1

Fall2011CSC339-Computer Communications and Networks 4(4,0)

Course Instructor: Dr. Sadaf Tanvirhttps://sites.google.com/site/sadaftanvir/activities/teaching

September 5 2011 1

COMSATS Institute of Information Technology, Islamabad

2

Course Objectives To familiarize the students with the world of computer

networks

Develop their understanding about the abstraction of OSI model and its layers

Familiarize them with the issues of network security

Introduce them to new network technologies like WiFi, Bluetooth and Zigbee

Provide hands on experience by engaging them in a project based on network programming

September 5 2011 2

COMSATS Institute of Information Technology, Islamabad

3

Text BookComputer Networks

A Systems Approach

By

Larry L. peterson and Bruce S. Davie

4th Edition

Reference Books:

Computer Networking: A Top Down Approach

By

James F. Kurose , Keith W. Ross

5th Edition

September 5 2011 3

COMSATS Institute of Information Technology, Islamabad

4

Course OutlineLec no.

Contents

1 How to build a network: Requirements, Applications

2 How to build a network: Network Architecture, Network Software

3 Network Software, Performance Metrics, Data Link Networks: Encoding

4 Data Link Layer, Framing

5 Error Detection, Reliable Transmission

6 Reliable Transmission, Ethernet

7 Ethernet, Rings, Wireless (Bluetooth, WiFi, Wimax, Zig-bee)

8 Packet Switching, Switching and Forwarding

9 Bridges and LAN switches

10 Internetworking, Simple Internetworking

September 5 2011 4

11 Address Resolution Protocol(ARP)

5

12 DHCP, ICMP, Virtual Network and Tunnels

13 Routing

14 Global Internet, Subnetting

15 Multicast

16 Multi-Protocol Label Switches

17 End to End Protocols

18 Congestion Control and Resource Allocation

19 End to End Data

20 Network Security

21 Cryptographic tools, Key pre-distribution

22 Authentication, Secure Systems

23 Firewalls

24 Applications: SMTP, MIME, IMAP

25 DNS, SNMP, Web Services, Multimedia Applications

26 Overlay Networks, Peer to peer networks

27 Content Distribution Networks

28 Revision

September 5 2011 5

6

Administrivia

Marks Breakdown

September 5 2011 6

Midterms 25% Assignments 10% Quiz 10% Project 5% Final Exam 50%

7

Chapter 1: Foundation

September 5 2011 7

ProblemsWhat is a computer network?

How to build a scalable network that will support different applications?

How is a computer network different from other types of networks?

What is a computer network architecture?

September 5 2011 Courtesy: Elsevier Inc 2010 8

Chapter OutlineApplications

Requirements

Network Architecture

Implementing Network Software

Performance

September 5 2011 Courtesy: Elsevier Inc 2010 9

Chapter GoalExploring the requirements that

different applications and different communities place on the computer network

Introducing the idea of network architecture

Introducing some key elements in implementing Network Software

Define key metrics that will be used to evaluate the performance of computer network

September 5 2011 Courtesy: Elsevier Inc 2010 10

ApplicationsMost people know about the Internet

(a computer network) through applications◦ World Wide Web◦ Email◦ Online Social Network◦ Streaming Audio Video◦ File Sharing◦ Instant Messaging◦ …

September 5 2011 Courtesy: Elsevier Inc 2010 11

Examples of applications

September 5 2011 12

Web pages

Video Conferencing

Video on demand

Application ProtocolURL

◦ Uniform resource locater ◦ http://ciit.edu.pk/◦ HTTP◦ Hyper Text Transfer Protocol

TCP◦ Transmission Control Protocol

17 messages for one URL request◦ 6 to find the IP (Internet Protocol) address◦ 3 for connection establishment of TCP◦ 4 for HTTP request and acknowledgement

Request: I got your request and I will send the data Reply: Here is the data you requested; I got the data

◦ 4 messages for tearing down TCP connection

September 5 2011 Courtesy: Elsevier Inc 2010 13

Requirements of Applications are different

September 5 2011 14Courtesy: Elsevier Inc 2010

• Nature of the applications like video on demand and videoconferencing in different

• we have strict timing constraint in the case of videoconferencing whereas we can wait for a while in case of vod.

• In case of vc data flow has to be bi-directional whereas in case of Vod it is uni directional.

• Similarly we have another application called google docs to exchange info on docs in real time

September 5 2011 15Courtesy: Elsevier Inc 2010

• Previous examples demonstrate the diversity of applications that can be built on top of the Internet, and hint at the complexity of the Internet’s design.

• Starting from the beginning, and addressing one problem at time, In this course, we will see how to build a network that supports such a wide range of applications

To build a network …

September 5 2011 16Courtesy: Elsevier Inc 2010

We will ask questions that arise naturally for building an actual network

For understanding, we would not accept the existing solutions the way they are

Instead, we will be asking (and answering) the question of why networks are designed the way they are

Since it is important to recognize the underlying concepts because networks are constantly changing as the technology evolves and new applications are invented

The first step is to identify the set of constraints and requirements that influence network design

RequirementsIt is important to understand that the

expectations you have of a network depend on your perspective

Application Programmer◦ List the services that his application needs:

delay bounded delivery of dataNetwork Designer

◦ Design a cost-effective network with sharable resources(What are resources?: links, nodes)

Network Provider◦ List the characteristics of a system that is

easy to manageSeptember 5 2011 Courtesy: Elsevier Inc 2010 17

The next few slides distill these different perspectives into a high-level introduction and identify major considerations that drive network design

September 5 2011 Courtesy: Elsevier Inc 2010 18

Limited Starting with the obvious, a network must provide connectivity

among a set of computers Sometimes it is enough to build a limited network that connects

only a few select machines. In fact, for reasons of privacy and security, many private

(corporate) networks

have the explicit goal of limiting the set of machines that are connected.

Scalable

In contrast, other networks (of which the Internet is the prime example) are designed to grow in a way that allows them the potential to connect all the computers in the world. A system that is designed to support growth to an arbitrarily large size is said to scale.

September 5 2011 Courtesy: Elsevier Inc 2010 19

Connectivity

ConnectivityNeed to understand

the following terminologies◦ Scale◦ Link◦ Nodes◦ Point-to-point◦ Multiple access◦ Connectivity is not

merely a direct physical connection

◦ Switched Network Circuit Switched Packet Switched

◦ Packet, message◦ Data block is a piece of

file,image,email etc.◦ Store-and-forward

September 5 2011 20Courtesy: Elsevier Inc 2010

(a) Point-to-point

(b) Multiple access

ConnectivityTerminologies (contd.)

◦ Cloud◦ Hosts◦ Switches◦ internetwork◦ Router/gateway◦ Host-to-host connectivity

Needs Address Routing Unicast/broadcast/multicast

September 5 2011 21Courtesy: Elsevier Inc 2010

(a) A switched network

(b) Interconnection of networks

(a)

(b)