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Module 1.1: Introduction (cont.)

Module 1.1: Introduction (cont.)

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Module 1.1: Introduction (cont.)

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  1. Module 1.1: Introduction (cont.) • Business Goals and Constraints • Analyzing Technical Goals K. Salah

  2. 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 K. Salah

  3. Business Goals • Before we look at the technical details, we first start at the business goals • Start with researching your client’s business • what industry are they in • their market • their suppliers • their products • their services • the competition they face K. Salah

  4. Business Goals - Continued • Need to understand the organizational structure of the client • their separate departments • lines of business • vendors • partners • remote offices • This will help characterize traffic flow and determine user communities K. Salah

  5. Business Goals - Continued • When you understand the corporate structure, you also identify who the key decision makers are, who will have final say on your design proposal when you are finished • You want to understand what are the overall goal of the network design project K. Salah

  6. Questions to Ask • Why are they doing the network design analysis? • What will the network be used for? • How does the customer think the new network will improve their business practices? • What is the criteria to be used to judge the network? K. Salah

  7. Success Criteria • What makes the network design a success? • May be defined differently by the different “stakeholders” • company executives • managers • end users • network administrators • system programmers • any other person or group who has a stake in the network design project K. Salah

  8. Failure Consequences • What happens if the project does not meet the design objectives? • How visible is the project to upper management? • To what extent could unforeseen behavior of the new network disrupt business operations? K. Salah

  9. The Internet Impact • The growth of the Internet has made interconnection with it almost a business priority for network design • Vast amounts of information is now being shared within the organization using the internet as a design example, normally called Intranets. K. Salah

  10. Typical Business Goals • Increase revenue and profit • Improve corporate communications • Shorten product development cycles • Build partnerships with other companies • Expand into other markets • Modernize out-dated technologies • Reduce network costs • Make more data available to more people • Improve network security and reliability K. Salah

  11. Business Constraints • Politics and Policies • Are there people who would like to see you fail? • What are the companies policy on suppliers • Budget and Staffing Constraints • Your design must fit the budget • Staff abilities may determine some of your design • Scheduling K. Salah

  12. Analyzing Technical Goals K. Salah

  13. Analyzing Technical Goals • Now that we have discussed Business Goals, lets examine the Technical Goals that we need to understand and should reflect in the design of a network • You need to match your network design to fit the customers technical needs K. Salah

  14. Technical Goals & Constraints • Scalability • Availability • Network Performance • Utilization, Throughput, Accuracy, Efficiency, Delay, and Response Time • Security • Manageability • Usability • Adaptability • Affordability K. Salah

  15. Scalability • Scalability - how much growth a network design must support • Need to examine the network needs out a few years - 3 years as a minimum • Key points to understand • How many more sites will be added? • How extensive will the networks be at each site? • How many more users will be added? • How many more servers will be added? K. Salah

  16. Availability • Availability is the amount of time a network is available to users • Can be expressed as percent uptime • 165 hours in 168 hours/week = 98.21% • Redundancy is used to increase a networks availability • Availability is also tied to disaster recovery • 99.70 - 30 minutes outage every week K. Salah

  17. Network Performance • There are several measures to look at • Utilization • Throughput • Accuracy • Efficiency – A key measure • Protocol Frame Size, Protocol Overhead, and Routing Protocol Overhead • Delay • Response Time K. Salah

  18. Network Performance - Utilization • Is the percent of total available capacity (bandwidth) in use • Bandwidth is measured over a time interval to determine the amount in use • There are several numbers used to describe when your network shows delays that impact the usability of the network - will will examine these later. K. Salah

  19. Network Performance - Throughput • Throughput is defined as the quantity of error-free data successfully transferred between nodes per unit of time • Depends on network access method, the load on the network and the error rate • Throughput can be expressed in Packets per Second (PPS) than can be sent by a device with dropping any packets K. Salah

  20. Network Performance -Accuracy • Accuracy is a measure to ensure that the data received at the destination must be the same as the data sent by the source • Data errors are caused by power surges, or spikes, poor physical connections, failing devices and electrical noise • Accuracy can be expressed in Bit Error Rate (BER), typically 1 in 105 K. Salah

  21. Network Performance -Efficiency • We measure how effective an operation is • How much “overhead” is needed to send traffic across the network - the traffic has our data in it • Overhead is due to several factors lets look at some of them: • Network Protocol Frame Size • Network Protocol Overhead • Routing Protocol Overheads K. Salah

  22. Efficiency and Network Protocol Frame Sizes • Since application data is sent over frames and each frame can hold some data. Key is how many frames do I need to sent my data? (each frame has some overhead in it) • Novell IPX 1,500 byte Frame Size • Telnet is only 60 bytes • HTTP (Web) is 1,500 bytes • Token Ring uses 4,096 bytes • ATM used 53 byte cells K. Salah

  23. Efficiency and Network Protocol Frame Sizes K. Salah

  24. Efficiency and Network Protocol Overhead • Remember data is packaged in protocol frames that contain overhead data, some have more overhead than others • Ethernet - 38 bytes per frame • IP - 20 bytes per frame • TCP - 20 bytes per frame • IPX - 30 bytes per frame • ATM - 5 bytes per cell K. Salah

  25. Efficiency and Network Protocol Overhead 802.2 – Logical Link Control header used with Ethernet and Token Ring Ethernet w LLC Token Ring w LLC K. Salah

  26. Efficiency and Routing Protocol Overheads • Remember each routing protocol also use up network bandwidth • IP RIP - every 30 seconds sends 532 byte packages • IP IGRP - every 90 seconds sends 1,488 byte packages • IPX SAP - every 60 seconds sends a 480 byte package K. Salah

  27. Efficiency and Routing Protocol Overheads K. Salah

  28. Network Performance -Efficiency - Summary • You want to use a protocol that has a large frame size, and one that also needs only small header information in each frame • You want an efficient Routing Protocol • This allows us to transfer more data at a higher efficiency across our network! K. Salah

  29. Network Performance - Delay • Interactive applications demand minimal delay when receiving a data stream • Delay must be constant for voice and video applications other wise you will get jitter causing disruptions in voice quality and jumpiness in video streams • Delay can be caused by physics, and by network devices that move the data within a network (use buffers to minimize effect) K. Salah

  30. Network Performance - Queuing Delay • Queuing delay is the number of packets in a queue on a packet switching device • As utilization increases, more packets must wait in the queue before being put on the wire • Queue depth = utilization/(1-utilization) K. Salah

  31. Network Performance - Response Time • Response time is a network performance goal that users care about most • Users recognize the amount of time to receive a response from the network system • Users begin to get frustrated when response time is 100ms (.1 seconds) or so K. Salah

  32. Security • Security design is getting to be one of the most important aspects of network design • Network design must ensure against loss of business data or disruption of business activity • Need to understand the risk of data loss • Need to understand ways to get to the data • Need to understand who wants the data K. Salah

  33. Manageability • There are different ways to manage a network and the different things to manage • Performance management • Fault management • Configuration management • Security management • Accounting management K. Salah

  34. Usability • Usability refers to the ease-of-use with which network users can access the network and services • Focus is on making the network users’ job easier • example is using host naming servers and easy to use configuration devices such as a DHCP server K. Salah

  35. Adaptability • You want to ensure the network can implement new technologies in the future • You want it to be able to adapt and change with technology • A flexible network can also adapt to changing network patterns and quality of service (QoS) requirements K. Salah

  36. Affordability • Affordability is sometimes called cost-effectiveness • Want to carry the maximum amount of traffic for a given financial cost • Financial costs include non-recurring equipment costs and recurring network operating costs • WAN costs are an area where a good design can save $ K. Salah