Business Data Communications and Networking--8 th Edition

1. Business Data Communications and Networking--8th Edition FitzGerald and Dennis

2. Computer NetworkingINSY-4304 Dr. R. Dash, Ph. D; Ph. D. MS, MSE, MSCSE INSY-Department

3. Physical Layer--Network Architectures-- ---Devices and Circuits--- Chapter-3A

4. Objectives of Chapter-3A Understand: • the difference between types of network architectures: • HB-NWA—Host-based NWA • CB-NWA—Client-based NWA • CS-NWA—Client-server NWA • the different types of networks circuits, • how multiplexing works. Become familiar with: • different types of servers and clients, • different media, • front end processors.

5. INTRODUCTION

6. 3-Basic Building Blocks---that make up a network--- • 1. Networking Hardware—aka—NW’s HW: • Computers, Cables, Modem • NW-Boards, HW-components • Connection Hardware, Printers, Plotters • 2. Networking Software—aka—NW’s SW: • NOS, Drivers, Client-SW • Communications Protocols • 3. Communication Protocols: • Transport Layer Protocols • Network Layer Protocols • Data Link Layer Protocols

7. #1---Networking Hardware • NW-Cabling: • Physical Cables—TPC, Coax, Fiber, HFC--Cop • Wireless Connection—thru air or vacuum. • NW-Components: • Client/Server computers, PCs/Workstations • Tape back-up System, Storage Devices • Printers, Plotters, Adapters, NW-boards • Hard-disk Tape-drives, CD-ROM Drive • NW-Connection-Hardware: • Connectors, Terminators, Hubs, Repeaters • Bridges, Switches, Routers, Brouters, Gateways

8. #2---Networking Software • NOS = Network Operating System • Windows—95/98/2000—CE/ME/NT/XP • SUN-OS, UNIX, LINUX, OS-400 • Mac-OS, Palm-OS, Novell Netware • Client-Software:—These are the software that reside in a user’s desktop or laptop computer. • Server-Software: • Software that resides in a server and provides services to multiple users on the network—Ex—Print Server, Mail Server, Web Server, Fax Servers, Appln Server. • Drivers • Small SW-programs and HW-devices that provide signals or electrical current to activate a transmission line and display screen pixels.

9. #3--NW’s Communication Protocols • Primarily 3-Types of NWC-Protocols: • Transport Layer Protocols—TCP, SPX, UDP—deal with packetizing—end-to-end connection---reliable delivery. • Network Layer Protocols—IP, IPX, AppleTalk—deal with the tracking of HW and network addresses—and establish traffic routing between receivers & transmitters. • Data Link Layer Protocols—Ethernet, Token Ring, AppleTalk, FDDI—create/transmit/receive data packets for the particular NWA—network architecture. • Protocols—set of rules/guidelines that control the processing and communication—regulate as to how all of the NW’s components communicate with each other. • NWC = Network Communications

10. Introduction • There are 6-fundamental hardware and software-- components in a data communications-NW. • The client computers • The servers or host computers • Network circuits/cabling that connect them • NIC = Network Interface Card • NOS = Network Operating System (Software) • Network Communication Devices • (hubs/routers/modem/gateway/switches, etc) • (NOS = Network Operating SW/System)

11. 5-Types of Computers • Laptop Computers: • It’s a portable computer having a flat screen and weighing less than a few pounds. • Microcomputers: • Are the type of computers we use (Cost--up to 50K) • Minicomputers: • Large general purpose computers(C--up to 100s of K) • Mainframe computers: • Are very large general purpose computers • Costs up to millions of dollars! • Clusters (of computer): • Is a group of computers linked together so that they can work and act together as one computer.

12. 5-Types of Client Computers • Microcomputer---are the ones that we use. • Terminal Device---has monitor and keyboard • Dumb terminal---does not do processing • Intelligent terminal—does some processing • Workstation—powerful microcomputers • Deals with—CAD, CAM, CAE, CASE, CANE, ICANE • Network Computer—Communicates using the Internet-based standards (like, HTTP). • Transaction Terminal—used for business transaction, such as: • ATM used by the banks • Point-of-sale terminals used in the supermarkets and big stores, such as—Wal-Mart, JCPenny, Kroger, etc.

13. Types of Server Computers Server—is defined as a computer or network device that manages the network resources: • File server, Print server, Terminal Server • Fax server, Logon server, Modem Server • News server, Proxy server, NW-Access Server • Communications server, Telephony Server • FTP-server, Audio-and-video server • Application server, database server • Web server, E-Mail server, Telnet server • Intranet Server, Merchant Server, Security server • Domain Name Server, News Group Server

14. NETWORK ARCHITECTURES

15. Architecture—Infrastructure • NW-Architecture: • It is the scientific art of making the structure express ideas—It is the style and method of design and also construction—It is the art and science of designing and erecting buildings—structures. • NW-Infrastructure: • It represents an underlying base or foundation—especially for an organization—provides the basic facilities, equipments and installations needed for the functioning of the system. • NW-Configuration: • Represents the structural arrangement of parts and the elements—represents the contour.

16. Network Architecture • NWA = Network Architecture: • Represents the design of a NW-Communications-SW. • It includes—HW, SW, Protocols and Access Methods. • It refers to a model—design—blueprint—that encompasses an entire computer environment. • The NWA-classification depends on the scope of discussion. • Access Methods (some examples): • Ethernet, Token Ring, ATM, FDDI, AppleTalk • IBM’s SNA (Systems-NWA), DEC’s DNA; • ---DEC = Digital Equipment Corp; • ---DNA = Distributed-NWA

17. NWA = Network Architectures • Traditional Network Architectures: • 1. HB-NWA—Host-based NWA • 2. CB-NWA—Client-based NWA • 3. CS-NWA—Client-Server NWA • 2-Tiered CS—NWA—aka---Single Server NWA • 3—4--tiered CS-NWA—aka---Multi-Server NWA • Multi-server NWA—aka---Enterprise-NWA • Advanced Network Architectures: • 4. PP-NWA—Peer-to-Peer NWA • 5. HY-NWA—Hybrid NWA

18. Traditional Network Architectures The 3-traditional, fundamental, network architectures---based on the 4-different application software/programs: • 1. HB-NWA = Host-Based NWA:—e host computer performs virtually all of the work • 2. CB-NWA = Client-Based NWA:—the client computer performs virtually---almost all of the work • 3. CS-NWA = Client-Server NWA:—the work is shared between the hosts and clients

19. Traditional Network Architectures • The work done by any application program can be divided into 4-general functions—aka—four Application-layer SW. • The Network Architecture classification is based on these—4-general functions—aka—four Application-layer SW. • Application SW—Programs do 4-things: • DS = data storage • DAL = data access logic • AL = application logic • PL = presentation logic

20. Traditional Network Architectures

21. Traditional Host-Based NWA • The very first data communications networks were host-based, with the host computer performing all four functions. • The clients enabled users to send and receive messages to and from the host computer. • This very simple architecture often works very well. Application software is developed and stored on one computer and all data are on the same computer.

22. Hosts and Clients • 4-Types of Hosts—one that provides service • Microcomputers (desktop/laptop) • Minicomputers, • Mainframe computers • Clusters of Computers • 5-Types of Client computers: ------an (input/output)-HW-device------ • Microcomputers, Terminal Devices • Workstations, NW-Computers • Transaction Terminals (Special-purpose terminals)

23. Network Definitions • Client—is a computer connected to the network that accesses services from the server. • Peer—is a computer that uses and provides resources to the network. • Peer—to—Peer Network—all computers in the network provide similar services including server functions. • Client—Server Network—server handles multiple requests from multiple clients for multiple services.

24. 1.Traditional Host-Based NWA

25. 1.Traditional Host-Based NWA • In the case of the HB-NWA, the host must process all messages and all functions. • The host will perform all the 4-general functions done by any application SW—program: • DS = Data Storage • AL = Application Logic • PL = Presentation Logic • DAL = Data Access Logic • In the late 1970s and early 1980s, intelligent terminals were developed that could perform some of the presentation function.

26. 2. Traditional Client-Based NWA • In the late 1980s, there was an explosion in the use of microcomputers and microcomputer-based local area networks. • Part of this expansion was fueled by a number of low-cost, highly popular computer-applications programs such as: • E-mail, Web, FTP, Telnet • Word Processors, Spreadsheets • Excel, Graphics, IM (Instant Messaging) • IRC—Internet Relay Chatting • Banking terminal programs and • Presentation graphics programs.

27. 2.Traditional Client-Based NWA • With client-based architectures, the clients are microcomputers on a local area network, and the host computer is a server on the same network. • Client deals with: PL, AL and DAL • Host/server deals with: DS= data storage • PCs and Workstations are connected to the host/server by high-speed LANs. • This simple architecture often works well. However, as the demands for more and more network applications grow, the network circuits can become overloaded.

28. 2. Traditional Client-Based NWA

29. 3.Traditional Client-Server NWA • More organizations today are moving to client-server architectures. • Both of them share the responsibilities. • Client deals with: AL and PL • Host/server deals with: DS and DAL. • Client-Server NWA attempts to balance the processing between the client and the server by having both do some of the processing.

30. 3.Traditional Client-Server NWA

31. Choosing an Architecture

32. Costs and Benefits of Client-Server Architectures • CS-NWA have some important benefits compared to HB-NWA—Architectures. • Client-server architectures are scaleable. • Client-server architectures can support many different types of clients and servers. • Because no single host computer supports all the applications, the network is generally more reliable.

33. Client-Server Architectures • CS-NWA is becoming increasingly popular for the following reasons: • Provides the best aspects of both the distributed as well as centralized computing. • Users work on powerful PCs and Workstations • Makes use of specialized distributed servers. • CS-NWA is quite flexible and cost-effective!

34. Client-Server Architectures • Benefits of the CS-NWA:—CS-NWA architectures are more efficient since they distribute processing between client and server. • Another strength:—is that they allow hardware and software from different servers—or—vendors to be used together. • This is also a weakness:—Since it is sometimes difficult to get software from different vendors to work together smoothly. • For this reason, a third category of software, called Middleware was developed to handle this weakness.

35. Client-Server Architectures • Critical Limitations of the CS-NWA: Client-server architectures also have some critical limitations, the most important of which is their complexity. • Even updating the network with a new version of the software is more complicated too. • Much of the debate between host-based and also client-server networks has centered on cost. • Microcomputer hardware is more than 1000 times cheaper than mainframe hardware for the same amount of computing power.

36. Middleware and CS-NWA • CS-NWA enables software and hardware from different vendors to be used together. Unfortunately, they have a few standards—to guarantee compatibility. • One solution is middleware— • A software that sits between the application software on both the client and the server. • Middleware provides an interface for allowing client application programs to interact with server application programs.

37. Middleware • It’s a kind of consolidator and integrator. • It is a software that functions as a conversion layer or a translation layer—because it does the conversion and translation from one format to another—or from one vendor to another. • Middleware provides: • Custom-programmed middleware solution. • Common programming interfaces between applications on diff platforms—thereby ensuring transport between these different applications.

38. Middleware Standards • There are dozens of standards for middleware, each of which is supported by different vendors, and each of which provides different functions. • 3-most imp middleware standards: • DCE = Distributed Computing Environment • ODBC = Open Database Connectivity—Providesa standard for DAL--data access logic • CORBA = Common Object Request BrokerArchitecture—provides an object-oriented approach to DCN and has the industry backing from IBM, Apple, Sun and other vendors.

39. Different Types of Middleware • MD = Messaging Middleware • Provides a common interface and also transport between applications between the sender/receiver nodes. • DBM = Database Middleware • Provides a common interface between a query and multiple distributed databases. • DDM = Distributed Database Middleware • Supports ODBC = Open Database Connectivity • ASM = Application Server Middleware • It’s a Web-based Application-server • Provides interfaces to a wide variety of applications. • Serves as a middleware between the browser and legacy systems.

40. Middleware and CS-NWA • Middleware does two things: 1. It provides a standard way of communicating --or communication—that can translate between software from different vendors. 2. It manages the message transfer from clients to servers so that the clients need not know the specific server that contains the application’s data.

41. Client-Server NWA—3-Types • 1. Single Server NWA: • Aka—2-tiered CS-NWA • Good for 10—to—50 users • 2. Multi-Server NWA: • Good for 50—to—500 users • Aka—3-tiered--CS-NWA, 4-tiered--CS-NWA, 5-tiered--CS-NWA, 6-tiered--CS-NWA, 7-tiered CS-NWA,--------, 10-tiered--CS-NWA,-----N-tiered-CS-NWA • 3. Enterprise-NWA: • Aka—Distributed CS-NWA • Good for 500—to—hundreds or thousands of users.

42. Client-Server NWA---3-Types • Single-Server NWA: • Many clients can be served by 1-server—either at any one given time or concurrently. • This server could work as a general purpose server—with multiple features. • Multi-Server NWA: • There could be specific servers. • In addition, this could also include one special server normally working as a general purpose server. • Just a Note:—In both these—SS-NWA and also MS-NWA—a client can run for a specific period of time while the server runs continuously.

43. Generic Client-Server Environment

44. Two-tier, Three-tier, and N-tier CS--NW--Architectures There are many ways in which the application logic can be partitioned between the client and the server. • Two-tiered—aka—Single-Server NWA • Three-tiered—aka—Multi-Server NWA • Four-tiered----aka—Multi-Server NWA • Five-tiered-----aka—Multi-Server NWA • N-tiered--------aka—Multi-Server NWA

45. Two-tiered Client-Server NWA---Aka—Single-Server NWA--- Two-tiered client-server architecture

46. Two-tiered Client-Server NWA----with a general server----

47. Three-tiered Client-Server NWA ---Aka—Multi-Server NWA--- Three-tiered client-server architecture

48. An N-tiered Client-Server NWA ---Aka—Multi-Server NWA--- N-tiered client-server architecture

49. Multi-tiered Client-Server NWA---with multiple dedicated servers---

50. Multi-tiered Client-Server NWA----with multiple servers---- • Aka—Multi-Server NWA • Has several servers working on 1-network. • Provides different services. • Is typical of networks with 50—to—500 users. • Provides—performance, reliability and also backup in case of failure on the part of a malfunctioning server.