Network Architecture and Communication Models: A Comprehensive Overview, Lecture notes of Computer Networks

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Computer Networks

Lecture # 01-

By: Sanjeev Patel Asst. Professor, CSE& IT Department JIIT, Noida Sector- Unit-1 1

Evaluation Schema

Test 1 : 20 (21 Hrs.) Test 2 : 20 (11 Hrs.) Test 3 : 35 (10 Hrs.) Quiz/Test : 10 Attendance: 5 Assignments/Tutorial: 10 Unit-1 2

Introduction 1- 4

Chapter 1: roadmap

1.1 Basics of Network. What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History

A Communications Model

• (^) Source
  • (^) generates data to be transmitted
• (^) Transmitter
  • (^) Converts data into transmittable signals
• (^) Transmission System
  • (^) Carries data
• (^) Receiver
  • (^) Converts received signal into data
• (^) Destination
  • (^) Takes incoming data Unit-1 5

What is “ Connectivity ”?

Direct or indirect access to every other node in the network  (^) Connectivity is the magic needed to communicate if you do not have a direct pt-pt physical link. Unit-1 7

Topologies: Indirect Connectivity

Unit-1 8 Ring Star S Tree

Networks Classification

Unit-1 10

Introduction 1- 11 What’s the Internet: “nuts and bolts” view  (^) millions of connected computing devices: hosts = end systems  (^) running network apps  (^) communication links  (^) fiber, copper, radio, satellite  (^) transmission rate = bandwidth  (^) routers: forward packets (chunks of data) local ISP company network regional ISP router workstation server mobile

Introduction 1- 13 What’s the Internet: a service view  (^) communication infrastructure enables distributed applications:  (^) Web, email, games, e- commerce, file sharing  (^) communication services provided to apps:  (^) Connectionless unreliable  (^) connection-oriented reliable

Introduction 1- 14

What’s a protocol?

human protocols:  (^) “what’s the time?”  (^) “I have a question”  (^) introductions … specific msgs sent … specific actions taken when msgs received, or other events network protocols:  (^) machines rather than humans  (^) all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt

Introduction 1- 16

Chapter 1: roadmap

1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History

Introduction 1- 17

A closer look at network

structure:

 (^) network edge: applications and hosts  (^) network core:  (^) routers  (^) network of networks  (^) access networks, physical media: communication links

Introduction 1- 19 Network edge: connection-oriented service Goal: data transfer between end systems  (^) handshaking: setup (prepare for) data transfer ahead of time  (^) Hello, hello back human protocol  (^) set up “state” in two communicating hosts  (^) TCP - Transmission Control Protocol  (^) Internet’s connection- oriented service TCP service [RFC 793]  (^) reliable, in-order byte- stream data transfer  (^) loss: acknowledgements and retransmissions  (^) flow control:  (^) sender won’t overwhelm receiver  (^) congestion control:  (^) senders “slow down sending rate” when network congested

Introduction 1- 20 Network edge: connectionless service Goal: data transfer between end systems  (^) same as before!  (^) UDP - User Datagram Protocol [RFC 768]:  connectionless  (^) unreliable data transfer  (^) no flow control  no congestion control App’s using TCP:  (^) HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) App’s using UDP:  (^) streaming media, teleconferencing, DNS, Internet telephony