Transcript Figure 2.1 Communication requires a message, a transmitter, a

Chapter 2
The Infrastructure
Understand the structure & elements
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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
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Figure 2.2 Communication requires five
elements.
Transmitter
Medium
Receiver
Message
Protocol: a set of rules for
transmitting a message.
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Message
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Information/content
Transmitter
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Source or sender
Medium
Path or pipe
Receiver
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Sink or destination
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Media Types
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Cable
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Physical wire
Twisted pair, coaxial, fiber optic
Wireless
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No physical wire
Cellular, digital cellular, satellite
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Connectivity
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Ability to operate over a connection
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Physical – medium
Logical – protocol
Line types
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Baseband – one signal at a time
Broadband – simultaneous signals in parallel
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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.
Central office
Source
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Long distance
connection
The cloud is a common way
to visualize an infrastructure
Central office
Destination
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Figure 2.4 Wireless communication.
BaseHub
station
Radio tow er
Mobile switching center
Trunk
Alice
Telephone
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Long distance
network
Both POTS and
wireless use the
same long distance
infrastructure.
Trunk
BaseHub
station
Mobile switching center
Radio tow er
Bob
Telephone
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Figure 2.5 POTS and wireless are alternative access
paths to the long distance infrastructure.
POTS
Wireless service
Long distance infrastructure
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Cable and satellite Internet services use the same long
distance lines.
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Figure 2.6 Bandwidth.
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Amount of data a
medium can transmit
in a given time.
Conventions
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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
Wireless
2G digital cellular
2.5G digital cellular
3G digital cellular
Bluetooth
Wi-Fi (802.11b)
19.2 Kbps
144 Kbps
2 Mbps
1 Mbps
Up to 11 Mbps
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
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Networks
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Network: two or more computers or
devices linked by communication lines.
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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
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Communication protocol
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An agreed-upon format or procedure for
transmitting data.
Implemented in hardware and/or software
Key issues
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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.
Message
Header
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The header carries delivery information
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Body
Information about the message
The trailer is often optional.
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Trailer
Network Structures
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LAN (local area network)
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Links nodes in close proximity
Point-to-point or broadcast
WAN (wide area network)
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Links geographically disbursed nodes
Typically utilizes common carrier
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Figure 2.8 Common LAN topologies.
Bus
Ring
Star
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Topology
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Describes shape or form
Defines interconnections
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Message Delivery
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Broadcast
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Every message sent to every node
Node picks out messages addressed to it
Bus and some star networks
Point-to-point
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Message moves node-to-node
Topology or routing determines path
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Collisions
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LAN traffic management problem
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Token passing (collision avoidance)
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Simultaneous transmission by two or more nodes
Electronic token passed from node to node
Given node can transmit when it holds token
Collision detection and recovery
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Let collision happen
Sense and retransmit affected messages
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Figure 2.9 An Ethernet network.
Wiring closet
Server
Wiring closet
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Figure 2.10 With point-to-point transmission,
the signal is routed node by node.
Router 1
Router 6
Router 8
Router 3
Source
Destination
Router 5
Router 4
Router 2
Router 7
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Router 9
Figure 2.11 Internetworking.
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Process of
linking two
or more
networks.
Workstation
Workstation
Workstation
Workstation
Workstation
Workstation
Server
Bridge
Server
A bridge links
similar networks
Workstation
A gateway links
dissimilar networks
Workstation
Server
Gateway
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Workstation
Workstation
A router accepts a message at one of several input
ports and forwards it to the appropriate output port.
Router
Routers are faster
and less expensive
than computers at
performing the
highly specialized
task of routing
messages.
Out
In
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Figure 2.12 A client/server network.
Client
Client
Server
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Server
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Printer
Controls resource
Normally software
Term sometimes applied
to hardware
Client
Client
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Requests resource
Workstation
File system
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Client
Figure 2.13 Most users access the Internet
through an Internet Service Provider (ISP).
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Access network
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ISP
Communication link
Most ISPs offer
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Workstation
E-mail, data access,
chat rooms, site
hosting, …
Internet
Workstation
ISP
Host or end system
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Runs server software
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http//thelist.internet.com
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Figure 2.14 The backbone.
Major
corporate
network
Major ISP
Network Service Provider (NSP)
Network
Access Point
(NAP)
Network
Access Point
(NAP)
Network Service Provider (NSP)
Major
corporate
network
Major ISP
Regional ISP
Major
corporate
network
Local ISP
Regional ISP
Local ISP
Regional ISP
Local ISP
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The Backbone
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Network Service Provider (NSP)
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Network Access Point (NAP)
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National wide-area network
Lease bandwidth to ISPs
Place where NSPs meet and exchange data
Chicago NAP
Regional ISP
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Statewide of regional backbones
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Figure 2.16 Packet switching.
Message A
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Objective:
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Efficiently utilize
bandwidth
Packet A1
Packet A2
Packet A3
Packet A3
Packet
Packet
Packet A1
Packet
Open
Packet
Packet A2
Packet
Packet
Packet
Open
Open
Packet
Packet
Packet
Packet
Packet
Process
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Break message into
packets
Transmit packets
independently
Multiple messages
share line
Reassemble message
at receiving end
Packet A1
Packet A2
Message A
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Packet A3
Figure 2.17 A message’s packets can
follow different paths.
Router 1
Router 6
Router 8
Router 3
Router 4
Router 4
Router 2
Router 5
Router 5
Router 5
Router 7
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Router 9
Figure 2.18 The TCP/IP model.
Application layer
The top two layers work with
the message.
Transport layer
Internet layer
The bottom two layers work with
packets and control the network.
Network access layer
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OSI layer
Responsibilities
The top four layers work with the message.
Application
Figure 2.19
The Open
Systems
Interconnect
(OSI) model.
Provides a logical link between an application program and
the lower-level protocols.
Presentation Performs necessary data representation and/or syntax
conversions; e.g., encryption/decryption.
Session
Establishes, maintains, and terminates a connection.
Transport
Breaks the message into packets. Ensures error free, end-toend delivery of the complete message.
The bottom three layers work with packets and control the network.
A blueprint.
Network
Determines the best route for sending a packet from the
source node to the destination node.
Data-link
Formats a packet for transmission to the next node.
Physical
Interfaces with the physical communication medium.
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Figure 2.20 The application layer
protocols support application programs.
From application program
Application layer
FTP
telnet
http
SMTP
POP
SNMP
Other
DNS
Transport layer
Internet layer
Network access layer
To transport layer
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Figure 2.21 Some common application
layer protocols.
Acronym
FTP
HTTP
POP
SMTP
SNMP
Telnet
Name
File transfer protocol
Function
Download a file from or upload a file to
another computer.
Hypertext transfer protocol Request and download a web page. HTTP is
the standard Web surfing protocol.
Post office protocol
Deliver accumulated mail from a mail server
to the recipient's computer.
Simple mail transfer
Send an e-mail message from the originator's
protocol
computer to the recipient's mail server.
Simple network
Monitor the activity of a network's hardware
management protocol
and software components.
Terminal emulation
Log into a remote computer. System operators
protocol
use telnet to remotely control a server.
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Figure 2.23 The next layer down is the
transport layer.
From application layer
Application layer
Transport layer
Other
transport
protocol
TCP
Internet layer
Network access layer
To Internet layer
The transport layer usually uses the TCP protocol.
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Figure 2.24 TCP adds its own header.
FTP request
Application program
FTP
header
Application layer
Transport layer
(each packet)
TCP
header
FTP
header
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FTP request
FTP request
Figure 2.25 The Internet layer uses the
Internet protocol (IP).
From transport layer
Application layer
Transport layer
Internet layer
IP
ARP
Network access layer
To network access layer
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Figure 2.26 IP adds its own header.
FTP request
Application program
FTP
header
Application layer
Transport layer
(each packet)
Internet layer
(each packet)
TCP
header
IP
header
TCP
header
FTP
header
FTP
header
FTP request
FTP request
FTP request
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FTP request
Application program
FTP
header
Application layer
Figure 2.27
The network
access layer
adds another
header.
Transport layer
(each packet)
Internet layer
(each packet)
TCP
header
IP
header
TCP
header
FTP
header
FTP
header
FTP request
FTP request
FTP request
Network access
layer
Network
header
IP
header
TCP
header
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FTP
header
FTP request
Open standards
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TCP/IP is an example
Promotes
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Platform independence
Interoperability
Open standards make the Internet a
true public medium.
Copyright © 2003, Addison Wesley
Figure 2.28 A domain name consists of
two to four words separated by dots.
sbaserver1.sba.muohio.edu
Top-level domain
Miami University domain
SBA sub-domain
Server within SBA sub-domain
Domain: a set of nodes administered as a unit.
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edu
com
org
134
The parts of a
domain name are
structured as a
hierarchy.
muohio
134.53
sba
cas
134.53.40
134.53.54
sbaserver1
sbadata
134.53.40.2
134.53.40.4
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Figure 2.29 Top-level domain names.
Domain
aero
biz
com
coop
edu
info
gov
mil
museum
name
net
org
pro
Signifies
Air-transport industry
Business organization
US commercial
Coooeratives
US educational
Unrestricted
US government
US military
Museums
Individuals
US network
US non-profit
Professionals
Domain
au
br
ca
cn
de
fi
fr
gb
in
it
jp
ru
za
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Signifies
Australia
Brazil
Canada
China
Germany
Finland
France
Great Britian
India
Italy
Japan
Russia
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
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Figure 2.32 The domain name system.
service.microsoft.com
1
2
sba DNS
5
service.microsoft.com
207.46.140.71
muohio DNS
com = 207
service
207.46.140.71
6
7
3
service.microsoft
207.46
4
com DNS
microsoft =
207.46
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microsoft DNS
service =
207.46.140.71
Figure 2.33 Well-known port assignments.
Port
5
20
21
23
25
79
80
110
119
Used for:
RJE (Remote Job Entry)
FTP (File Transfer Protocol) data
FTP (File Transfer Protocol) control
TELNET (Terminal emulator)
SMTP (Simple Mail Transfer Protocol)
FINGER (Given e-mail address, identify user)
HTTP (Hypertext Transfer Protocol)
POP3 (Post Office Protocol, Version 3)
NNTP (Network News Transfer Protocol)
Port: location at an IP address which
services a particular application
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