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Requirements Analysis I Lecture Outline Network Design Lecture Outline TELE302 Lecture 15 1 General guidelines Requirements Analysis I 2 Starting from the Top Jeremiah Deng 3 Application Requirements TELE / InfoSci, University of Otago 4 Other Requirements 31 August 2015 5 Network Requirements TELE302 Lecture 15 2 / 30 TELE302 Lecture 15 3 / 30 General guidelines Network Design: A Systems Approach Defining Requirements Analysis Requirements analysis consists of identifying, gathering, and understanding system requirements and their characteristics, and developing thresholds for performance to distinguish services (low-, high-performance, specified services etc.) Fundamental to network design. TELE302 Lecture 15 4 / 30 TELE302 Lecture 15 6 / 30 General guidelines General guidelines Payoffs of R.A. Sources of Requirements More objective, informed choices of network Users technologies and services. Applications The ability to match interconnection strategy Hosts to networks. Networks Networks and components properly sized to Functional (security, management ... ) users and applications. Finance A better understanding of where and how to apply services in the network. Enterprise (regulations, policies etc.) TELE302 Lecture 15 7 / 30 TELE302 Lecture 15 8 / 30 General guidelines Starting from the Top Requirements Categorization Analyzing Business Goals Requirements gathered or derived from users, Working with clients management and staff need to be analysed and Identifying the scope of the Network Design separated into the following categories: Project Core requirements for the network Build a network from scratch? Desirable features for the network A test bed only? Upgrade of an existing network? Requirements for future revisions / upgrades Rejected requirements Identifying network applications Any Mission-Critical ones? Informational requirements Necessary System Applications TELE302 Lecture 15 9 / 30 TELE302 Lecture 15 11 / 30 Starting from the Top Application Requirements Analyzing Business Constraints Application Delay Types Politics and policies Personnel issues Survive the partners and testers Designation of vendors? Standardization of desktops, OS, and protocols? Budgetary and staffing Use a Business Goals Checklist TELE302 Lecture 15 12 / 30 TELE302 Lecture 15 14 / 30 Application Requirements Application Requirements Application Types User Service Req. Performance Req. → Timeliness Interactivity Mission-critical applications have specified Reliability (deterministic and/or guaranteed) reliability. Quality Capacity Controlled-rate applications have specified Adaptability → Security Delay capacity. → User Numbers Reliability → Real-time (and possibly interactive) applications User Locations Functionality have specified delay requirements. User Growth → Affordability Management Supportability TELE302 Lecture 15 15 / 30 TELE302 Lecture 15 16 / 30 Application Requirements Application Requirements Reliability Capacity System’s ability to provide deterministic and Applications that require an amount of capacity accurate delivery of information. are termed controlled-rate applications. Connectivity, performance, security ... Consequences of poor reliability They require thresholds, bounds, or guarantee on Loss of revenue or customers: banking, airline minimum capacity, peak capacity, or sustained reservation capacity. Loss of information: telemetry, teleconferencing Loss of sensitive data: customer ID/billing They have control in network resource to Loss of life: transportation, health-care monitoring guarantee a certain (minimum) level of capacity, Applications requiring predictable, high degree of which is often tied to end-to-end delay of the reliability, are mission-critical. network. TELE302 Lecture 15 17 / 30 TELE302 Lecture 15 18 / 30 Application Requirements Other Requirements Delay Host Requirements Delay: a measure of time differences in the Desktop computers transfer and processing of information. Workstations Sources: propagation, transmission, queueing, Servers routing, processing, ... File / print Web / e-mail Applications tend to focus on optimizing the DNS total round-trip or end-to-end delay rather than Computing on individual sources (lower-layer optimization). Specialized equipments Applications with delay requirements are Process-specific: high-end display, supercomputer, migrating to the Internet esp. using VPNs. sensors Location-dependent: e.g. Wind tunnels, ATMs TELE302 Lecture 15 19 / 30 TELE302 Lecture 15 21 / 30 Other Requirements Other Requirements More Host Requirements Location Dependence Maintenance Special conditioning Cooling Power Floor loading Security Disaster Recovery Network performance requirements Software compatibility Fault tolerance TELE302 Lecture 15 22 / 30 TELE302 Lecture 15 23 / 30 Other Requirements Network Requirements Use of Location Information Network Requirements Location of applications, servers, users, devices, ... Helps to determine flow characteristics Existing networks Outsourcing / relocating computing resources Network migration Outsourcing agents may relocate resources according Functional requirements to their OAM need E.g. Moving resources from Giga-Ethernet LAN to Financial requirements WAN may run down applications Location change Reevaluate system Enterprise requirements requirements → TELE302 Lecture 15 24 / 30 TELE302 Lecture 15 26 / 30 Network Requirements Network Requirements Dealing with Existing Networks Network Migration Shall we migrate to another networking technology? Avoid the Lemming’s tragedy Scaling “The lemming has been known to migrate en-masse across Network Services vast bodies of water. Sometimes they underestimate the Interoperability distance and drown in large numbers.” Performance “5P”: Prior Planning Prevents Poor Performance Location dependencies Requirements analysis (current, future) Migration path Network infrastructure analysis and preparation Pre-deployment and pilot testing Deployment and Monitoring TELE302 Lecture 15 27 / 30 TELE302 Lecture 15 28 / 30 Network Requirements Network Requirements Management Requirements Recap Categories for network management: Requirements analysis – what it is, why Monitoring for event notification important Monitoring for metrics, capacity/reliability/delay Categorization of requirements engineering Network configuration Be aware of business goals and constraints. Troubleshooting Application requirements Categorization of applications Requirements Important application characteristics Monitoring methods Management protocols Network requirements Characteristic sets Functional requirements Centralized/Distributed, in-band / out-of-band Next Lecture: R.A. Practice TELE302 Lecture 15 29 / 30 TELE302 Lecture 15 30 / 30.
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