Mc nurlin 05

Distributed Systems: The Overall Architecture

Chapter 5Information Systems Management In

Practice 7EMcNurlin & Sprague

PowerPoints prepared by Michael MatthewVisiting Lecturer, GACC, Macquarie University – Sydney Australia

©2006 Barbara C. McNurlin. Published by Pearson Education. 5-2

Part II – Managing the Essential Technologies - Next Few Chapters

• Part II – Chapters 5 through 8– Focuses on infrastructure management (Figure P2-1)

• Purpose– Present the technological underpinnings of a corporate IS

function and – Point out the issues that must be addressed for it to be well

managed• Chapters 5 & 6 deal with the structure of distributed systems

– Chapter 5 = various kinds of distributed systems architectures• IT Architecture and Infrastructure

– Chapter 6 = Telecommunications• Chapter 7 = ‘Content’ or Information Resources

– Data• Chapter 8 = Operations

– Day-to-Day concerns of keeping systems, networks etc. up and running



Chapter 5• This lecture / chapter

– Describes seven types of distributed systems– Defines the overall IT architecture and – Discusses the importance of IT infrastructure

• Case examples include Northwest Airlines, an aerospace company, Chubb & Son Insurance Company, The SABRE Group, 3i, General Motors, FMC Corporation, Credit Suisse and the City of Sunnyvale


Today’s Lecture• Introduction

– Four Attributes of Distributed Systems– When to Distribute Computing Responsibilities– Two Guiding Frameworks

• Seven Types of Distributed Systems– Host-Based Hierarchy– Decentralized Stand-Alone Systems– Peer-to-Peer LAN-Based Systems– Hybrid Enterprise wide Systems– Client-Server Systems– Internet-Based Computing– Web Services


Today’s Lecture cont.

• Defining The Overall IT Architecture– An Enterprise Architecture Framework– The ‘Coming Architecture’: Service-Oriented

Architecture

• The Importance of the IT Infrastructure– The Structure of the IT Infrastructure– Three Views of Infrastructure


Introduction - Definitions• An IT architecture is a blueprint. A blueprint shows how a

system, house, vehicle, or product will look and how the parts interrelate

• An IT infrastructure is the implementation of an architecture. The IT infrastructure includes the processors, software, databases, electronic links, and data centers as well as the standards that ensure the components work together, the skills for managing the operation etc.

• Lately = rather than talk about hardware, software, data, communications etc. as the components of computing, some people now refer only to applications and infrastructure


Introduction – The Evolution of Distributed Systems

• First IT architecture = mainframes (batch processing) with dumb terminals (no processing capabilities)

• With minicomputers = moved into departments but the ‘master-slave’ computing model persisted. Processing was mainly centralized

• Microcomputer = model changed significantly because processing power moved first onto desktops, then into briefcases and now into pockets

• Now = ‘interesting twist’: Power returning to a type of centralized processing with networks of servers and the Internet– Information appliances and diskless computers (‘thin clients’) make

requests– More important in the future as Web Services continues to develop


Four Attributes of Distributed Systems

Degree to which a system is distributed can be determined by answering four questions:

1. Where is the processing done? 2. How are the processors and other devices

interconnected?3. Where is the information stored?4. What rules or standards are used?


Attributes of Distributed Systems:1. Where is the processing done?

• Distributed processing is the ability for more than one interconnected processor to be operating at the same time, typically for processing an application on more than one computer at a time • Goal: move the appropriate processing as close to the user as possible and to let other machines handle the work they do best • Permits interoperability-capability of different computers using different O.S. on different networks to work together on tasks • Two forms of interoperability (capability for different machines to work together on tasks):

– communication between systems– two-way flow between user applications


• Connectivity among processors means that each processor in a distributed system can send data and messages to any other processor through electronic communication links

• Desirable to have at least two independent paths between two nodes to provide automatic alternate routing (Planned Redundancy)

Attributes of Distributed Systems: 2. How are the processors and other devices interconnected?


• Distributed databases either:– Divide a database and distribute its

portions throughout a system without duplicating the data

• Users do not need to know where a piece of data is located to access it, because the system knows where all the data is stored

– Store the same data at several different locations, with one site containing the master file

• Issue: synchronization of data is a significant problem

Attributes of Distributed Systems: 3. Where is the information stored?


• System wide rules mean that an operating discipline for the distributed system has been developed and is enforced at all times

• These rules govern communication between nodes, security, data accessibility, program and file transfers, and common operating procedures

• Since the 1990s = “Open systems” concept-mix products from vendors using open standards. Based on “open-systems” - standardized interfaces that allow products to inter-operate across multi-vendor networks, operating systems and databases

• Now = also API’s - Application Program Interfaces: define the way to present data to another system component. Makes writing distributed systems much easier

Attributes of Distributed Systems:4. What rules or standards are used?


When to Distribute Computing Responsibilities

• IS management needs a corporate policy for deciding when the development, operation and maintenance of an application should be distributed

• Individual end users and departments should not be left on their own to make such decisions, especially where enterprise connectivity is important


When to Distribute Computing Responsibilities cont.

Systems responsibilities can be distributed unless the following are true:

1. Are the operations interdependent? – When it is important that one operation knows what other is doing;

their planning, development, resources, and operations must be centralized

2. Are the businesses really homogenous? – If they have a lot in common; e.g., IT needs for a fast-food

franchise: processing may be distributed, but planning and hardware selection should be centralized

3. Does the corporate culture support decentralization? – Even if the business units do quite different things and don’t need

to know what each other is doing, corporate culture (management control?) might still centralize finance, HR, and systems planning


Two Guiding Frameworks 1. An Organizational Framework

• A driving force behind distributed processing is to give people more control over their work. This autonomy can happen at any of seven levels:

1. Business ecosystem or value chain (inter-enterprise)2. Enterprise 3. Country or region4. Site (plants, warehouses, branch offices)5. Department or process 6. Work group or team7. Individuals


Two Guiding Frameworks for DS: 1. An Organizational Framework

• Locate processing power and DB at each level in the organization

• Top level deals with organizations that work closely together as buyer-seller, partner etc.

• Next three levels (Enterprise, Region and Site) are traditional domain of IS, where computers resided in the past.

• Bottom three levels (Department, Team and Individual) are where the bulk of employees are

• Intent: give autonomy and decision-making power to better serve customers



• Migration of computer power to end users will be driving force for network-based IS. SUMURU - single user, multiple user, remote utility.

1. Processors:• SU: single user, stand-alone and connected to LNs;

clients• MU: multiple user, serve local groups of users;

server. Also heavy duty computation for SUs, backups for MUs, program libraries for SUs, and database management.

• RU: remote utility, heavy-duty computing, corporate DB management, corporation mainframes and value-added network services

Two Guiding Frameworks for DS: 2. A Technical Framework


2. Networks:• LN: local networks, high-speed

information transfer, LAN• RN: remote networks, lower transfer

speeds, WAN, MAN, Internet

Two Guiding Frameworks for DS: 2. Technical cont.


3. Services that this network architecture provides:• access• file transfer• e-mail

4. Standards needed in three areas: • OS • communication protocols: TCP/IP • DBMS: SQL

Two Guiding Frameworks for DS:Technical cont.




Seven Types of Distributed Systems:1. Host-Based Hierarchy

• See Figure 5-4

• A central, controlling mainframe at the top, PCs at the bottom, minicomputers in between• Master/slave• First data processing distributed system. Host computer central, controlling component; terminals are access systems• Where is the data stored?:

– Could be at any level



Types of Distributed Systems: 2. Decentralized Stand-Alone Systems

See Figure 5-5

• Decentralized but does not really form a distributed system• ‘Holdover’ from the past where departments put in their own minicomputers with no intention of connecting them to the corporate host or to other departmental systems

– Still a valid method for some companies • Many such “islands of computing”:

– Little data flow amongst, except upward to corporate systems

• A major goal in introducing ERP systems was to replace such disparate systems – in finance, manufacturing, administration – with a single platform of inter-connectable modules to serve these various functions



• See Figure 5-6

• No hierarchy• “Peer-to-peer” communications• Interconnecting LANs rather than hierarchical communications through a central hub • No “superior” computer

Types of Distributed Systems:3. Peer-to-Peer LAN-Based Systems



• See Figure 5-7

• Combination hierarchy (mainframe-based, favored for corporate computing) and LAN-based (favored by departments)• Connected via WANs etc. • The structure of choice for many years• Allows company to link “automation islands” and retain IT investments, begin to automate business processes (cooperative processing)

• Such cooperating processes allow companies to take advantage of specialized computer programs, while at the same time extending the usefulness of some legacy systems

– The process of pulling together such individual applications or components is called systems integration

Types of Distributed Systems: 4. Hybrid Enterprisewide Systems



• Northwest Airlines built a distributed passenger revenue accounting system with products from eleven vendors and just about as many different technologies:– Expert systems– Imaging– Relational databases– High-resolution workstations– Servers, and – LANs

NORTHWEST AIRLINESCase example: Hybrid Enterprisewide Systems and Systems Integration


• Purpose: improve revenue estimate accuracy by ‘auditing’ all the redeemed tickets (few airlines did this)

• Developed with Accenture (Andersen Consulting) BIG $$$

• The system integrates products from 11 vendors– Uses a cooperative processing architecture and – Integrates expert systems, image processing, relational

databases, high resolution UNIX workstations, servers, and LANs

NORTHWEST AIRLINESCase example: Hybrid Enterprisewide Systems and Systems Integration cont.


Read the case for:• Managements goals

– Reasons for investing BIG $ in ‘new’ systems and infrastructure• Enforcing of rules• $$$

• The Distributed Architecture– Mainframe, WANs, LANs etc.– Data communication = integral– Image processing

• Revenue Accounting Process



Lessons learned:• Benchmark and prototype new technologies to verify

vendors’ claims• An open architecture works on mission-critical

applications• Large distributed system projects need a vendor

coordinator• Use of CASE was mandatory

Huge system (65,000 workdays) which became a ‘model’ for airlines



• The ’90s version of distributed systems• Arose to take advantage of the processing capabilities of both host machines and PCs in the same system • Splits the computing workload between the client, which is a computer used by the user and can sit on the desktop or be carried around (e.g. WAP mobile phone), and the server, which answers the request

Types of Distributed Systems:5. Client-Server Systems


• Figure 5-8 shows the possibilities for splitting work between clients and servers. Three components being split are:– Presentation software: what user sees (P)– Application software (A)– Data (D)

• Distributed presentation• Remote presentation• Distributed application function• Remote data management• Distributed database(s)

Types of Distributed Systems:5. Client-Server Systems cont.



Another way to look at it = to view their architecture– Preferred: three-tier architecture (see Fig.5-9):

• Tier 3: the superserver/mainframe. Allows inclusion of legacy applications, short-lived and fast-changing data, and integrity rules

• Tier 2: specialized servers, dedicated to housing databases or middleware-software to ease connection between client and server. Also, department-specific data that does not change often

• Tier 1: clients (some of which could be portable) connected through network




• Systems group’s goal = never build monolithic applications again

• Builds client-server systems with:– Application code on the clients– Data on the servers– Communication middleware software shared– Object oriented technology, most from a library

• Data = at the heart of the architecture is a repository which allows the reuse of objects

AN AEROSPACE COMPANYCase example: Client-Server Systems



• Network = integral part of the architecture. Each company site has three components:

– Desktop machines– Servers– One or more site hubs

• Architecture = ‘remote data management’. Data resides on servers and applications reside on clients

• Company uses the distribution function and remote data management because they minimize total costs

AN AEROSPACE COMPANYCase example: Client-Server Systems cont.


• Benefits of Client-Server Computing:– Better access to information:

• Improved customer service– Ability to communicate customer needs, and – Anticipate customer needs.

• Reduce cycle times and • Allow companies to compete better.

– Empowered employees: • Blend autonomy of PCs with system wide rules

and connectivity of traditional IS• Shifts focus of computing to users



• Benefits of Client-Server Computing (cont.):– Increases organizational flexibility:

• allows new technology to be added more easily without affecting rest of system

• streamlines work flow between functional areas • encourages people to work together via networks• Supports new organizational structures via its connectivity

• Drawbacks: – Not lower in cost than mainframes because they entail so much

coordination– Easier for users, far more complex for IS (drawback?)– What looked like simple connections have turned into large, often

fragile, complex systems



• In the late 1990s, the client-server trend was ‘interrupted’ (augmented?) by the ‘Internet’

• Model of a distributed system includes the Internet (heart?)

• The tenets of client-server remain

• Network-centric computing = a computer and a cloud (Figure 5-11)

Types of Distributed Systems:6. Internet-Based Computing



• Network computers have (had?) not taken off (desktops) but the concept of utilizing programs off the Internet has

– ‘Network’ computers (thin clients, toasters etc.) now = coming into their own!

– Thin clients = logical for hand held but now = increasingly popular for the ‘desktop’ Updating new versions of software Authorized software (firm and purchased) ‘One copy’ of software

Types of Distributed Systems:6. Internet-Based Computing cont.


• The company took advantage of the Internet by converting their legacy cargo certificate issuance system to a Java-based extranet application

• It has also done the same with other applications

• All the apps feed into Chubb’s mainframe but have a Java-based Web front end so that client machines only need access to the Web to perform the application

CHUBB & SON INSURANCE COMPANYCase example: Internet-Based Computing


• This airline reservation company is working with Nokia (the handheld phone manufacturer) to create a real-time, interactive travel service delivered via mobile phone

• The service draws on SABRE’s online corporate travel purchasing system and Nokia’s server (which transmits the travel information to a wireless network and to its Internet-enabled phones)

• Qantas etc. also have and doesn’t need to be web-enabled mobiles e.g. text messaging

THE SABRE GROUPCase example: Internet-Based Computing


Server-Based Computing• With more use of laptops which do not have strong

security features– Updating en masse is not easy– Even individual downloads can require helpdesk support

• Solution = server based computing– Applications reside on corporate servers rather than on laptops– Applications can be securely accessed by any device, they can

be updated directly on the server, and they do not have to be tailored to run on specific machines



• UK based venture capital firm• Needed to give its investment professionals

anytime-anywhere access to its systems

• Remote employees dial in (secure modem)• Using Windows terminal server software and

Citrix software = the create a ‘virtual office’ for themselves

3iCase example: Server-Based Computing (mobile)


Peer-to-Peer Computing

• This form of Internet computing distributes a task over a wide number of computers (peers) connected to the Internet

• This grassroots movement, like the open source movement, is now taken seriously by some corporations. It became famous with Napster, the music swapping P2P network

• The main issue now is how to make money in this environment. One answer: subscriptions, where people pay for access rather than for ownership



Types of Distributed Systems:7. Web Services This second-generation Internet-based distributed

system gives software modules URLs (Internet addresses) so they can be called upon to perform their function as a service via the Internet

This development will permit widespread computer-to-computer use of the Internet. One computer program or Web Service makes a request of another Web Service to perform its task (or set of tasks) and pass back the answer


Types of Distributed Systems:7. Web Services cont.

• Hot topic (the future?):1. Next generation of distributed systems (big!)2. Makes the Internet the hub of computing3. Permits flexible systems not possible before4. Releases companies from ‘building’ and maintaining

systems ‘in house’5. Will draw on existing systems

• Wrapping – encapsulate functionality from an existing application in an XML envelope

• Exposing – for use by others

• The promises go on! And the vying for position!



• Web Services Standards:– Three software standards:

XML (eXtensible Markup Language) WSDL (Web Services Definition Standard) UDDI (Universal Discovery, Description, and

Integration– Three communication standards

SOAP (Simple Object Access Protocol) HTTP (HyperText Transfer Protocol) TCP/IP (Transmission Control Protocol /

Internet Protocol)



• Significance of Web Services– Viewing IS as proprietary has led to rigid

business processes, which are slow to change and respond to market changes

– Web Services offers an IT architecture based on the openness of the Internet. Rather than build proprietary systems, companies can obtain the functionality they need from the Internet

• This modularity permits handling a huge variety of possibilities by mixing and matching, and allows easier cross-company system linking

• Companies thus only pay for the functionality they use when they use it, which reduces the number of IT assets companies need to house and maintain


GENERAL MOTORSCase Example: Web Services• One GM executive believes that the Web

Services architecture could be used to move GM from its supply-driven, build-to-stock business model to a demand-driven, build-to-order business model – an otherwise impossible feat

• To begin, GM first enhanced its supply-driven model by offering new functions via a Web Services architecture

• One Web Service is a locate-to-order service that dealers can use to easily find a specific car a customer might want in the inventory of other GM dealers


GENERAL MOTORSCase Example: Web Services cont.

• Another Web Service is order-to-delivery which shortens the time to deliver a custom-ordered vehicle– Paving the way to eventually convert to a

make to order business model• The ‘Rewards’?:

– Cut its $25B inventory in half– Potentially shave $1,000 off the cost of

each vehicle


Defining the Overall IT Architecture

• The intent of an IT architecture is to bring order to the otherwise chaotic world of information systems by defining a set of guidelines and standards, and then adhering to them

• Because the architecture needs to support how the company operates, it reflects the business strategy

• Furthermore = as business changes, the architecture needs to keep pace

• Chief Technology Officer


An Enterprise Architecture Framework

• To describe the IS architecture, look at the roles people and components play (5th edition Fig.5-12):– Rows: Views must be taken into account when

building complex products: • planner (scope statement) • owner (model of the enterprise) • designer (model of the information system)• builder (technology model)• subcontractor (description of the components)• user (functioning system)



An Enterprise Architecture Framework cont.

• Columns: • IS components:

– Data models (what it is made of)– Functional models (how it works)– Network models (where the components are located)– Represent physical manifestations of the system.

• Also: – People (who)– Time (when)– Motivation (why)

• Use of the framework: When IS users bring in a package that follows a data model inconsistent with the rules of the company, a lot will be spent fixing the package.

• Figure 5-13 - the ‘whole’ picture



FMC CORPORATIONCase Example: IT Architecture Development• When FMC split in two, it designed two new IT

architectures• The architecture and technology director led five

teams – for data, applications, integration, desktop, and platform

• Each created a today architecture, a tomorrow architecture, and the “next minute” steps

• The companies have now split and the tomorrow architecture has given FMC a standard that everyone agrees with, making standard-setting far easier

• Now it is working on a new tomorrow architecture, for 2004-2005, when voice-over IP and Web Services kick in


THE SABRE SYSTEMCase Example: IT Architecture• When they looked at the underlying databases

– Customer profiles, AAdvantage, NetSAAver– = found heaps of data redundancy (common!) leading to a

huge redesign– American consolidated and linked these databases to have

just one profile for each flyer

• The architecture underlying American Airline’s Website is now modular– The existing SABRE computer reservation system serves as

“the reservation service” module – Other modules perform the functions related to the Web

• Due to this component-based architecture, it was fairly easy to add new functions


The Coming Architecture:Service–Oriented Architecture• Importance of an architecture is that it spells out the

relationships between the components of an airplane, building, system etc.

• In the past with IS these interactions have been ‘hard-coded’ point-to-point– Efficient but costly to maintain– Changing one component might require changing the others that

interact with it

• Relatively new system architecture moves away from this = Service Oriented Architecture (SOA)– Emergence parallels Web Services – uses the same architectural

concept– Thinks about how to expose the data and functions in a way that

other systems can easily use

• Holy Grail? Which has long eluded IS organizations and addresses the need to be more agile


CREDIT SUISSECase example: Service Oriented Architecture

• Large Swiss global financial services company– Pioneering the implementation of SOA– Old = depended on proprietary middleware

• Maintenance = increasingly expensive– Revamped its IT infrastructure to be a SOA by implementing

two “information buses”• Service bus

– Takes a request-reply approach– Integrates front-end and back-end applications (Figure 5-14)

• Event bus– Integrates the back-end systems– Also uses SOA but it uses a supply-push mode of operation using

publish and subscribe• When an event occurs in one system it is “published”• All of the systems that need to know about the event are

“subscribed” and are notified (update is pushed to them)



IT infrastructure is the foundation of an enterprise’s IT portfolio:

• Provides the capability for reliable services and sharing

• Includes both the technical and managerial expertise required to provide these services

• Is linked to external industry infrastructure– Banking payments, airline reservations etc.

The IT Infrastructure- What is an IT Infrastructure?


• Shared characteristics differentiate an infrastructure from IT investments used by just one function

• Elements can include:– Company-wide networks– Data warehouses– Large scale computing facilities– EDI capabilities

• Applications ‘sit on top’ and directly support the business Vs. infrastructure ‘indirect’ support

The IT Infrastructure- What is an IT Infrastructure? cont.


• Infrastructure investments are a vital part of corporate information systems portfolios

• Yet they are the most difficult to cost-justify initially and to quantify benefits afterwards

The Importance of IT Infrastructure


• The IT infrastructure is the shared and reliable services that provide the foundation for the enterprise IT portfolio. IT infrastructure is very similar to public infrastructure; on top of an IT infrastructure sit applications that perform a business’s processes. – The bottom of four layers consists of technology components, such as

computers and database management system packages. – The third layer is the human IT infrastructure layer, which translates the

components (which technologists can understand) into services (which business users can understand).

– The second layer is shared IT services, which present the infrastructure as a set of services that users can draw upon and share to conduct business.

– The top layer is the shared and standard applications layer, which includes

stable applications (such as accounting and HR)

The Importance of IT Infrastructure- The Structure of the IT Infrastructure




• Similar to public infrastructure:– Roads– Hospitals– Sewers– Schools– etc.

• Everyone wants but no-one wants to ‘pay’• Provided by a ‘central authority’

– Government or IT Department– Delicate and ‘difficult’ investment balance

The Importance of IT Infrastructure- Similar to Public Infrastructure


IT investments can provide:1. Economies of scale (utility):

– Infrastructure cost as an administrative expense– Minimize expense– Outsourcing may be viewed favorably because the IT

infrastructure is not seen as strategic2. Support for business programs (dependent):

– Infrastructure treated as business expense– Measured by short-term business benefits– Infrastructure planning in current business plan– Network = critical

Three views of Infrastructure


3. Flexibility to meet changes in the marketplace (enabling):

– Primary benefit long-term flexibility– Intended to provide the foundation for

changing direction in the future– IT cost seen as business investment

Three views of Infrastructure cont.


• Director of IT hired to “move the city into the future”

• First = get its house into order – “capturing accurate information and delivering that information in a timely manner”

• Provides connectivity between the city’s myriad of IT facilities: mainframes, LANs, WANs, PCs etc.

• Like a foundation for a home

– Able to withstand all the weight, noise and “things you want to plug into it”

• Infrastructure investments are paid through chargeback

• “Super” rules guide technology investments

CITY OF SUNNYVALE, CALIFORNIACase example: Investing in Infrastructure


Conclusion• Distributing processing, databases, and

communications allow companies to move more quickly because they can more easily “snap in” new products and services into their existing systems

• The advent of Web Services is fueling the use of the Internet to extend the tenets of distributed systems even further


Conclusion cont.

• Distributed systems dominate the computing environment– They create an enterprise architecture to cope

with complexity of change

• IT infrastructures should provide the platform for allowing interconnection and organizational flexibility– Very challenging for CIOs, CEOs etc.

• Infrastructure is difficult to change BUT is important to organizational success– Need to make the ‘right’ decisions