Chapter 2 The Infrastructure. Copyright © 2003, Addison Wesley Understand the structure & elements...

Chapter 2

The Infrastructure

Copyright © 2003, Addison Wesley

Understand the structure & elements

As a business student, it is important that you understand what the technology can and cannot do, when a particular technology is appropriate, and when it is not.

If you recognize the potential, you can always get the necessary help.

If you do not recognize the potential, your competitors probably will.


Figure 2.1 This chapter introduces the technology that makes e-commerce possible.

Applications

The World Wide Web

The Internet

The global data communication network


Figure 2.2 Communication requires five elements.

Message Information/content

Transmitter Source or sender

Medium Path or pipe

Receiver Sink or destination

Transmitter ReceiverMediumMessage

Protocol: a set of rules fortransmitting a message.


Media Types

Cable Physical wire Twisted pair, coaxial, fiber optic

Wireless No physical wire Cellular, digital cellular, satellite


Connectivity

Ability to operate over a connection Physical – medium Logical – protocol

Line types Baseband – one signal at a time Broadband – simultaneous signals in parallel

Example – cable TV Cable can be baseband or broadband Wireless can be baseband or broadband


Figure 2.3 Plain old telephone service.

The cloud is a common way to visualize an infrastructure

Central office

Long distanceconnection

Source

Central office

Destination


Figure 2.4 Wireless communication.

Both POTS and wireless use the same long distance infrastructure.

Telephone

Alice

Mobile switching center

Mobile switching center

Long distancenetwork

Trunk

Trunk

Radio tow er

HubBase station

Telephone

Bob

Radio tow er

HubBase station


Figure 2.5 POTS and wireless are alternative

access paths to the long distance infrastructure.

Cable and satellite Internet services use the same long distance lines.

POTS Wireless service

Long distance infrastructure


Figure 2.6 Bandwidth.

Amount of data a medium can transmit in a given time.

Conventions B – bytes (8 bits) b – bits K – c. 1,000 M – c. 1,000,000 G – c. 1,000,000,000

Connection Type Bandwidth

Local telephone line 56 Kbps

Home satellite service 400 Kbps

DSL 1.44 Mbps

Cable service 2 to 10 Mbps

Leased line (T-1, T-3) 1.5 to 43 Mbps

Fiber optic cable Up to 10 Gbps

Wireless2G digital cellular2.5G digital cellular3G digital cellularBluetoothWi-Fi (802.11b)

19.2 Kbps144 Kbps2 Mbps1 MbpsUp to 11 Mbps


Networks

Network: two or more computers or devices linked by communication lines. Each computer/device is a node Transmitter and receiver are nodes

The network is the medium Communication rules are defined

by a protocol


Protocols

Communication protocol An agreed-upon format or procedure

for transmitting data. Implemented in hardware and/or

software Key issues

Deliver message efficiently Detect errors Correct errors


Figure 2.7 An electronic message consists of a header, a body, and a trailer.

The header carries delivery information Information about the message

The trailer is often optional.

Message

Header Body Trailer


Network Structures

LAN (local area network) Links nodes in close proximity Point-to-point or broadcast

WAN (wide area network) Links geographically disbursed nodes Typically utilizes common carrier


Figure 2.8 Common LAN topologies.

Topology Describes shape or

form Defines

interconnections

Ring

Bus

Star


Message Delivery

Broadcast Every message sent to every node Node picks out messages addressed

to it Bus and some star networks

Point-to-point Message moves node-to-node Topology or routing determines path


Collisions

LAN traffic management problem Simultaneous transmission by two or more

nodes Token passing (collision avoidance)

Electronic token passed from node to node Given node can transmit when it holds token

Collision detection and recovery Let collision happen Sense and retransmit affected messages


Figure 2.9 An Ethernet network.

Server

Wiring closet

Wiring closet


Figure 2.10 With point-to-point transmission, the signal is routed node by node.

Router 3

Router 4

Router 5

Router 6

Router 7 Router 9

Router 8Router 1

Router 2

Source Destination


Figure 2.11 Internetworking.

Process of linking two or more networks. Server

Bridge

Gateway

Server

WorkstationWorkstation

Workstation

Server


Workstation


Workstation Workstation

A bridge links similar networks

A gateway links dissimilar networks


A router accepts a message at one of several input ports and forwards it to the appropriate

output port.

In

Out

Router

Routers are faster and less expensive than computers at performing the highly specialized task of routing messages.


Figure 2.12 A client/server network.

Server Controls resource Normally software Term sometimes

applied to hardware Client

Requests resource Workstation

File system

Printer

Server

Client Client

Client Client


Figure 2.13 Most users access the Internet through an Internet Service Provider (ISP).

Access network Communication link

Most ISPs offer E-mail, data access, chat rooms, site hosting, …

Host or end system Runs server software

Workstation ISP

Workstation ISP

Internet

http//thelist.internet.com


Figure 2.14 The backbone.

Network Service Provider (NSP)

NetworkAccess Point

(NAP)

NetworkAccess Point

(NAP)

Network Service Provider (NSP)

Regional ISPRegional ISP Regional ISP

Local ISP Local ISPLocal ISP

Major ISP

Major ISPMajor

corporatenetwork

Majorcorporatenetwork

Majorcorporatenetwork


The Backbone

Network Service Provider (NSP) National wide-area network Lease bandwidth to ISPs

Network Access Point (NAP) Place where NSPs meet and exchange

data Chicago NAP

Regional ISP Statewide of regional backbones


Figure 2.16 Packet switching.

Objective: Efficiently utilize

bandwidth Process

Break message into packets

Transmit packets independently

Multiple messages share line

Reassemble message at receiving end

Packet A1 Packet A2 Packet A3

Message A

Packet A1 Packet A2 Packet A3

Message A

Packet A3 Packet Packet

Packet Packet A2 Packet

Open Packet Packet

Packet A1 Packet Open

Packet Packet Open

Packet Packet Packet


Figure 2.17 A message’s packets can follow different paths.

Router 3

Router 4

Router 6

Router 7 Router 9

Router 8Router 1

Router 2

Router 4 Router 5

Router 5Router 5


Figure 2.18 The TCP/IP model.

Application layer

Transport layer

Internet layer

Network access layer

The top two layers work withthe message.

The bottom two layers work withpackets and control the network.


Figure 2.19 The Open Systems Interconnect (OSI) model.

OSI layer Responsibilities

Application Provides a logical link between an application program andthe lower-level protocols.

Presentation Performs necessary data representation and/or syntaxconversions; e.g., encryption/decryption.

Session Establishes, maintains, and terminates a connection.

Transport Breaks the message into packets. Ensures error free, end-to-end delivery of the complete message.

Network Determines the best route for sending a packet from thesource node to the destination node.

Data-link Formats a packet for transmission to the next node.

Physical Interfaces with the physical communication medium.

The top four layers work with the message.

The bottom three layers work with packets and control the network.

A blueprint.


Figure 2.20 The application layer protocols support application programs.

Application layer

Transport layer

Internet layer


FTP

POP

telnet

SNMP

http SMTP

Other DNS

From application program

To transport layer


Figure 2.21 Some common application layer protocols.

AcronymFTP

HTTP

POP

SMTP

SNMP

Telnet

Hypertext transfer protocol

File transfer protocolName

Post office protocol

Simple mail transferprotocolSimple networkmanagement protocolTerminal emulationprotocol

Send an e-mail message from the originator'scomputer to the recipient's mail server.

FunctionDownload a file from or upload a file toanother computer.Request and download a web page. HTTP isthe standard Web surfing protocol.Deliver accumulated mail from a mail serverto the recipient's computer.

Monitor the activity of a network's hardwareand software components.Log into a remote computer. System operatorsuse telnet to remotely control a server.


Figure 2.23 The next layer down is the transport layer.

Application layer

Transport layer

Internet layer


TCPOther

transportprotocol

From application layer

To Internet layer

The transport layer usually uses the TCP protocol.


Figure 2.24 TCP adds its own header.

TCPheader

FTP requestFTP

header

FTP requestFTP

header

FTP requestApplication program

Application layer

Transport layer (each packet)


Figure 2.25 The Internet layer uses the Internet protocol (IP).

Application layer

Transport layer

Internet layer


IP

From transport layer

To network access layer

ARP


Figure 2.26 IP adds its own header.

FTP requestFTP

headerTCP

headerIP

header

TCPheader

FTP requestFTP

header

FTP requestFTP

header


Application layer


Internet layer(each packet)


Figure 2.27 The network access layer adds another header.

FTP requestFTP

headerTCP

headerIP

header

TCPheader

FTP requestFTP

header

FTP requestFTP

header


Application layer


Internet layer(each packet)

FTP requestFTPheader

TCPheader

IPheader

Networkheader

Network accesslayer


Open standards

TCP/IP is an example Promotes

Platform independence Interoperability

Open standards make the Internet a true public medium.


Figure 2.28 A domain name consists of two to four words separated by dots.

sbaserver1.sba.muohio.edu

Server within SBA sub-domain

SBA sub-domain

Miami University domain

Top-level domain

Domain: a set of nodes administered as a unit.


The parts of a domain name are structured as a hierarchy.

edu

134com org

muohio

134.53

sba

134.53.40

cas

134.53.54

sbaserver1

134.53.40.2

sbadata

134.53.40.4


Figure 2.29 Top-level domain names.

Domain Signifies Domain Signifies aero Air-transport industry au Australia biz Business organization br Brazil com US commercial ca Canada coop Coooeratives cn China edu US educational de Germany info Unrestricted fi Finland gov US government fr France mil US military gb Great Britian museum Museums in India name Individuals it Italy net US network jp Japan org US non-profit ru Russia pro Professionals za South Africa


Figure 2.30 An IP address.

134.53.40.2

Server within SBA domain

SBA domain

Miami University domain

Top-level domain

Wrong


Figure 2.32 The domain name system.

sba DNSmuohio DNS

com = 207

com DNSmicrosoft =

207.46

microsoft DNSservice =

207.46.140.71

service.microsoft.com

service.microsoft.com

service.microsoft

service

207.46.140.71

207.46

207.46.140.71

12

3

4

5

67


Figure 2.33 Well-known port assignments.

Port Used for: 5 RJE (Remote Job Entry) 20 FTP (File Transfer Protocol) data 21 FTP (File Transfer Protocol) control 23 TELNET (Terminal emulator) 25 SMTP (Simple Mail Transfer Protocol) 79 FINGER (Given e-mail address, identify user) 80 HTTP (Hypertext Transfer Protocol) 110 POP3 (Post Office Protocol, Version 3) 119 NNTP (Network News Transfer Protocol)

Port: location at an IP address which services a particular application

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Chapter 2 The Infrastructure. Copyright © 2003, Addison Wesley Understand the structure & elements...

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