COMPUTER NETWORKS & THE
INTERNET EXAM QUESTIONS AND
ANSWERS
What is queue delay ? - Answer-The output buffer / output queue stores packets
needing to be sent through the outbound link. When there is alot of congestion on the
link a backup occurs and outgoing packets are stored on the output buffer / output
queue until they can be processed. This creates a queue delay
What is packet loss ? - Answer-Since the output buffer / output queue has finite space,
when the queue becomes full and there is no space to store the packet
What does a packet switch use to determine where to send a packet ? - Answer-The
forwarding table. This may point it to its final destination or progress it closer to its
destination
What is the difference between packet switching and circuit switching ? - Answer-1)
Circuit switching reserves 100% of the line until the transmission is complete
2) Packet switching uses resources on demand
3) Circuit switching has minimal switch delay
4) Packet switching may suffer switch delay pending on link congestion
5)Packet switching offers more sharing of transmission capacity
6)Packet switching is simpler, more cost efficient, and efficient
What are 'silent periods' - Answer-In circuit switching this is when a link is idle and using
none of its reserved bandwidth. This is wasteful.
What are the two kinds of multiplexing used for circuit switched networks ? - Answer-
Frequency Division Muliplexing (FDM) and Time Division Multiplexing (TDM)
How does Frequency Division Multiplexing Work ? - Answer-Frequency Division
Multiplexing is dividing up the bandwidth into different frequency chunks. The link
dedicated a frequency band to each connection for the duration of the connection. FM
radio uses this type of multiplexing
How does Time Division Multiplexing Work ? - Answer-Time Division Multiplexing
divides up each frame into time slots, giving each connection a time slot for the duration
of the connection in every frame sent.
, For TDM the transmission rate of a circuit is equal to ? - Answer-The rate of the circuit is
equal to the frame rate multiplied by the number of bits in a slot. eg: 8,000 frames per
second, each slot has 8 bits = 64kbps
What are the different kinds of delay ? - Answer-processing, queueing, transmissiong
and propogation delay
Define the different kinds of delay - Answer-queue - time packet waits before it can be
processed
processing - time it takes for the packet switch to read the header data, check its
forwarding table, error checking and send the packet to the appropriate outbound link
transmission - time it takes to transfer the packet to the link (transmission delay = size of
packet / transmission speed)
propogation - time it takes for the packet to travel through the medium ( propagation
delay = length of medium / propagation speed)
What is the difference between propagation and transmission delay ? - Answer-
propagation has to do with the transfer of the packet through the medium where as
transmission has to do with transferring the packet to the medium
what is traffic intensity ? Explain - Answer-In general, it is the ratio of the amount of
traffic incoming over the speed in which it can be processed onto the outbound link
(La/R | L = bits per packet | a = average packet rate | R = transmissiong rate). The
closer this ratio gets to 1 the large the queue delay becomes until it reaches inifinity or
the queue size is reached
What is instantaneous throughput - Answer-The throughput at the current instance that
it is being sampled at
How do u determine the average throughput of a packet delivery involving multiple
packet switches ? - Answer-File Size / min { packet switch 1 transmission rate, patche
switch 2 transmission rate, ... }
You take the transmission rate of the slowest link and divide the size of the packet by
that value
What is a bottleneck - Answer-The slowest part of a system. In networking likely the
slowest link
In the network layered architecture, a service layer must do at least two things so that
changes to the service have no effect on the other layers - Answer-The service must
provide the same services to the layer above it, and use the services of the layer below
it
INTERNET EXAM QUESTIONS AND
ANSWERS
What is queue delay ? - Answer-The output buffer / output queue stores packets
needing to be sent through the outbound link. When there is alot of congestion on the
link a backup occurs and outgoing packets are stored on the output buffer / output
queue until they can be processed. This creates a queue delay
What is packet loss ? - Answer-Since the output buffer / output queue has finite space,
when the queue becomes full and there is no space to store the packet
What does a packet switch use to determine where to send a packet ? - Answer-The
forwarding table. This may point it to its final destination or progress it closer to its
destination
What is the difference between packet switching and circuit switching ? - Answer-1)
Circuit switching reserves 100% of the line until the transmission is complete
2) Packet switching uses resources on demand
3) Circuit switching has minimal switch delay
4) Packet switching may suffer switch delay pending on link congestion
5)Packet switching offers more sharing of transmission capacity
6)Packet switching is simpler, more cost efficient, and efficient
What are 'silent periods' - Answer-In circuit switching this is when a link is idle and using
none of its reserved bandwidth. This is wasteful.
What are the two kinds of multiplexing used for circuit switched networks ? - Answer-
Frequency Division Muliplexing (FDM) and Time Division Multiplexing (TDM)
How does Frequency Division Multiplexing Work ? - Answer-Frequency Division
Multiplexing is dividing up the bandwidth into different frequency chunks. The link
dedicated a frequency band to each connection for the duration of the connection. FM
radio uses this type of multiplexing
How does Time Division Multiplexing Work ? - Answer-Time Division Multiplexing
divides up each frame into time slots, giving each connection a time slot for the duration
of the connection in every frame sent.
, For TDM the transmission rate of a circuit is equal to ? - Answer-The rate of the circuit is
equal to the frame rate multiplied by the number of bits in a slot. eg: 8,000 frames per
second, each slot has 8 bits = 64kbps
What are the different kinds of delay ? - Answer-processing, queueing, transmissiong
and propogation delay
Define the different kinds of delay - Answer-queue - time packet waits before it can be
processed
processing - time it takes for the packet switch to read the header data, check its
forwarding table, error checking and send the packet to the appropriate outbound link
transmission - time it takes to transfer the packet to the link (transmission delay = size of
packet / transmission speed)
propogation - time it takes for the packet to travel through the medium ( propagation
delay = length of medium / propagation speed)
What is the difference between propagation and transmission delay ? - Answer-
propagation has to do with the transfer of the packet through the medium where as
transmission has to do with transferring the packet to the medium
what is traffic intensity ? Explain - Answer-In general, it is the ratio of the amount of
traffic incoming over the speed in which it can be processed onto the outbound link
(La/R | L = bits per packet | a = average packet rate | R = transmissiong rate). The
closer this ratio gets to 1 the large the queue delay becomes until it reaches inifinity or
the queue size is reached
What is instantaneous throughput - Answer-The throughput at the current instance that
it is being sampled at
How do u determine the average throughput of a packet delivery involving multiple
packet switches ? - Answer-File Size / min { packet switch 1 transmission rate, patche
switch 2 transmission rate, ... }
You take the transmission rate of the slowest link and divide the size of the packet by
that value
What is a bottleneck - Answer-The slowest part of a system. In networking likely the
slowest link
In the network layered architecture, a service layer must do at least two things so that
changes to the service have no effect on the other layers - Answer-The service must
provide the same services to the layer above it, and use the services of the layer below
it
