Which
of the following LAN protocols use token passing for exchanging signals among various stations on
the network? Each correct answer represents a complete solution. Choose two.
A.
Ethernet (IEEE 802.3)
B.
Token ring (IEEE 802.5)
C.
Fiber Distributed Data Interface (FDDI)
D.
Wireless LAN (IEEE 802.11b)
Explanation:
Originally developed by IBM, the token ring is an intricate but highly dependable
networking technology that follows the IEEE 802.5 standard.
The type of topology used in this technology is physically a star, but implemented logically as a ring,
in which all the computers are attached toa central unit called a multistation access unit (MAU OR MSAU). Token ring networks use token
passing to send their signals over the network.
Token is a type of data packet, which circulates in the entire network. If the token is free, the
computer waiting to send data takes it,
attaches the data and the destination address to the token, and sends it. When the token reaches its
destination computer, the data is
received. Then, the token gets back to the originator. If the originator finds that the message has
been received, it removes the message
from the token. Now, the token is free and can be used by the other computers in the network to
send data.
Developed by the American National Standards Institute, FDDI is a ring-based network that uses
fiber optic cables to provide very fast and
reliable communication between the connected computers. It uses token passing to control the
network access but does not use a hub like
the token ring networks; instead, it uses a central device called concentrator to connect the
computers in the network. In these networks, the
computers are connected using physical ring topology.
Answer option A is incorrect. Ethernet is the oldest and most popular data link layer protocol (or
network technology) used in today’s
networks. Ethernet networks use a bus or star topology and control the flow of data through the
media access control (MAC) method known
as Carrier Sense Multiple Access Collision Detection (CSMA/CD).
Answer option D is incorrect. The IEEE 802.11b standard applies to wireless LAN Networks that use
radio waves as the transmission medium.
These networks have their separate media access control mechanism known as Carrier Sense
Multiple Access with Collision Avoidance
(CSMS/CA), that works like the CSMA/CD mechanism used by the Ethernet. The difference is that in
this protocol, when a computer sends its
signals, the receiving computer performs a cyclical redundancy check and sends an
acknowledgement message to the sending computer if no
error is detected.