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U.S.N.

BMS College of Engineering, Bangalore-560019 (Autonomous Institute, Affiliated to VTU, Belgaum)

January 2017 Semester End Make Up Examinations Course: Computer Networks Course Code: 16CS5DCCON

Duration: 3 hrs Max Marks: 100

Date: 11.01.2017 Instructions: 1.Answer any five full questions choosing one from each unit. 2. Assume missing data (if any) suitably

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a) b) c)

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a) b)

c)

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a) b) c)

UNIT 1 Discuss HTTP response message format with a neat diagram. Analyze the need for cookies and illustrate the different components of cookies with a neat diagram for an HTTP request. Discuss the importance of proxy server with a neat diagram. UNIT 2 Illustrate with an example how hierarchy of DNS servers are involved in Internet Directory service. Suppose a client wants to establish multiple connections to the same web server using port number 80 and another client needs to connect to the same server, demonstrate the communication process for the above scenario with the neat diagram. Develop a client-server program by using TCP/IP sockets, to make client sending the file name and the server to send back the number of words in the requested file if present. UNIT 3 Discuss the UDP segment structure with an example for creating a checksum for the data. With a pseudo code explain the events involved in reliable data transfer. Consider Figure below. Assuming TCP Reno is the protocol experiencing the behavior shown. Answer the following questions. In all cases, justify your answer. a. Identify the intervals of time when TCP slow start is operating. b. After the 22nd transmission round, is segment loss detected by a triple duplicate ACK or by a timeout? c. What is the value of ssthresh at the 18th transmission round? d. During what transmission round is the 70th segment sent?

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UNIT 4 Illustrate with a scenario of the network that consists of Four Senders, Routers with Finite Buffers and Multihop Paths the principle of congestion control. Discuss the switching techniques inside a router. Discuss the approach of Network assisted congestion control with a scenario. OR With a scenario explain the Network layer functions. With an FSM explain the components of an algorithm for TCP congestion control. Illustrate with a neat diagram Head-of-the line blocking at an input queued switch. UNIT 5 Explain with a neat diagram IPV4 datagram format. With a DHCP client server scenario explain the steps involved in client server. interaction. Explain the importance of UPnP in NAT. OR With an algorithm explain the Distance vector Routing Protocol. Discuss a link-state protocol that uses flooding of link-state information and a Dijkstra least-cost path algorithm. *******

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U.S.N.

BMS College of Engineering, Bangalore-560019 (Autonomous Institute, Affiliated to VTU, Belgaum)

July / August 2017 Supplementary Semester Examinations Course: Computer Networks Course Code: 16CS5DCCON

Duration: 3 hrs Max Marks: 100

Date: 28.07.2017 Instructions: 1.Answer any five full questions choosing one from each unit. 2. Assume missing data (if any) suitably

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a) b)

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a)

b)

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a) b) c)

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a) b) c)

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a) b)

UNIT 1 Differentiate between Persistent and Non-persistent connetions and illustrate without Pipelining and with pipeling connections with an example. Analyse the need for different mail access protocol with suitable examples UNIT 2 Assume that your friend wants to host domain name domain.com, Design the steps involved from registering domain name till accessing the domain name by specifying recursive or iterative queries. Develop a client-server program by using TCP/IP sockets, to make client sending the file name and the server to send back the contents of the requested file if present. UNIT 3 Analyse the need for Initial sequence number in TCP connection management Explain TCP Segment structure with a diagram by specifying usage of 6 reserved bits Suppose Host A sends two TCP segments back to back to Host B over a TCP connection. The first segment has sequence number 90; the second has sequence number 110. a.How much data is in the first segment? b. Suppose that the first segment is lost but the second segment arrives at B. In the acknowledgment that Host B sends to Host A, what will be the acknowledgment number? UNIT 4 Describe the Router Architecture with a neat diagram Illustrate with a scenario of the network that consists of Four Senders, Routers with Finite Buffers and Multihop Paths of the principle of congestion control. Analyse the need for different congestion control approaches OR Describe the Three switching technique with a neat diagram with functionalities of each method Suppose that the five measured SampleRTT values are 100 ms, 120 ms, 140 ms, 90 ms, and 115 ms. Compute the EstimatedRTT after each of these SampleRTT values is obtained, using a value of α= 0.125 and assuming that the value of EstimatedRTT

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was 100 ms just before the first of these five samples were obtained. Compute also the DevRTT after each sample is obtained, assuming a value of β= 0.25 and assuming the value of DevRTT was 5 ms just before the first of these five samples was obtained. Last, compute the TCP TimeoutInterval after each of these samples is obtained. UNIT 5 Consider the following network, with the indicated link costs, use Dijkstra’s shortest-path algorithm to compute the shortest path from x to all network nodes. Show how the algorithm works by computing a table

Consider the network fragment shown below. x has only two attached neighbors, w and y. w has a minimum-cost path to destination u (not shown) of 5, and y has a minimum-cost path to u of 6. The complete paths from w and y to u (and between w and y) are not shown. All link costs in the network have strictly positive integer values. a. Give x’s distance vector for destinations w, y, and u. b. Give a link-cost change for either c(x,w) or c(x,y) such that x will inform its neighbors of a new minimum-cost path to u as a result of executing the distance-vector algorithm. c. Give a link-cost change for either c(x,w) or c(x,y) such that x will not inform its neighbors of a new minimum-cost path to u as a result of executing the distance-vector algorithm.

OR Diffrentiate between IPV4 and IPV6 protocol and Illustrate the different transitioning techniques from IPV4 to IPV6. Analyse the need for NAT and Illustrate an example of NAT transtion table for a network consisting of 3 nodes with a NAT router by specifying all the required details. *******

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U.S.N.

BMS College of Engineering, Bangalore-560019 (Autonomous Institute, Affiliated to VTU, Belgaum)

December 2016 Semester End Main Examinations Course: Computer Networks Course Code: 16CS5DCCON

Duration: 3 hrs Max Marks: 100

Date: 26.12.2016 Instructions: 1.Answer any five full questions choosing one from each unit. 2. Assume missing data (if any) suitably

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a)

b) c) 2

a)

b)

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a)

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a) b)

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UNIT 1 How do you consider that P2P architecture is scalable? Will P2P still function in an environment where nodes are highly distributed and decentralized? Provide peer-topeer application architecture. What do you mean by a non-persistent connection? Depict the steps of transferring a web page from server to client for non persistent connection. Illustrate with a neat diagram the working principle of POP3 mail access protocol UNIT 2 How does the DNS protocol facilitate the HTTP protocol to obtain the IP- address of the requested destination? What are the important services offered by DNS, discuss? How a distributed database can be implemented by DNS in order to scale to obtain hostname-to-IP-address service? What are the services offered by TCP? Illustrate with a neat diagram the working while you implement connectionless multiplex and demultiplex service. UNIT 3 UDP use 1’s Complement for their checksums. Suppose you have the following three 8-bit Bytes: 01010101, 01110000, 01001100. What is the 1’s complement of the sum of these 8-bit bytes? Why does UDP take the 1’s complement of the sum and not just the sum? How does the receiver detect errors, with 1’s complement scheme? Is it possible that a 1-bit error will go undetected? Illustrate with a neat diagram how segment exchange happens in TCP. Provide a typical sequence of TCP states visited by a client TCP. UNIT 4 Discuss how you tackle congestion in a scenario, where there are two senders, a router with finite and infinite buffer space allotted. What is the principle behind Additive-Increase, Multiplicative- Decrease for congestion control OR Illustrate with a neat diagram how congestion can be controlled for ATM which uses ABR service Provide a high-level view of generic router architecture. Discuss the three different switching techniques.

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UNIT 5 Illustrate with a neat diagram the datagram format of IPv6 and discuss the fields. Why do we need to shift from IPv4 to IPv6? Suppose that an ISP has advertised to the outside world that the IP address is 200.23.16.0/20. Show how the address aggregation is achieved if this ISP supports eight organization with first longest prefix match. OR Provide the routing table for node y using distance vector algorithm

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z 7 Provide the BGP route selection process and routing policy applied on an autonomous system. *******

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U.S.N.

BMS College of Engineering, Bengaluru-560019 Autonomous Institute Affiliated to VTU

December 2017 Semester End Main Examinations Course: Computer Networks Course Code: 16CS5DCCON

Instructions:

Duration: 3 hrs. Max Marks: 100 Date:23.12.2017

Answer any FIVE full questions, choosing one from each Unit.

UNIT 1 1.

a) b) c)

Explain the different types of Network Application Architectures. Compare Non persistent and persistent connection with respect to HTTP. Explain the high level view of the Internet email system.

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UNIT 2 2.

a) b) c)

Explain how a distributed database can be implemented in the Internet. Demonstrate Socket programming with TCP and UDP. Differentiate between transport layer multiplexing and demultiplexing.

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UNIT 3 3.

a) b) c)

Compare and Contrast UDP and TCP segment structure. Show the FSM representation of RDT 3.0 over a Lossy channel with Bit Errors. Suppose that TCP's current estimated values for the round trip time (estimatedRTT) and deviation in the RTT (DevRTT) are 200 msec and 20 msec, respectively. Suppose that the next three measured values of the RTT are 300, 400, and 320respectively.Compute TCP's new value of estimatedRTT, DevRTT, and the TCP timeout value after each of these three measured RTT values is obtained. Use the values of α = 0.125 and β = 0.25.

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UNIT 4 4.

a) b)

What are the Causes and the Costs of Congestion? Explain with examples. What are the different approaches to Congestion Control ? Explain any one in detail.

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OR 5.

a) b)

Analyze the high-level view of Generic Router Architecture in detail. Explain in detail the different types of services offered by Network Layer.

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UNIT 5 6.

a) b) c)

Distinguish between the IPV4 and IPV6 datagram formats used for addressing. Explain ICMP in detail. Determine the least cost path for the graph in Figure1 using Dijikstras algorithm. Consider A as Source Node.

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Differentiate Link state and Distance Vector Algorithms for routing of packet in network layer. Explain the features of OSPF protocol. Determine least cost path for the graph in Figure 2 using Distance Vector algorithm.

Figure - 2

*******

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U.S.N.

BMS College of Engineering, Bengaluru-560019 Autonomous Institute Affiliated to VTU

January 2018 Semester End Make Up Examinations Course: Computer Networks Course Code: 16CS5DCCON

Instructions:

Duration: 3 hrs. Max Marks: 100 Date:13.01.2018

Answer any FIVE full questions, choosing one from each Unit.

UNIT 1 1.

a)

b)

c)

List the four broad classes of services that a transport layer protocol can provide. For each of the service classes, indicate if either UDP or TCP (or both) provides such a service. Give the General format of HTTP request and response message. Answer the following questions: a. Explain the mechanism used for signaling between the client and server to indicate that a persistent connection is being closed. Can the client, the server, or both signal the close of a connection? b. Does HTTP provide encryption services. c. Can a client open three or more simultaneous connections with a given server? d. Either a server or a client may close a transport connection between them if either one detects the connection has been idle for some time. Is it possible that one side starts closing a connection while the other side is transmitting data via this connection? Explain.

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Suppose Alice wants to send a message to Bob. Illustrate the basic operation of SMTP for the above scenario. Construct the transcript of messages exchanged between SMTP client and SMTP Server as soon as a TCP Connection is established.

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b)

Suppose a client wants to get the IP address of a new website www.abc.com. Design the sequence of events that take place to access the IP address and show the interaction of various DNS servers by considering appropriate example. Develop an application program for server side to count the number of characters from a file stored in the client using connectionless, unreliable transport services.

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