BITCIT506R03

COMPUTER NETWORKS LAB

Department of Information Technology,

School of Computing,

Shanmugha Arts, Science, Technology and Research Academy SASTRA University,

Tirumalaisamudram, Thanjavur

List of experiments

1. Simple network programs

a). Program to find IP address of a computer.

b). Program for using Ping command.

c). Program to send messages to other users in a network.

2. Programs for information exchange between client and server using TCP and UDP.

3. Secured communication through encryption and decryption of messages.

4. Program for remote procedure call under client server environment (RMI).

5. Implement data link layer framing method bit stuffing.

6. a). Program for error correction using CRC.

b). Program for error detection using Hamming Code.

7. Serial Communication between PCs (Character Transfer) - Communication via RS

232.

8. Implementation of Sliding window protocols - go back n and selective repeat.

9. Take a sample subnet graph with weights indicating delay between nodes. Now

obtain the routing table at each node using distance vector routing.

10. a) Tuning the TCP Kernel: Use the sysctl command to read and manipulate the

various TCP parameters. e.g sysctl -a , sysctl -p and sysctl -w.

b)TCP Keep alive time: Display the current TCP keepalive time value using the

sysctl command and change that using echo command - e.g echo 3600 >

/proc/sys/net/ipv4/tcp keepalive time.

11. Simulation of wired and wireless networks.

12. Network performance evaluation using simulator.

13. Study of SASTRA network infrastructure.

1. a). Program to find IP address of a computer.

Objective

To find the IP address of the local host

To find the IP address of the remote systems in the current network

To get the name of the specified IP address

Procedure

Import the java.net package to utilize the built-in classes

Use InetAddress class for invoking the following methods.

isReachable() - to check the availability

getHostAddress() getting address

getHostName() getting name

Input Output

System name / IP availability, name and IP address

1.b . Program for using Ping command

Objective

To check the availability of any system in the current network.

Procedure

-- Import the java.io package to utilize the built-in classes

Use Process and Runtime class for invoking the following methods.

getRunTime()

exec()

Form the String pingCmd = ping + IP / name

Command pingcmd is executed using the above methods.

Read the information from the process object and display it in the console

using BufferedReader.

Input Output

System IP / Name No. of Packet throughput

Approximate round trip

time

1. c). Program to send messages to other users in a network

Objective

To transfer messages between the systems within the current network

Procedure

-- Import the java.io package to utilize the built-in classes

Use Process and Runtime class for invoking the following methods.

getRunTime()

exec()

Form the String Cmd = net send + IP / name + + msg

Command cmd is executed using the above methods.

Input Output

System IP /name and message Successfully sent

Pre Lab: Practice the DOS commands ipconfig , ping, net send with all possible options.

Prior working knowledge in Java.

2. Programs for information exchange between client and server using TCP and UDP.

a. Objective

To transfer a text file from one machine to other using TCP.

Procedure

-- Import java. io and java.net packages to utilize the built-in classes

Socket Class for Client program

ServerSocket Class for ServerSide program

In server script should be bound with a particular port number and the client

req should be forwared to that specific port.

accept() is used to accept the client connection request.

Using FileWriter Class, the received text is written in the new file.

b. Objective

To transfer a text file from one machine to other using UDP.

Procedure

-- Import java. io and java.net packages to utilize the built-in classes

DatagramSocket Class for generating UDP socket

DatagramPacket Class for form the data container .

send() to send the packet to the destination.

receive() to receive the packet from the client/server

Using FileWriter Class, the received text is written in the new file.

Pre Lab: knowledge about Transport layer protocols- TCP and UDP

Basic client server program.

3. Secured communication through encryption and decryption of messages.

Objective

To encrypt a plain text using a key and transmit the cipher text; decrypt the cipher text at the

receiver side to get back the original message (Hint: Use Ceaser Cipher)

Procedure

1. Get the key.

2. Replace each character with the character, which is, key positions ahead.

3. Send the encrypted message.

4. Decrypt the message received by replacing each character with the character, which is

key positions behind.

For data transfer, use either TCP or UDP.

INPUT OUTPUT

HELLO , 2 => JGNNQ JGNNQ=> HELLO

Pre Lab: Counting the number of vowels, characters, and words.

4. Program for remote procedure call under client server environment (RMI)

Objectives

Learn the concepts of Remote Procedure Call and Remote Method

Invocation

Learn to develop applications which uses Distributed Objects

Learn the working and significance of stub object (Client side )and

Skeleton objects (Server side).

Procedures

Creating the RMI server

Contains both class and interface

Creating an interface

Both client and server have to agree

Implementing the interface

Binding with RMI registry

Should contain the operational code

Creating the RMI client

Call Registry to obtain reference to remote object

Compiling and starting the server

Input Output

Parameters (operands) Return value ( Computed results)

(e.g 44

) 256

5. Implement data link layer framing method bit stuffing

Objectives

Learn the importance of bit stuffing in communication and network protocols

Learn to synchronize sender and receiver

Learn to create communication protocols having fixed frame size

Procedures

Creating two file pointers, one is read and another in write mode for input and output

files

Access the given input binary file in read mode

If there is any consecutive five 1s, add a stuff bit 0

Open the output file and write the stuffed string

At receiver end the additional stuffed bits are rejected at the Data Link layer

Pre Lab: Bitwise arithmetic operation and shifting operation.

6. a). Program for error detection using CRC.

Objectives

Learn error detection concepts

Learn how to choose Pattern P (divisor for CRC algorithms

Learn to generate Frame Check Sequence (FCS which is to be added at end of

the message bits

Procedures

Choose n and k(number of msg bits) value

Where (n-k) is the frame check sequence(FCS) size.

Choose pattern P where as it should be atleast one bit greater than the FCS.

LSB and MSB in P should be 1.

Divide the msg bit by P . Add the remainder with the msg bit.

At the receiver end the transmitted data is divided by the same pattern P.

If the remainder is zero , No Error in the code Otherwise Error is Detected.

6.B Hamming code Error detection and correction

Objectives

Learn Error detection and correction Mechanisms

Procedure

calculate the redundancy bit r1,r2,r4 and r8

Calculate the parity for each parity bit (a ? represents the bit position being set):

Position 1 checks bits 1,3,5,7,9,11:

? _ 1 _ 0 0 1 _ 1 0 1 0. Even parity so set position 1 to a 0: 0 _ 1 _ 0 0 1 _ 1 0 1 0

Position 2 checks bits 2,3,6,7,10,11:

0 ? 1 _ 0 0 1 _ 1 0 1 0. Odd parity so set position 2 to a 1: 0 1 1 _ 0 0 1 _ 1 0 1 0

Position 4 checks bits 4,5,6,7,12:

0 1 1 ? 0 0 1 _ 1 0 1 0. Odd parity so set position 4 to a 1: 0 1 1 1 0 0 1 _ 1 0 1 0

Position 8 checks bits 8,9,10,11,12:

0 1 1 1 0 0 1 ? 1 0 1 0. Even parity so set position 8 to a 0: 0 1 1 1 0 0 1 0 1 0 1 0

Code word: 011100101010.

Error Detection and correction

Calculate r1,r2,r4 and r8.

if r1,r2,r4 and r8 are zero, No single bit error occurred.

By using these check bit values we can detect the error bit position.

Pre Lab: simple division in binary number format.

7. Serial Communication between PCs (Character Transfer) - Communication via

RS 232.

Objective

To demonstrate using JAVA code, the data transfer between two

machines using RS232 serial interface

Procedure:

For writing into serial port:

Design a window at the sender side that will have a text field to accept the

message and a button to send.

Use the static method CommPortIdentifier. getPortIdentifier to get the list of

available ports.

Create SerialPort object for each of the entries in CommPortIdentifier list and

open the port with port number 2000.

Set the SerialPort parameters like baudrate, databits, stopbits and parity.

Write the message to the output port created.

Use SerialPortEventListener Interface to monitor the port for reading and

capturing the data.

For reading from serial port:

Design a window at the sender side that will have a text field to accept the

message and a button to send.

Use the static method CommPortIdentifier.getPortIdentifier to get the list of

available ports.

Create SerialPort object for each of the entries in CommPortIdentifier list and

open the port with port number 2000.

Set the SerialPort parameters like baudrate, databits, stopbits and parity.

Bind the SerialPortEventListener to the SerialPort object.

Set notifyonDataAvailable as True.

Implement the serialEvent method to read the data available on the port.

8. Sliding window protocols - go back n and selective repeat

Objectives

Learn transmission control protocols

Go Back n

Divide the input data in to n packets

Predetermined number of packets k should be sent to the receiver without ACK.

Send will be waiting for the ACK , until it receives ACK.

If ACK is missed for the any PKT r , all the pkts after r will be retransmitted.

Selective Repeat

Divide the input data in to n packets

Predetermined number of packets k should be sent to the receiver without ACK.

Send will be waiting for the ACK , until it receives ACK.

If ACK is missed for the any PKT r , the pkt r alone will be retransmitted

Pre Lab: Packet transmission with ACK between client and server.

9.Information transfer using Distance vector routing protocols

Description:

Routers using distance-vector protocol do not have knowledge of the entire path to a

destination

Simulation of Distance vector routing protocols by constructing and displaying the

routing table at each node.

Prelab

Knowledge of functioning of the protocol and the routing table format for the protocol

10. Using sysctl configure kernel parameters at runtime

Objectives

Learn to read and modify the TCP kernel parameters using sysctl in linux.

Procedure

Tuning the TCP Kernel: Use the sysctl command to read and

manipulate the various TCP parameters. e.g sysctl -a , sysctl -p and

sysctl -w.

TCP Keep alive time: Display the current TCP keepalive time value

using the sysctl command and change that using echo command -

e.g echo 3600 > /proc/sys/net/ipv4/tcp keepalive time.

Pre Lab: Prior working knowledge in Linux/unix platform and unix system commands.

11. Simulation of wired and wireless networks.

Objectives

Learn to construct the wired and wireless network in NS2 simulator.

Procedure

Create N nodes

Make connectivity between the nodes.

Simulate data transmission

1 to 1 transmission

1 to N transmission

12.Network performance evaluation using simulator.

Objectives

To evaluate the network parameters using ns2 simulator

Procedure

Link connectivity

Monitor the Bandwidth of the network

Analyse Round trip time taken for the Test packet.

13. Study of SASTRA network infrastructure

Objective:

To study and understand the architecture, topology adopted in SASTRAs

infrastructure.

Study about the Wireless and wired network architecture and server configuration.

ADDITIONAL EXERCISES

1. Write a java program to read the characters from a file and write its uppercase

counterpart in a new file.(File concept)

2. Create a LAN chat application(GUI) in java.(Network UDP)

3. Write a java program to transfer a data file to the specific destination.