Transcript Document 7525408

Information Systems: Creating
Business Value
by
Mark Huber, Craig Piercy, and Patrick McKeown
Field Guide C: The Details of
Networking
What We Will Cover:
 Network Architecture
 Network Layer Model
 Local Area Networks
 The Internet: A Network of Networks
 The World Wide Web
Student ROI (Return on Investment)
Your investment of time and effort in this course will result in your being
able to answer these questions:
1.
What is the client/server architecture, and how does it work?
2.
How does the network layer model describe a wide area network?
3.
How are local area networks configured?
4.
How does the Internet work?
5.
What makes the World Wide Web valuable to knowledge workers?
Client/Server Computing
 The most common network architecture is the
client/server architecture.1
1R.
T. Watson, Organizational Memory, 5th ed. (New York: John Wiley,
2006, p. 360
Client/Server
 Processing is shared among multiple small computers known as
clients that are connected via a network to a host computer
known as a server.
 Clients - typically PCs, a type of high-powered small computer
built for specialized applications called a workstation, or a
network computer.
 Server - typically dedicated to a specific type of processing,
such as providing files with a file server, responding to database
queries with a database server, or handling high-speed
processing with an application server.
 Because both the client and the server are capable of
processing, processing is shared between the two computers
depending on the capability of each.
Three-Tiered Architecture
Types of Servers
Server Type
Purpose
File
Provides both software and data files to users
Database
Handles queries to a large database and returns
matching records
Application
Handles high speed processing
Web
Handles requests for Web pages
Mail
Sends and receives e-mail for entire organization
Fax
Sends and receives faxes for entire organization
Servers on a Network
Client/Server Advantages and Disadvantages
Advantages
Disadvantages
Computing burden can be shared
among servers and clients
Programming relationship between
clients and servers is more complex
Servers can be specialized to one
particular type of task
System upgrades require that all
clients and servers be upgraded
regardless of location
Upgrading system can be done in
small steps
Loss of client does not stop other
clients from accessing server
Peer-to-Peer Networks
 It is possible to set up a peer-to-peer network, where
each computer in the network is on the same level as other
computers, and each computer is equally responsible for
overseeing the functions of the network.
 Any two computers in a peer-to-peer network may
communicate directly with one another, or they may
communicate through intermediate peer computers.
 Peer-to-peer networks may be easier to setup, but are not
as efficient as client/server networks.
Comparing Client/Server and Peer-toPeer Networks
3 Software Layers on the Computer
Computer
Operating System
/ Environment
Applications
You
Black Boxes and Layers
3-Layer Model
4-Layer Model
Applications
Applications
Operating System/
Environment
Redirector
OS
Network
OS
Local
H/W
Network
H/W
Hardware
Network Layer Model
Network Standard: OSI Architecture
Application Layer: User software (e.g. spreadsheet).
Presentation Layer: Operating system functionality.
Session Layer: Connection between user & network (e.g. logins).
Transport Layer: Find best path for transmission.
Network Layer: Routing (to which host, etc.)
Seven
OSI
Layers
Data Link Layer: Error checking (parity, etc).
Physical Layer: Packets on the media (T/P, Fiber, etc).
The Internet’s TCP/IP Standard
Application
Layer
Application or
Process Layer
Presentation
Layer
Session
Layer
Host-to-Host Transport Layer
Transport
Layer
Internet Protocol (IP)
Network
Layer
Network Interface
Data Link
Layer
Physical Layer
Physical
Layer
Application Software Layer
 Application software is the software on each computer on the
network that the user sees and uses to send and receive messages
and data between computers.
 Web browsers, e- mail, etc.
 Application layer protocols: simple mail transfer protocol (SMTP) for
e-mail, hypertext transfer protocol (HTTP), Electronic data
interchange (EDI)
 The message may also be encrypted.
Network Connection Layer
 The message from the application software layer is
formatted according to whatever protocol will actually
be used to send it over the network.
 Commonly used protocols:


Transmission Control Protocol/Internet Protocol
(TCP/IP).
Ansi X 12 or EDIFACT for EDI.
Converting Data into Packets
 IP Address – a unique identifier given to each device directly
connected to the network.
 Consists of four groups of numbers in the range 0 to 255
separated by periods or decimal points.
 The message is divided into smaller digital units called packets,
each of which contains a specific number of bytes.
Packet Switching
 The physical layer sends packets over telephone lines, or other
media, using packet switching.
 Packet switching - individual packets are routed through the
network based on the destination address contained in each packet.
With packet switching, the same data path can be shared among
many computers in the network, and if a computer on the network is
inoperable, the packet finds another way to reach its destination.
 A router is a special type of computer that has the sole purpose of
accepting packets and determining the best way to send them to the
destination computer--that is, the router specializes in switching the
packets.
 The sequence order allows the receiving computer to reconstruct
the message.
Sending Data Between Computers on
the Internet
Data Components Layer
 Twisted pair - consists of twisted pairs of copper wires and is




similar to the wiring used in much of the existing telephone
system.
Coaxial cable - used to transmit cable television signals into
your home. It is also widely used in networks.
Fiber optic cable - consists of hundreds of glass fiber strands
that can transmit a large number of signals at extremely high
rates of speed.
Microwaves - high-frequency radio transmissions that can be
sent between two stations
Wireless – several technologies that allow data to be
transmitted without wires
Copper Wire Compared to Fiber
Optics
Data Component Media
2
Media
Cost
Error Rates
Speed
Twisted Pair
Low
Low
Low-high
Coaxial Cable
Moderate
Low
Low-high
Fiber Optics
High
Very Low
High - very
High
Radio
Low
Moderate
Low
Infrared
Low
Moderate
Low
Microwave
Moderate
Low- Moderate
Moderate
Satellite
Moderate
Low- Moderate
Moderate
2Source:
Jerry Fitzgerald and Alan Dennis, Business Data Communications and
Networking, 8th ed., p. 85, New York: John Wiley, 2005.
Data Rate and Bandwidth Issues
 The data rate is measured in bits per second (bps).
 A digital subscriber line (DSL) transmits computer data in a
digital form along the same telephone line that is used for
analog voice communications.
 T-carrier circuits are dedicated digital lines that are leased
from a telecommunications company to carry data between
specific points.
 The term bandwidth is often used in relationship to data rate
and is a measure of how fast data flows on a transmission path.
 Baseband - only a single digital signal is carried through the
media.
 Broadband - variety of different analog signals are being
transmitted.
Baseband Compared to Broadband
Maximum Data Rates
Transmission Method
Maximum Data Rate
Comments
Standard telephone service
56 Kbps
Available everywhere
Digital Subscriber line (DSL)
6 Mbps in; 640 Kbps out
Becoming more
available. Does not slow
down as more people
sign up.
Cable
As high as 55 Mbps but
averages between 200 Kbps
and 2 Mbps
Cable must support twoway communication;
available in many
locations but slows down
as more people use it in
a specific location
T-1 to T-4
1.544 Mbps - 274 Mbps
Leased lines used for
commercial
telecommunication
Local Area Networks
 Local Area Networks (LAN) – a network
connected over a small geographic area. LANs
are popular for




Sharing information
Sharing resources
Sharing software
Sharing hardware
 Most LANs are client/server networks
 LANs can also be implemented through peer-topeer networks
LAN Terminology
 Ethernet protocol – technology standards
for connecting computers into a LAN.
 A bus network uses a a main cable, called a
bus, to connect all clients and servers on the
network.
 A gateway is the combination of hardware
and software that connects two dissimilar
computer networks.
 A bridge connects two similar networks.
Wireless LANs
 Wireless LANs (WLANs) – replaces cabling with
wireless transmissions that use radio frequencies to
transmit information between individual computers
 The individual computers do not communicate
directly with each other; instead they communicate
with a wireless network hub or router, which is also
used to bridge the wireless network to traditional
ethernet or provide a shared Internet connection.
 Wi-Fi (for Wireless Fidelity) – also called IEEE
802.11b standard, the current popular standard for
wireless networking supports data rate of 11
megabits/second, with a typical range through open
air of about 220-1100 yards (200-1000 meters).
Laptops Connected to a Wireless LAN
Bluetooth and PANs
 Personal Area Network (PAN) - a technology that enables
wireless devices such as mobile telephones, computers, and
PDAs to communicate over a short distance—less than 33 feet
(10 meters).
 Bluetooth - embeds a low-cost transceiver chip in each device,
making it possible for wireless devices to be totally synchronized
without the user having to initiate any operation.
 The overall goal of Bluetooth might be stated as enabling
pervasive connectivity between personal technology devices
without the use of cabling.
The Internet: Network of Networks
 Originally developed in the 1960s and 1970s as a
way of sharing information and resources among
universities and research institutions, the Internet
began its dramatic growth in 1991.
 Today, the Internet is growing so fast that no one can
say exactly how many people are using it, with
estimates ranging as high as over 1.10 billion in
2005.
 A primary reason for the explosive growth of the
Internet is the tremendous amount of data,
information, and resources that people can access.
What is the Internet?
 The Internet is a network of networks.
 To connect to the Internet, your computer will usually first connect to
a LAN through a network interface card (NIC) or to an ISP through a
modem and telephone line.
 The LAN, mainframe, or ISP is, in turn, connected to a regional
network via a high-speed (T-1) telephone line. The regional network
in turn links into the backbone of the Internet.
 With each network, there is at least one host computer that is
connected to the Internet with full two-way access to other
computers on the Internet and with a unique Internet address.
 Each host computer that connects to the Internet uses the TCP/IP
protocol for assigning addresses and uses packet switching for
exchanging information.
Connecting to the Internet
Addresses
 An e-mail address is composed of two parts: the user name and
the server address.
 The user name is assigned to a person or organization that is
connected to a server, and it is separated from the server
address by the at symbol (@).
 Server address (a.k.a. domain name) – the IP address of the
email host. The right-most part of the address is known as the
top level domain.
 Server addresses are easy-to-remember versions of the
numeric IP addresses.
Top Level Domains
Type of Organization
Designation
Example
Commercial company
.com
www.ebay.com (eBay Auctions)
Educational institution
.edu
www.uga.edu (The University of Georgia)
Nonprofit organization
.org
www.redcross.org (The Red Cross)
Network provider
.net
www.netscape.net (Netscape)
Government
.gov
www.ustreas.gov (U.S. Treasury Department)
Military
.mil
www.usmc.mil (The U.S. Marine Corps)
Aerospace organizations*
.aero
www.ba.aero (British Airways)
Businesses*
.biz
www.webmaster-resource.biz (Webmaster-Resource.biz, an e-commerce company)
Cooperatives*
.coop
www.credit-cooperatif.coop (Crédit Coopératif Group in France)
Various*
.info
www.lanka.info (Information on Sri Lanka)
Museums*
.museum
mhp.moscow.museum (Moscow House of Photography in Russia)
Various*
.name
www.yourname.name
Professionals*
.pro
www.broadway.pro
(Broadway theater shows)
Internet Operations
Internet Operations
Purpose
E-mail
Asynchronously exchange electronic messages with
other Internet users
FTP
Download files (software, documents, or data) from
or upload files to a server located on the Internet
Newsgroups
Participate in a wide variety of online discussion
groups
Telnet
Work on a computer elsewhere on the Internet
Internet Relay Chat
Synchronously exchange electronic messages with
other Internet users
World Wide Web
Transfer text, images, video, and sound to your
computer; search for information on Internet
The World Wide Web
 The Web is a body of software and a set of
protocols and conventions based on
hypertext and multimedia that make the
Internet easy to use and browse.
 Hypertext is a method of linking related
information in which there is no hierarchy or
menu system.
 Multimedia is an interactive combination of
text, graphics, animation, images, audio, and
video displayed by and under the control of a
computer.
Using a Browser
 The Web is a special type of client/server network. To access the
Web, the client computer uses software called a browser that
initiates activity by sending a request to a Web server for certain
information. The Web server responds by retrieving the
information from its disk and then transmitting it to the client.
 Browser – application layer software used for sending requests
and displaying the results
 Hypertext markup language (HTML) - tags in World Wide Web
documents that are part of a special publishing language
 Documents on the Web are referred to as Web pages, and their
location is a Web site.
A Web Page and Source Code
Web Pages vs. Physical Pages
Characteristics
Web Page
Physical Page
Form
Electronic
Ink on paper
Amount of information
Can extend beyond single
screen
Restricted to single piece
of paper
Types of information
Can include text, images,
audio, and video
information
Restricted to text and
images
Links to other pages
Can be linked to other
pages through hypertext
Can be linked only
through a separate index
Creation
Can be created with
HTML and saved to a
server
Can be created using
word processor and
printer
Web Technology
 IP Address
Four numbers that identify a node on the Internet
 e.g. 72.21.206.5 (a.k.a. www.amazon.com)
 Hypertext Transfer Protocol (HTTP)
 Communication protocol used to transfer pages
from Web server to browser
 HTTPS is a more secure version
 Uniform Resource Locator (URL)
 Mnemonic Web address corresponding with IP
address
 Also includes folder location and html file name

Communication
Protocol
Domain Name
Folder
Path
Web Page
HTML File
http://www.amazon.com/gp/homepage.html
Internet Protocols
Protocol
Purpose
http
Retrieve Web pages
file
Retrieve files from local hard disk
telnet
Log on to a remote computer
connected to the Internet
ftp
Download or upload files from an
Internet FTP server
mailto
Send outgoing e-mail
news
Display news group
Wireless Networks
 The fastest growing trend in networks is wireless networks, both WANs





and LANs.
Primary advantage: devices connected to the network can go virtually
anywhere
In the case of wireless WANs, a mobile telephone client is the most
popular method of connecting to the Internet and Web.
A number of mobile telephone companies have collaborated to create a
special protocol, called Wireless Application Protocol (WAP), just so
their telephones can connect to the Internet.
Short Message Service (SMS ) is a service for sending text messages
up to 160 characters long to mobile telephones.
Global System for Mobile communication (GSM) protocol is the
most widely used standard mobile telephone protocol in the world, with
the exception of the United States where it is gaining ground.
How we make phone calls…
 Changing due to VOIP
Voice over Internet Protocol
 Vonage, Time-Warner (and others)
 How you call
 ATA



IP-Phones


analog/digital converter to translate your voice into digital for
transmission over the Internet.
Have the circuitry necessary to do the A/D conversion onboard.
Your Computer

Any multi-media computer with a network connection and the
necessary software (actually one can get the software for free
at http://www.skype.com/).
Advantages & Issues
 For the user, flexibility – one can take their softphone, or ATA, or





software on a laptop anywhere there’s a network connection
For businesses, it should be cheaper (should be for individuals
too)
For the available bandwidth, a more efficient way to allocate
space to phone calls (see arguments about circuit versus packet
switching)
See http://computer.howstuffworks.com/ip-telephony.htm for
more details
FCC doesn’t have clear rules yet – for example, current
traditional telecoms pay for stuff like 911 and associated
services.
How will pricing eventually pan out?