Distributed Systems: The Overall Architecture

1. Distributed Systems: The Overall Architecture Chapter 5 Information Systems Management In Practice 7E McNurlin & Sprague PowerPoints prepared by Michael Matthew Visiting Lecturer, GACC, Macquarie University – Sydney Australia

2. Part II – Managing the EssentialTechnologies- 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. Four Attributes of Distributed Systems Degree to which a system is distributed can be determined by answering four questions: • Where is the processing done? • How are the processors and other devices interconnected? • Where is the information stored? • What rules or standards are used?

10. 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

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

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

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

14. 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

15. When to Distribute Computing Responsibilities cont. Systems responsibilities can be distributed unless the following are true: • 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 • 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 • 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

16. Two Guiding Frameworks1. 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: • Business ecosystem or value chain (inter-enterprise) • Enterprise • Country or region • Site (plants, warehouses, branch offices) • Department or process • Work group or team • Individuals

17. 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

19. Two Guiding Frameworks for DS: 2. A Technical Framework • Migration of computer power to end users will be driving force for network-based IS. SUMURU - single user, multiple user, remote utility. • 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

20. Two Guiding Frameworks for DS: 2. Technical cont. • Networks: • LN: local networks, high-speed information transfer, LAN • RN: remote networks, lower transfer speeds, WAN, MAN, Internet

21. Two Guiding Frameworks for DS:Technical cont. • Services that this network architecture provides: • access • file transfer • e-mail • Standards needed in three areas: • OS • communication protocols: TCP/IP • DBMS: SQL

24. 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

26. 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

28. Types of Distributed Systems:3. Peer-to-Peer LAN-Based Systems • See Figure 5-6 • No hierarchy • “Peer-to-peer” communications • Interconnecting LANs rather than hierarchical communications through a central hub • No “superior” computer

30. Types of Distributed Systems: 4. Hybrid Enterprisewide 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

32. NORTHWEST AIRLINES Case example: Hybrid Enterprisewide Systems and Systems Integration • 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

33. NORTHWEST AIRLINES Case example: Hybrid Enterprisewide Systems and Systems Integration cont. • 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

34. NORTHWEST AIRLINES Case 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

35. NORTHWEST AIRLINES Case example: Hybrid Enterprisewide Systems and Systems Integration cont. 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

36. Types of Distributed Systems:5. Client-Server Systems • 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

37. Types of Distributed Systems:5. Client-Server Systems cont. • 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)

39. 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

41. AN AEROSPACE COMPANY Case example: Client-Server Systems • 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

43. AN AEROSPACE COMPANY Case example: Client-Server Systems cont. • 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

44. Types of Distributed Systems:5. 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

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

46. Types of Distributed Systems:6. Internet-Based Computing • 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)

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

49. CHUBB & SON INSURANCE COMPANY Case example: Internet-Based Computing • 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

50. THE SABRE GROUP Case 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