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  1. 1. Introduction Chapter 1 Copyright 1998, 1999 Panko Revised May 1999
  2. 2. Stars <ul><li>Material that is especially important, or </li></ul><ul><li>Material that is especially difficult or easy to confuse with similar material. </li></ul>
  3. 3. Part A: The Networking Revolution An overview of trends and the importance of networking to your career
  4. 4. The Networking Revolution <ul><li>The Traditional Career Ladder </li></ul><ul><ul><li>Programmer </li></ul></ul><ul><ul><li>Systems Analyst </li></ul></ul><ul><ul><li>IS (information systems) Management </li></ul></ul><ul><ul><li>Chief Information Officer (CIO) </li></ul></ul>
  5. 5. The Networking Revolution <ul><li>Many Factors, including Networking, are Changing this Career Ladder </li></ul><ul><ul><li>Networking specialties </li></ul></ul><ul><ul><li>User support specialties (combine PC support and networking support groups of) </li></ul></ul><ul><ul><li>Programmers create groups of programs that interact by exchanging messages across networks, not just stand-alone programs on single machines. </li></ul></ul>
  6. 6. Changes in IT <ul><li>Transforming the Corporation </li></ul><ul><ul><li>Intranets : using Internet technology and applications internally </li></ul></ul><ul><ul><ul><li>Many good, standardized applications </li></ul></ul></ul><ul><ul><ul><li>Inexpensive, standardized transmission technology </li></ul></ul></ul><ul><ul><ul><li>Add security </li></ul></ul></ul><ul><ul><li>Extranets : Using Internet technology to reach business partners and customers </li></ul></ul><ul><ul><li>Enterprise networks connect any two computers in the organization, even if they are at different sites </li></ul></ul>
  7. 7. Changes in IT <ul><li>Networking </li></ul><ul><ul><li>High demand for networking skills </li></ul></ul><ul><ul><li>Knowledge beyond wires and bits </li></ul></ul><ul><ul><ul><li>TCP/IP standards </li></ul></ul></ul><ul><ul><ul><li>Higher-layer standards (applications, etc.) </li></ul></ul></ul><ul><ul><ul><li>Systems management (server and client PC management) </li></ul></ul></ul>
  8. 8. IS versus CS and EE <ul><li>Hiring Organizations </li></ul><ul><ul><li>CS & EE graduates are trained to work in hardware, software, and networking vendor firms , such as Microsoft, IBM, Oracle, and Cisco Systems. </li></ul></ul><ul><ul><li>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. </li></ul></ul>
  9. 9. IS versus CS and EE <ul><li>Make versus Buy </li></ul><ul><li>CS and EE Professionals </li></ul><ul><ul><li>Make products for sale </li></ul></ul><ul><li>IS Professionals </li></ul><ul><ul><li>Buy these products instead of making things </li></ul></ul><ul><ul><li>Must select products appropriately </li></ul></ul><ul><ul><li>Must integrate these products together </li></ul></ul>
  10. 10. Comparing Products <ul><li>Dimensions for Comparing Products in Purchase Selection </li></ul><ul><li>Performance </li></ul><ul><ul><li>Whatever is appropriate for specific user needs </li></ul></ul><ul><ul><li>In some cases, speed </li></ul></ul><ul><ul><li>In other cases, reliability or something else </li></ul></ul><ul><li>Feasibility for the firm </li></ul><ul><ul><li>Products based on new standards may be too much work to implement </li></ul></ul><ul><li>Cost (can never be ignored) </li></ul>
  11. 11. Comparing Products <ul><li>Costs </li></ul><ul><li>Total purchase cost for all hardware and software </li></ul><ul><ul><li>Typically, “base price” are only a fraction of total cost </li></ul></ul><ul><li>Labor costs to plan, install </li></ul><ul><ul><li>Often greatly outweigh product purchase costs </li></ul></ul><ul><li>Life cycle costs from initial purchase to final abandonment </li></ul><ul><ul><li>Often greatly outweigh initial costs </li></ul></ul>
  12. 12. Comparing Products <ul><li>Emphasis: Cost is Always Important </li></ul><ul><ul><li>User demands are surging </li></ul></ul><ul><ul><li>Budgets are not growing rapidly </li></ul></ul><ul><li>You must buy the least expensive technology that will meet user requirements </li></ul><ul><li>No comparison of alternatives is complete without a cost analysis </li></ul>
  13. 13. User Needs <ul><li>Drive everything else </li></ul><ul><li>Must communicate with users to understand their needs </li></ul><ul><li>Must support important user needs without bankrupting the firm </li></ul>
  14. 14. Standards <ul><li>Standards are rules of operation that are followed by most or all vendors . </li></ul><ul><li>Standards allow products from different vendors to work together (interoperate) </li></ul><ul><ul><li>You are not limited to buying from one firm. </li></ul></ul><ul><ul><li>Competition will drive down costs and increase options </li></ul></ul><ul><ul><li>You do not have to worry if a single vendor falls behind or fails </li></ul></ul>
  15. 15. 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.
  16. 16. Accessing the WWW from Home <ul><li>A Common and Important Situation </li></ul><ul><ul><li>Must be understood </li></ul></ul><ul><ul><li>Good way of introducing concepts </li></ul></ul>
  17. 17. The Internet <ul><li>Network </li></ul><ul><ul><li>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 . </li></ul></ul><ul><li>Key Ideas </li></ul><ul><ul><li>Any-to-any. Fully interconnected </li></ul></ul><ul><ul><li>Interact through the exchange of messages </li></ul></ul><ul><ul><li>Network delivers messages based on their destination addresses, like the address on a postal envelope </li></ul></ul>
  18. 18. The Internet <ul><li>A Worldwide Group of Networks </li></ul><ul><ul><li>Not a single network </li></ul></ul>
  19. 19. The Internet <ul><li>Messages are Broken into Small Packets for Transmission </li></ul><ul><ul><li>More efficient than sending long messages </li></ul></ul>Message Packets
  20. 20. The Internet <ul><li>Routers </li></ul><ul><ul><li>Connect the Internet’s networks </li></ul></ul><ul><ul><li>Cooperate to give an end to end route for each packet </li></ul></ul>Routers Route
  21. 21. The Internet <ul><li>Hosts </li></ul><ul><ul><li>Any computer attached to the Internet is a host </li></ul></ul><ul><ul><li>Webservers are host </li></ul></ul><ul><ul><li>Desktop and notebook PCs are hosts too </li></ul></ul>Host Host
  22. 22. The Internet <ul><li>Host internet addresses </li></ul><ul><ul><li>Four number segments separated by dots </li></ul></ul><ul><ul><li>For example, </li></ul></ul><ul><ul><li>Official addresses for hosts </li></ul></ul><ul><ul><li>Also called IP addresses </li></ul></ul>
  23. 23. The Internet <ul><li>Internet Addresses </li></ul><ul><ul><li>Really strings of 32 bits (1s and 0s) </li></ul></ul><ul><ul><ul><li>10000000101010100001000100001101 </li></ul></ul></ul><ul><ul><li>For convenience, divide them into four bytes (also called octets) </li></ul></ul><ul><ul><ul><li>10000000 10101010 00010001 00001101 </li></ul></ul></ul><ul><ul><li>Both octets and bytes are collections of eight bits </li></ul></ul>
  24. 24. The Internet <ul><li>Internet Addresses </li></ul><ul><ul><li>Convert each octet into a decimal number </li></ul></ul><ul><ul><ul><li>10000000 is 128 </li></ul></ul></ul><ul><ul><ul><li>10101011 is 171 </li></ul></ul></ul><ul><ul><ul><li>00010001 is 17 </li></ul></ul></ul><ul><ul><ul><li>00001101 is 13 </li></ul></ul></ul>
  25. 25. Computing Internet Addresses Value (2 N ) 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 Binary 10100011 = Decimal 163 Note: Starts with 0
  26. 26. The Internet <ul><li>Host Names </li></ul><ul><ul><li>Easy to remember </li></ul></ul><ul><ul><ul><li> </li></ul></ul></ul><ul><ul><ul><li> </li></ul></ul></ul><ul><ul><ul><li>Two or more text “labels” separated by dots </li></ul></ul></ul><ul><ul><ul><li>No relationship between segments and labels </li></ul></ul></ul><ul><ul><li>Like nicknames </li></ul></ul><ul><ul><ul><li>Not official names </li></ul></ul></ul><ul><ul><ul><li>If have host name, browser can look up internet address of host </li></ul></ul></ul>CNN.COM
  27. 27. The Internet <ul><li>Internet Service Providers (ISPs) </li></ul><ul><ul><li>You must have an account with an ISP </li></ul></ul><ul><ul><li>Connects you to the Internet </li></ul></ul><ul><ul><li>Provides other services (e-mail account, etc.) </li></ul></ul><ul><li>Carrier </li></ul><ul><ul><li>Connects you to the ISP </li></ul></ul><ul><ul><li>You pay for this separately from your ISP charges </li></ul></ul>ISP Carrier Line
  28. 28. The Internet <ul><li>The Internet is Not Free </li></ul><ul><ul><li>You pay your ISP around $20 per month </li></ul></ul><ul><ul><li>Part of this pays for ISP expenses </li></ul></ul><ul><ul><li>Part of this pays the Internet backbone to carry your messages </li></ul></ul><ul><li>You Also Pay the Carrier Separately for the Carrier Line </li></ul>ISP Carrier Line
  29. 29. The Internet <ul><li>Internet Backbone </li></ul><ul><ul><li>Consists of competing carriers called network service providers (NSPs) </li></ul></ul><ul><ul><li>NSPs are all interconnected for any-any communication among hosts </li></ul></ul>Internet Backbone NSPs ISP ISP
  30. 30. The Internet <ul><li>ISPs and NSPs </li></ul><ul><ul><li>Began in the United States </li></ul></ul><ul><ul><li>Is being copied and adapted by other countries </li></ul></ul><ul><ul><li>However, not universal </li></ul></ul>
  31. 31. Internet Standards <ul><li>Framework for standards setting is called TCP/IP </li></ul><ul><ul><li>Originally under DARPA (Defense Advanced Research Projects Agency) </li></ul></ul><ul><ul><li>Now under an independent body, the IETF (Internet Engineering Task Force) </li></ul></ul>
  32. 32. Internet Standards <ul><li>TCP/IP Standards are Layered </li></ul><ul><ul><li>Application </li></ul></ul><ul><ul><li>Transport </li></ul></ul><ul><ul><li>Internet </li></ul></ul><ul><ul><li>Subnet </li></ul></ul>Application Transport Internet Subnet
  33. 33. Internet Standards <ul><li>Application Layer Standards </li></ul><ul><ul><li>allow two application programs to work together, even if they come from different vendors </li></ul></ul><ul><ul><li>For example, browser on user PC and webserver application program on webserver </li></ul></ul>Browser Webserver Application Program
  34. 34. Internet Standards <ul><li>HTTP (HyperText Transfer Protocol) </li></ul><ul><ul><li>World Wide Web standard for browser-webserver application program exchanges </li></ul></ul>Browser Webserver Application Program HTTP
  35. 35. Internet Standards <ul><li>Protocol </li></ul><ul><ul><li>A standard to govern communication between peer processes at the same layer on different systems </li></ul></ul><ul><ul><li>Browser and webserver programs are at the same layer (application) </li></ul></ul><ul><ul><li>Browser and webserver programs are on different machines (user PC and webserver) </li></ul></ul><ul><ul><li>So HTTP is a protocol. </li></ul></ul>
  36. 36. Internet Standards <ul><li>Transport Layer Protocols </li></ul><ul><ul><li>allow any two computers to exchange messages even if they come from different vendors and even if they are of different platform types </li></ul></ul><ul><ul><li>For instance, PC and non-PC webserver </li></ul></ul>PC PC or Other Computer
  37. 37. Internet Standards <ul><li>The Transport Layer Gives Platform Independence </li></ul><ul><ul><li>Two computers do not have to be of the same platform type </li></ul></ul><ul><li>A PC user does not even know what kind of computer the webserver is </li></ul>PC ?
  38. 38. Internet Standards <ul><li>HTTP Requires the Use of the TCP Transport Standard </li></ul><ul><ul><li>Transmission Control Protocol </li></ul></ul><ul><ul><li>The TCP in TCP/IP </li></ul></ul>TCP
  39. 39. Internet Standards <ul><li>Internet Layer Protocols </li></ul><ul><ul><li>allow packets to be routed across multiple routers from a source host to a destination host, even if the routers come from different vendors </li></ul></ul>Route
  40. 40. Internet Standards <ul><li>The Internet Protocol (IP) is the Main Protocol for Routing Packets Across the Internet. </li></ul><ul><ul><li>The IP in “TCP/IP” </li></ul></ul>IP
  41. 41. Internet Standards <ul><li>Subnets </li></ul><ul><ul><li>Single networks (LANs, WANs, point-to-point link) </li></ul></ul><ul><ul><li>A packet will pass through several subnets along its route across the Internet </li></ul></ul>Subnet Subnet Subnet
  42. 42. Internet Standards <ul><li>Different Subnets Can Have Different Subnet Protocols </li></ul><ul><ul><li>IP at the internet layer routes across different protocols at the subnet layer </li></ul></ul>LAN Subnet Protocol 1 WAN Subnet Protocol 2 Point-to-Point Subnet Protocol 3
  43. 43. Internet Standards <ul><li>The IETF Does Not Create Subnet Standards </li></ul><ul><ul><li>Uses standards from another architecture, OSI </li></ul></ul><ul><ul><li>Reference Model of Open Systems Interconnection </li></ul></ul>Application Transport Internet Subnet: Use OSI Standards
  44. 44. Internet Standards <ul><li>OSI Divides Subnet Standards into Two Layers </li></ul><ul><ul><li>Data Link </li></ul></ul><ul><ul><li>Physical </li></ul></ul>Application Transport Internet Subnet OSI Standards Data Link Physical
  45. 45. Internet Standards <ul><li>Link </li></ul><ul><ul><li>Transmission connection in which there is only one possible path between any two stations </li></ul></ul><ul><ul><li>Simplest is a point-to-point link </li></ul></ul>Point- to- Point
  46. 46. Internet Standards <ul><li>Link </li></ul><ul><ul><li>Other possibilities for a single possible route between any two stations </li></ul></ul>Multidrop Ring Hierarchy Star Daisy Chain
  47. 47. Internet Standards <ul><li>Data Link Layer Standards </li></ul><ul><ul><li>organize transmissions into collections of bits called frames and manage the transmission of these frames within a single network (subnet) </li></ul></ul>10010001001 Data Link Frame
  48. 48. Internet Standards <ul><li>Data Link Layer Standards </li></ul><ul><ul><li>For accessing the Internet from home ... </li></ul></ul><ul><ul><li>Point-to-Point Protocol (PPP) dominates </li></ul></ul><ul><ul><li>Only used between home and ISP! </li></ul></ul><ul><ul><li>Low performance. Other subnets connecting routers are likely to use different subnet protocols! </li></ul></ul>ISP PPP
  49. 49. Internet Standards <ul><li>Physical Layer Standards </li></ul><ul><ul><li>standardize connector plugs, transmission media, electrical signaling, and other physical matters you can see and touch, even if they come from different vendors </li></ul></ul><ul><ul><li>Work bit by bit. No frame organization. </li></ul></ul>
  50. 50. Internet Standards <ul><li>Physical Layer Standards in Internet Access from Home </li></ul><ul><ul><li>Telephone jack (RJ11) </li></ul></ul><ul><ul><li>Telephone wire </li></ul></ul><ul><ul><li>Serial port connection to external modem </li></ul></ul><ul><ul><li>Modem </li></ul></ul>Serial Port External Modem Telephone Wire Wall Jack
  51. 51. Internet Standards <ul><li>Subnet Versus Internet Layer Standards </li></ul><ul><ul><li>Internet layer provides routing across multiple subnets </li></ul></ul><ul><ul><li>Subnet layer standards (data link and physical) provide for transmission within a single network </li></ul></ul>Internet Layer Subnet Layer
  52. 52. Internet Standards <ul><li>Subnet Versus Internet Layer Standards </li></ul><ul><ul><li>Internet layer provides routing across multiple subnets </li></ul></ul><ul><ul><li>Subnet layer standards (data link and physical) provide for transmission within a single network </li></ul></ul><ul><li>Analogy for Subnet versus Internet </li></ul><ul><ul><li>Take a vacation </li></ul></ul><ul><ul><li>Route from beginning to end (like internet layer) </li></ul></ul><ul><ul><li>For different parts, may travel by car, airplane, or boat (like subnet layer) </li></ul></ul>
  53. 53. Internet Standards <ul><li>5-Layer Hybrid TCP/IP-OSI Framework </li></ul><ul><li>Use TCP/IP for Higher Layers, OSI for Subnets </li></ul><ul><ul><li>Application </li></ul></ul><ul><ul><li>Transport </li></ul></ul><ul><ul><li>Internet </li></ul></ul><ul><ul><li>Data link </li></ul></ul><ul><ul><li>Physical </li></ul></ul>
  54. 54. Internet Standards <ul><li>Accessing the WWW from Home </li></ul>App Trans Int DL Phy User PC Int DL Phy Router App Trans Int DL Phy Webserver HTTP TCP IP PPP Modem IP ? ?
  55. 55. Internet Standards <ul><li>End-to-End Layers </li></ul><ul><ul><li>Between peer processes on hosts </li></ul></ul>App Trans Int DL Phy User PC Int DL Phy Router App Trans Int DL Phy Webserver HTTP TCP End-to-End Layers
  56. 56. Internet Standards <ul><li>Communication Between Host and First Router </li></ul>App Trans Int DL Phy User PC Int DL Phy First Router App Trans Int DL Phy Webserver IP PPP Modem Between Host and First Router
  57. 57. Internet Standards <ul><li>Other Connections </li></ul><ul><ul><li>Router-Router and Router-Destination-Host </li></ul></ul><ul><ul><li>IP at internet layer </li></ul></ul><ul><ul><li>Subnet standard is unknown to user PC </li></ul></ul>Int DL Phy Next or Last Router App Trans Int DL Phy Webserver IP ? ? Int DL Phy First Router IP ? ?
  58. 58. Flexibility of Layering <ul><li>Can Change Only One or Two Layer Standards for Different Application </li></ul><ul><ul><li>Base Case: Accessing the WWW from home with a V.90 modem </li></ul></ul><ul><ul><li>Application HTTP </li></ul></ul><ul><ul><li>Transport TCP </li></ul></ul><ul><ul><li>Internet IP </li></ul></ul><ul><ul><li>Data Link PPP </li></ul></ul><ul><ul><li>Physical Serial Port, V.90 Modem, telephone </li></ul></ul>
  59. 59. Flexibility of Layering <ul><li>Can Change Only One or Two Layer Standards for Different Application </li></ul><ul><ul><li>New Case: Accessing a File Transfer Protocol (FTP) host from home with a V.90 modem </li></ul></ul><ul><ul><li>Application FTP instead of HTTP </li></ul></ul><ul><ul><li>Transport TCP: No change </li></ul></ul><ul><ul><li>Internet IP: No change </li></ul></ul><ul><ul><li>Data Link PPP: No change </li></ul></ul><ul><ul><li>Physical Serial Port, V.90 Modem, telephone: No change </li></ul></ul>
  60. 60. Flexibility of Layering <ul><li>Can Change Only One or Two Layer Standards for Different Application </li></ul><ul><ul><li>New Case: Accessing an POP mail host (see Ch. 7) from home with a V.34 modem. Compared to Base Case: </li></ul></ul><ul><ul><li>Application POP instead of HTTP </li></ul></ul><ul><ul><li>Transport TCP: No change </li></ul></ul><ul><ul><li>Internet IP: No change </li></ul></ul><ul><ul><li>Data Link PPP: No change </li></ul></ul><ul><ul><li>Physical Serial Port, V.34 modem instead of V.90 modem, telephone </li></ul></ul>
  61. 61. 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
  62. 62. PC Networks <ul><li>The Most Common Platform in Organizations </li></ul><ul><ul><li>Allows PCs to share resources </li></ul></ul><ul><ul><li>Both Wintel (Windows/Intel) PCs and Macintoshes </li></ul></ul>Network
  63. 63. PC Network Components <ul><li>Desktop Machines are Called Client PCs </li></ul><ul><ul><li>The customers of services </li></ul></ul><ul><ul><li>Large networks have thousands of client PCs </li></ul></ul><ul><ul><li>~$50 in hardware makes a stand-alone PC a client PC </li></ul></ul>Client PC
  64. 64. PC Network Components <ul><li>Servers Provide Services to Client PCs </li></ul><ul><ul><li>Most PC networks have several servers </li></ul></ul><ul><ul><li>Large PC networks can have hundreds of servers </li></ul></ul>Service Server Client PC
  65. 65. PC Network Components <ul><li>File Servers </li></ul><ul><ul><li>Store files (data files and programs) </li></ul></ul><ul><ul><li>The most common type of server in PC networks </li></ul></ul><ul><ul><li>Almost all file servers are themselves PCs </li></ul></ul>File Server
  66. 66. File Server Program Access <ul><li>The Most Common Way to Execute Programs in PC Networks </li></ul><ul><ul><li>Program files are stored on the file server before execution </li></ul></ul>File Server Client PC Stored on the File Server
  67. 67. File Server Program Access <ul><li>File Server Program Access </li></ul><ul><ul><li>Program and data files are downloaded (copied) to the Client PC </li></ul></ul><ul><ul><li>Executed on the client PC, not on the file server </li></ul></ul><ul><ul><li>File server merely stores programs and data files </li></ul></ul>File Server Client PC Downloaded to Client PC, Executed There
  68. 68. File Server Program Access <ul><li>PC Processing Power Limits FSPA Programs </li></ul><ul><ul><li>Client PCs have slow processors, limited RAM </li></ul></ul><ul><ul><li>Can only execute small programs: WP, Email, etc. </li></ul></ul><ul><ul><li>This is especially true of older client PCs, which still must be supported. </li></ul></ul>File Server Client PC Executed on the Client PC
  69. 69. Client/Server Processing <ul><li>Client and Server Machines </li></ul><ul><ul><li>Neither has to be a PC </li></ul></ul><ul><ul><li>Platform independent </li></ul></ul>Client Machine Server
  70. 70. Client/Server Processing <ul><li>Two Programs </li></ul><ul><ul><li>Client program on client machine </li></ul></ul><ul><ul><li>Server program on server machine </li></ul></ul><ul><ul><li>Work together to do the required processing </li></ul></ul>Client Machine Server Client Program Server Program
  71. 71. Client/Server Processing <ul><li>Division of Labor </li></ul><ul><ul><li>Client program handles lighter user interface chores and light processing chores </li></ul></ul><ul><ul><li>Server program handles heavy work, such as database retrieval </li></ul></ul>Client Machine Server Client Program Server Program
  72. 72. Client/Server Processing <ul><li>Cooperation Through Message Exchange </li></ul><ul><ul><li>Client program sends Request , such as a database retrieval request </li></ul></ul><ul><ul><li>Server program sends a Response message to deliver the requested information or an explanation for failure </li></ul></ul>Client Machine Server Client Program Server Program Request Response
  73. 73. Client/Server Processing <ul><li>Widely Used on the Internet </li></ul><ul><li>For instance, webservice </li></ul><ul><ul><li>Client program (browser) sends an HTTP request (GET command) asking for a webserver file </li></ul></ul><ul><ul><li>Server program (webserver application program) sends an HTTP response message with the requested webpage </li></ul></ul>HTTP Request Message HTTP Response Message
  74. 74. Client/Server Processing <ul><li>On the Internet, a Single Client Program--the Browser (also known as the client suite)--Works with Many Kinds of C/S server applications </li></ul><ul><ul><li>WWW, E-mail, etc. </li></ul></ul>Browser Webserver E-mail Server
  75. 75. Terminal-Host Systems <ul><li>Created in the 1960s </li></ul><ul><ul><li>Central host computer does all the processing </li></ul></ul><ul><ul><li>Terminal is dumb--only a remote screen and keyboard </li></ul></ul><ul><ul><li>Created in the 1960s, microprocessors for terminal intelligence did not exist </li></ul></ul>Terminals Host
  76. 76. Terminal-Host Systems <ul><li>Sizes </li></ul><ul><ul><li>Mainframes are the largest business hosts </li></ul></ul><ul><ul><ul><li>Optimized for business uses--file access speed is more crucial than mathematical processing </li></ul></ul></ul><ul><ul><li>Supercomputers are faster for intensive computations but not necessarily for business applications that have high file access needs </li></ul></ul><ul><ul><li>Minicomputers are smaller hosts than mainframes </li></ul></ul><ul><ul><li>Small business computers are minicomputers optimized for business use (file processing) </li></ul></ul>
  77. 77. Terminal-Host Systems <ul><li>Many Mainframe Applications Were Created in the 1960s through 1980s </li></ul><ul><ul><li>No longer cost effective </li></ul></ul><ul><ul><li>Legacy systems --systems created by your predecessors </li></ul></ul><ul><ul><li>Too expensive to rewrite all legacy applications at once </li></ul></ul><ul><ul><li>Must live with many host legacy applications </li></ul></ul><ul><ul><li>T-H transmission will be important for some years to come </li></ul></ul><ul><ul><li>Mainframes are beginning to be used as very servers in client/server processing </li></ul></ul>
  78. 78. “Host” on the Internet <ul><li>In terminal-host systems, a host is a central computer with many terminals </li></ul><ul><li>Originally, only such hosts connected to the Internet </li></ul><ul><li>By the time smaller computers, such as PCs, connected to the Internet, the term “host” had stuck </li></ul><ul><li>So now any computer connected to the Internet is called a host </li></ul>
  79. 79. Program Functionality (Size) <ul><li>File Server Program Access </li></ul><ul><ul><li>Poor: many client PCs are small </li></ul></ul><ul><li>Client/Server Processing </li></ul><ul><ul><li>Good: not limited to client PC processing power </li></ul></ul><ul><ul><li>Heavy work can be done on the server machine </li></ul></ul><ul><li>Terminal-Host Systems </li></ul><ul><ul><li>Good: Hosts can be very large </li></ul></ul>
  80. 80. Scalability (Ability to Grow) <ul><li>File Server Program Access </li></ul><ul><ul><li>Poor: client PC sizes are limited </li></ul></ul><ul><li>Client/Server Processing </li></ul><ul><ul><li>Very good: Platform independence allows servers to be larger than PCs </li></ul></ul><ul><ul><li>To grow, leave client machine the same, increase the size of the server machine </li></ul></ul><ul><li>Terminal-Host Systems </li></ul><ul><ul><li>Excellent: hosts have an enormous range of processing power </li></ul></ul>
  81. 81. Platform Independence <ul><li>File Server Program Access </li></ul><ul><ul><li>Poor: Only works with PC clients and PC file servers </li></ul></ul><ul><ul><li>OK for word processing, etc. </li></ul></ul><ul><ul><li>Unacceptable for large databases </li></ul></ul><ul><li>Client/Server Processing </li></ul><ul><ul><li>Excellent: use any server you want, also any client </li></ul></ul><ul><li>Terminal-Host Systems </li></ul><ul><ul><li>Poor: Hosts require terminals and only work with a few terminal types </li></ul></ul>
  82. 82. User Interface <ul><li>File Server Program Access </li></ul><ul><ul><li>Very good: uses local PC processing power </li></ul></ul><ul><li>Client/Server Processing </li></ul><ul><ul><li>Very good: uses local PC processing power for user interface </li></ul></ul><ul><li>Terminal-Host System </li></ul><ul><ul><li>Poor: Relies on distant hosts. User interface quality limited by transmission costs. Monochrome, text-only screen. No animation </li></ul></ul>
  83. 83. Response Time (When User Hits a Key) <ul><li>File Server Program Access </li></ul><ul><ul><li>Very good: uses local PC processing power </li></ul></ul><ul><li>Client/Server Processing </li></ul><ul><ul><li>Very good: local PC processing power for user interface </li></ul></ul><ul><ul><li>But retrievals from the server can cause delays </li></ul></ul><ul><li>Terminal-Host System </li></ul><ul><ul><li>Poor: Relies on distant hosts. Long delays if overloaded. </li></ul></ul><ul><ul><li>Some systems use smart terminals with limited editing capability to reduce response time for simple editing tasks only </li></ul></ul>
  84. 84. Less Common Platforms <ul><li>Workstations </li></ul><ul><ul><li>More powerful (and expensive) than PCs </li></ul></ul><ul><ul><li>Do not use standard Intel PC microprocessors </li></ul></ul><ul><ul><li>Usually run the UNIX operating system </li></ul></ul><ul><ul><li>Client and server workstations </li></ul></ul><ul><ul><li>Confusingly, Windows NT client operating system is called Windows NT Workstation, where workstation is synonymous with “client” </li></ul></ul><ul><ul><li>Workstation servers are often used as client/server servers </li></ul></ul>
  85. 85. Less Common Platforms <ul><li>Network Computers </li></ul><ul><ul><li>Clients are simple machines without hard drives </li></ul></ul><ul><ul><li>Programs downloaded from NC servers as needed </li></ul></ul><ul><ul><li>Much like file server program access </li></ul></ul><ul><ul><li>But only run programs written in Java </li></ul></ul><ul><ul><li>Cannot run programs written for Windows </li></ul></ul>NC Java
  86. 86. Less Common Platforms <ul><li>Network Computers </li></ul><ul><ul><li>Originally offered to reduce costs </li></ul></ul><ul><ul><li>Low-cost Wintel (Windows/Intel) machines are minimizing the cost advantages </li></ul></ul><ul><ul><li>Use mostly in traditional terminal-host environments, providing more processing power than dumb terminals </li></ul></ul>
  87. 87. Less Common Platforms <ul><li>Distributed Processing </li></ul><ul><ul><li>Programs are small units called objects </li></ul></ul><ul><ul><li>Run on multiple machines (not just 2 as in C/S) </li></ul></ul><ul><ul><li>Coordinate by exchanging messages </li></ul></ul><ul><ul><li>Should be important in the future </li></ul></ul>Obj Obj Obj Obj Message
  88. 88. Less Common Platforms <ul><li>Information Appliances </li></ul><ul><ul><li>Distributed processing pushed to its limits </li></ul></ul><ul><ul><li>Even coffeemakers may become intelligent </li></ul></ul><ul><ul><li>Small devices everywhere may coordinate with one another </li></ul></ul>
  89. 89. C. Standards Architectures Beyond TCP/IP, to work with different platforms
  90. 90. Standards Architectures <ul><li>Standards Cannot be Created in Isolation </li></ul><ul><ul><li>Must work together to provide complete connection between two application programs on different computers, perhaps on different networks </li></ul></ul>Application Standards Transport Standards Internet Standards Data Link Standards Physical Standards
  91. 91. Standards Architecture <ul><li>Begin With an Architecture (Framework) </li></ul><ul><ul><li>General plan for dividing up the work of allowing application programs to work together across a network </li></ul></ul><ul><ul><li>Defines individual layers </li></ul></ul><ul><ul><li>Defines how layers work together </li></ul></ul><ul><li>Then Create Standards for Individual Layers </li></ul><ul><li>We Have Already Seen One Architecture: TCP/IP </li></ul><ul><ul><li>Layers: application, transport, internet, subnet </li></ul></ul>
  92. 92. Standards Architectures <ul><li>Usually, Multiple Standards at Each Layer </li></ul><ul><ul><li>For instance, HTTP and e-mail standards at the application layer </li></ul></ul><ul><ul><li>To allow customization for individual application needs </li></ul></ul><ul><ul><li>To allow new technology to be supported </li></ul></ul><ul><ul><li>Inability of standards agencies to reach agreement </li></ul></ul>
  93. 93. Standards Architectures <ul><li>Standards Agencies </li></ul><ul><ul><li>Responsible for the standards architecture </li></ul></ul><ul><ul><li>In TCP/IP, this is the IETF (Internet Engineering Task Force) </li></ul></ul>
  94. 94. TCP/IP <ul><li>TCP/IP is the Dominant Architecture above the Subnet Layer </li></ul><ul><ul><li>Standards are simple </li></ul></ul><ul><ul><ul><li>Often even have “simple” in the standard’s name </li></ul></ul></ul><ul><ul><ul><li>Simple standards are developed rapidly </li></ul></ul></ul><ul><ul><li>Simplicity also allows rapid product development </li></ul></ul><ul><ul><li>Simplicity also allows products to be inexpensive and easy to implement </li></ul></ul><ul><ul><li>“Fast to market and inexpensive” because of simplicity has led to TCP/IP’s dominance </li></ul></ul>
  95. 95. OSI <ul><li>OSI (Reference Model of Open Systems Interconnection) </li></ul><ul><ul><li>Open systems are those that are open to communicating with all other systems </li></ul></ul><ul><ul><li>“Reference model” is another name for “architecture” </li></ul></ul>
  96. 96. OSI Standards Agencies <ul><li>ISO (International Organization for Standardization) </li></ul><ul><ul><li>Traditional standards agency for industrial products </li></ul></ul><ul><li>ITU-T (International Telecommunications Union-Telecommunications Standards Sector) </li></ul><ul><ul><li>Traditional standards agency for telecommunications </li></ul></ul><ul><li>Work Together because Networking Involves both Computers and communications </li></ul>
  97. 97. OSI <ul><li>TCP/IP versus OSI </li></ul><ul><ul><li>OSI Has 7 Layers While TCP/IP Has 4 </li></ul></ul>OSI Application (7) Presentation (6) Session (5) Transport (4) Network (3) Data Link (2) Physical (1) TCP/IP Application Transport Internet Subnet
  98. 98. OSI Application Layer (OSI Layer 7) <ul><li>For Communication Between Specific Types of Application Programs </li></ul><ul><ul><li>Email-Email </li></ul></ul><ul><ul><li>Database-Database </li></ul></ul><ul><li>Not Widely Used </li></ul><ul><ul><li>Sometimes simplified then adopted by IETF as a TCP/IP standard </li></ul></ul><ul><li>Similar to TCP/IP Application Layer </li></ul><ul><ul><li>But not exactly the same </li></ul></ul>
  99. 99. OSI Presentation Layer (Layer 6) <ul><li>For Standards Used in Multiple Applications </li></ul><ul><ul><li>Standards for text formatting </li></ul></ul><ul><ul><li>Standards for graphics formatting </li></ul></ul><ul><ul><li>No need to create for each application </li></ul></ul><ul><li>To Provide a Generalized Way to Represent Data </li></ul><ul><ul><li>Abstract Syntax Notation 1 (ASN1) </li></ul></ul><ul><ul><li>Allows for exchanges between machines with different ways of representing data </li></ul></ul><ul><li>Nothing Like this in TCP/IP </li></ul>
  100. 100. OSI Session Layer (OSI Layer 5) <ul><li>Provides a Connection Between Application Programs on Different Machines </li></ul><ul><ul><li>If the connection is broken, it can be reestablished </li></ul></ul><ul><ul><li>In general, standards at this layer manage exchanges between application programs </li></ul></ul><ul><li>TCP/IP Transport Layer Provides Some of this Functionality </li></ul>Session (5) Transport (4) Application Transport
  101. 101. OSI Transport Layer <ul><li>Provides Connection Between Different Machines </li></ul><ul><ul><li>Needed because machines may be of different platform types </li></ul></ul><ul><li>Similar to TCP/IP Transport Layer </li></ul><ul><ul><li>But TCP/IP transport layer also provides some of the functionality of the OSI Session layer </li></ul></ul>Session (5) Transport (4) Application Transport
  102. 102. OSI Network Layer (OSI Layer 3) <ul><li>The Most Difficult to Characterize </li></ul><ul><li>Originally Created for Subnets (Single Networks) that had a mesh of switches </li></ul><ul><ul><li>Defined a route within a single mesh subnet </li></ul></ul>
  103. 103. OSI Network Layer (OSI Layer 3) <ul><li>ISO and ITU-T “Forgot” to Have an Internetting Layer </li></ul><ul><ul><li>Internetting--routing across subnets was later added to Layer 3 </li></ul></ul><ul><li>So OSI Networking Layer is for BOTH Mesh Subnets AND for Routing Across Subnets </li></ul><ul><ul><li>Inelegant </li></ul></ul>
  104. 104. OSI Network Layer (OSI Layer 3) <ul><li>However, OSI Only Developed One Three-Layer Subnet Standard (X.25) </li></ul><ul><ul><li>All subsequent subnet standards do not use Layer 3 </li></ul></ul><ul><ul><li>Highest layer is Layer 2 </li></ul></ul><ul><li>So in practice, OSI Layer 3 is an Internetting Layer </li></ul>Network (3) Data Link (2) Physical (1) Internet Subnet
  105. 105. OSI Data Link and Physical Layers <ul><li>We Saw These Earlier </li></ul><ul><li>Data Link Layer (OSI Layer 2) </li></ul><ul><ul><li>Manages the transmission of frames across a single link </li></ul></ul><ul><li>Physical Layer (OSI Layer 2) </li></ul><ul><ul><li>For physical and electrical standards within a single link </li></ul></ul><ul><ul><li>Works bit-by-bit </li></ul></ul>Data Link (2) Physical (1) Subnet
  106. 106. OSI Subnet Dominance <ul><li>OSI Standards are Dominant for Subnet Transmission </li></ul><ul><ul><li>Local Area Networks (LANs) </li></ul></ul><ul><ul><li>Wide Area Networks (WANs) </li></ul></ul><ul><ul><li>TCP/IP Does Not Challenge that Dominance </li></ul></ul><ul><li>IETF Generally Does Not Create Subnet Standards for TCP/IP </li></ul><ul><ul><li>If it does (as in the case of the Point-to-Point protocol, by the way), it follows the OSI architecture </li></ul></ul>
  107. 107. Hybrid TCP/IP-OSI Architecture <ul><li>As Noted Earlier, Most Firms Today Use a Hybrid TCP/IP-OSI Architecture for Most of their Internal Communication </li></ul><ul><li>Application TCP/IP </li></ul><ul><li>Transport TCP/IP </li></ul><ul><li>Internet TCP/IP </li></ul><ul><li>Data Link OSI </li></ul><ul><li>Physical OSI </li></ul>
  108. 108. SNA <ul><li>Systems Network Architecture </li></ul><ul><ul><li>Another Standards Architecture </li></ul></ul><ul><li>Proprietary </li></ul><ul><ul><li>Controlled by IBM </li></ul></ul><ul><ul><li>However, IBM shares specifications, so most mainframe systems from all vendors use SNA or a variant </li></ul></ul><ul><li>Dominant for Mainframe Communication </li></ul><ul><ul><li>Still accounts for a very large part of long-distance data traffic </li></ul></ul>
  109. 109. IPX/SPX <ul><li>Created by Novell </li></ul><ul><ul><li>For NetWare PC network software </li></ul></ul><ul><ul><li>Novell dominated PC networking for years </li></ul></ul><ul><ul><li>So IPX/SPX is still widely used in PC networking with Novell NetWare servers </li></ul></ul><ul><ul><li>Even Novell is switching to TCP/IP </li></ul></ul><ul><ul><li>However, many PC networks have not converted their Novell servers and clients to TCP/IP </li></ul></ul><ul><ul><li>Must be considered in PC networking </li></ul></ul>
  110. 110. Recap <ul><li>Trends in Networking and its Impacts </li></ul><ul><li>Standards for WWW Access from Home to Introduce Basic Networking Principles </li></ul><ul><li>Popular Computer Platforms Found in Networked Environments </li></ul><ul><li>Standards Architectures that Tend to Differ by Platform </li></ul><ul><li>The Dominant TCP/IP-OSI Hybrid Architecture </li></ul>