– Business (e.g.,support XYZ application), Technical (availability, delay, bandwidth, security, etc.,). • Constraints[r]
(1)Business and Technical Goals and
Business and Technical Goals and
Requirements
Requirements
David Tipper
Associate Professor
Associate Professor
Department of Information Science and Telecommunications
University of Pittsburgh Slides
http://www.sis.pitt.edu/~dtipper/2110.html
http://www.sis.pitt.edu/~dtipper/2110.html
Last Week
• Network Design is not a precise science.
– Many different types of problems • greenfield vs incremental,
• LAN vs MAN vs WAN • wired vs wireless • Etc
– There can be many good answers - no best solution – Design involves trade-offsamong cost vs
performance
• Top Down Design approach useful as a framework
(2)TELCOM 2110 3
Top Down Network Design • Top Down Network Design
– Conceptual Model • Objectives
– Business Goals, Technical Goals
• Requirements
– Business (e.g.,support XYZ application), Technical (availability, delay, bandwidth, security, etc.,)
• Constraints
– Business (organizational, budget, etc.,) and Technical (vendor, technology, sites to connect, etc.)
– Logical Model
• Technology, network graph, node location, link size, etc (where algorithms are used to minimize cost)
– Physical Model
• Specific hardware/software implementations • (e.g., wiring diagram, repeater locations, etc.)
Objectives
• Identify Business Objectives of the network design project
– Through surveys/questionnaires, meetings
• What will the network be used for? Mission critical uses? • How does the customer think the new network will
improve their business practices?
• What is the criteria to be used to judge the network success/failure?
• Example objectives
– Provide new services/Modernize out-dated technologies – Reduce network costs
– Make more data available to more people – Improve network security and reliability
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Business Goals • What is the scope of the project?
– Greenfield or incremental design – Network Size
• (LAN, Campus net, enterprise WAN, backbone, etc.) • Sites to be connected, distances, etc
– What are current/existing networks and services – Identify applications and services to be provided from
surveys and meetings – Quantify user behavior
– As a guideline construct a table with the following info
Very No/hourly
Distributed client/server Sales
Tracking
Comments Criticality
New App? Freq of use Type of
Application Application
Application Modeling
• Need to quantify application behavior
• Can roughly classify applications into categories – Distributed Client Server
– Cooperative Computing – Distributed Computing – Peer-to-Peer Model
• Classifications used to define
– application flows directions and characteristics
• Unidirection or bidirectional • Symmetric or asymmetric • low, medium, or high bit rate
– flow boundaries
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Application Types • Distributed Client
Server
– Tend to be produce asymmetric traffic – larger in downstream direction
– Hierarchical organization – Examples:
• Web applications • Sales Tracking etc
Application Types • Cooperative Computing
– Tend to be produce asymmetric traffic – larger in downstream direction
– Managed correlated distributed servers – Variation of client server – Examples:
• Collaborative Document Processing
• Inventory
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Application Types • Distributed
Computing
– Tend to be produce symmetric traffic – Managed correlated
computers – Examples:
• Computer Aid Manufacturing • Computer Aided
Design
Application Types • Peer-to-Peer
Model
– No obvious hierarchy or asymmetry to traffic
– Examples: • ftp, telnet • Video/audio
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Security Impact on Network
• Security Mechanisms must be put in place to provide security
– Physical Security Measures
• Servers/cabling in locked rooms • Backup power and storage, etc • Impacts physical design
– Electronic Security Measures
• Authentication, packet filters, encryption • Firewalls
– Impacts network performance => > capacity
Manageability
• There are different ways to manage a network and the different things to manage
– Performance, security, fault, configuration, accounting, etc
• Management architecture needs to be deterimined
– In-band versus out-of-band monitoring/signaling – Centralized vs distributed monitoring
– Estimate additional traffic due to management flows
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Affordability
• Affordability is sometimes called cost-effectiveness
• Want to carry the maximum amount of traffic for a given financial cost
• Financial costs include non-recurring equipment costs and recurring network operating costs
• Campus, Metro and WAN costs are areas where a good design can save $
Ranking
• Useful to have users/management rank
performance goals
– Low delay more important than availability
– Ease of management more important than security
– Comparative ranking or absolute
– One approach is assume 100 point to be distributed among the categories of interest and users must allocate the points among the performance categories
• (scalability, availability,delay, security, etc.)