June 1996

Question Paper of CS-09 – Data Communication & Network of June 1996 from IGNOU

1 (a) If a bit string 011111101111101111110 is subjected to bit stuffing, what would be the output string? [3]

(b) What is the remainder obtained by dividing X9 + X7 + 1 by generator polynomial X5 + X3 + 1? [5]

(c) Compare the advantages and disadvantages of Bus and Ring topologies. Can a ring topology be used for Wide Area network (WAN)? [5]

(d) Suggest communication media for the following communication requirements: � Within room between computer and terminal. � Within a campus at about 10 Mbps transmission rate. � Within a city at about 100 Mbps transmission rate. � Within a building at about 1 Mbps transmission rate. [4]

(e) List four advantages of digital transmission over analog transmission. [4]

(f) What is a RPC (Remote Procedure Call)? Discuss the four key issues related to design of RPC. [9]

2 (a) Explain the following with respect to performance. [12]

(i) How a slotted ALOHA type of satellite packet broadcasting network is an improvement over pure Aloha?

(ii) A 1- persistent CSMA Local Area Network is an improvement over slotted ALOHA.

(iii) Non persistent CSMA is an improvement over 1- persistent CSMA.

(iv) CSMA | CD (Ethernet) protocol is an improvement over CSMA protocol

(b) List 3 advantages of broadband network over baseband network. [3]

3 (a) Discuss flow control mechanism of X.25 protocol. [7]

(b) Compare two data link protocols: Go Back N and Selective Repeat in terms of flow control, error recovery and packet loss. [8]

4 ( a) Compare X.75 & IP. What are the principal strengths and weaknesses of each other? [10]

(b) X.75 does not include the following packet types: Call indication, Call Accepted and Clear Indication, Why not? [5]

5 (a) TCP uses a single transport protocol header, whereas OSI has many of them. Discuss advantages and disadvantages of them. [7]

(b) Give two application examples each of which connection oriented service and connectionless service are appropriate. [4]

(c) Explain the difference between asynchronous and synchronous communication. [4]

6 (a) List 3 similarities and 3 differences between a session and a transport connection. [6]

(b) Discuss 5 facilities provided by X.25 | X.75. [5] (c) Differentiate between a bridge and a router. Differentiate between a router and a gateway. [4]

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