IntroductionChapter 1

Copyright 1998, 1999 PankoRevised May 1999

2Stars

Material that is especially important, or

Material that is especially difficult or easy to confuse with similar material.

Part A:The Networking Revolution

An overview of trends and the importance of networking to your career

4The Networking Revolution

The Traditional Career Ladder

– Programmer

– Systems Analyst

– IS (information systems) Management

– Chief Information Officer (CIO)

5The Networking Revolution

Many Factors, including Networking, are Changing this Career Ladder

– Networking specialties

– User support specialties (combine PC support and networking support groups of)

– Programmers create groups of programs that interact by exchanging messages across networks, not just stand-alone programs on single machines.

6Changes in IT

Transforming the Corporation

– Intranets: using Internet technology and applications internally

Many good, standardized applications Inexpensive, standardized transmission technology Add security

– Extranets: Using Internet technology to reach business partners and customers

– Enterprise networks connect any two computers in the organization, even if they are at different sites

7Changes in IT

Networking

– High demand for networking skills

– Knowledge beyond wires and bits

TCP/IP standards

Higher-layer standards (applications, etc.)

Systems management (server and client PC management)

8IS versus CS and EE

Hiring Organizations

– CS & EE graduates are trained to work in hardware, software, and networking vendor firms, such as Microsoft, IBM, Oracle, and Cisco Systems.

– IS graduates are trained to work in end user organizations, which use IT to enhance business value, such as banks, government agencies, and manufacturing firms--organizations that use IT to get their work done.

9IS versus CS and EE

Make versus Buy

CS and EE Professionals– Make products for sale

IS Professionals– Buy these products instead of making things

– Must select products appropriately

– Must integrate these products together

10Comparing Products

Dimensions for Comparing Products in Purchase Selection

Performance– Whatever is appropriate for specific user needs– In some cases, speed– In other cases, reliability or something else

Feasibility for the firm– Products based on new standards may be too much work

to implement

Cost (can never be ignored)

11Comparing Products

Costs

Total purchase cost for all hardware and software– Typically, “base price” are only a fraction of total cost

Labor costs to plan, install– Often greatly outweigh product purchase costs

Life cycle costs from initial purchase to final abandonment– Often greatly outweigh initial costs

12Comparing Products

Emphasis: Cost is Always Important– User demands are surging– Budgets are not growing rapidly

You must buy the least expensive technology that will meet user requirements

No comparison of alternatives is complete without a cost analysis

13User Needs

Drive everything else

Must communicate with users to understand their needs

Must support important user needs without bankrupting the firm

14Standards

Standards are rules of operation that are followed by most or all vendors.

Standards allow products from different vendors to work together (interoperate)– You are not limited to buying from one firm.

– Competition will drive down costs and increase options

– You do not have to worry if a single vendor falls behind or fails

Part B:Accessing the World Wide Web from Home

Many students access the World Wide Web from home. Here is how it works, in terms of standards.

16Accessing the WWW from Home

A Common and Important Situation– Must be understood

– Good way of introducing concepts

17The Internet

Network

– A collection of computers that are interconnected so that any computer can send messages to any other computer simply by giving the receiver’s network address at the start of the message.

Key Ideas– Any-to-any. Fully interconnected– Interact through the exchange of messages– Network delivers messages based on their destination

addresses, like the address on a postal envelope

18The Internet

A Worldwide Group of Networks– Not a single network

19The Internet

Messages are Broken into Small Packets for Transmission– More efficient than sending long messages

Message Packets

20The Internet

Routers– Connect the Internet’s networks– Cooperate to give an end to end route for each packet

Routers

Route

21The Internet

Hosts– Any computer attached to the Internet is a host– Webservers are host– Desktop and notebook PCs are hosts too

Host

Host

22The Internet

Host internet addresses– Four number segments separated by dots– For example, 128.171.17.13– Official addresses for hosts– Also called IP addresses

127.18.47.145

127.47.17.47

23The Internet

Internet Addresses

– Really strings of 32 bits (1s and 0s) 10000000101010100001000100001101

– For convenience, divide them into four bytes (also called octets)

10000000 10101010 00010001 00001101

– Both octets and bytes are collections of eight bits

24The Internet

Internet Addresses

– Convert each octet into a decimal number 10000000 is 128 10101011 is 171 00010001 is 17 00001101 is 13

25

Computing Internet Addresses

Value(2N) Bit Decimal

128 1 128

64 0 0

32 1 32

16 0 0

8 0 0

4 0 0

2 1 2

1 1 1

163

Position(N)

7

6

5

4

3

2

1

0

Binary10100011

=Decimal

163

Note: Starts with 0

26The Internet

Host Names– Easy to remember

www.microsoft.com voyager.cba.hawaii.edu Two or more text “labels” separated by dots No relationship between segments and labels

– Like nicknames Not official names If have host name, browser can look up internet

address of host

CNN.COM

27The Internet

Internet Service Providers (ISPs)– You must have an account with an ISP– Connects you to the Internet– Provides other services (e-mail account, etc.)

Carrier– Connects you to the ISP– You pay for this separately from your ISP charges

ISPCarrier Line

28The Internet

The Internet is Not Free– You pay your ISP around $20 per month– Part of this pays for ISP expenses– Part of this pays the Internet backbone to carry your

messages

You Also Pay the Carrier Separately for the Carrier Line

ISPCarrier Line

29The Internet

Internet Backbone– Consists of competing carriers called network service

providers (NSPs)

– NSPs are all interconnected for any-any communication among hosts

Internet Backbone

NSPs

ISPISP

30The Internet

ISPs and NSPs– Began in the United States

– Is being copied and adapted by other countries

– However, not universal

31Internet Standards

Framework for standards setting is called TCP/IP

– Originally under DARPA (Defense Advanced Research Projects Agency)

– Now under an independent body, the IETF (Internet Engineering Task Force)

32Internet Standards

TCP/IP Standards are Layered– Application– Transport– Internet– Subnet Application

Transport

Internet

Subnet

33Internet Standards

Application Layer Standards– allow two application programs to work together, even

if they come from different vendors– For example, browser on user PC and webserver

application program on webserver

Browser

WebserverApplication

Program

34Internet Standards

HTTP (HyperText Transfer Protocol)– World Wide Web standard for browser-webserver

application program exchanges

Browser

WebserverApplication

Program

HTTP

35Internet Standards

Protocol

– A standard to govern communication between peer processes at the same layer on different systems

– Browser and webserver programs are at the same layer (application)

– Browser and webserver programs are on different machines (user PC and webserver)

– So HTTP is a protocol.

36Internet Standards

Transport Layer Protocols– allow any two computers to exchange messages even if

they come from different vendors and even if they are of different platform types

– For instance, PC and non-PC webserver

PCPC or

Other Computer

37Internet Standards

The Transport Layer Gives Platform Independence– Two computers do not have to be of the same platform

type

A PC user does not even know what kind of computer the webserver is

PC?

38Internet Standards

HTTP Requires the Use of the TCP Transport Standard– Transmission Control Protocol– The TCP in TCP/IP

TCP

39Internet Standards

Internet Layer Protocols– allow packets to be routed across multiple routers from

a source host to a destination host, even if the routers come from different vendors

Route

40Internet Standards

The Internet Protocol (IP) is the Main Protocol for Routing Packets Across the Internet.– The IP in “TCP/IP”

IP

41Internet Standards

Subnets– Single networks (LANs, WANs, point-to-point link)– A packet will pass through several subnets along its

route across the Internet

Subnet

Subnet

Subnet

42Internet Standards

Different Subnets Can Have Different Subnet Protocols– IP at the internet layer routes across different protocols

at the subnet layer

LAN SubnetProtocol 1

WAN SubnetProtocol 2

Point-to-Point Subnet Protocol 3

43Internet Standards

The IETF Does Not Create Subnet Standards– Uses standards from another architecture, OSI– Reference Model of Open Systems Interconnection

Application

Transport

Internet

Subnet: Use OSI Standards

44Internet Standards

OSI Divides Subnet Standards into Two Layers– Data Link– Physical

Application

Transport

Internet

SubnetOSI

Standards

Data Link

Physical

45Internet Standards

Link– Transmission connection in which there is only one

possible path between any two stations

– Simplest is a point-to-point link

Point-to-

Point

46Internet Standards

Link– Other possibilities for a single possible route between

any two stations

Multidrop Ring

HierarchyStarDaisy Chain

47Internet Standards

Data Link Layer Standards– organize transmissions into collections of bits called

frames and manage the transmission of these frames within a single network (subnet)

10010001001

Data Link

Frame

48Internet Standards

Data Link Layer Standards– For accessing the Internet from home ...

– Point-to-Point Protocol (PPP) dominates

– Only used between home and ISP!

– Low performance. Other subnets connecting routers are likely to use different subnet protocols!

ISPPPP

49Internet Standards

Physical Layer Standards– standardize connector plugs, transmission media,

electrical signaling, and other physical matters you can see and touch, even if they come from different vendors

– Work bit by bit. No frame organization.

50Internet Standards

Physical Layer Standards in Internet Access from Home– Telephone jack (RJ11)– Telephone wire– Serial port connection to external modem– Modem

SerialPort

External Modem TelephoneWire Wall Jack

51Internet Standards

Subnet Versus Internet Layer Standards– Internet layer provides routing across multiple subnets– Subnet layer standards (data link and physical) provide

for transmission within a single network

InternetLayer

Subnet Layer

52Internet Standards

Subnet Versus Internet Layer Standards– Internet layer provides routing across multiple subnets– Subnet layer standards (data link and physical) provide

for transmission within a single network

Analogy for Subnet versus Internet– Take a vacation– Route from beginning to end (like internet layer)– For different parts, may travel by car, airplane, or boat

(like subnet layer)

53Internet Standards

5-Layer Hybrid TCP/IP-OSI Framework

Use TCP/IP for Higher Layers, OSI for Subnets– Application– Transport– Internet– Data link– Physical

54Internet Standards

Accessing the WWW from Home

AppApp

TransTrans

IntInt

DLDL

PhyPhy

User PC

IntInt

DLDL

PhyPhy

Router

AppApp

TransTrans

IntInt

DLDL

PhyPhy

Webserver

HTTP

TCP

IP

PPP

Modem

IP

?

?

55Internet Standards

End-to-End Layers– Between peer processes on hosts

AppApp

TransTrans

IntInt

DLDL

PhyPhy

User PC

IntInt

DLDL

PhyPhy

Router

AppApp

TransTrans

IntInt

DLDL

PhyPhy

Webserver

HTTP

TCP

End-to-EndLayers

56Internet Standards

Communication Between Host and First Router

AppApp

TransTrans

IntInt

DLDL

PhyPhy

User PC

IntInt

DLDL

PhyPhy

FirstRouter

AppApp

TransTrans

IntInt

DLDL

PhyPhy

Webserver

IP

PPP

Modem

BetweenHost and

First Router

57Internet Standards

Other Connections– Router-Router and Router-Destination-Host– IP at internet layer– Subnet standard is unknown to user PC

IntInt

DLDL

PhyPhy

Next or LastRouter

AppApp

TransTrans

IntInt

DLDL

PhyPhy

Webserver

IP

?

?

IntInt

DLDL

PhyPhy

FirstRouter

IP

?

?

58Flexibility of Layering

Can Change Only One or Two Layer Standards for Different Application– Base Case: Accessing the WWW from home with a

V.90 modem

– Application HTTP– Transport TCP– Internet IP– Data Link PPP– Physical Serial Port, V.90 Modem,

telephone

59Flexibility of Layering

Can Change Only One or Two Layer Standards for Different Application

– New Case: Accessing a File Transfer Protocol (FTP) host from home with a V.90 modem

– Application FTP instead of HTTP– Transport TCP: No change– Internet IP: No change– Data Link PPP: No change– Physical Serial Port, V.90 Modem,

telephone:No change

60Flexibility of Layering

Can Change Only One or Two Layer Standards for Different Application– New Case: Accessing an POP mail host (see Ch. 7) from

home with a V.34 modem. Compared to Base Case:

– Application POP instead of HTTP– Transport TCP: No change– Internet IP: No change– Data Link PPP: No change– Physical Serial Port, V.34 modem instead

of V.90 modem, telephone

Part C:Platforms

The networking implications of the main computer platforms--file server program access, client/server processing, and mainframes--and of less common platforms

62PC Networks

The Most Common Platform in Organizations– Allows PCs to share resources– Both Wintel (Windows/Intel) PCs and Macintoshes

Network

63PC Network Components

Desktop Machines are Called Client PCs– The customers of services– Large networks have thousands of client PCs– ~$50 in hardware makes a stand-alone PC a client PC

Client PC

64PC Network Components

Servers Provide Services to Client PCs– Most PC networks have several servers– Large PC networks can have hundreds of servers

Service

ServerClient PC

65PC Network Components

File Servers– Store files (data files and programs)– The most common type of server in PC networks– Almost all file servers are themselves PCs

File Server

66File Server Program Access

The Most Common Way to Execute Programs in PC Networks– Program files are stored on the file server before

execution

File ServerClient PC

Storedon the

FileServer

67File Server Program Access

File Server Program Access– Program and data files are downloaded (copied) to the

Client PC– Executed on the client PC, not on the file server– File server merely stores programs and data files

File ServerClient PC

Downloaded toClient PC,Executed There

68File Server Program Access

PC Processing Power Limits FSPA Programs– Client PCs have slow processors, limited RAM– Can only execute small programs: WP, Email, etc.– This is especially true of older client PCs, which still

must be supported.

File ServerClient PC

Executed on theClient PC

69Client/Server Processing

Client and Server Machines– Neither has to be a PC– Platform independent

Client Machine Server

70Client/Server Processing

Two Programs– Client program on client machine– Server program on server machine– Work together to do the required processing

Client Machine Server

Client ProgramServer

Program

71Client/Server Processing

Division of Labor– Client program handles lighter user interface chores

and light processing chores

– Server program handles heavy work, such as database retrieval

Client Machine Server

Client ProgramServer

Program

72Client/Server Processing

Cooperation Through Message Exchange– Client program sends Request, such as a database

retrieval request

– Server program sends a Response message to deliver the requested information or an explanation for failure

Client Machine Server

Client ProgramServer

Program

Request

Response

73Client/Server Processing

Widely Used on the Internet

For instance, webservice– Client program (browser) sends an HTTP request (GET

command) asking for a webserver file

– Server program (webserver application program) sends an HTTP response message with the requested webpage

HTTP Request Message

HTTP Response Message

74Client/Server Processing

On the Internet, a Single Client Program--the Browser (also known as the client suite)--Works with Many Kinds of C/S server applications– WWW, E-mail, etc.

Browser

Webserver

E-mailServer

75Terminal-Host Systems

Created in the 1960s– Central host computer does all the processing– Terminal is dumb--only a remote screen and keyboard– Created in the 1960s, microprocessors for terminal

intelligence did not exist

Terminals Host

76Terminal-Host Systems

Sizes

– Mainframes are the largest business hosts Optimized for business uses--file access speed is more

crucial than mathematical processing

– Supercomputers are faster for intensive computations but not necessarily for business applications that have high file access needs

– Minicomputers are smaller hosts than mainframes

– Small business computers are minicomputers optimized for business use (file processing)

77Terminal-Host Systems

Many Mainframe Applications Were Created in the 1960s through 1980s– No longer cost effective

– Legacy systems--systems created by your predecessors

– Too expensive to rewrite all legacy applications at once

– Must live with many host legacy applications

– T-H transmission will be important for some years to come

– Mainframes are beginning to be used as very servers in client/server processing

78“Host” on the Internet

In terminal-host systems, a host is a central computer with many terminals

Originally, only such hosts connected to the Internet

By the time smaller computers, such as PCs, connected to the Internet, the term “host” had stuck

So now any computer connected to the Internet is called a host

79Program Functionality (Size)

File Server Program Access– Poor: many client PCs are small

Client/Server Processing– Good: not limited to client PC processing power– Heavy work can be done on the server machine

Terminal-Host Systems– Good: Hosts can be very large

80Scalability (Ability to Grow)

File Server Program Access– Poor: client PC sizes are limited

Client/Server Processing– Very good: Platform independence allows servers to be

larger than PCs– To grow, leave client machine the same, increase the size

of the server machine

Terminal-Host Systems– Excellent: hosts have an enormous range of processing

power

81Platform Independence

File Server Program Access– Poor: Only works with PC clients and PC file servers– OK for word processing, etc.– Unacceptable for large databases

Client/Server Processing– Excellent: use any server you want, also any client

Terminal-Host Systems– Poor: Hosts require terminals and only work with a few

terminal types

82User Interface

File Server Program Access– Very good: uses local PC processing power

Client/Server Processing– Very good: uses local PC processing power for user

interface

Terminal-Host System– Poor: Relies on distant hosts. User interface quality

limited by transmission costs. Monochrome, text-only screen. No animation

83Response Time (When User Hits a Key)

File Server Program Access– Very good: uses local PC processing power

Client/Server Processing– Very good: local PC processing power for user interface– But retrievals from the server can cause delays

Terminal-Host System– Poor: Relies on distant hosts. Long delays if overloaded.– Some systems use smart terminals with limited editing

capability to reduce response time for simple editing tasks only

84Less Common Platforms

Workstations– More powerful (and expensive) than PCs

– Do not use standard Intel PC microprocessors

– Usually run the UNIX operating system

– Client and server workstations

– Confusingly, Windows NT client operating system is called Windows NT Workstation, where workstation is synonymous with “client”

– Workstation servers are often used as client/server servers

85Less Common Platforms

Network Computers– Clients are simple machines without hard drives– Programs downloaded from NC servers as needed– Much like file server program access– But only run programs written in Java– Cannot run programs written for Windows

NC Java

86Less Common Platforms

Network Computers

– Originally offered to reduce costs

– Low-cost Wintel (Windows/Intel) machines are minimizing the cost advantages

– Use mostly in traditional terminal-host environments, providing more processing power than dumb terminals

87Less Common Platforms

Distributed Processing– Programs are small units called objects– Run on multiple machines (not just 2 as in C/S)– Coordinate by exchanging messages– Should be important in the future

Obj

Obj

Obj

Obj

Message

88Less Common Platforms

Information Appliances– Distributed processing pushed to its limits– Even coffeemakers may become intelligent– Small devices everywhere may coordinate with one

another

C.Standards Architectures

Beyond TCP/IP, to work with different platforms

90Standards Architectures

Standards Cannot be Created in Isolation– Must work together

to provide completeconnection betweentwo applicationprograms on differentcomputers, perhapson different networks

Application Standards

Transport Standards

Internet Standards

Data Link Standards

Physical Standards

91Standards Architecture

Begin With an Architecture (Framework)– General plan for dividing up the work of allowing

application programs to work together across a network– Defines individual layers– Defines how layers work together

Then Create Standards for Individual Layers

We Have Already Seen One Architecture: TCP/IP– Layers: application, transport, internet, subnet

92Standards Architectures

Usually, Multiple Standards at Each Layer– For instance, HTTP and e-mail standards at the

application layer

– To allow customization for individual application needs

– To allow new technology to be supported

– Inability of standards agencies to reach agreement

93Standards Architectures

Standards Agencies– Responsible for the standards architecture– In TCP/IP, this is the IETF (Internet Engineering Task

Force)

94TCP/IP

TCP/IP is the Dominant Architecture above the Subnet Layer

– Standards are simple Often even have “simple” in the standard’s name Simple standards are developed rapidly

– Simplicity also allows rapid product development

– Simplicity also allows products to be inexpensive and easy to implement

– “Fast to market and inexpensive” because of simplicity has led to TCP/IP’s dominance

95OSI

OSI (Reference Model of Open Systems Interconnection)– Open systems are those that are open to communicating

with all other systems

– “Reference model” is another name for “architecture”

96OSI Standards Agencies

ISO (International Organization for Standardization)– Traditional standards agency for industrial products

ITU-T (International Telecommunications Union-Telecommunications Standards Sector)– Traditional standards agency for telecommunications

Work Together because Networking Involves both Computers and communications

97OSI

TCP/IP versus OSI– OSI Has 7 Layers While TCP/IP Has 4

OSIApplication (7)Presentation (6)

Session (5)Transport (4)

Network (3)

Data Link (2)Physical (1)

TCP/IP

Application

Transport

Internet

Subnet

98OSI Application Layer (OSI Layer 7)

For Communication Between Specific Types of Application Programs– Email-Email– Database-Database

Not Widely Used– Sometimes simplified then adopted by IETF as a

TCP/IP standard

Similar to TCP/IP Application Layer– But not exactly the same

99OSI Presentation Layer (Layer 6)

For Standards Used in Multiple Applications– Standards for text formatting– Standards for graphics formatting– No need to create for each application

To Provide a Generalized Way to Represent Data– Abstract Syntax Notation 1 (ASN1)– Allows for exchanges between machines with different

ways of representing data

Nothing Like this in TCP/IP

100OSI Session Layer (OSI Layer 5)

Provides a Connection Between Application Programs on Different Machines– If the connection is broken, it can be reestablished

– In general, standards at this layer manage exchanges between application programs

TCP/IP Transport Layer Provides Some of this Functionality

Session (5)Transport (4)

Application

Transport

101OSI Transport Layer

Provides Connection Between Different Machines– Needed because machines may be of different platform

types

Similar to TCP/IP Transport Layer– But TCP/IP transport layer also provides some of the

functionality of the OSI Session layer

Session (5)Transport (4)

Application

Transport

102OSI Network Layer (OSI Layer 3)

The Most Difficult to Characterize

Originally Created for Subnets (Single Networks) that had a mesh of switches– Defined a route within a single mesh subnet

103OSI Network Layer (OSI Layer 3)

ISO and ITU-T “Forgot” to Have an Internetting Layer– Internetting--routing across subnets was later added to

Layer 3

So OSI Networking Layer is for BOTH Mesh Subnets AND for Routing Across Subnets– Inelegant

104OSI Network Layer (OSI Layer 3)

However, OSI Only Developed One Three-Layer Subnet Standard (X.25)– All subsequent subnet standards do not use Layer 3– Highest layer is Layer 2

So in practice, OSI Layer 3 is an Internetting Layer

Network (3)Data Link (2)Physical (1)

Internet

Subnet

105OSI Data Link and Physical Layers

We Saw These Earlier

Data Link Layer (OSI Layer 2)– Manages the transmission of frames across a single link

Physical Layer (OSI Layer 2)– For physical and electrical standards within a single

link– Works bit-by-bit

Data Link (2)Physical (1)

Subnet

106OSI Subnet Dominance

OSI Standards are Dominant for Subnet Transmission– Local Area Networks (LANs)– Wide Area Networks (WANs)– TCP/IP Does Not Challenge that Dominance

IETF Generally Does Not Create Subnet Standards for TCP/IP– If it does (as in the case of the Point-to-Point protocol,

by the way), it follows the OSI architecture

107Hybrid TCP/IP-OSI Architecture

As Noted Earlier, Most Firms Today Use a Hybrid TCP/IP-OSI Architecture for Most of their Internal Communication

Application TCP/IP

Transport TCP/IP

Internet TCP/IP

Data Link OSI

Physical OSI

108SNA

Systems Network Architecture– Another Standards Architecture

Proprietary– Controlled by IBM– However, IBM shares specifications, so most mainframe

systems from all vendors use SNA or a variant

Dominant for Mainframe Communication– Still accounts for a very large part of long-distance data

traffic

109IPX/SPX

Created by Novell– For NetWare PC network software

– Novell dominated PC networking for years

– So IPX/SPX is still widely used in PC networking with Novell NetWare servers

– Even Novell is switching to TCP/IP

– However, many PC networks have not converted their Novell servers and clients to TCP/IP

– Must be considered in PC networking

110Recap

Trends in Networking and its Impacts

Standards for WWW Access from Home to Introduce Basic Networking Principles

Popular Computer Platforms Found in Networked Environments

Standards Architectures that Tend to Differ by Platform

The Dominant TCP/IP-OSI Hybrid Architecture