Presentation on theme: "Network Design and Implementation EEB_7_876"— Presentation transcript:
1 Network Design and Implementation EEB_7_876 For MSc TeCNE and EDS
2 Methods of Teaching and Learning : Lectures and Workshops Website:Methods of Teaching and Learning : Lectures and WorkshopsAssessment of the Module : 2-hour written examination -- 50% Two laboratory work reports %Lecturer: Ya Bao and Perry Xiao.
6 Part 1 Identifying Your Customer’s Needs and Goals Analyzing Business Goals and ConstraintsAnalyzing Technical Goals and TradeoffsCharacterizing the Existing InternetworkCharacterizing Network Traffic
7 Chapter One Analyzing Business Goals and Constraints Systematic, Top-down network design methodologyAnalysing your customer’s business objectivesAnalysing the business constrains; budgets, timeframes, workplace politics.
8 Network DesignGood 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.
9 Structured Network Design Four fundamental network design goals:ScalabilityAvailabilitySecurityManageabilityGraphic:
10 Network requirements: How a Structured Network Design Creates a Stable, Reliable, Scalable NetworkNetwork requirements:Ease of managementFast recoveryApplication response timeFast troubleshootingGraphic:
11 Structured Network Design Core Layer: connects Distribution Layer devicesDistribution Layer: interconnects smaller LANsAccess Layer: provides connections for hosts and end devicesGraphic: —run to end to show the three layers
12 Structured Network Design Steps in network design projects:Identify the network requirementsCharacterize the existing network (for network upgrading only)Design the network topology and solutionsTesting, optimizing and documentingGraphic:
13 Start from the Top Application Presentation Session Transport Network Data LinkPhysicalLayer 1Layer 7Layer 6Layer 5Layer 4Layer 3Layer 2
15 Systems Development Life Cycles (SDLC) Typical systems are developed and continue to exist over a period of time, often called a systems development life cycle (SDLC).
16 Top-Down Network Design Steps systems development life cycle (SDLC).Analyze requirementsMonitor and optimize network performanceDevelop logical designDevelop physical designImplement and test networkTypical systems are developed and continue to exist over a period of time, often called a systems development life cycle (SDLC).Test, optimize, and document design
17 The PDIOO Network Life Cycle Plan Design Implement Operate OptimizePlanDesignRetireOptimizeImplementOperate
18 Network Design Steps Phase 1 – Analyze Requirements Today’s topic Analyze business goals and constraintsAnalyze technical goals and tradeoffsCharacterize the existing networkCharacterize network traffic
19 Network Design Steps Phase 2 – Logical Network Design Design a network topologyDesign models for addressing and namingSelect switching and routing protocolsDevelop network security strategiesDevelop network management strategies
20 Network Design Steps Phase 3 – Physical Network Design Select technologies and devices for campus networksSelect technologies and devices for enterprise networks
21 Network Design StepsPhase 4 – Testing, Optimizing, and Documenting the Network DesignTest the network designOptimize the network designDocument the network design
22 Business Goals Increase revenue Reduce operating costs Improve communicationsShorten product development cycleExpand into worldwide marketsBuild partnerships with other companiesOffer better customer support or new customer services
23 Recent Business Priorities MobilitySecurityResiliency (fault tolerance)Business continuity after a disasterNetwork projects must be prioritized based on fiscal goalsNetworks must offer the low delay required for real-time applications such as VoIPResiliency means how much stress a network can handle and how quickly the network can rebound from problems, including security breaches, natural and unnatural disasters, human error, and catastrophic software or hardware failures.Some experts, including Howard Berkowitz, have a mild dislike of the word “resiliency” as it sounds too much like a stretched rubber band or a trampoline. As Berkowitz says in his excellent book, WAN Survival Guide (Wiley 2001), “I avoid designing networks that stretch too far, bounce up and down, or oscillate between normal and backup states.”So he likes “fault tolerance,” but he points out that it does not mean “immune to any conceivable threat.” Berkowitz states that, “A sufficient quantity of explosives can overcome the tolerance of any network.” :-)fiscal[ˈfɪsk(ə)l]adjectiveof or relating to government revenue, especially taxes
24 Business ConstraintsBudgetStaffingSchedulePolitics and policies
25 Collect Information Before the First Meeting Before meeting with the client, whether internal or external, collect some basic business-related informationSuch asProducts produced/Services suppliedFinancial viabilityCustomers, suppliers, competitorsCompetitive advantage
26 Meet With the Customer Try to get A concise statement of the goals of the projectWhat 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?
27 Meet With the Customer Get a copy of the organization chart This will show the general structure of the organizationIt will suggest users to account forIt will suggest geographical locations to account for
28 Meet With the Customer 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 protectHardware, software, applications, and dataLess obvious, but still important, intellectual property, trade secrets, and a company's reputation
29 The Scope of the Design Project Small in scope?Allow sales people to access network via a VPNLarge in scope?An entire redesign of an enterprise networkUse the OSI model to clarify the scopeNew 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?
30 Gather More Detailed Information ApplicationsNow and after the project is completedInclude both productivity applications and system management applicationsUser communitiesData storesProtocolsCurrent logical and physical architectureCurrent performanceUser communities, data stores, protocols, and the current architecture and performance will be discussed in the next few chapters. This chapter focuses on business needs and applications, which should be the first area of research in a top-down network design project. Network design is iterative, however, so many topics are addressed more than once as the designer gathers more detailed information and conducts more precise planning. So, gaining a general understanding of the size and location of user communities, for example, might be appropriate at this stage of the design project, but user communities should be investigated again when characterizing network traffic.
31 Summary Systematic approach Focus first on business requirements and constraints, and applicationsGain an understanding of the customer’s corporate structureGain an understanding of the customer’s business style
32 Review QuestionsWhat 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?
33 Chapter Two Analyzing Technical Goals and Tradeoffs Copyright 2010 Cisco Press & Priscilla Oppenheimer
34 Technical Goals Scalability Availability Performance Security ManageabilityUsabilityAdaptabilityAffordabilityYour lab report should reflect some of these goals of your own designed network.Scalability: How much growth a network design must support.Availability: The amount of time a network is available to users, often expressed as a percent uptime, or as a mean time between failure (MTBF) and mean time to repair (MTTR). Availability goals can also document any monetary cost associated with network downtime.Security: Goals for protecting the organization's ability to conduct business without interference from intruders inappropriately accessing or damaging equipment, data, or operations. Specific security risks should be documented.Manageability: Goals for fault, configuration, accounting, performance, and security (FCAPS) managementUsability: Goals regarding the ease with which network users can access the network and its services, including goals for simplifying user tasks related to network addressing, naming, and resource discovery.Adaptability: The ease with which a network design and implementation can adapt to network faults, changing traffic patterns, additional business or technical requirements, new business practices, and other changes.Affordability: The importance of containing the costs associated with purchasing and operating network equipment and services.
35 Scalability Scalability refers to the ability to grow Some technologies are more scalableFlat network designs, for example, don’t scale wellTry to learnNumber of sites to be addedWhat will be needed at each of these sitesHow many users will be addedHow many more servers will be added
38 AvailabilityAvailability can be expressed as a percent uptime per year, month, week, day, or hour, compared to the total time in that periodFor example:24/7 operationNetwork is up for 165 hours in the 168-hour weekAvailability is 98.21%Different applications may require different levelsSome enterprises may want % or “Five Nines” availability
39 AvailabilityAvailability 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 hour4,000/4,001 = 99.98% availability
40 Availability Downtime in Minutes Per HourPer DayPer WeekPer Year99.999%.0006.01.10599.98%.012.29210599.95%.03.72526399.70% availability sounds pretty good, but it could mean that the network is down for 0.18 minutes every hour. This is 11 seconds. If those 11 seconds were spread out over the hour, nobody would notice possibly. But if there were some bug, for example, that caused the network to fail for 11 seconds every hour on the hour, people would notice. Users these days are very impatient.Notice that 99.70% availability also could mean one catastrophic problem caused the network to be down for 1577 minutes all at once. That’s 26 hours. If it were on a Saturday and the network was never down for the rest of the year, that might actually be OK. So, you have to consider time frames with percent availability numbers.Consider the holy grail: % availability. That’s 5 minutes downtime per year! Be sure to explain to the customer that scheduled maintenance and upgrades don’t count! Either that or plan for a network with triple redundancy (that could be extremely expensive to implement and operate).99.90%.061.441052699.70%.184.32301577(26 H)
41 99.999% Availability May Require Triple Redundancy ISP 1ISP 2ISP 3EnterpriseIn the event of failure of the primary router, the secondary becomes the primary and still has a backup. Fix the previous primary and have it become the tertiary.This helps with maintenance too. Pull out the tertiary and upgrade it. The primary still has a backup. After extensive testing, put the tertiary back in as the primary. Pull out the original primary and upgrade it. Put it back as the secondary. Finally pull out the original secondary and upgrade it.Of course, the picture brings up all sorts of other questions because it uses an ISP example.Does the customer have provider independent addressing?Does the customer have an autonomous system number?Are the ISPs really independent? Is there true circuit diversity?Are the speeds the same on the three links to the ISPs so that performance degradation is minimized during upgrades or failures?Can load balancing be used when all three routers are operational?What are the routing protocols inside the enterprise network? Can traffic really get to all three routers, regardless of failures inside the enterprise network? Can the routing protocols adjust to changes?Will traffic flow out the “closest” router? Will traffic come in from the Internet via the “closest” entry?Instructor note: The slide is not meant to be a design recommendation! It’s just a slide to get a discussion going on the ramifications of % availability.Can the customer afford this?
42 Server FarmsMany 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.
45 Benefits of creating a server farm Network traffic enters and leaves the server farm at a defined point. This arrangement makes it easier to secure, filter and prioritise traffic.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.Load balancing and failover can be provided between servers and between networking devices.The number of high-capacity switches and security devices is reduced, helping to lower the cost of providing services.
46 Network Performance Common performance factors include Bandwidth ThroughputBandwidth utilizationOffered loadAccuracyEfficiencyDelay (latency) and delay variationResponse time
47 Bandwidth Vs. Throughput Bandwidth and throughput are not the sameBandwidth is the data carrying capacity of a circuit, fixed.Usually specified in bits per second-bpsThroughput is the quantity of error free data transmitted per unit of timeMeasured in bps, Bps, or packets per second (pps)Depend on offered load, access method and error rateThroughput < Bandwidth
48 Bandwidth, Throughput, Load 100 % of CapacityThroughputActualIdeal100 % of CapacityOffered Load
49 Other Factors that Affect Throughput The size of packetsInter-frame gaps between packetsPackets-per-second ratings of devices that forward packetsClient speed (CPU, memory, and HD access speeds)Server speed (CPU, memory, and HD access speeds)Network designMAC Protocols (ALOHA 18.4%)DistanceErrorsTime of day, etc., etc., etc.
50 Throughput Vs. GoodputAre you referring to bytes per second, regardless of whether the bytes are user data bytes or packet header bytesOr 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
51 Performance (continued) EfficiencyHow 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 damagedHow many packets can be sent in one bunch without an acknowledgment?
53 Delay from the User’s Point of View Response TimeA function of the application and the equipment the application is running on, not just the networkMost users expect to see something on the screen in 100 to 200 milliseconds
54 Delay from the Engineer’s Point of View Propagation delayA signal travels in a cable at about 2/3 the speed of light in a vacuum (3×108 m/s)Transmission delay (also known as serialization delay)Time to put digital data onto a transmission lineFor example, it takes about 5 ms to output a 1,024 byte packet on a Mbps T1 linePacket-switching delayQueuing delay
55 Queuing Delay and Bandwidth Utilization Number of packets in a queue increases exponentially as utilization increasesQueue depth = utilization/(1- utilization)
56 ExampleA packet switch has 5 users, each offering packets at a rate of 10 packets per secondThe average length of the packets is 1,024 bitsThe packet switch needs to transmit this data over a 56-Kbps WAN circuitLoad = 5 x 10 x 1,024 = 51,200 bpsUtilization = 51,200/56,000 = 91.4%Average number of packets in queue =(0.914)/( ) = packets
57 Security Focus on requirements first Detailed security planning later (Chapter 8)Identify network assetsIncluding their value and the expected cost associated with losing them due to a security problemAnalyze security risks
59 UsabilityUsability: the ease of use with which network users can access the network and servicesNetworks should make users’ jobs easierSome design decisions will have a negative affect on usability:Strict security, for example
60 AdaptabilityAvoid incorporating any design elements that would make it hard to implement new technologies in the futureChange can come in the form of new protocols, new business practices, new fiscal goals, new legislationA flexible design can adapt to changing traffic patterns and Quality of Service (QoS) requirements
61 AffordabilityA network should carry the maximum amount of traffic possible for a given financial costAffordability is especially important in campus network designsWANs are expected to cost more, but costs can be reduced with the proper use of technologyQuiet routing protocols, for example
62 Making Tradeoffs (example) Scalability 20Availability 30Network performance 15SecurityManageabilityUsabilityAdaptabilityAffordabilityTotal (must add up to 100) 100
63 Summary 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 affordabilityTradeoffs are almost always necessary
64 Review QuestionsWhat 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?
65 Chapter Three Characterizing the Existing Internetwork Copyright 2010 Cisco Press & Priscilla Oppenheimer
66 What’s the Starting Point? 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.”whitherinterrogative adverbto what place
67 Where Are We? Characterize the exiting internetwork in terms of: Its infrastructureLogical structure (modularity, hierarchy, topology)Physical structureAddressing and namingWiring and mediaArchitectural and environmental constraintsHealth
68 Diagram a Physical Network and Document the Existing Network Network documentation:Logical and physical diagramsFloor plansComplete lists for equipments and applicationsCurrent network configuration filesinventory[ˈɪnv(ə)nt(ə)ri](pl. -ies)a complete list of items such as property, goods in stock, or the contents of a building
70 Diagram a Physical Network and Document the Existing Network Identify and document the strengths and weaknesses of the existing networkFocus on finding ways to overcome weaknessesStateful firewallFrom Wikipedia, the free encyclopediaJump to: navigation, searchIn computing, a stateful firewall (any firewall that performs stateful packet inspection (SPI) or stateful inspection) is a firewall that keeps track of the state of network connections (such as TCP streams, UDP communication) traveling across it. The firewall is programmed to distinguish legitimate packets for different types of connections. Only packets matching a known active connection will be allowed by the firewall; others will be rejected.
72 Characterize Addressing and Naming IP addressing for major devices, client networks, server networks, and so onAny addressing oddities, such as discontiguous subnets?Any strategies for addressing and naming?For example, sites may be named using airport codesSan Francisco = SFO, Oakland = OAKIn LSBU, T-tower block; K-keyworth building; B-Borough road building; L- london road building
73 Discontinuous Subnets – make problems for some routing protocols Area 0NetworkRouter ARouter BArea 1SubnetsArea 2Subnets
74 Characterize the Wiring and Media Single-mode fiberMulti-mode fiberShielded twisted pair (STP) copperUnshielded-twisted-pair (UTP) copperCoaxial cableMicrowaveLaserRadioInfra-red
75 Architectural Constraints Make sure the following are sufficientAir conditioningHeatingVentilationPowerProtection from electromagnetic interferenceDoors that can lock
76 Architectural Constraints Make sure there’s space for:Cabling conduitsPatch panelsEquipment racksWork areas for technicians installing and troubleshooting equipment
78 Check the Health of the Existing Internetwork PerformanceAvailabilityBandwidth utilizationAccuracyEfficiencyResponse timeStatus of major routers, switches, and firewalls
79 Characterize Availability Cause of Last Major DowntimeDate and Duration of Last Major DowntimeFix for Last Major DowntimeMTBFMTTREnterpriseSegment 1Segment 2Segment nMean time between failures (MTBF)Mean time to recovery (MTTR)
82 Bandwidth Utilization by Protocol Relative Network UtilizationAbsolute Network UtilizationBroadcast RateMulticast RateProtocol 1Protocol 2Protocol 3Protocol nRelative usage specifies how much bandwidth is used by the protocol in comparison to the total bandwidth currently in use on the segment. Absolute usage specifies how much bandwidth is used by the protocol in comparison to the total capacity of the segment (for example, in comparison to 100 Mbps on Fast Ethernet).
87 SummaryCharacterize the exiting internetwork before designing enhancementsHelps you verify that a customer’s design goals are realisticHelps you locate where new equipment will goHelps you cover yourself if the new network has problems due to unresolved problems in the old network
88 Review QuestionsWhat 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?
90 Network Traffic Factors Traffic flowLocation of traffic sources and data storesTraffic loadTraffic behaviorQuality of Service (QoS) requirements
91 User Communities, a set of worker who use a particular application or set of applications. User Community NameSize of Community (Number of Users)Location(s) of CommunityApplication(s) Used by Community
92 Data Stores (sinks), an area in a network where application layer data resides. Server, or any device where large quantities of data are stored.Data StoreLocationApplication(s)Used by User Community(or Communities)
93 Traffic Flow, involves identifying and characterizing individual traffic flows between traffic source and stores.Destination 1 Destination 2 Destination 3 Destination MB/sec MB/sec MB/sec MB/secSource 1Source 2Source 3Source n
94 Library and Computing Center Business and Social Sciences Traffic Flow Example10-Mbps Metro Ethernet to Internet30 Library Patrons (PCs)30 Macs and 60 PCs in Computing CenterApp KbpsApp KbpsApp KbpsApp KbpsApp KbpsTotal 808 KbpsServer FarmApp KbpsApp KbpsApp KbpsApp KbpsTotal 220 Kbps25 Macs50 PCs50 PCsArts and HumanitiesAdministrationApp KbpsApp KbpsApp KbpsApp KbpsTotal 126 KbpsApp KbpsApp KbpsApp KbpsApp KbpsApp KbpsApp KbpsApp KbpsTotal 1900 KbpsMath and Sciences30 PCs50 PCsBusiness and Social Sciences
96 Traffic Flow for Voice 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 flowA phone needs to talk to a server or phone switch that understands phone numbers, IP addresses, capabilities negotiation, and so on.
97 Identifying Application Impacts on Network Design File transfer and applications:Unpredictable bandwidth usageLarge packet sizeCentralization of file and mail servers in a secure locationRedundancy to ensure reliable serviceGraphic:
98 Identifying Application Impacts on Network Design HTTP and web traffic:Network mediaRedundancySecurityGraphic:
99 Network Applications Traffic Characteristics Name of ApplicationType of Traffic FlowProtocol(s) Used by ApplicationUser Communities That Use the ApplicationData Stores (Servers, Hosts, and so on)Approximate Bandwidth RequirementsQoS Requirements
100 Traffic LoadTo calculate whether capacity is sufficient, you should know:The number of stationsThe average time that a station is idle between sending framesThe time required to transmit a message once medium access is gainedThat level of detailed information can be hard to gather, however
101 Size of Objects on Networks Terminal screen: 4 KbytesSimple 10 KbytesSimple web page: 50 KbytesHigh-quality image: 50MbytesDatabase backup: 1Gbytes or more
102 Traffic Behavior Broadcasts Multicasts All ones data-link layer destination addressFF: FF: FF: FF: FF: FFDoesn’t necessarily use huge amounts of bandwidthBut does disturb every CPU in the broadcast domainMulticastsFirst bit sent is a one01:00:0C:CC:CC:CC (Cisco Discovery Protocol)Should just disturb NICs that have registered to receive itRequires multicast routing protocol on internetworks
104 QoS Requirements 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)
105 QoS Requirements 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 specificationsControlled load serviceProvides client data flow with a QoS closely approximating the QoS that same flow would receive on an unloaded networkGuaranteed serviceProvides firm (mathematically provable) bounds on end-to-end packet-queuing delaysInternet Engineering Task Force The Internet Engineering Task Force (IETF) develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite. It is an open standards organization, with no formal membership or membership requirements.
106 QoS Requirements per IETF IETF differentiated services working group specificationsRFC 2475IP 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
107 How Quality of Service is Implemented on the LAN/WAN Where QoS can be implemented to affect traffic flow:Layer 2 devicesLayer 3 devicesGraphic:
108 Document the Network Requirements of Specific Categories of Applications Estimate the volume of application traffic during the initial design phase.Document projected applications and associated hardware in a network diagram.Graphic:
109 Summary Continue to use a systematic, top-down approach Don’t select products until you understand network traffic in terms of:FlowLoadBehaviorQoS requirements
110 Review QuestionsList 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?
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