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Presentation on theme: "N ETWORK D ESIGN AND I MPLEMENTATION EEB_7_876 For MSc TeCNE and EDS 1."— Presentation transcript:


2 2 Website: Methods of Teaching and Learning : Lectures and Workshops Assessment of the Module : 2-hour written examination -- 50% Two laboratory work reports -- 50% Lecturer: Ya Bao and Perry Xiao.

3 3 Top-Down Network Design, 3 rd Edition Priscilla Oppenheimer Designing and Supporting Computer Networks (CCNA)

4 B ACKGROUND R EADING 4 Networking Systems Design and Development

5 T EACHING CALENDAR  Network Programming (Week 1 – 6)  Network Design (Week 7 – 12) Week 7, 8 Identifying Your Customer’s Needs and Goals Week 8, 9 Logical Network Design Week 10 Physical Network Design Week 11 Testing, Optimizing and Documenting Week 12 Review  Christmas vacation (3 weeks)  Revision (week 13)  Examination (week 14-15) 5

6 P ART 1 I DENTIFYING Y OUR C USTOMER ’ S N EEDS AND G OALS 6  Analyzing Business Goals and Constraints  Analyzing Technical Goals and Tradeoffs  Characterizing the Existing Internetwork  Characterizing Network Traffic

7 C HAPTER O NE A NALYZING B USINESS G OALS AND C ONSTRAINTS  Systematic, Top-down network design methodology  Analysing your customer’s business objectives  Analysing the business constrains; budgets, timeframes, workplace politics. 7

8 N ETWORK D ESIGN Good network design must recognizes customer’s requirements. Network design choices and tradeoffs must be made when designing the logic network before any physical devices are selected. 8

9 S TRUCTURED N ETWORK D ESIGN Four fundamental network design goals: Scalability Availability Security Manageability 9

10 H OW A S TRUCTURED N ETWORK D ESIGN C REATES A S TABLE, R ELIABLE, S CALABLE N ETWORK Network requirements: Ease of management Fast recovery Application response time Fast troubleshooting 10

11 S TRUCTURED N ETWORK D ESIGN Core Layer: connects Distribution Layer devices Distribution Layer: interconnects smaller LANs Access Layer: provides connections for hosts and end devices 11

12 S TRUCTURED N ETWORK D ESIGN Steps in network design projects: Identify the network requirements Characterize the existing network (for network upgrading only) Design the network topology and solutions Testing, optimizing and documenting 12

13 S TART FROM THE T OP 13 Application Presentation Session Transport Network Data Link Physical Layer 1 Layer 7 Layer 6 Layer 5 Layer 4 Layer 3 Layer 2

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15 S YSTEMS D EVELOPMENT L IFE C YCLES (SDLC) Typical systems are developed and continue to exist over a period of time, often called a systems development life cycle (SDLC). 15

16 Analyze requirements Develop logical design Develop physical design Test, optimize, and document design Monitor and optimize network performance Implement and test network T OP -D OWN N ETWORK D ESIGN S TEPS 16 systems development life cycle (SDLC).

17 T HE PDIOO N ETWORK L IFE C YCLE Plan Design Implement Operate Optimize Retire Plan Design Implement Operate Optimize 17

18 N ETWORK D ESIGN S TEPS Phase 1 – Analyze Requirements Analyze business goals and constraints Analyze technical goals and tradeoffs Characterize the existing network Characterize network traffic 18 Today’s topic

19 N ETWORK D ESIGN S TEPS Phase 2 – Logical Network Design Design a network topology Design models for addressing and naming Select switching and routing protocols Develop network security strategies Develop network management strategies 19

20 N ETWORK D ESIGN S TEPS Phase 3 – Physical Network Design Select technologies and devices for campus networks Select technologies and devices for enterprise networks 20

21 N ETWORK D ESIGN S TEPS Phase 4 – Testing, Optimizing, and Documenting the Network Design Test the network design Optimize the network design Document the network design 21

22 B USINESS G OALS Increase revenue Reduce operating costs Improve communications Shorten product development cycle Expand into worldwide markets Build partnerships with other companies Offer better customer support or new customer services 22

23 R ECENT B USINESS P RIORITIES Mobility Security Resiliency (fault tolerance) Business continuity after a disaster Network projects must be prioritized based on fiscal goals Networks must offer the low delay required for real-time applications such as VoIP 23

24 B USINESS C ONSTRAINTS Budget Staffing Schedule Politics and policies 24

25 C OLLECT I NFORMATION B EFORE THE F IRST M EETING Before meeting with the client, whether internal or external, collect some basic business-related information Such as Products produced/Services supplied Financial viability Customers, suppliers, competitors Competitive advantage 25

26 M EET W ITH THE C USTOMER Try to get A concise statement of the goals of the project What problem are they trying to solve? How will new technology help them be more successful in their business? What must happen for the project to succeed? 26

27 M EET W ITH THE C USTOMER Get a copy of the organization chart This will show the general structure of the organization It will suggest users to account for It will suggest geographical locations to account for 27

28 M EET W ITH THE C USTOMER Get a copy of the security policy How does the policy affect the new design? How does the new design affect the policy? Is the policy so strict that you (the network designer) won’t be able to do your job? Start cataloging network assets that security should protect Hardware, software, applications, and data Less obvious, but still important, intellectual property, trade secrets, and a company's reputation 28

29 T HE S COPE OF THE D ESIGN P ROJECT Small in scope? Allow sales people to access network via a VPN Large in scope? An entire redesign of an enterprise network Use the OSI model to clarify the scope New financial reporting application versus new routing protocol versus new data link (wireless, for example) Does the scope fit the budget, capabilities of staff and consultants, schedule? 29

30 G ATHER M ORE D ETAILED I NFORMATION Applications Now and after the project is completed Include both productivity applications and system management applications User communities Data stores Protocols Current logical and physical architecture Current performance 30

31 S UMMARY Systematic approach Focus first on business requirements and constraints, and applications Gain an understanding of the customer’s corporate structure Gain an understanding of the customer’s business style 31

32 R EVIEW Q UESTIONS What are the main phases of network design per the top-down network design approach? What are the main phases of network design per the PDIOO approach? Why is it important to understand your customer’s business style? What are some typical business goals for organizations today? 32

33 C HAPTER T WO A NALYZING T ECHNICAL G OALS AND T RADEOFFS 33 Copyright 2010 Cisco Press & Priscilla Oppenheimer

34 T ECHNICAL G OALS Scalability Availability Performance Security Manageability Usability Adaptability Affordability 34 Your lab report should reflect some of these goals of your own designed network.

35 S CALABILITY Scalability refers to the ability to grow Some technologies are more scalable Flat network designs, for example, don’t scale well Try to learn Number of sites to be added What will be needed at each of these sites How many users will be added How many more servers will be added 35

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38 A VAILABILITY Availability can be expressed as a percent uptime per year, month, week, day, or hour, compared to the total time in that period For example: 24/7 operation Network is up for 165 hours in the 168-hour week Availability is 98.21% Different applications may require different levels Some enterprises may want % or “Five Nines” availability 38

39 A VAILABILITY Availability can also be expressed as a mean time between failure (MTBF) and mean time to repair (MTTR) Availability = MTBF/(MTBF + MTTR) For example: The network should not fail more than once every 4,000 hours (166 days) and it should be fixed within one hour 4,000/4,001 = 99.98% availability 39

40 A VAILABILITY D OWNTIME IN M INUTES (26 H) 99.70% % % % Per HourPer DayPer WeekPer Year %.012

41 99.999% A VAILABILITY M AY R EQUIRE T RIPLE R EDUNDANCY Can the customer afford this? 41 Enterprise ISP 1ISP 2ISP 3

42 S ERVER F ARMS 42 Many enterprise networks provide users with Internet- accessible services, such as and e-commerce. The availability and security of these services are crucial to the success of a business. Managing and securing numerous distributed servers at various locations within a business network is difficult. Recommended practice centralised servers in server farms. Server farms are typically located in computer rooms and data centres.

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45 B ENEFITS OF CREATING A SERVER FARM 45 1.Network traffic enters and leaves the server farm at a defined point. This arrangement makes it easier to secure, filter and prioritise traffic. 2.Redundant, high-capacity links can be installed to the servers and between the server farm network and the main LAN. This configuration is more cost-effective than attempting to provide a similar level of connectivity to servers distributed throughout the network. 3.Load balancing and failover can be provided between servers and between networking devices. 4.The number of high-capacity switches and security devices is reduced, helping to lower the cost of providing services.

46 N ETWORK P ERFORMANCE Common performance factors include Bandwidth Throughput Bandwidth utilization Offered load Accuracy Efficiency Delay (latency) and delay variation Response time 46

47 B ANDWIDTH V S. T HROUGHPUT Bandwidth and throughput are not the same Bandwidth is the data carrying capacity of a circuit, fixed. Usually specified in bits per second-bps data Throughput is the quantity of error free data transmitted per unit of time Measured in bps, Bps, or packets per second (pps) Depend on offered load, access method and error rate Throughput < Bandwidth 47

48 B ANDWIDTH, T HROUGHPUT, L OAD 48 Offered Load ThroughputThroughput Actual Ideal 100 % of Capacity

49 O THER F ACTORS THAT A FFECT T HROUGHPUT The size of packets Inter-frame gaps between packets Packets-per-second ratings of devices that forward packets Client speed (CPU, memory, and HD access speeds) Server speed (CPU, memory, and HD access speeds) Network design MAC Protocols (ALOHA 18.4%) Distance Errors Time of day, etc., etc., etc. 49

50 T HROUGHPUT V S. G OODPUT Are you referring to bytes per second, regardless of whether the bytes are user data bytes or packet header bytes Or are you concerned with application-layer throughput of user bytes, sometimes called “goodput” In that case, you have to consider that bandwidth is being “wasted” by the headers in every packet 50

51 P ERFORMANCE ( CONTINUED ) Efficiency How much overhead is required to deliver an amount of data? How large can packets be? Larger better for efficiency (and goodput) But too large means too much data is lost if a packet is damaged How many packets can be sent in one bunch without an acknowledgment? 51

52 E FFICIENCY 52 Small Frames (Less Efficient) Large Frames (More Efficient)

53 D ELAY FROM THE U SER ’ S P OINT OF V IEW Response Time A function of the application and the equipment the application is running on, not just the network Most users expect to see something on the screen in 100 to 200 milliseconds 53

54 D ELAY FROM THE E NGINEER ’ S P OINT OF V IEW Propagation delay A signal travels in a cable at about 2/3 the speed of light in a vacuum (3×10 8 m/s) Transmission delay (also known as serialization delay) Time to put digital data onto a transmission line For example, it takes about 5 ms to output a 1,024 byte packet on a Mbps T1 line Packet-switching delay Queuing delay 54

55 Q UEUING D ELAY AND B ANDWIDTH U TILIZATION Number of packets in a queue increases exponentially as utilization increases Queue depth = utilization/(1- utilization)

56 E XAMPLE A packet switch has 5 users, each offering packets at a rate of 10 packets per second The average length of the packets is 1,024 bits The packet switch needs to transmit this data over a 56-Kbps WAN circuit Load = 5 x 10 x 1,024 = 51,200 bps Utilization = 51,200/56,000 = 91.4% Average number of packets in queue = (0.914)/( ) = packets 56

57 S ECURITY Focus on requirements first Detailed security planning later (Chapter 8) Identify network assets Including their value and the expected cost associated with losing them due to a security problem Analyze security risks 57

58 M ANAGEABILITY Fault management Configuration management Accounting management Performance management Security management 58

59 U SABILITY Usability: the ease of use with which network users can access the network and services Networks should make users’ jobs easier Some design decisions will have a negative affect on usability: Strict security, for example 59

60 A DAPTABILITY Avoid incorporating any design elements that would make it hard to implement new technologies in the future Change can come in the form of new protocols, new business practices, new fiscal goals, new legislation A flexible design can adapt to changing traffic patterns and Quality of Service (QoS) requirements 60

61 A FFORDABILITY A network should carry the maximum amount of traffic possible for a given financial cost Affordability is especially important in campus network designs WANs are expected to cost more, but costs can be reduced with the proper use of technology Quiet routing protocols, for example 61

62 M AKING T RADEOFFS ( EXAMPLE ) Scalability 20 Availability 30 Network performance 15 Security 5 Manageability 5 Usability 5 Adaptability 5 Affordability 15 Total (must add up to 100)100 62

63 S UMMARY Continue to use a systematic, top-down approach Don’t select products until you understand goals for scalability, availability, performance, security, manageability, usability, adaptability, and affordability Tradeoffs are almost always necessary 63

64 R EVIEW Q UESTIONS What are some typical technical goals for organizations today? How do bandwidth and throughput differ? How can one improve network efficiency? What tradeoffs may be necessary in order to improve network efficiency? 64

65 C HAPTER T HREE C HARACTERIZING THE E XISTING I NTERNETWORK 65 Copyright 2010 Cisco Press & Priscilla Oppenheimer

66 W HAT ’ S THE S TARTING P OINT ? According to Abraham Lincoln: “If we could first know where we are and whither we are tending, we could better judge what to do and how to do it.” 66

67 W HERE A RE W E ? Characterize the exiting internetwork in terms of: Its infrastructure Logical structure (modularity, hierarchy, topology) Physical structure Addressing and naming Wiring and media Architectural and environmental constraints Health 67

68 D IAGRAM A P HYSICAL N ETWORK AND D OCUMENT THE E XISTING N ETWORK Network documentation: Logical and physical diagrams Floor plans Complete lists for equipments and applications Current network configuration files

69 G ET A N ETWORK M AP ( PHYSICAL ) 69 Gigabit Ethernet Eugene Ethernet 20 users Web/FTP server Grants Pass HQ Gigabit Ethernet FEP (Front End Processor) IBM Mainframe T1 Medford Fast Ethernet 50 users Roseburg Fast Ethernet 30 users Frame Relay CIR = 56 Kbps DLCI = 5 Frame Relay CIR = 56 Kbps DLCI = 4 Grants Pass HQ Fast Ethernet 75 users Internet T1

70 D IAGRAM A P HYSICAL N ETWORK AND D OCUMENT THE E XISTING N ETWORK Identify and document the strengths and weaknesses of the existing network Focus on finding ways to overcome weaknesses

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72 C HARACTERIZE A DDRESSING AND N AMING IP addressing for major devices, client networks, server networks, and so on Any addressing oddities, such as discontiguous subnets? Any strategies for addressing and naming? For example, sites may be named using airport codes San Francisco = SFO, Oakland = OAK In LSBU, T-tower block; K-keyworth building; B- Borough road building; L- london road building 72

73 D ISCONTINUOUS S UBNETS – make problems for some routing protocols 73 Area 1 Subnets Area 0 Network Area 2 Subnets Router ARouter B

74 C HARACTERIZE THE W IRING AND M EDIA Single-mode fiber Multi-mode fiber Shielded twisted pair (STP) copper Unshielded-twisted-pair (UTP) copper Coaxial cable Microwave Laser Radio Infra-red 74

75 A RCHITECTURAL C ONSTRAINTS Make sure the following are sufficient Air conditioning Heating Ventilation Power Protection from electromagnetic interference Doors that can lock 75

76 A RCHITECTURAL C ONSTRAINTS Make sure there’s space for: Cabling conduits Patch panels Equipment racks Work areas for technicians installing and troubleshooting equipment 76

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78 C HECK THE H EALTH OF THE E XISTING I NTERNETWORK Performance Availability Bandwidth utilization Accuracy Efficiency Response time Status of major routers, switches, and firewalls 78

79 C HARACTERIZE A VAILABILITY 79 Enterprise Segment 1 Segment 2 Segment n MTBFMTTR Date and Duration of Last Major Downtime Cause of Last Major Downtime Fix for Last Major Downtime Mean time between failures (MTBF) Mean time to recovery (MTTR)



82 B ANDWIDTH U TILIZATION BY P ROTOCOL 82 Protocol 1 Protocol 2 Protocol 3 Protocol n Relative Network Utilization Absolute Network Utilization Broadcast Rate Multicast Rate


84 C HARACTERIZE R ESPONSE T IME 84 Node A Node B Node C Node D Node ANode BNode CNode D X X X X

85 C HECK THE S TATUS OF M AJOR R OUTERS, S WITCHES, AND F IREWALLS show buffers show environment show interfaces show memory show processes show running-config show version 85 Use Cisco IOS show command

86 T OOLS Protocol analyzers Multi Router Traffic Grapher (MRTG) Remote monitoring (RMON) probes Cisco Discovery Protocol (CDP) Cisco IOS NetFlow technology CiscoWorks 86

87 S UMMARY Characterize the exiting internetwork before designing enhancements Helps you verify that a customer’s design goals are realistic Helps you locate where new equipment will go Helps you cover yourself if the new network has problems due to unresolved problems in the old network 87

88 R EVIEW Q UESTIONS What factors will help you decide if the existing internetwork is in good enough shape to support new enhancements? When considering protocol behavior, what is the difference between relative network utilization and absolute network utilization? Why should you characterize the logical structure of an internetwork and not just the physical structure? What architectural and environmental factors should you consider for a new wireless installation? 88

89 C HAPTER F OUR C HARACTERIZING N ETWORK T RAFFIC 89 Copyright 2010 Cisco Press & Priscilla Oppenheimer

90 N ETWORK T RAFFIC F ACTORS Traffic flow Location of traffic sources and data stores Traffic load Traffic behavior Quality of Service (QoS) requirements 90

91 U SER C OMMUNITIES, a set of worker who use a particular application or set of applications. 91 User Community Name Size of Community (Number of Users) Location(s) of Community Application(s) Used by Community

92 D ATA S TORES ( SINKS ), an area in a network where application layer data resides. Server, or any device where large quantities of data are stored. 92 Data StoreLocationApplication(s)Used by User Community(or Communities)

93 T RAFFIC F LOW, involves identifying and characterizing individual traffic flows between traffic source and stores. 93 Destination 1Destination 2Destination 3Destination MB/secMB/secMB/secMB/sec Source 1 Source 2 Source 3 Source n

94 T RAFFIC F LOW E XAMPLE 94 Administration Business and Social Sciences Math and Sciences 50 PCs 25 Macs 50 PCs 30 PCs 30 Library Patrons (PCs) 30 Macs and 60 PCs in Computing Center Library and Computing Center App Kbps App 2 60 Kbps App Kbps App 4 48 Kbps App Kbps Total 808 Kbps App 1 48 Kbps App 2 32 Kbps App 3 96 Kbps App 4 24 Kbps App Kbps App Kbps App Kbps Total 1900 Kbps App 1 30 Kbps App 2 20 Kbps App 3 60 Kbps App 4 16 Kbps Total 126 Kbps App 2 20 Kbps App 3 96 Kbps App 4 24 Kbps App 9 80 Kbps Total 220 Kbps Arts and Humanities Server Farm 10-Mbps Metro Ethernet to Internet

95 T YPES OF T RAFFIC F LOW Terminal/host Client/server Thin client Peer-to-peer Server/server Distributed computing 95

96 T RAFFIC F LOW FOR V OICE OVER IP The flow associated with transmitting the audio voice is separate from the flows associated with call setup and teardown. The flow for transmitting the digital voice is essentially peer-to-peer. Call setup and teardown is a client/server flow A phone needs to talk to a server or phone switch that understands phone numbers, IP addresses, capabilities negotiation, and so on. 96

97 I DENTIFYING A PPLICATION I MPACTS ON N ETWORK D ESIGN File transfer and applications : Unpredictable bandwidth usage Large packet size Centralization of file and mail servers in a secure location Redundancy to ensure reliable service

98 I DENTIFYING A PPLICATION I MPACTS ON N ETWORK D ESIGN HTTP and web traffic: Network media Redundancy Security

99 N ETWORK A PPLICATIONS T RAFFIC C HARACTERISTICS 99 Name of Application Type of Traffic Flow Protocol(s) Used by Application User Communities That Use the Application Data Stores (Servers, Hosts, and so on) Approximate Bandwidth Requirements QoS Requirements

100 T RAFFIC L OAD To calculate whether capacity is sufficient, you should know: The number of stations The average time that a station is idle between sending frames The time required to transmit a message once medium access is gained That level of detailed information can be hard to gather, however 100

101 S IZE OF O BJECTS ON N ETWORKS Terminal screen: 4 Kbytes Simple 10 Kbytes Simple web page: 50 Kbytes High-quality image: 50Mbytes Database backup: 1Gbytes or more 101

102 T RAFFIC B EHAVIOR Broadcasts All ones data-link layer destination address FF: FF: FF: FF: FF: FF Doesn’t necessarily use huge amounts of bandwidth But does disturb every CPU in the broadcast domain Multicasts First bit sent is a one 01:00:0C:CC:CC:CC (Cisco Discovery Protocol) Should just disturb NICs that have registered to receive it Requires multicast routing protocol on internetworks 102

103 N ETWORK E FFICIENCY Frame size Protocol interaction Windowing and flow control Error-recovery mechanisms 103

104 Q O S R EQUIREMENTS ATM service specifications Constant bit rate (CBR) Realtime variable bit rate (rt-VBR) Non-realtime variable bit rate (nrt-VBR) Unspecified bit rate (UBR) Available bit rate (ABR) Guaranteed frame rate (GFR) 104

105 Q O S R EQUIREMENTS PER IETF (Internet Engineering Task Force, develops and promotes Internet standards, It is an open standards organization, with no formal membership or membership requirements.) IETF integrated services working group specifications Controlled load service Provides client data flow with a QoS closely approximating the QoS that same flow would receive on an unloaded network Guaranteed service Provides firm (mathematically provable) bounds on end-to-end packet-queuing delays 105

106 Q O S R EQUIREMENTS PER IETF IETF differentiated services working group specifications RFC 2475 IP packets can be marked with a differentiated services codepoint (DSCP) to influence queuing and packet-dropping decisions for IP datagrams on an output interface of a router 106

107 H OW Q UALITY OF S ERVICE IS I MPLEMENTED ON THE LAN/WAN Where QoS can be implemented to affect traffic flow: Layer 2 devices Layer 3 devices

108 D OCUMENT THE N ETWORK R EQUIREMENTS OF S PECIFIC C ATEGORIES OF A PPLICATIONS Estimate the volume of application traffic during the initial design phase. Document projected applications and associated hardware in a network diagram.

109 S UMMARY Continue to use a systematic, top-down approach Don’t select products until you understand network traffic in terms of: Flow Load Behavior QoS requirements 109

110 R EVIEW Q UESTIONS List and describe six different types of traffic flows. What makes traffic flow in voice over IP networks challenging to characterize and plan for? Why should you be concerned about broadcast traffic? How do ATM and IETF specifications for QoS differ? 110

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