chapter 2 the infrastructure. copyright © 2003, addison wesley understand the structure &...
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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.
Copyright © 2003, Addison Wesley
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
Copyright © 2003, Addison Wesley
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.
Copyright © 2003, Addison Wesley
Media Types
Cable Physical wire Twisted pair, coaxial, fiber optic
Wireless No physical wire Cellular, digital cellular, satellite
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Figure 2.8 Common LAN topologies.
Topology Describes shape or
form Defines
interconnections
Ring
Bus
Star
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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
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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
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Figure 2.9 An Ethernet network.
Server
Wiring closet
Wiring closet
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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
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Figure 2.11 Internetworking.
Process of linking two or more networks. Server
Bridge
Gateway
Server
WorkstationWorkstation
Workstation
Server
WorkstationWorkstation
Workstation
WorkstationWorkstation
Workstation Workstation
A bridge links similar networks
A gateway links dissimilar networks
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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.
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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
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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
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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
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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
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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
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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
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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.
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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.
Copyright © 2003, Addison Wesley
Figure 2.20 The application layer protocols support application programs.
Application layer
Transport layer
Internet layer
Network access layer
FTP
POP
telnet
SNMP
http SMTP
Other DNS
From application program
To transport layer
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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.
Copyright © 2003, Addison Wesley
Figure 2.23 The next layer down is the transport layer.
Application layer
Transport layer
Internet layer
Network access layer
TCPOther
transportprotocol
From application layer
To Internet layer
The transport layer usually uses the TCP protocol.
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Figure 2.24 TCP adds its own header.
TCPheader
FTP requestFTP
header
FTP requestFTP
header
FTP requestApplication program
Application layer
Transport layer (each packet)
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Figure 2.25 The Internet layer uses the Internet protocol (IP).
Application layer
Transport layer
Internet layer
Network access layer
IP
From transport layer
To network access layer
ARP
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Figure 2.26 IP adds its own header.
FTP requestFTP
headerTCP
headerIP
header
TCPheader
FTP requestFTP
header
FTP requestFTP
header
FTP requestApplication program
Application layer
Transport layer (each packet)
Internet layer(each packet)
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Figure 2.27 The network access layer adds another header.
FTP requestFTP
headerTCP
headerIP
header
TCPheader
FTP requestFTP
header
FTP requestFTP
header
FTP requestApplication program
Application layer
Transport layer (each packet)
Internet layer(each packet)
FTP requestFTPheader
TCPheader
IPheader
Networkheader
Network accesslayer
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Open standards
TCP/IP is an example Promotes
Platform independence Interoperability
Open standards make the Internet a true public medium.
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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.
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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
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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
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Figure 2.30 An IP address.
134.53.40.2
Server within SBA domain
SBA domain
Miami University domain
Top-level domain
Wrong
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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
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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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