Ch 03: Network Topologies and Technologies
QUESTION TYPE:
Subjective Short Answer
HAS VARIABLES:
False
A physical star is the easiest topology to setup and expand. You are only limited by
your available ports. You can easily expand the number of ports by adding yet
another device and forming an extended star. The centralized design makes
monitoring and managing network traffic easier. With a bus, the bandwidth is limited
to 10Mbps and half-duplex mode. A star can operate at much higher speeds and, if a
switch is used, is capable of operating in full-duplex mode. There is only one main
disadvantage-that is that the central device represents a single point of failure.
44. Describe the structure of an Ethernet frame.
An Ethernet frame is composed of three parts. The first part is called the header. It contains
the source and destination MAC addresses along with a 2-byte type field. The type field is a
code that tells what network protocol is being used in the data portion of the frame. The
second part of the frame is the data portion, which is referred to as the payload. This is the
actual data that an application is sending across the network. The part also includes the
header from the network protocol. The last part of a frame is the FCS, which contains an
error-checking code called a CRC. It is the result of applying a mathematical formula to the
data portion of the frame. It is used to verify that the frame was not damaged in transmission.
45. What is CSMA/CD and how does it work?
CSMA/CD is the media access method used by Ethernet, which is a set of rules that govern
how and when a device can transmit on an Ethernet network. When two devices transmit a
signal at the same time, they cause a collision to occur. Then the devices must try to transmit
again, and again, causing a bottleneck. To avoid these collisions, CSMA/CD says that a
device must first listen to see whether it can detect any other signal on the medium. If no
other signal is detected, then the device can transmit. If another device transmits at the same
time and a collision occurs, then both transmitting stations must wait for a random period
before they can try to transmit again.