DOEACC Society 2007 Advanced Level Course In Computer Science A9-R3: DATA COMMUNICATION

2.5 Routing is a function of data link layer.
2.6 Flow control is needed to prevent collision ranging from sender and receiver.
2.7 HDLC is an true protocol designed to support both half-duplex and full duplex communication over point-to-point and multipoint links.
2.8 UDP and TCP are both network layer protocols.
2.9 An ARP request is broadcast to all devices on the network.
2.10 Routing and switching in frame relay are performed by the data link layer.

3. Match words and phrases in column X with the nearest related meaning/ word(s)/phrases in column Y. Enter your selection in the “tear-off” ans sheet attached to the ques. paper, subsequent instructions therein. (1 x 10)

X Y
3.1 It is the function of network layer. A. MAC
3.2 It is the connectionless protocol in Transport layer. B. ARP
3.3 It is the internetworking protocol suite. C. DNS
3.4 This sublayer is responsible for the operation of the CSMS/CD access method. D. Bridge
3.5 The protocol maps an IP address to a MAC address. E. Frame Relay
3.6 It is a client-server application that identifies every host on the Internet with a unique user-friendly name. F. Congestion control
3.7 It connects 2 LAN segments at Data Link layer. G. TDM
3.8 It is a virtual circuit WAN that was designed to respond to allow bursty data and a frame size of 9000 bytes. H. TCP
3.9 It is a second-generation cellular phone system. I. MODEM
3.10 It is known as simultaneous transmission of multiple signals across a single data link. J. UDP
K. Satellite
L. TCP/IP
M. Gateway
N. GSM
O. RARP




4. Each statement beneath has blank space to fit 1 of the word(s) or phrases in the list beneath. Enter your option in the “tear-off” ans sheet attached to the ques. paper, subsequent instructions therein. (1 x 10)

A. Network B. Increases C. WDM
D. Circuit E. Presentation F. Packet
G. TCP H. ICMP I. CRC
J. Remains the same K. TDM L. UDP
M. Data Link N. Physical O. Decreases
P. Token Bus Q. CSMA/CD R. SNMP

4.1 The _________ layer modifications bits into electromagnetic signals.
4.2 As the bit rate of an FSK signal increases, the bandwidth __________.
4.3 __________ is similar in concept to FDM. The signals being multiplexed, however, are light waves.
4.4 __________ is a powerful redundancy checking technique, which appends a sequence of redundant bits derived from binary division to the data unit.
4.5 In __________ protocol, a station must listen to a medium prior to sending data onto the line.
4.6 __________ layer provides services to transport layer.
4.7 The main Internet transport protocol is __________.
4.8 __________ switching statically reserves the needed bandwidth in advance.
4.9 __________ LAN supports priorities and can be configured to give a guaranteed fraction of the bandwidth to high-priority traffic.
4.10 The operation of the Internet is monitored closely by the routers. When something unexpected occurs, the event is reported by the __________.


























PART TWO
(Answer Any 4 questions)

5.
a) What is the transmission rate on Ethernet LANs? For a provided transmission rate, can every user on the LAN continuously transmit at the rate?
b) What are a few of the physical media that Ethernet can run over?
c) What advantage does a circuit-switched network have over a packet-switched network? What advantages does TDM have over FDM in a circuit-switched network?
(5+5+5)

6.
a) List 2 ways in which the OSI reference model and the TCP/IP reference model are the identical. Now, list the 2 ways in which they differ.
b) What is the principle difference ranging from connectionless communication and connection-oriented communication?
c) Why would the token-ring protocol be inefficient if the LAN has a very large perimeter?
(6+6+3)

7.
a) What is the main difference ranging from TCP and UDP?
b) Give an advantage and disadvantage of frame relay over a leased telephone line.
c) What are the 2 main functions of a datagram based network layer? What additional functions does a VC-based network layer have?
(3+6+6)

8.
a) Compare and contrast link-state and distance-vector routing algorithms.
b) Each Internet host will have at lowest 1 local name serve and 1 authoritative name server. What role does every of these servers have in DNS?
c) What is an important difference ranging from a Symmetric key system and a Public key system?
(5+5+5)

9. Write short notes on any 3 of the following:
i) X.25
ii) HDLC
iii) DNS
iv) SNMP
(3x5)

Earning:   Approval pending.