CS 31204: Computer Networks

INDIAN INSTITUTE OF TECHNOLOGY

KHARAGPUR

Sandip Chakraborty

sandipc@cse.iitkgp.ac.in

​

Department of Computer Science and Engineering

Abhijnan Chakraborty

abhijnan@cse.iitkgp.ac.in

​

Few slides in this presentation has been adopted from the online resources accompanying the book Computer Networking: A Top-Down Approach by Jim Kurose and Keith Ross

https://gaia.cs.umass.edu/kurose_ross/eighth.php

Indian Institute of Technology Kharagpur

Objectives of the Course

• Understand how two computers in the Internet talk to each other
• Go through the basic functionalities of the computer networks
• Learn how to program the network
• Learn the future of the computer network – Do we need any further changes in the design?

​

Functionalities

Protocols

Network Architecture

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

• A way to visualize how two remote computers talk to each other

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Physical

Requirement: Convert digital data to analog signal and vice versa

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Physical

Requirement: Ensure proper scheduling in media access

Data Link

L2 Switch

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Physical

Requirement: Find out a suitable path to forward data

Data Link

Network

L3 Switch or Routers

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Physical

Requirement: End to end traffic control in the network

Data Link

Network

Transport

Indian Institute of Technology Kharagpur

So, What is Network Architecture?

Indian Institute of Technology Kharagpur

Services, Layering and Encapsulation

source

• transport-layer protocol encapsulates application-layer message, M, with transport layer-layer header H_t to create a transport-layer segment
• H_t used by transport layer protocol to implement its service

destination

Application exchanges messages to implement some application service using services of transport layer

Indian Institute of Technology Kharagpur

Services, Layering and Encapsulation

source

Transport-layer protocol transfers M (e.g., reliably) from one process to another, using services of network layer

• network-layer protocol encapsulates transport-layer segment [H_t | M] with network layer-layer header H_n to create a network-layer datagram
• H_n used by network layer protocol to implement its service

destination

Indian Institute of Technology Kharagpur

Services, Layering and Encapsulation

source

• link-layer protocol encapsulates network datagram [H_n| [H_t |M], with link-layer header H_l to create a link-layer frame

destination

Link-layer protocol transfers datagram [H_n| [H_t |M] from host to neighboring host, using network-layer services

Network-layer protocol transfers transport-layer segment [H_t | M] from one host to another, using link layer services

Indian Institute of Technology Kharagpur

Services, Layering and Encapsulation

source

destination

Indian Institute of Technology Kharagpur

Encapsulation: An end-end View

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

source

segment

datagram

destination

router

switch

message

frame

link

physical

Indian Institute of Technology Kharagpur

Protocols at Different Layers

Ethernet, WiFi, Bluetooth, UMTS, LTE

IPv4, IPv6, MPLS

TCP, UDP, RTP

HTTP, FTP, SMTP

Indian Institute of Technology Kharagpur

Network Management and Control – Cross Layer Protocols

Ethernet, WiFi, Bluetooth, UMTS, LTE

IPv4, IPv6, MPLS

TCP, UDP, RTP

HTTP, FTP, SMTP

DNS

SNMP

ARP, DHCP

Indian Institute of Technology Kharagpur

Two Ways to Learn Computer Networks

Indian Institute of Technology Kharagpur

Books to Follow …

Indian Institute of Technology Kharagpur

Books to Follow …

Indian Institute of Technology Kharagpur

Books to Follow (Online Books)…

http://www.redbooks.ibm.com/abstracts/gg243376.html

http://www.tcpipguide.com/

Indian Institute of Technology Kharagpur

Internet Resources

Indian Institute of Technology Kharagpur

Course Evaluations

• Teacher’s Assessment: 40%
• Four surprise tests during regular classes: Average: 30%
• No request for retest will be entertained
• Attendance: 10%

​

• Mid-semester Examination: 30%

​

• End-semester Examination: 30%

Indian Institute of Technology Kharagpur

Sections

• Section - 1
• Odd roll numbers
• Class Room: NR 213
• Time Slot: MON (10:00-10:55), WED (08:00-08:55), WED(09:00-09:55), �THURS (10:00-10:55)
• Primary Teacher: Prof. Abhijnan Chakraborty

​

• Section - 2
• Even roll numbers
• Class Room: NR 314
• Time Slot: MON (10:00-10:55) , WED (08:00-08:55), WED(09:00-09:55), �THURS (10:00-10:55)
• Primary Teacher: Prof. Sandip Chakraborty

Indian Institute of Technology Kharagpur

Other Course Related Information

• Course Website: https://sandipc-iitkgp.github.io/sandip-web/courses/cs31204/cs31204.html
• All course materials will be posted on teams and/or the website
• We have set up a Microsoft Teams group – please use the group for any discussions (Both theory and lab)
• Join the group using this link: Computer Networks 2026 | Microsoft Teams
• Make the class live – no question is a stupid question !!!

Indian Institute of Technology Kharagpur