1. Chapter 4 Panko and Panko Business Data Networks and Telecommunications, 8 th Edition © 2011 Pearson Education, Inc. Publishing as Prentice Hall Panko and Panko Business Data Networks and Telecommunications, 8 th Edition © 2011 Pearson Education, Inc. Publishing as Prentice Hall Panko and Panko Business Data Networks and Telecommunications, 8 th Edition © 2011 Pearson Education, Inc. Publishing as Prentice Hall

2.  Chapter 4 is the final introductory chapter.  It deals with network management, with a strong focus on network design.  Subsequent chapters will apply the concepts in these four introductory chapters to specific situations, including wired switched and wireless LANs and WANs, internets, and applications. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 2

3. Core concerns Quality of service (QoS)Network designSelection among alternativesOngoing management (OAM&P)Network visibility (SNMP) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 3

4. 4 Networking must go beyond the systems development life cycle to the full system life cycle over the network’s life. It also needs to understand the business system in which each network component operates. Networking must go beyond the systems development life cycle to the full system life cycle over the network’s life. It also needs to understand the business system in which each network component operates.

5. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 5 User demand is growing much faster than network budgets. Cost efficiency is always critical. User demand is growing much faster than network budgets. Cost efficiency is always critical.

6. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6

7.  Legacy Decisions ◦ Decisions that lock your network in for a considerable period of time ◦ Multi-year leases ◦ Decisions about alternate strategic directions to take ◦ Deserve very careful attention © 2011 Pearson Education, Inc. Publishing as Prentice Hall 7

8. Core concerns Quality of service (QoS) Network designSelection among alternativesOngoing management (OAM&P)Network visibility (SNMP) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 8

9.  Networks today must work well.  Companies measure quality-of-service (QoS) metrics to measure network performance.  Examples: ◦ Speed ◦ Availability ◦ Cost ◦ And so on © 2011 Pearson Education, Inc. Publishing as Prentice Hall 9

10.  Normally measured in bits per second (bps) ◦ Not bytes per second ◦ Occasionally measured in bytes per second  If so, labeled as Bps ◦ Metric prefixes increase by factors of 1,000 (not 1,024 as in computer memory) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 10

11. PrefixMeaningExample kbps*1,000 bps17,000 bps is 17 kbps 3 kbps is 3,000 bps 34.7 kbps is 3,700 bps Mbps1,000 kbps8,720,000 bps is 8.7 Mbps 14.75 Mbps is 14,750,000 bps Gbps1,000 Mbps87 Gbps = 87,000,000,000 bps Tbps1,000 Gbps © 2011 Pearson Education, Inc. Publishing as Prentice Hall 11 *Note that the metric prefix kilo is abbreviated with a lowercase k

12.  Expressing speed in proper notation ◦ There must be one to three places before the decimal point, and leading zeros do not count. ◦ There must be a space before the metric suffix. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 12 As WrittenPlaces before decimal point Space between number and prefix? Properly written 23.72 Mbps2YesOK as is 2,300 kbps4Yes2.3 Mbps 0.5Mbps0No500 kbps

13.  Doing Conversions ◦ Improperly written: 3,625 Mbps ◦ Four places before the (implicit) decimal point ◦ Must divide the number by 1,000: 3.625  (Shift the decimal point three places to the right) ◦ Therefore, must multiply the metric prefix by 1,000: So Mbps  Gbps ◦ Properly written: 3.625 Gbps © 2011 Pearson Education, Inc. Publishing as Prentice Hall 13

14.  Doing Conversions ◦ Improperly written: 0.3 Mbps ◦ Zero places before the decimal point ◦ Must multiply the number by 1,000: 300  (Shift the decimal point three places to the left) ◦ Therefore must divide the metric prefix by 1,000: So Mbps  kbps ◦ Properly written: 300 kbps © 2011 Pearson Education, Inc. Publishing as Prentice Hall 14

15.  Perspective ◦ If the number has one to three places before the decimal point, it is fine. ◦ Otherwise, you must multiply or divide the number by 1,000. ◦ You do the opposite to the metric prefix. ◦ This leaves the number the same  0.4 Mbps = 400,000 bps  400 kbps = 400,000 bps © 2011 Pearson Education, Inc. Publishing as Prentice Hall 15

16.  Rated Speed ◦ The speed a system should achieve, ◦ According to vendor claims or the standard that defines the technology.  Throughput ◦ The speed a system actually provides to users ◦ (Almost always lower) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 16

17.  Aggregate Throughput ◦ The aggregate throughput is the total throughput available to all users.  Individual Throughput ◦ An individual’s share of the aggregate throughput © 2011 Pearson Education, Inc. Publishing as Prentice Hall 17

18. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 18 Individual throughput Aggregate throughput Rated speed

19.  Availability ◦ The time (percentage) a network is available for use  Example: 99.9% ◦ Downtime is the amount of time (minutes, hours, days, etc.) a network is unavailable for use.  Example: An average of 12 minutes per month © 2011 Pearson Education, Inc. Publishing as Prentice Hall 19

20.  Error Rates ◦ Errors are bad because they require retransmissions. ◦ More subtly, when an error occurs, TCP assumes that there is congestion and slows its rate of transmission. ◦ Packet error rate: the percentage of packets that have errors. ◦ Bit error rate (BER): the percentage of bits that have errors. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 20

21.  Latency ◦ Latency is delay, measured in milliseconds. ◦ When you ping a host’s IP address, you get the latency to the host. ◦ When you use tracert, you get average latency to each router along the route. ◦ Beyond about 250 ms, turn-taking in conversations becomes almost impossible. ◦ Latency hurts interactive gaming. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 21

22.  Jitter ◦ Jitter is variation in latency between successive packets. ◦ Makes voice and music speed up and slow down over milliseconds—sounds jittery. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 22

23.  Application Response Time (4.8) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 23

24.  Application Response Time ◦ Not purely a network matter. ◦ To control application response time, networking, server, and application people must work together to improve user experiences. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 24

25.  Service Level Agreements (SLA) ◦ Guarantees for performance ◦ Increasingly demanded by users ◦ Penalties if the network does not meet its QoS metric guarantees © 2011 Pearson Education, Inc. Publishing as Prentice Hall 25

26.  Service Level Agreements (SLA) ◦ Guarantees are often written on a percentage of time basis  “No worse than 100 Mbps 99.95% of the time”  As percentage of time requirement increases, the cost to provide service increases exponentially  So SLAs cannot be met 100% of the time © 2011 Pearson Education, Inc. Publishing as Prentice Hall 26

27.  Service Level Agreements (SLA) ◦ SLAs specify worst cases (minimum performance to be tolerated)  Penalties if worse than the specified performance  Example: latency no higher than 50 ms 99.99% of the time ◦ If specified the best case (maximum performance), you would rarely get better  Example: No higher than 100 Mbps 99% of the time. Who would want that? © 2011 Pearson Education, Inc. Publishing as Prentice Hall 27

28.  Examples  Jitter ◦ No higher than 2% variation in packet arrival time 99% of the time  Latency ◦ No higher than 125 Mbps 99% of the time  Availability ◦ No lower than 99.99% ◦ Availability is a percentage of time, so its SLA does not include a percentage of time © 2011 Pearson Education, Inc. Publishing as Prentice Hall 28

29. Core concernsQuality of service (QoS) Network design Selection among alternativesOngoing management (OAM&P)Network visibility (SNMP) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 29

30.  To manage a network, it helps to be able to draw pictures of it. ◦ Network drawing programs do this. ◦ There are many network drawing programs. ◦ One is Microsoft Office Visio.  Must buy the correct version to get network and computer templates ◦ We will show examples from OPNET IT Guru. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 30

31.  Nodes are hosts, switches, routers, and so on. 31 © 2011 Pearson Education, Inc. Publishing as Prentice Hall Just drag nodes onto the canvas.

32. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 32 Then drag link icons between nodes. There are many types of link icons. Then drag link icons between nodes. There are many types of link icons.

33.  You must be able to compute what traffic a line must carry in each direction to select an appropriate transmission line. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 33

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37.  Topologies describe the physical arrangement of nodes and links. ◦ “Topology” is a physical layer concept.  Many standards require specific topologies.  In other cases, you can select topologies that make sense in terms of transmission costs, reliability through redundancy, and so on. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 37

38. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 38 How many possible paths are there between A and B? How many possible paths are there between A and B?

39. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 39 How many possible paths are there between A and B? How many possible paths are there between A and B?

40. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 40 In a hierarchy, each node has one parent. How many possible paths are there between A and B?

41. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 41 How many possible paths are there between A and B? 1 4 3 2

42. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 42 What do you think will happen if A and B would transmit at the same time?

43. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 43 Many real networks have complex topologies incorporating the pure topologies we have just seen.

44. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 44

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46.  Full-mesh and hub-and-spoke topologies are opposite ends of a spectrum.  Real network designers must balance cost and reliability when designing complex networks. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 46

47.  Normally, network capacity is higher than the traffic.  Sometimes, however, there will be momentary traffic peaks above the network’s capacity—usually for a fraction of a second to a few seconds. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 47

48.  This congestion causes latency because switches and routers must store frames and packets waiting to send them out.  Buffers are small, so packets are often lost. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 48

49.  Overprovisioning is providing far more capacity than the network normally needs.  This avoids nearly all momentary traffic peaks but is wasteful. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 49

50.  With priority, latency-intolerant traffic, such as voice, is given high priority and will go first if there is congestion.  Latency-tolerant traffic, such as e-mail, must wait.  More efficient than overprovisioning; also more labor-intensive. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 50

51.  QoS guarantees reserved capacity for some traffic, so this traffic always gets through.  Other traffic, however, must fight for the remaining capacity. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 51

52.  Overprovisioning, priority, and QoS reservations deal with congestion; traffic shaping prevents congestion by limiting incoming traffic. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 52

53.  Filtering out or limiting undesirable incoming traffic can also substantially reduce overall network costs. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 53

54.  Some traffic can be banned and simply filtered out.  Other traffic has both legitimate and illegitimate uses; it can be limited to a certain percentage of traffic. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 54

55.  Compression can help if traffic chronically exceeds the capacity on a line. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 55 8 Gbps is needed. The line can only carry 1 Gbps. 8 Gbps is needed. The line can only carry 1 Gbps.

56.  Data often contains redundancies and can be compressed. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 56

57.  Must have compatible compression equipment at the two ends of the line. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 57

58.  Often, the design of a building naturally constrains the topology of a design.  In a multistory building, for in- stance, it often makes sense to place an Ethernet workgroup switch on each floor and a core switch in the basement. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 58

59.  Network drawing tools show the elements of the network and how they are interconnected.  Network simulation software goes farther by creating a computer model of the network, not just a picture. ◦ The model has the capacity and configuration of each node and transmission link. ◦ Simulation can indicate congestion points, underused lines, and so on. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 59

60.  What-If Analysis ◦ Try alternative designs to close performance gaps. ◦ Select the optimum design in terms of performance and cost. ◦ Trying many designs will probably result in the selection of a very good design. ◦ Far cheaper than changing around the real network. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 60

61. Core concernsQuality of service (QoS)Network design Selection among alternatives Ongoing management (OAM&P)Network visibility (SNMP) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 61

62.  Comparing Alternatives ◦ Designers must select among competing approaches and even competing technologies. ◦ When learning about technologies and network designs, you need to look carefully at pros and cons. ◦ Comparing alternatives is a major theme of this book. ◦ Do not study concepts in isolation. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 62

63.  4.22: Scalability © 2011 Pearson Education, Inc. Publishing as Prentice Hall 63 There is a maximum expected traffic volume. There is a maximum expected traffic volume.

64.  4.22: Scalability © 2011 Pearson Education, Inc. Publishing as Prentice Hall 64

65.  Minimum Requirements ◦ Specifications that set particular requirements must be met. ◦ Noncompliant products that do not meet a minimum requirement cannot be considered further. ◦ A failure to scale to meet expected traffic would be an example. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 65

66.  Multicriteria decision making is a disciplined way to look at and evaluate all aspects of alternatives. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 66 Product AProduct B Criterion Weight (Max 5) Product Rating (Max 10) Criterion Score Product Rating (Max 10) Criterion Score Functionality5840420 Ease of management 28168 Cost*428832 Total Score6468 *Higher cost ratings indicate lower cost.

67.  Cost is difficult to measure.  Systems Development Life Cycle Costs ◦ Hardware: full price—base price plus necessary optional components ◦ Software: full price—base price plus necessary optional modules ◦ Labor costs: Network staff and user costs during development ◦ Outsourced development cost ◦ Total development cost © 2011 Pearson Education, Inc. Publishing as Prentice Hall 67

68.  System Life Cycle Costs ◦ Development cost plus ongoing cost, which usually is much larger than development cost ◦ Measured as the total cost of ownership (TCO)  All costs over a system’s total life ◦ Ongoing costs include carrier costs  Carrier pricing is complex and difficult to analyze  Often locked in by multi-year leases © 2011 Pearson Education, Inc. Publishing as Prentice Hall 68

69. Core concernsQuality of service (QoS)Network designSelection among alternatives Ongoing management (OAM&P) Network visibility (SNMP) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 69

70.  Described as OAM&P  Operations ◦ Moment-by-moment traffic management ◦ Network operations center  Administration ◦ Paying bills, administering contracts, and so on ◦ Dull but necessary © 2011 Pearson Education, Inc. Publishing as Prentice Hall 70

71.  Described as OAM&P  Maintenance ◦ Fixing things that go wrong ◦ Also, preventative maintenance ◦ Maintenance staff should be separate from the operations staff  Different skill set © 2011 Pearson Education, Inc. Publishing as Prentice Hall 71

72.  Described as OAM&P  Provisioning (providing service) ◦ Includes physical installation ◦ Includes setting up user accounts and services ◦ Reprovisioning when things change ◦ Deprovisioning when accounts and services are no longer appropriate ◦ Collectively, extremely expensive © 2011 Pearson Education, Inc. Publishing as Prentice Hall 72

73. Core concernsQuality of service (QoS)Network designSelection among alternativesOngoing management (OAM&P) Network visibility (SNMP) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 73

74.  It is desirable to have network visibility—to know the status of all devices at all times.  The simple network management protocol (SNMP) is designed to collect information needed for network visibility. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 74

75.  Central manager program communicates with each managed device.  Actually, the manager communicates with a network management agent on each device. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 75

76.  The manager sends commands and gets responses.  Agents can send traps (alarms) if there are problems. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 76

77.  Information from agents is stored in the SNMP management information base. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 77

78.  Network visualization programs analyze information from the MIB to portray the network, do troubleshooting, and answer specific questions.  SNMP interactions are standardized, but network visualization program functionality is not, in order not to constrain developers of visualization tools. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 78

79. Core concernsQuality of service (QoS)Network designSelection among alternativesOngoing management (OAM&P)Network visibility (SNMP) © 2011 Pearson Education, Inc. Publishing as Prentice Hall 79

80.  We have finished the four introductory chapters ◦ How we got here ◦ Network standards ◦ Network security ◦ Network design and management  We will apply the concepts you learned in these chapters throughout the book © 2011 Pearson Education, Inc. Publishing as Prentice Hall 80

81.  The remaining chapters go “up through the layers” ◦ Chapter 5: Wired physical layer propagation (L1) ◦ Chapter 6: switched wired networks (L1 and L2) ◦ Chapters 7 and 8: Wireless networks (L1 and L2) ◦ Chapters 9 and 10: Internetworking (L3 and L4) ◦ Chapter 11: Networked Applications (L5) ◦ You will apply introductory concepts to the materials in each chapter. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 81

82. © 2011 Pearson Education, Inc. Publishing as Prentice Hall 82 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America.