems can transmit 
data over the network medium. The token travels in a logical loop among all members 
of the LAN. Token Ring can be employed on ring or star network topologies. It is rarely 
used today because of its performance limitations, higher cost compared to Ethernet, and 
increased difficulty in deployment and management. Token Ring hasn’t been seen in most 
networks for a decade or more.
Token Ring can be deployed as a physical star using a 
multistation access unit (MAU)
. 
A MAU allows for the cable segments to be deployed as a star while internally the device 
makes logical ring connections.

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