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-to-Peer Networks

3 Software Layers on the Computer

Computer

Operating System / Environment

Applications

You

Black Boxes and Layers

Applications

Operating System/Environment

Hardware

3-Layer Model

Applications

Redirector

OSNetwork

OS

LocalH/W

NetworkH/W

4-Layer Model

Network Layer Model

Network Standard: OSI Architecture

Application Layer: User software (e.g. spreadsheet).Application Layer: User software (e.g. spreadsheet).

Presentation Layer: Operating system functionality.Presentation Layer: Operating system functionality.

Session Layer: Connection between user & network (e.g. logins). Session Layer: Connection between user & network (e.g. logins).

Transport Layer: Find best path for transmission.Transport Layer: Find best path for transmission.

Network Layer: Routing (to which host, etc.)Network Layer: Routing (to which host, etc.)

Data Link Layer: Error checking (parity, etc).Data Link Layer: Error checking (parity, etc).

Physical Layer: Packets on the media (T/P, Fiber, etc). Physical Layer: Packets on the media (T/P, Fiber, etc).

SevenOSILayers

The Internet’s TCP/IP Standard

Application orProcess Layer

Internet Protocol (IP)

Host-to-Host Transport Layer

Network Interface

Physical Layer

ApplicationLayer

PresentationLayer

SessionLayer

TransportLayer

NetworkLayer

Data LinkLayer

PhysicalLayer

OS

I M

od

el

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 Media2

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 two-way 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-to-

peer 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

http://www.amazon.com/gp/homepage.html

CommunicationProtocol Domain Name

FolderPath

Web Page HTML File

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

analog/digital converter to translate your voice into digital for transmission over the Internet.

IP-Phones 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?