Question $1[28]$

a$.$ In this course we had two layered models that we worked with. One of them is the TCP$/$IP model. Give $2$ examples of protocols that are associated with each layer of the TCP$/$IP model. $[8]$

b$.$ What is a network "protocol"? $[2]$

c$.$ Differentiate between guided media and unguided media. $[2]$

d$.$ Differentiate between an analog and a digital electromagnetic signal. $[2]$

e$.$ What is attenuation? $[2]$

f$.$ Define channel capacity. $[2]$

g$.$ What are three important characteristics of a periodic signal? $[3]$

h$.$ What function does a modem perform? $[1]$

i$.$ An alternative to a LAN is simply a big timesharing system with terminals for all users. Give two advantages of a client$-$server system using a LAN. $[2]$

$j.$ If the unit exchanged at the data link level is called a frame and the unit exchanged at the network level is called a packet, do frames encapsulate packets or do packets encapsulate frames? Explain your answer. $[2]$

k$.$ Wireless networks are easy to install, which makes them inexpensive since installation costs usually far overshadow equipment costs. Nevertheless, they also have some disadvantages. Name two of them. $[2]$

Question $2[22]$

Consider the wireless topology above, comprised of $6$ nodes. Circles around each node illustrate their transmission range, e$.$g$.$ A$\text{'}$s range is shown by the dotted, shaded circle. Assume that the transmissions of two nodes will interfere at a location if and only if they transmit at the same time and their transmission areas overlap. In these problems, assume that losses only occur due to collisions.

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Degree and Diploma Examinations: June $2018$

Introduction to Data Communication and Networking: CSI $21$M$2$

List both the hidden and exposed terminals in each of the following:

a$.$ When node A transmits to node B$.[3]$

b$.$ When node B transmits to node C$.[3]$

You are considering using a "Request to Send $($RTS$)/$ Clear to Send $($CTS$)"$ protocol to reduce these potential problems from hidden and exposed terminals.

c$.$ When using RTS$/$CTS$,$ explain what would prevent a hidden terminal from clobbering a sender$?[2]$

d$.$ When using RTS$/$CTS$,$ explain how an exposed terminal decides it is safe to send to another destination? $[2]$

e$.$ Is RTS$/$CTS more like statistical $($time$-$division$)$ multiplexing, normal time division multiplexing, or frequency$-$division multiplexing? No explanation needed. $[1]$

f$.$ Why csma$/$cd is not suitable for wireless LAN? Explain your answer. $[4]$

Consider the Ethernet like network of self$-$learning switches $$1,$$$2,$$$3,$$$4,S5$ and $S6$ shown below. Assume the following $3$ frames delivered since the switches have started working: F$->$A $($frame sent from F to A$),$ D$->$C and C$->$ B$.$ List the switches through which the $4^{th}$ frame sent from A to $E($A$->$E will be sent$).[3]$

g$.$ Why do we need the spanning tree protocol in Ethernet LANs? Use an example. $[4]$

Question $3[25]$

a$.$ What is the typical size of the header for an IPv$4$ datagram? $[1]$

b$.$ How is the $16-$bit IP checksum field calculated? $[2]$

c$.$ How is the TTL field used on the Internet? What purpose does it serve? $[2]$

d$.$ Which field is used for IP congestion control? How does it work? $[2]$

e$.$ Why is datagram fragmentation not an issue in IPv$6?$ How is this achieved? $[2]$

f$.$ A message of $2300$ bytes is to be transmitted over $2$ IP networks. The first has an MTU of $2300$ bytes and the second network has an MTU of $1500$ bytes. How many fragments are expected at the destination? Show the values of the following IP header fields and flags for each fragment on the two networks: Packet length, MF$,$ Fragment Offset and Identification. $[7]$

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