Lec1 Network Computing

8/8/2019 Lec1 Network Computing

http://slidepdf.com/reader/full/lec1-network-computing 1/35

Universi ty of Mauri t iusUniversi ty of Mauri t iusUniversi ty of Mauri t iusUniversi ty of Mauri t ius

CSE 2247– Network Computing

Semester 2 –Year 2010-2011

Lecture 1 – Introduction to Networks



What is a Computer Network?

A computer network is a system for communicating

between two or more computers and associated devices.It is an interconnection of computers for the purposes of

sharing information and resources.

popu ar examp e o a computer networ s t e nternet,which allows millions of users to share information.

(c) Mr. Chiniah, Lecturer CSE 20112



Example of a network

3 (c) Mr. Chiniah, Lecturer CSE 2011



Uses of Computer Network Resource sharing and communication, are two principal

reasons of building and using Computer Network.

Examples of resources shared: Printer, File sharing, Internet Connection, etc.

Some of most popular network applications include:

E-mail, Web-browsing, Digital libraries, Video-on-demand

4 (c) Mr. Chiniah, Lecturer CSE 2011



Types of Computer Network Class 1: Function-Based Classification

Data

Voice Multimedia

Class 2: Location-and-Distance-based Classification PAN (Personal Area Network)

LAN (Local Area Network)

MAN (Metropolitan Area Network) WAN (Wide Area Network)




Types of Computer Network (cont..) Class 3: Forwarding-based Classification

Switched Network

Circuit-switching Network Packet-switching Network

Shared Network

Class 4: Ownership-based Classification

Public Networks

Private Networks

Virtual Private Networks

Leased Networks




Terminology

Bit Rate

Number of bits per second

Given in bps

Bandwidth Maximum frequency supported by the medium.




ExerciseAn image is 1024 × 768 pixels with 3 bytes/pixel.

a. How long will it take to transmit it over a 56 kbps

modem channel?b. Over a 1-Mbps cable modem?

c. Over a 10-Mb s cable?

d. Over 100-Mbps cable?




Transmission Medium Guided Transmission Media

Coaxial Cable




Transmission Medium (cont..) Twisted Pair




Transmission Medium (cont..) Fibre-Optics

Monomode Fibre-optics cable




Transmission Medium (Cont..) Multimode Fibre-optics cable




Transmission Medium (Cont..) Unguided Transmission Media

Electromagnetic Spectrum




Transmission Medium (Cont..) Radiowave Transmission




Transmission Medium (Cont..) Microwave Transmission


Microwave Tower

Transmission path between

Microwave towers



Transmission Medium (Cont..) Communication Satellite




Transmission Medium (Cont..) Infrared

Bluetooth

Piconet Scatternet

Wifi




Reference Models

• The OSI Reference Model

• The TCP/IP Reference Model

•




Protocol Hierarchies Protocol are used for communication between computers in different

computer networks. Protocol achieves:

What is communicated between computers?

How it is communicated?

When it is communicated?

What conformance (bit sequence) between computers?

Key elements of a protocol are:

SYNTAC: Data format and signal levels

SEMANTICS: Control information for coordination and error handling

TIMING: Synchronization, speed matching, and sequencing




Protocol HierarchiesI like

rabbits

Location A

3

2

3

2

Location B

Message Philosopher

TranslatorInformationfor the remotetranslator

L: Dutch

Ik vind

konijnen

J'aimebien leslapins

L: Dutch

Ik vind

konijnen

• The philosopher-translator-secretary architecture.

1 1

Secretary

Informationfor the remotesecretary

Fax #---

L: Dutch

Ik vind

konijnen

leuk

Fax #---

L: Dutch

Ik vind

konijnen

leuk




Open System Interconnection




OSI Reference Model

• Layered model:

7. Application6. Presentation

5. Session

. ransport

3. Network

2. Data Link

1. Physical




The Physical Layer

• Responsibility:

– transmission of raw bits over a communicationchannel.


– mechanical and electrical interfaces

– time per bit

– distances



Responsibility:

provide an error-free communication link

Issues:

The Data Link Layer - Data Link Control

header & trailer bits Addressing (Mac Address)


10110110101 01100010011 10110000001



The Network Layer Responsibilities:

path selection between end-systems (routing).

subnet flow control. fragmentation & reassembly

translation between different network types.

Issues: packet headers

virtual circuits




The Transport Layer Responsibilities:

provides virtual end-to-end links between peer processes.

end-to-end flow control Issues:

headers

error detection reliable communication




The Session Layer

Responsibilities:

establishes, manages, and terminates sessions betweenapplications.

service location lookup

Many protocol suites do not include a session layer.




The Presentation Layer

Responsibilities:

data encryption data compression

data conversion

Many protocol suites do not include a Presentation Layer.




The Application Layer Responsibilities:

anything not provided by any of the other layers

Issues: application level protocols

appropriate selection of “type of service”




Summary of OSI RM

Presentation

Application

Formatting, Compression,Encryption

Provide services to applications

LAYERS FUNCTIONSCORRESPONDING

PROCOTÏLS

HTTP, SMTP, FTP, NFS, Telnet,SMB

JPEG, MIDI, MPEG etc etc

Network File S stem NFS

30

Physical

Data Link

Network

Transport

ess on

Transmit data on media

Reliable data transfer across media;physical addressing

Path selection,logical addressing, routing

Quality and reliability,

ensures data received, segments

, ,control data exchange

SQL, RPC

TCP, UDP, SPX, NetBEUI

IP, IPX, RIP, ICMP, ARP, RARP,

OSPF, NetBEUI, DLC, DecNET

HDLC, SLIP, PPP

NONE




TCP/IP Reference Model




Protocols in TCP/IP model




Comparing OSI and TCP/IP Models

Concepts central to the OSI model

- Services

-

- Protocols


A Critique of the OSI Model and



A Critique of the OSI Model and

Protocols Why OSI did not take over the world

• Bad timing• Bad technology

• Bad implementations• Bad politics




Bad TimingThe apocalypse of the two elephants.


Lec1 Network Computing

Documents

Transcript of Lec1 Network Computing