8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 1/22

1)FTP uses two well-known TCP ports: ________is used for the controlconnection, and ______ is used for the data connection

a) Port 21, port 20 b) port 20, Port 21

c) Port 23, Port 25 d) Port 23, Port 21

2)TELNET is an abbreviation for ______________

a) Telephone Network b) Television Network

c) Terminal Net OS d) Terminal Network

3)TELNET uses the______________________ system to encode characterson the local system.

a) MVT b) NVT

c) NVTS d) NMV

4)Which of the following well-known TCP ports are used by FTP ?

a) 20,21 b) 19,20

c) 80,80 d) 20,80

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 2/22

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 3/22

11) In TFTP block of less than _________ signals the end of file.

a) 256 bytes b) 512 bytes

c) error d) FIN packet

12) To deal with zero window size advertisement _____________ timer isused.

a) Persistence Timer b) Keepalive Timer

c) TIME-WAIT d) Retransmission Timer

13) ______________ used when amount of work required to handle arequest is unknown.

a) Concurrent server b) Iterative server

c) Parallel server d) Passive server

14) ______________ used when amount of work required to handle arequest is known.

a) Concurrent server b) Iterative server

c) Parallel server d) Passive server

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 4/22

15)________ is bidirectional communication abstraction via whichapplication can send or receive data.

A)Port no B) Socket

C) IP address D) all of above

16)_________ socket is reliable socket.

A)SOCK_STREAM B) SOCK_DGRAM

C)SOCK_RAW D) None of above

17) In _____ least significant bit is at lowest address.

A) Little Endian B) BIG Endian

18) 

A socket system call returns an integer called ___________whichuniquely defines the created socket.

a) Socket number b) Socket descriptor

c) Socket address d) All

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 5/22

1) What is socket? Draw and explain socket structure.

(5 marks Nov 2010)

A socket is bidirectional communication abstraction via

which application can send or receive data.

Socket=IP Address + port no

Types of socket

Header file #include <sys/types.h>

#include <sys/socket.h>

struct sockaddr_in {

uint8_t sin_len;

sa_family_t sin_family;in_port_t sin_port;

struct in_addr sin_addr;

char sin_zero[8];

};

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 6/22

2) Describe following system calls 1) connect 2)accept

(5 marks Nov 2010)

int accept (int sid , struct sockaddr *addrPtr , int *lenPtr )

int connect(int sid ,struct sockaddr *addrPtr,int len )

1) Header files2) Socket structure

3) Side of execution

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 7/22

3) Describe Connectionless iterative server concept

(5 marks may 2011)

• Definition of iterative server

• Connectionless properties

• Working

•diagram

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 8/22

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 9/22

4) Explain Socket system call with example

( 5 marks may 2011)

a) Definition of socket

b) Syntax of socket system call

c) Header files required

d) Meaning of each parameter

e) Example

socket(AF_INET,SOCK_STREAM,0)

socket(AF_INET,SOCK_DGRAM,0)

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 10/22

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 11/22

TCP client server interaction.

socket()

 bind()

listen()

accept()

write()

read()

read()

close()

socket()

connect()

write()

read()

close()

connection establishment

data request

data r eply

TCP Client

TCP Server

 Blocks until

connection from client

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 12/22

6) Describe connection establishment and termination in TCP

( 10 marks Nov 2011)

a) Features of TCP

b) Three way handshaking

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 13/22

b)Four-step connection termination

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 14/22

7) Describe sliding window protocol. What is silly window

syndrome? Describe its solutions? (10 marks Nov 2010)

• Sending window

• Receiving window

• Piggybacking

Window is in three statesa) closing

b) opening

c) shrinking

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 15/22

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 16/22

8) List and explain different types of timers

( 5 Marks nov 2011)

a) Persistence Timer

b) Retransmission timer

c) Keepalive timer

d) TIME-WAIT timer

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 17/22

9) What is UDP ? Draw and explain user datagram format

( 5 marks Nov 2010)

•Includes three sections

• UDP header

• data

• Pseudoheader

 – Part of header of IP packet.

 – Ensures that if IP header is corrupted that the user datagram is not to be submitted to

wrong host.

20 Bytes 8 Bytes

IP header UDP header UDP data

UDP datagram

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 18/22

9) Describe in congestion control in detail

( 10 marks nov 2010)

• BECN-Backward explicitly congestion notification

• FECN-Forward explicitly congestion notification

A. Monitor the system .

 –  detect when and where congestion occurs.

B. Pass information to where action can be taken.

C. Adjust system operation to correct the problem.

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 19/22

Retransmission Policy

Window policy

Acknowledgment Policy

Discarding Policy

Admission Policy

Back Pressure

Choke packet

Implicit signaling

Explicit signaling

Congestion Control

Open Loop Closed Loop

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 20/22

Traffic Shaping The Leaky Bucket Algorithm

(a) A leaky bucket with water. (b) a leaky bucket with packets.

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 21/22

The Token Bucket Algorithm

(a) Before. (b)  After.

5-34

Token bucket allows some burstiness (up to the number of tokenthe bucket can hold)

8/11/2019 Computer Network Model Solutions

http://slidepdf.com/reader/full/computer-network-model-solutions 22/22