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CSE 550 Computer Network Design
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CSE 550 Computer Network Design

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  1. CSE 550Computer Network Design Dr. Mohammed H. Sqalli COE, KFUPM Spring 2012 (Term 112)

  2. Introduction • What is a Network? • What is “Network Design”? • Top-Down Network Design • Network Development Life Cycle (NDLC) • Network Analysis and Design Methodology • Types of Network Design • And Then What? Lecture Notes - 1

  3. What is a Network? • Management view • Technical view Lecture Notes - 1

  4. The Management View (1/3) • A network is a utility • Computers and their users are customers of the network utility • The network must accommodate the needs of customers • As computer usage increases so does the requirements of the network utility • Resources will be used to manage the network • The Network Utility is NOT free! • Someone must pay the cost of installing and maintaining the network • Manpower is required to support the network utility Lecture Notes - 1

  5. The Management View (2/3) • Utilities don’t bring money into the organization • Expense item to the Corporation • Cannot justify Network based on “Productivity Improvements” • As a network designer, you need to explain to management how the networkdesign, even with the high expense, can save money or improve the company’s business • If users cannot log on to your commerce site, they will try your competitor, and you have lost sales • If you cannot get the information your customers are asking about due to a network that is down, they may go to your competitor Lecture Notes - 1

  6. The Management View (3/3) • You need to understand how the network assists the company in making money and play on that strength when you are developing the network design proposal • Try to show a direct correlation between the network design project and the company’s business • “Because you want a faster network” is not good enough, the question that management sends back is WHY DO I NEED A FASTER ONE? Lecture Notes - 1

  7. The Technical View (1/2) • A “Network” really can be thought of as three parts and they all need to be considered when working on a network design project: • Connections • Communications/Protocols • Services • Connections • Provided by Hardware that ties things together • Wire/Fiber/Wireless Transport Mechanisms • Routers • Switches/Hubs • Computers Lecture Notes - 1

  8. The Technical View (2/2) • Communications/Protocols • Provided by Software • A common language for 2 systems to communicate with each other • TCP/IP (Internet/Windows NT) • IPX / SPX (Novell Netware 4) • AppleTalk • Other Network OS • Services • The Heart of Networking • Cooperation between 2 or more systems to perform some function - Applications • telnet • FTP • HTTP • SMTP Lecture Notes - 1

  9. Traditional Network Design • Based on a set of general rules • “80/20” • “Bridge when you can, route when you must” • Can’t deal with scalability & complexity • Focused on capacity planning • Throw more bandwidth at the problem • No consideration to delay optimization • No guarantee of service quality • Less importance given to network RMA (Reliability, Maintainability, and Availability) compared to throughput Lecture Notes - 1

  10. Application Characteristics Lecture Notes - 1

  11. Application Bandwidths Transaction Processing 100 Bytes Few Kbps Word Processing 100s Kbps Few Mbps File Transfers Few Mbps 10s Mbps Real-Time Imaging 10s Mbps 100s Mbps Lecture Notes - 1

  12. A Look on Multimedia Networking Lecture Notes - 1

  13. Some Networking Issues • LAN, MAN and WAN • Switching and routing • Technologies: Ethernet, FDDI, ATM … • Wireless/Mobile networking • Internetworking • Applications • Service quality • Security concerns Lecture Notes - 1

  14. Network Design: Achievable? Response Time Cost Business Growth Reliability Lecture Notes - 1

  15. Where to begin? Addressing TrafficPatterns WWW Access Campus Users Dial in Users NetworkManagement Security WAN Lecture Notes - 1

  16. Traditional Network Design Methodology • Many network design tools and methodologies that have been used resemble the “connect-the-dots” game • These tools let you place internetworking devices on a palette and connect them with LAN or WAN media • Problem with this methodology: • It skips the steps of analyzing a customer's requirements, and selecting devices and media based on those requirements Lecture Notes - 1

  17. Top-Down Network Design Methodology (1/2) • Good network design • Recognizes that a customer’s requirements embody many business and technical goals • May specify a required level of network performance, i.e.,service level • Includes difficult network design choices and tradeoffs that must be made when designing the logical network before any physical devices or media are selected • When a customer expects a quick response to a network design request • A bottom-up (connect-the-dots) network design methodology can be used, if the customer’s applications and goals are well known Lecture Notes - 1

  18. Top-Down Network Design Methodology (2/2) • Network designers often think they understand a customer’s applications and requirements. • However, after the network installation, they may discover that: • They did not capture the customer's most important needs • Unexpected scalability and performance problems appear as the number of network users increases Lecture Notes - 1

  19. Top-Down Network Design Process (1/2) • Begins at the upper layers of the OSI reference model before moving to the lower layers • Focuses on applications, sessions, and data transport before the selection of routers, switches, and media that operate at the lower layers • Explores divisional structures to find the people: • For whom the network will provide services, and • From whom to get valuable information to make the design succeed Lecture Notes - 1

  20. Top-Down Network Design Process (2/2) • It is an iterative process: • It is important to first get an overall view of a customer's requirements • More detail can be gathered later on protocol behavior, scalability requirements, technology preferences, etc. • Recognizes that the logical model and the physical design may change as more information is gathered • A top-down approach lets a network designer get “the big picture” first and then spiral downward into detailed technical requirements and specifications Lecture Notes - 1

  21. Network Development Life Cycle Analysis Management Design Simulation/ Prototyping Monitoring Implementation Lecture Notes - 1

  22. Network Design and Implementation Cycle Lecture Notes - 1

  23. Network Design and Implementation Cycle (1/3) • Analyze requirements: • Interviews with users and technical personnel • Understand business and technical goals for a new or enhanced system • Characterize the existing network: logical and physical topology, and network performance • Analyze current and future network traffic, including traffic flow and load, protocol behavior, and QoS requirements Lecture Notes - 1

  24. Network Design and Implementation Cycle (2/3) • Develop the logical design: • Deals with a logical topology for the new or enhanced network • Network layer addressing and naming • Switching and routing protocols • Security planning • Network management design • Initial investigation into which service providers can meet WAN and remote access requirements Lecture Notes - 1

  25. Network Design and Implementation Cycle (3/3) • Develop the physical design: • Specific technologies and products to realize the logical design are selected • The investigation into service providers must be completed during this phase • Test, optimize, and document the design: • Write and implement a test plan • Build a prototype or pilot • Optimize the network design • Document your work with a network design proposal Lecture Notes - 1

  26. Another Perspective • Data collection • Traffic • Costs • Constraints • Design process • Performance analysis • Fine tuning • A painstaking iterative process Lecture Notes - 1

  27. PDIOO Network Life Cycle (1/3)(Cisco) • Plan: • Network requirements are identified in this phase • Analysis of areas where the network will be installed • Identification of users who will require network services • Design: • Accomplish the logical and physical design, according to requirements gathered during the Plan phase • Implement: • Network is built according to the Design specifications • Implementation also serves to verify the design Lecture Notes - 1

  28. PDIOO Network Life Cycle (2/3)(Cisco) • Operate: • Operation is the final test of the effectiveness of the design • The network is monitored during this phase for performance problems and any faults, to provide input into the Optimize phase • Optimize: • Based on proactive network management which identifies and resolves problems before network disruptions arise • The optimize phase may lead to a network redesign • if too many problems arise due to design errors, or • as network performance degrades over time as actual use and capabilities diverge • Redesign may also be required when requirements change significantly Lecture Notes - 1

  29. PDIOO Network Life Cycle (3/3)(Cisco) • Retire: • When the network, or a part of the network, is out-of-date, it may be taken out of production • Although Retire is not incorporated into the name of the life cycle (PDIOO), it is nonetheless an important phase Lecture Notes - 1

  30. One More Look BusinessPlanning Network Design ImplementNetwork Operations Develop OperationsPolicies andCapabilities Define Objectivesand Requirements DevelopArchitecture CreateImplementation Plan Create InitialSolution Develop DetailedDesign Procure Resourcesand Facilities FaultManagement Define DeploymentStrategy Create BuildDocumentation ConfigurationManagement Stage and Install ChangeManagement Review andApprove Review and VerifyDesign Certify and Hand-offto Operations PerformanceManagement Lecture Notes - 1

  31. Information Flows between Network Analysis, Architecture, and Design Lecture Notes - 1

  32. Network Analysis and Design Methodology- Overall Characteristics - • Requirements (business, application, and data) definition is required prior to network design activities • Expected compliance with requirements in a Request For Proposal (RFP) by both in-house personnel and outside consultants • Activities from various stages often take place simultaneously and backtrack to previous activities is sometimes needed • This methodology is an overall guideline to the network development process rather than “cookbook” instructions Lecture Notes - 1

  33. Network Analysis and Design Methodology-Critical Success Factors of the NDLC (1/3) - • Identification of all potential customers and constituencies • All groups must be consulted • Political awareness: • Corporate culture: hierarchical, distributed, or open • Backroom politics can play a role in systems design • Find ways to ensure objectivity of the analysis and design process (e.g., measurable goals) • Buy-in: • Reach consensus on the acceptability of results of each stage • Approved results of one stage become the foundation or starting point for the next stage • Makes the final presentation smoother Lecture Notes - 1

  34. Network Analysis and Design Methodology-Critical Success Factors of the NDLC (2/3) - • Communication: • With all groups • Write memos, communicate with key people in person, etc. • Detailed project documentation: • Prepare agendas • Take meeting minutes • Action items • Use a project binder for all the above Lecture Notes - 1

  35. Network Analysis and Design Methodology- Critical Success Factors of the NDLC (3/3) - • Process/Product awareness: • Stay focused: what is the process/product at each stage? • Keep meeting on track: no off-subject discussions • Be honest with yourself: • Be your own harshest critic (no one else knows the potential weaknesses or areas for improvement in your proposal better than you) • Use peer reviews • Not all weaknesses can be corrected (e.g., financial or time constraints) Lecture Notes - 1

  36. Network Analysis and Design Methodology- Overall Guidelines - • Start with a clearly defined problem: • Identify affected parties and representatives • Held brainstorming sessions to define problems and requirements of a solution • Understand strategic business objectives defined by senior management • Collect baseline data from customer groups about the current status of the system and network • This is used to measure eventual impact of the installed network • Perform a feasibility study: problem definition and associated alternative recommendations for further study Lecture Notes - 1

  37. Customer’s Requirements- Understanding the Customer - • A good network design must recognize the customer’s requirements - need to make sure your design meets THEIR needs and not just YOURS! • The “Customer” may be your own firm, the “who” you are designing the network for • Need an overview of a customer’s requirements • The best designed network will fail miserably without the support of people Lecture Notes - 1

  38. Customer’s Requirements- Users’ Needs - • What do the users want? • Services • What do the users need? • What don’t they know but they need? • Organize and Prioritize Requirement Lecture Notes - 1

  39. Customer’s Requirements- How they are used - • User Requirements  Performance Requirements • Timeliness • Interactivity • Reliability • Quality • Security • Affordability • User Numbers • User Locations • User Growth Delay Reliability Capacity Lecture Notes - 1

  40. Analysis and Design Processes • Set and achieve goals • Maximizing performance • Minimizing cost • Optimization with trade-offs • Recognizing trade-offs • No single ‘best’ answer • Hierarchies • Provide structure in the network • Redundancy • Provides availability & reliability Lecture Notes - 1

  41. Approaches Used for Design • Heuristic – by using various algorithms • Exact – by working out mathematical solutions based on linear programming, etc., minimizing certain cost functions • Simulation – often used when no exact analytical form exists. Experiments are conducted on simplified models to see the performance of a network Lecture Notes - 1

  42. Design and Study of a System Lecture Notes - 1

  43. Art or Science? • The Art of Network Design • Technology choices • Relations to business goals The Science of Network Design • Understanding of network technologies • Analysis of capacity, redundancy, delay … Lecture Notes - 1

  44. Types of Network Design • New network design • Re-engineering a network design • Network expansion design Lecture Notes - 1

  45. New Network Design • Actually starting from scratch • No legacy networks to accommodate • Major driver is the budget, no compatibility issues to worry about • Getting harder to find these situations Lecture Notes - 1

  46. Re-engineering a Network Design • Modifications to an existing network to compensate for original design problems • Sometimes required when network users change existing applications or functionality • More of the type of problems seen today Lecture Notes - 1

  47. Network Expansion Design • Network designs that expand network capacity • Technology upgrades • Adding more users or networked equipment Lecture Notes - 1

  48. This Whole Thing is Messy

  49. This Whole Thing is Messy • Ambiguous Requirements • The network will only transport IP • The application requires Novell IPX Lecture Notes - 1

  50. This Whole Thing is Messy • Conflicting Requirements • Keep costs down • High performance costs money Lecture Notes - 1