Intro to Networking (midterm 1)
What is the transmission rate of Ethernet LANs? - ANS-Ethernet LANs have transmission rates
of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.
What are some of the physical media that Ethernet can run over? - ANS-Ethernet most
commonly runs over twisted-pair copper wire and "thin" coaxial cable. It also can run over fiber
optic links and thick coaxial cable.
Suppose there is exactly one packet switch between a sending host and a receiving host. The
transmission rates between the sending host and the switch and between the switch and the
receiving host are R1 and R2, respectively.
Assuming that the switch uses store-and-forward packet switching, what is the total end-to-end
delay to send a packet of length L? - ANS-At time t0 the sending host begins to transmit. At time
t1 = L/R1, the sending host completes
transmission and the entire packet is received at the router (no propagation delay). Because the
router has the entire packet at time t1, it can begin to transmit the packet to the receiving host
at time t1. At time t2 = t1 + L/R2, the router completes transmission and the entire packet is
received at the receiving host (again, no propagation delay). Thus, the end-to-end delay is >
L/R1 + L/R2.
What is a circuit switch network? What is the major difference between circuit switch network
and package switch network? - ANS-In circuit switching network dedicated channel has to be
established before the call is made between users. The channel is reserved between the users
till the connection is active. For half duplex communication, one channel is allocated and for full
duplex communication, two channels are allocated. It is mainly used for voice communication
requiring real time services without any much delay.
In packet switching network unlike CS network, it is not required to establish the connection
initially. The connection/channel is available to use by many users. But when capacity or
number of users increases then it will lead to congestion in the network. Packet switched
networks are mainly used for data and voice applications requiring non-real time scenarios.
Give an example of circuit switching: - ANS-Example of circuit-switching: You pick up your land
phone and dial your friend. At that point, the telco provider creates a dedicated circuit for that
session and connects you to your friend's telephone. No matter how long you keep the line open
with your friend, the circuit will remain, and packets flowing between both telephones will always
follow the same path. This is an example of a circuit-switched network.
Give an example of packet switching: - ANS-Example of packet-switching: In the second
example, you switch on your PC and connect to your favorite site that offers a number of
, applications you can download from, so you begin downloading one application at a time. Each
packet has to find its own route to the destination, i.e., your computer. Each packet finds its way
using the information it carries, such as the source and destination IP address. If network
congestion occurs, the routers responsible for routing packets between networks will
automatically select different paths to ensure data is transferred as required. This is an example
of a packet-switched network.
What is TDM? How does it work? - ANS-Time Division Multiplexing (TDM): a method of
transmitting and receiving independent signals over a common signal path by means of
synchronized switches at each end of the transmission line so that each signal appears on the
line only a fraction of time in an alternating pattern.
What is FDM? How does it work? - ANS-Frequency Division Multiplexing (FDM) is a networking
technique in which multiple data signals are combined for simultaneous transmission via a
shared communication medium. FDM uses a carrier signal at a discrete frequency for each data
stream and then combines many modulated signals.
How long does it take a packet of length 1,000 bytes to propagate over a link of distance 2,500
km, propagation speed 2.5 · 108 m/s, and transmission rate 2 Mbps? More generally, how long
does it take a packet of length L to propagate over a link of distance d, propagation speed s,
and transmission rate R bps? Does this delay depend on packet length? Does this delay
depend on transmission rate? - ANS-1. (2500*10^3)/(2.5*10^8) = 0.01s = 10ms
2. d/s
3. no
4. no
Suppose Host A wants to send a large file to Host B. The path from Host A to Host B has three
links, of rates R1 = 500 kbps, R2 = 2 Mbps, and R3 = 1 Mbps.
a. Assuming no other traffic in the network, what is the throughput for the file transfer?
b. Suppose the file is 4 million bytes. Dividing the file size by the throughput, roughly how long
will it take to transfer the file to Host B?
c. Repeat (a) and (b), but now with R2 reduced to 100 kbps. - ANS-a. 500kpbs
b. (4*10^6)*8/(500*10^3)= 64 seconds
c. 100kbps, 4*10^6*8/100*10^3= 320 seconds
What are the five layers in the Internet protocol stack? - ANS-1. Application Layer
2. Transport Layer
3. Network Layer
4. Link Layer
5. Physical Layer
PLNTA (bottom up)
What is the transmission rate of Ethernet LANs? - ANS-Ethernet LANs have transmission rates
of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.
What are some of the physical media that Ethernet can run over? - ANS-Ethernet most
commonly runs over twisted-pair copper wire and "thin" coaxial cable. It also can run over fiber
optic links and thick coaxial cable.
Suppose there is exactly one packet switch between a sending host and a receiving host. The
transmission rates between the sending host and the switch and between the switch and the
receiving host are R1 and R2, respectively.
Assuming that the switch uses store-and-forward packet switching, what is the total end-to-end
delay to send a packet of length L? - ANS-At time t0 the sending host begins to transmit. At time
t1 = L/R1, the sending host completes
transmission and the entire packet is received at the router (no propagation delay). Because the
router has the entire packet at time t1, it can begin to transmit the packet to the receiving host
at time t1. At time t2 = t1 + L/R2, the router completes transmission and the entire packet is
received at the receiving host (again, no propagation delay). Thus, the end-to-end delay is >
L/R1 + L/R2.
What is a circuit switch network? What is the major difference between circuit switch network
and package switch network? - ANS-In circuit switching network dedicated channel has to be
established before the call is made between users. The channel is reserved between the users
till the connection is active. For half duplex communication, one channel is allocated and for full
duplex communication, two channels are allocated. It is mainly used for voice communication
requiring real time services without any much delay.
In packet switching network unlike CS network, it is not required to establish the connection
initially. The connection/channel is available to use by many users. But when capacity or
number of users increases then it will lead to congestion in the network. Packet switched
networks are mainly used for data and voice applications requiring non-real time scenarios.
Give an example of circuit switching: - ANS-Example of circuit-switching: You pick up your land
phone and dial your friend. At that point, the telco provider creates a dedicated circuit for that
session and connects you to your friend's telephone. No matter how long you keep the line open
with your friend, the circuit will remain, and packets flowing between both telephones will always
follow the same path. This is an example of a circuit-switched network.
Give an example of packet switching: - ANS-Example of packet-switching: In the second
example, you switch on your PC and connect to your favorite site that offers a number of
, applications you can download from, so you begin downloading one application at a time. Each
packet has to find its own route to the destination, i.e., your computer. Each packet finds its way
using the information it carries, such as the source and destination IP address. If network
congestion occurs, the routers responsible for routing packets between networks will
automatically select different paths to ensure data is transferred as required. This is an example
of a packet-switched network.
What is TDM? How does it work? - ANS-Time Division Multiplexing (TDM): a method of
transmitting and receiving independent signals over a common signal path by means of
synchronized switches at each end of the transmission line so that each signal appears on the
line only a fraction of time in an alternating pattern.
What is FDM? How does it work? - ANS-Frequency Division Multiplexing (FDM) is a networking
technique in which multiple data signals are combined for simultaneous transmission via a
shared communication medium. FDM uses a carrier signal at a discrete frequency for each data
stream and then combines many modulated signals.
How long does it take a packet of length 1,000 bytes to propagate over a link of distance 2,500
km, propagation speed 2.5 · 108 m/s, and transmission rate 2 Mbps? More generally, how long
does it take a packet of length L to propagate over a link of distance d, propagation speed s,
and transmission rate R bps? Does this delay depend on packet length? Does this delay
depend on transmission rate? - ANS-1. (2500*10^3)/(2.5*10^8) = 0.01s = 10ms
2. d/s
3. no
4. no
Suppose Host A wants to send a large file to Host B. The path from Host A to Host B has three
links, of rates R1 = 500 kbps, R2 = 2 Mbps, and R3 = 1 Mbps.
a. Assuming no other traffic in the network, what is the throughput for the file transfer?
b. Suppose the file is 4 million bytes. Dividing the file size by the throughput, roughly how long
will it take to transfer the file to Host B?
c. Repeat (a) and (b), but now with R2 reduced to 100 kbps. - ANS-a. 500kpbs
b. (4*10^6)*8/(500*10^3)= 64 seconds
c. 100kbps, 4*10^6*8/100*10^3= 320 seconds
What are the five layers in the Internet protocol stack? - ANS-1. Application Layer
2. Transport Layer
3. Network Layer
4. Link Layer
5. Physical Layer
PLNTA (bottom up)
