Presentation on theme: "Network Design and Implementation EEB_7_876"— Presentation transcript:
1Network Design and Implementation EEB_7_876 For MSc TeCNE and EDS
2Methods 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.
6Part 1 Identifying Your Customer’s Needs and Goals Analyzing Business Goals and ConstraintsAnalyzing Technical Goals and TradeoffsCharacterizing the Existing InternetworkCharacterizing Network Traffic
7Chapter One Analyzing Business Goals and Constraints Systematic, Top-down network design methodologyAnalysing your customer’s business objectivesAnalysing the business constrains; budgets, timeframes, workplace politics.
8Network 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.
9Structured Network Design Four fundamental network design goals:ScalabilityAvailabilitySecurityManageabilityGraphic:
10Network requirements: How a Structured Network Design Creates a Stable, Reliable, Scalable NetworkNetwork requirements:Ease of managementFast recoveryApplication response timeFast troubleshootingGraphic:
11Structured 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
12Structured 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:
13Start from the Top Application Presentation Session Transport Network Data LinkPhysicalLayer 1Layer 7Layer 6Layer 5Layer 4Layer 3Layer 2
15Systems 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).
16Top-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
17The PDIOO Network Life Cycle Plan Design Implement Operate OptimizePlanDesignRetireOptimizeImplementOperate
18Network Design Steps Phase 1 – Analyze Requirements Today’s topic Analyze business goals and constraintsAnalyze technical goals and tradeoffsCharacterize the existing networkCharacterize network traffic
19Network 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
20Network Design Steps Phase 3 – Physical Network Design Select technologies and devices for campus networksSelect technologies and devices for enterprise networks
21Network Design StepsPhase 4 – Testing, Optimizing, and Documenting the Network DesignTest the network designOptimize the network designDocument the network design
22Business 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
23Recent 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
24Business ConstraintsBudgetStaffingSchedulePolitics and policies
25Collect 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
26Meet 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?
27Meet 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
28Meet 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
29The 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?
30Gather 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.
31Summary 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
32Review 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?
33Chapter Two Analyzing Technical Goals and Tradeoffs Copyright 2010 Cisco Press & Priscilla Oppenheimer
34Technical 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.
35Scalability 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
38AvailabilityAvailability 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
39AvailabilityAvailability 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
40Availability 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)
4199.999% 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?
42Server 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.
45Benefits 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.
46Network Performance Common performance factors include Bandwidth ThroughputBandwidth utilizationOffered loadAccuracyEfficiencyDelay (latency) and delay variationResponse time
47Bandwidth 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
48Bandwidth, Throughput, Load 100 % of CapacityThroughputActualIdeal100 % of CapacityOffered Load
49Other 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.
50Throughput 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
51Performance (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?
53Delay 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
54Delay 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
55Queuing Delay and Bandwidth Utilization Number of packets in a queue increases exponentially as utilization increasesQueue depth = utilization/(1- utilization)
56ExampleA 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
57Security 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
59UsabilityUsability: 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
60AdaptabilityAvoid 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
61AffordabilityA 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
62Making Tradeoffs (example) Scalability 20Availability 30Network performance 15SecurityManageabilityUsabilityAdaptabilityAffordabilityTotal (must add up to 100) 100
63Summary 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
64Review 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?
65Chapter Three Characterizing the Existing Internetwork Copyright 2010 Cisco Press & Priscilla Oppenheimer
66What’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
67Where Are We? Characterize the exiting internetwork in terms of: Its infrastructureLogical structure (modularity, hierarchy, topology)Physical structureAddressing and namingWiring and mediaArchitectural and environmental constraintsHealth
68Diagram 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
70Diagram 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.
72Characterize 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
73Discontinuous Subnets – make problems for some routing protocols Area 0NetworkRouter ARouter BArea 1SubnetsArea 2Subnets
74Characterize the Wiring and Media Single-mode fiberMulti-mode fiberShielded twisted pair (STP) copperUnshielded-twisted-pair (UTP) copperCoaxial cableMicrowaveLaserRadioInfra-red
75Architectural Constraints Make sure the following are sufficientAir conditioningHeatingVentilationPowerProtection from electromagnetic interferenceDoors that can lock
76Architectural Constraints Make sure there’s space for:Cabling conduitsPatch panelsEquipment racksWork areas for technicians installing and troubleshooting equipment
78Check the Health of the Existing Internetwork PerformanceAvailabilityBandwidth utilizationAccuracyEfficiencyResponse timeStatus of major routers, switches, and firewalls
79Characterize 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)
82Bandwidth 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).
87SummaryCharacterize 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
88Review 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?
90Network Traffic Factors Traffic flowLocation of traffic sources and data storesTraffic loadTraffic behaviorQuality of Service (QoS) requirements
91User 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
92Data 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)
93Traffic 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
94Library 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
95Types of Traffic Flow Terminal/host Client/server Thin client Peer-to-peerServer/serverDistributed computing
96Traffic 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.
97Identifying 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:
98Identifying Application Impacts on Network Design HTTP and web traffic:Network mediaRedundancySecurityGraphic:
99Network 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
100Traffic 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
101Size of Objects on Networks Terminal screen: 4 KbytesSimple 10 KbytesSimple web page: 50 KbytesHigh-quality image: 50MbytesDatabase backup: 1Gbytes or more
102Traffic 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
104QoS 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)
105QoS 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.
106QoS 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
107How Quality of Service is Implemented on the LAN/WAN Where QoS can be implemented to affect traffic flow:Layer 2 devicesLayer 3 devicesGraphic:
108Document 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:
109Summary Continue to use a systematic, top-down approach Don’t select products until you understand network traffic in terms of:FlowLoadBehaviorQoS requirements
110Review 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?