Computer Networks — DU B.Sc. (Prog) Physical Science courses pertaining to Computer Science Previous Year Question Papers

Parts of a question must be attempted together. Q2 (a) The following character encoding is used in a data link protocol: 7 A: 01000111 B: 11100011 FLAG: 01111110 ESC: 11100000 Show the bit sequence transmitted (in binary) for the four-character frame A B ESC FLAG when each of the following framing methods is used: (i) Byte count. (ii) Flag bytes with byte stuffing. (iii) Starting and ending flag bytes with bit stuffing. (b) Construct a Hamming code for the data 1010101 using even parity. Clearly 8 (i) Number of parity bits (ii) Position of parity bits (ill) Final codeword (iv) The received codeword is 10101000101. Detect and correct the error, and write the correct data bits. Q3 (a) Discuss the advantages and disadvantages of allowing browsers to be 7 extended using plug-ins and helper applications. Can a single-threaded web server handle multiple client requests at the same time? Justify your answer with reasons related to server architecture and performance. Describe the role of multithreading in improving Web server throughput (b) An organization is assigned the IP address 192.168.10.0/24. The network 8 administrator needs to create one subnet to accommodate at least 120 For the required subnet, determine: (i) The required subnet mask in dotted-decimal notation (ii) The number of usable host IP addresses available (iii) The network address and broadcast address (iv) The range of usable IP addresses Q4 (a) Given the following weighted graph, apply Dijkstra's Algorithm to find 7 the shortest path from source node A to all other nodes. (i) Show step-by-step execution of Dijkstra's algorithm. (ii) Write the final shortest distances from A to all nodes. (iii) Draw the sink tree. (b) A network uses Carrier Sense Multiple Access. 8 Stations A, B, and C attempt to transmit data simultaneously: A senses channel idle and transmits immediately B waits for a random time before transmitting C continuously senses before transmission (i) Identify which CSMA type each station is using (1-persistent, non-persistent, or p-persistent). (i) Explain what happens when two stations transmit at the same time.- Q5 (a) Write short notes on the following: 8 (1) Address Resolution Protocol (ii) Internet Control Messaging Protocol (ill) Piggybacking (iv) Domain Name System (b) A sender uses Go-Back-N ARQ with a window size of 4. The sender 7 transmits frames 1, 2, 3, and 4. Frame 2 is lost during transmission. (i) Show, with proper reasoning, which frames will be retransmitted in Go-Back-N ARQ. (i) Explain how Go-Back-N ARQ handles acknowledgements after frame loss. (iii) Explain how Selective Repeat ARQ would handle the same situation differently. Which frames are retransmitted, and how does buffering work at the receiver end? Q6 (a) Explain the TCP/IP Reference Model as a layered architecture in Computer 7 (b) Explain simplex, half duplex, and full duplex transmission modes with a 8 suitable, example. Also mention one advantage and one limitation of each mode.