Network Analysis and Design

Network Analysis and Design

اسلاید 1: Network Analysis and Design

اسلاید 2: Computer Networks do not of themselves justify their existenceNetworks exist to do somethingIt is what they do which justifies their existence

اسلاید 3: Computer Networksexistto supportBusiness, Government, Social, Educational ….Functions

اسلاید 4: Computer Networks - New and ExistingIn the case of designing a NEW network ask: What is the new network for ? What are the specific functions that must be supported ? etcIn the case of upgrading an EXISTING network ask: What is the existing network supposed to be doing, that it is not ? Which transmission links need to be upgraded ? etc

اسلاید 5: Business Factors that Influence Network Development and ExpansionExpansion into NEW Geographic AreasMerger or Acquisition of companiesCompetition to provide service to customersDistribution of Centralised FunctionsInterface with other organisations’ computer systemsCapture of transactions at point of origin to reduce errorsOn line sales of goods and servicesetc

اسلاید 6: Systems AnalysisNetwork Analysis and Design should be seen as “Systems Analysis” within a SDLC Model.

اسلاید 7: General StepsFeasibility StudyNetwork Design PlanAssess geographic statusscopeWhat are the business’ operations and procedures ?Link Speed to Handle Aggregate Data Rate ?Link Speed to Handle Response Time Requirements ?Review EstimatesNetwork ConfigurationsDerive Cost estimates by referring to available Telecommunications services

اسلاید 8: Feasibility StudyIdentify the Purpose of Network development or expansion to support point of sale transactions from discount storesto support timely submission of stock orders to suppliers etcIdentify factors that indicate need for Network development or expansion - Needs Assessment FactorsPreliminary Identification of COSTSResult should be either a GO or NO GO Decision

اسلاید 9: Network Design PlanThe Plan should take into account: Technical feasibility of network Leading edge or stable technology ?Is support available for ongoing operation ?Operational feasibility For the users who conduct their daily business by using the networkIdentify users (managers, sales staff etc) and their requirementsWill security constraints make access difficult ?Economic feasibilityNeed to keep the network within budgetary limitations

اسلاید 10: Network Design PlanGoals of Network DesignNetwork Evaluation CriteriaUsed for measuring the success of the network at completion

اسلاید 11: Geographic StatusScopeAssess geographic statusscope of the projected network by identifying the sites to be (served) connected to the networkInternational, worldwide network, WAN, can be variations in telecomms stds - ISDN primary service, Australia 30 B channels of 64kbps, US 23telecomms regulatory environment - Private vs Public TelcosCountry, within boundaries and laws of a single country, WANCity, within boundaries of a specific city/state/province or local government jurisdiction, MANLocal facility, within a specific building or confined to a series of buildings located on the same contiguous property, LAN

اسلاید 12: What are the business operations and procedures ?By identifying the types of transaction generated by the organisation we can determine the business operations and procedures Create a Workload Table Shows the network traffic that will be generated by each site that is to be attached to the networkAllow for: future growth eg Sales and Marketing Dept predict that sales will grow by 10% per annum over the next 5 yearsProtocol Overhead

اسلاید 13: TransactionsFor each site:Determine transaction types - Customer inquiry etcDetermine volumes expected in the peak period (hour) for each transaction type: TxVol of Customer inquiries = 400 By focusing on the peak period (hour) we ensure that sufficient resources will be available and response time will be adequate throughout the day.

اسلاید 14: TransactionsFor each site:Determine the size (total bytes exchanged - includes request and response) of the transaction in bytes TxSize of Customer inquiry = 500 bytesWe can derive this information by looking at the CURRENT or a SIMILAR system.

اسلاید 15: Link Speed to handle Aggregate Data Rate - ADR The Aggregate Data Rate is the amount of data generated by a site in the peak hour of businessFor each site:Calculate the message volume in bytes for each transaction type: Customer Enquiry - TxVol x TxSize = 400 x 500 = 200,000 bytesAllow for protocol overheadAllow for growth in transaction volumeAggregate volume across transaction types to obtain estimate of Aggregate Data Rate: ADR = Sum of (TxVol x TxSize + Protocol Overhead + Growth) bytes

اسلاید 16: Link Speed to handle Aggregate Data Rate - ADR For each site:The Link Speed needed to handle ADR in peak hour = ((ADR x bits per byte)/secs per hour) bps eg Headquarters [(1,267,125 x 11bits/byte)/3600] = 3872 bpsRefer Workload Table

اسلاید 17: Link Speed to Handle Transaction Response Time RequirementsCheck Link Speed chosen to handle ADR will satisfy Response Time (R/T) requirements for each transaction(R/T) has two components - Transmission time (T/T) and Processing time (P/T).Suppose the design objective for the Customer Inquiry transaction is a R/T of 3 secs.If P/T is 1 sec, then T/T must be <= 2 secs.

اسلاید 18: Link Speed to Handle Transaction Response Time RequirementsAs the Customer Inquiry transaction involves the exchange of 500 bytes then the Link Speed can be calculated as: size in bytes / link speed in bytes <= 2 secs 500bytes/[ x bytes/sec] <= 2 secs hence x >= 500bytes /2 secs >= 250bytes/secThis can be converted to bps: (250 x 8bits/byte)/sec = 2000 ~ 2400bps hence a 2400bps link is needed to satisfy R/T requirements of the Customer Inquiry Transaction

اسلاید 19: Review EstimatesReview estimates with users to make sure the volumes make business sense and are representativeShould there be six times as many inquiries on Inventory as compared to those on Orders ?

اسلاید 20: Network Configurations and CostsPropose alternative network configurations: Point-to-PointMultipointDerive cost estimates for the WAN by referring to Telco Services ATM DDSAustpac ISDN Frame Relay

اسلاید 21: Telestra’s Charging PrinciplesLine Access ChargesOnce Only InstallationAccess - Annual RentalTransmission Charges - can be based on: Connect Time - STD, MobilesTime of dayVolume of data - AustpacDistance ZonesArea within a zoneLink Speed

اسلاید 22: Telstra - ISDNProvides Integrated Services - voice, data, videoMicrolinkBasic Rate access for small business/residentialTwo Full Duplex 64kbps B channels for dataOne “ 16kbps D channel for control signallingMacrolinkPrimary Rate access for large organisations with high volume requirements30 B channels One D channel at 64kbps

اسلاید 23: Telstra - ISDNCharging PrinciplesAccessInstallation ChargeAnnual RentalUsageConnect Time

اسلاید 24: Telstra - AustpacX.25 Packet Switching Network for Data transmission, up to 128kbpsCharging PrinciplesX.25 DedicatedAccess - Zone BasedInstallation Charge Annual RentalUsageVolume of packets sentTime of dayVolume Capping

اسلاید 25: Telstra - AustpacCharging Principles X.28 Dial-Up Usage Zone BasedConnect Time/Time of dayVolumeCharging ZonesMetroCountry

اسلاید 26: Telstra - DDSDigital Data Service - up to 48kbpsCharging PrinciplesZone Based, 9 ZonesArea Based, within each zone have Primary, Secondary and Tertiary AreasAccessInstallationAnnual RentalTransmission Fees - depend on distance, Areas and Zones

اسلاید 27: Other IssuesThough cost minimisation is a major factor you must not forget:BackupRecoveryMaintenanceTrainingSecurity etc

اسلاید 28: Staged ApproachRecommend staged approach to implementationHigh Priority/Low Priority sites can be selected and linked firstLater sites will benefit from experience gained

اسلاید 29: DeliverablesEstimation of traffic load on network including future growthEstimation of transmission requirements between any two sites to be connectedIdentification of hardware needed at each site.Interface issues - WAN to WAN etcSupport required once network operationalCosting of alternative network configurationsSecurity and Reliability issue