Question 1
a) Discuss how Ethernet Transmitter Algorithm, CSMA/CD, works? How does it
address the situation when a collision is detected? How does the jamming
sequence and delay process take place in such case of collision?
b) Consider a client and server using an RPC mechanism. Give a scenario
involving server reboot in which an RPC request is sent twice by the client and is
executed twice by the server, with only a single ACK.
c) Post Office Protocol (POP3) is a simple mail access protocol. With the TCP
connection established, POP3 progresses through three phases. List these
three phases and explain what happens during each phase.
d) Describe the role of firewall to protect the local network at your institution. Clearly
identify what incoming and outgoing requests your firewall should intercept.
Question 2
a) Discuss the following lossless compression techniques: i) Run length Encoding,
and ii) Differential Pulse Code Modulation.
b) Explain in detail what a denial of service attack is. Can firewalls prevent such
attacks? Suggest methods other than a firewall that are available to deal with
such attacks.
c) Explain the following terms in Mobile IP: i) home agent, ii) home address, iii) foreign
agent, and iv) CoA.
Question 3
a) Explain Image representation and compression methods that are used in JPEG.
b) Differentiate between recursive and iterative DNS queries.
c) What is the justification for the exponential increase in timeout value in TCP
communication?
d) By considering the operation of the TCP protocol, explain how it is able to
overcome errors in the transmission and ensure that data is transferred reliably
over a network.
Question 4
a) Discuss in details with the help of forwarding tables and diagrams how packets
are sent from Host A to Host B in the following diagram. Give all the details.

b) What aspect of IP addresses makes it necessary to have one address per
network interface, rather than just one per host? In light of your answer, why
does IP tolerate point-to-point interfaces that have non-unique addresses or no
addresses?

c) How do routers determine that an incoming IP packet is to be multicast? Give
answers for both IPv4 and IPv6.

d) Pure ALOHA is a random access scheme that suffers from partial and complete
collisions. Use a diagram to explain how partial and complete collisions occur.
Offer an access mechanism that reduces/eliminates partial collisions. Illustrate the
access mechanism to avoid partial collisions in 3 nodes with the aid of a diagram.
Q5
a) Give an example of a situation in which multicast addresses might be beneficial.
b) Explain with a diagram 'Additive Increase Multiplicative Decrease' TCP
Congestion Control scheme.
c) Can the bridge learn on which port the various hosts reside? How does it learn?
Q6

a) What differences in traffic patterns account for the fact that STDM is a cost-
effective form of multiplexing for a voice telephone network and FDM is a cost-
effective form of multiplexing for television and radio networks, yet we reject both as

not being cost effective for a general-purpose computer network?
b) Explain with diagram how data transfer takes place in Mobile IP.
c) What factors govern the triggering transmission in TCP?
Q7.
a) How long does it take to transmit x KB over a y-Mbps link? Give your answer as a
ratio of x and y.
b) What aspect of IP addresses makes it necessary to have one address per network

interface, rather than just one per host? In light of your answer, why does IP tolerate point-
to-point interfaces that have non-unique addresses or no addresses?

Q8 Suppose a 1-Gbps point-to-point link is being set up between the Earth and a
new lunar colony. The distance from the moon to the Earth is approximately 385,000
km, and data travels over the link at the speed of light—3×108 m/s.

(a) Calculate the minimum RTT for the link.
(b) Using the RTT as the delay, calculate the delay × bandwidth product for the link.
(c) What is the significance of the delay × bandwidth product computed in (b)?
Q9 For each of the following operations on a remote file server, discuss whether they
are more likely to be delay sensitive or bandwidth sensitive:
(a) Open a file.
(b) Read the contents of a file.
(c) List the contents of a directory.
(d) Display the attributes of a file.
Q10 Discuss the relative performance needs of the following applications in terms of
average bandwidth, peak bandwidth, latency, jitter, and loss tolerance:
(a) File server.
(b) Print server.
(c) Digital library.
(d) Voice.