Free CISSP Certification Practice Questions:
Which of the following LAN transmission protocols is ideal for a factory automation environment where transmission delays must be predictable and deterministic?
A) CSMA/CD
B) CSMA/CA
C) Ethernet network
D) Token Ring network
E) IEEE 802.3
-
[Ans: D]
Token passing networks are deterministic
and predictable. In a token ring network,
it is possible to calculate the maximum
transmission delay experienced by any end
station. Token passing networks use a token,
or series of bits, to grant a device permission
to transmit over the network. The token
acts like a ticket, enabling its owner to
send a message across the network. When
transmission is complete, the device passes
the token along to the next device in the
topology. Since there is only one token
for each network, there is no possibility
that a collision will occur, i.e. two computers
attempting to transmit messages at the same
time. In addition, rules in the protocol
specifications mandate how long a device
may keep the token, how long it can transmit
for and how to generate a new token if there
isn't one circulating. Hence, token passing
networks, such as Token Ring networks, are
ideal for environments where transmission
delays must be predictable.
On the other hand, CSMA/CD (specified in the IEEE 802.3 standard) networks, such as Ethernet networks, are non-deterministic. In these types of networks, nodes constantly monitor the line to make sure that no other hosts are transmitting. A node must wait until the line is clear before starting to transmit and must continue to monitor the line while transmitting. If two nodes transmit at the same time, the transmission will be corrupted and the frames will be discarded. In this situation, each device then waits a random amount of time and retries until transmission is successful. As a result of its non-deterministic nature, CSMA/CD (IEEE 802.3) networks, such as Ethernet, are NOT ideal for network environment where transmission delays must be predictable and deterministic.
BACK | NEXT