CSE 550 Computer Network Design

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CSE 550Computer Network Design

• Dr. Mohammed H. Sqalli
• COE, KFUPM
• Spring 2008 (Term 072)

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Introduction

• What is a Network?
• What is Network Design?
• Top-Down Network Design
• Network Development Life Cycle (NDLC)
• Network Analysis and Design Methodology
• Types of Network Design
• And Then What?

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What is a Network?

• Management view
• Technical view

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The Management View (1/3)

• A network is a utility
• Computers and their users are customers of the
  network utility
• The network must accommodate the needs of
  customers
• As computer usage increases so does the
  requirements of the network utility
• Resources will be used to manage the network
• The Network Utility is NOT free!
• Someone must pay the cost of installing and
  maintaining the network
• Manpower is required to support the network
  utility

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The Management View (2/3)

• Utilities dont bring money into the organization
• Expense item to the Corporation
• Cannot justify Network based on Productivity
  Improvements
• As a network designer, you need to explain to
  management how the network design, even with the
  high expense, can save money or improve the
  companys business
• If users cannot log on to your commerce site,
  they will try your competitor, and you have lost
  sales
• If you cannot get the information your customers
  are asking about due to a network that is down,
  they may go to your competitor

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The Management View (3/3)

• You need to understand how the network assists
  the company in making money and play on that
  strength when you are developing the network
  design proposal
• Try to show a direct correlation between the
  network design project and the companys business
• Because you want a faster network is not good
  enough, the question that management sends back
  is WHY DO I NEED A FASTER ONE?

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The Technical View (1/2)

• A Network really can be thought of as three
  parts and they all need to be considered when
  working on a network design project
• Connections
• Communications/Protocols
• Services
• Connections
• Provided by Hardware that ties things together
• Wire/Fiber/Wireless Transport Mechanisms
• Routers
• Switches/Hubs
• Computers

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The Technical View (2/2)

• Communications/Protocols
• Provided by Software
• A common language for 2 systems to communicate
  with each other
• TCP/IP (Internet/Windows NT)
• IPX / SPX (Novell Netware 4)
• AppleTalk
• Other Network OS
• Services
• The Heart of Networking
• Cooperation between 2 or more systems to perform
  some function - Applications
• telnet
• FTP
• HTTP
• SMTP

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Traditional Network Design

• Based on a set of general rules
• 80/20
• Bridge when you can, route when you must
• Cant deal with scalability complexity
• Focused on capacity planning
• Throw more bandwidth at the problem
• No consideration to delay optimization
• No guarantee of service quality
• Less importance given to network RMA
  (Reliability, Maintainability, and Availability)
  compared to throughput

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Application Characteristics
Applications Message Length Message arrival rate Delay need Reliability need
Interactive terminals Short Low Moderate Very high
File transfer Very long Very low Very low Very high
Hi-resolution graphics Very long Low to moderate High Low
Packetized voice Very short Very high High Low
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Application Bandwidths
Transaction Processing
100 Bytes Few Kbps
Word Processing
100s Kbps Few Mbps
File Transfers
Few Mbps 10s Mbps
Real-Time Imaging
10s Mbps 100s Mbps
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A Look on Multimedia Networking
Video standard Bandwidth per user WAN services
Digital video interactive 1.2 Mbps DS1 lines ISDN H11, Frame Relay, ATM
Motion JPEG 10 to 240 Mbps ATM 155 or 622 Mbps
MPEG-1 1.5 Mbps DS1 lines ISDN H11, Frame Relay, ATM
MPEG-2 46 Mbps DS2, DS3, ATM at DS3 rate
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Some Networking Issues

• LAN, MAN and WAN
• Switching and routing
• Technologies Ethernet, FDDI, ATM
• Wireless/Mobile networking
• Internetworking
• Applications
• Service quality
• Security concerns

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Generations of Networking
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Network Design Achievable?
Response Time
Cost
Business Growth
Reliability
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Where to begin?
TrafficPatterns
Addressing
WWW Access
Campus
Users
Dial in Users
NetworkManagement
Security
WAN
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Traditional Network Design Methodology

• Many network design tools and methodologies in
  use today resemble the connect-the-dots game
• These tools let you place internetworking devices
  on a palette and connect them with LAN or WAN
  media
• Problem with this methodology
• It skips the steps of analyzing a customer's
  requirements, and selecting devices and media
  based on those requirements

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Top-Down Network Design Methodology (1/2)

• Good network design
• Recognizes that a customers requirements embody
  many business and technical goals
• May specify a required level of network
  performance, i.e., service level
• Includes difficult network design choices and
  tradeoffs that must be made when designing the
  logical network before any physical devices or
  media are selected
• When a customer expects a quick response to a
  network design request
• A bottom-up (connect-the-dots) network design
  methodology can be used, if the customers
  applications and goals are well known

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Top-Down Network Design Methodology (2/2)

• Network designers often think they understand a
  customers applications and requirements.
• However, after the network installation, they may
  discover that
• They did not capture the customer's most
  important needs
• Unexpected scalability and performance problems
  appear as the number of network users increases

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Top-Down Network Design Process (1/2)

• Begins at the upper layers of the OSI reference
  model before moving to the lower layers
• Focuses on applications, sessions, and data
  transport before the selection of routers,
  switches, and media that operate at the lower
  layers
• Explores divisional structures to find the
  people
• For whom the network will provide services, and
• From whom to get valuable information to make the
  design succeed

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Top-Down Network Design Process (2/2)

• It is an iterative process
• It is important to first get an overall view of a
  customer's requirements
• More detail can be gathered later on protocol
  behavior, scalability requirements, technology
  preferences, etc.
• Recognizes that the logical model and the
  physical design may change as more information is
  gathered
• A top-down approach lets a network designer get
  the big picture first and then spiral downward
  into detailed technical requirements and
  specifications

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Structured Network Design Process- A Systems
Approach (1/2) -

• The system is designed in a top-down sequence
• Several techniques and models can be used to
  characterize the existing system, new user
  requirements, and a structure for the future
  system
• A focus is placed on understanding
• Data flow, data types, and processes that access
  or change the data
• The location and needs of user communities that
  access or change data and processes

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Structured Network Design Process- A Systems
Approach (2/2) -

• A logical model is developed before the physical
  model
• The logical model represents the basic building
  blocks, divided by function, and the structure of
  the system
• The physical model represents devices and
  specific technologies and implementations
• For large network design projects, modularity is
  essential
• The design should be split functionally to make
  the project more manageable

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Network Development Life Cycle
Analysis
Management
Design
Simulation/ Prototyping
Monitoring
Implementation
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Network Design and Implementation Cycle
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Network Design and Implementation Cycle (1/3)

• Analyze requirements
• Interviews with users and technical personnel
• Understand business and technical goals for a new
  or enhanced system
• Characterize the existing network logical and
  physical topology, and network performance
• Analyze current and future network traffic,
  including traffic flow and load, protocol
  behavior, and QoS requirements

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Network Design and Implementation Cycle (2/3)

• Develop the logical design
• Deals with a logical topology for the new or
  enhanced network
• Network layer addressing and naming
• Switching and routing protocols
• Security planning
• Network management design
• Initial investigation into which service
  providers can meet WAN and remote access
  requirements

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Network Design and Implementation Cycle (3/3)

• Develop the physical design
• Specific technologies and products to realize the
  logical design are selected
• The investigation into service providers must be
  completed during this phase
• Test, optimize, and document the design
• Write and implement a test plan
• Build a prototype or pilot
• Optimize the network design
• Document your work with a network design proposal

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Another Perspective

• Data collection
• Traffic
• Costs
• Constraints
• Design process
• Performance analysis
• Fine tuning
• A painstaking iterative process

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PDIOO Network Life Cycle (1/3)(Cisco)

• Plan
• Network requirements are identified in this phase
• Analysis of areas where the network will be
  installed
• Identification of users who will require network
  services
• Design
• Accomplish the logical and physical design,
  according to requirements gathered during the
  Plan phase
• Implement
• Network is built according to the Design
  specifications
• Implementation also serves to verify the design

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PDIOO Network Life Cycle (2/3)(Cisco)

• Operate
• Operation is the final test of the effectiveness
  of the design
• The network is monitored during this phase for
  performance problems and any faults, to provide
  input into the Optimize phase
• Optimize
• Based on proactive network management which
  identifies and resolves problems before network
  disruptions arise
• The optimize phase may lead to a network redesign
• if too many problems arise due to design errors,
  or
• as network performance degrades over time as
  actual use and capabilities diverge
• Redesign may also be required when requirements
  change significantly

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PDIOO Network Life Cycle (3/3)(Cisco)

• Retire
• When the network, or a part of the network, is
  out-of-date, it may be taken out of production
• Although Retire is not incorporated into the name
  of the life cycle (PDIOO), it is nonetheless an
  important phase

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One More Look
BusinessPlanning
ImplementNetwork
Network Design
Operations
Develop OperationsPolicies andCapabilities
Define Objectivesand Requirements
DevelopArchitecture
CreateImplementation Plan
Create InitialSolution
Develop DetailedDesign
Procure Resourcesand Facilities
FaultManagement
Define DeploymentStrategy
Create BuildDocumentation
ConfigurationManagement
Stage and Install
ChangeManagement
Review and VerifyDesign
Certify and Hand-offto Operations
Review andApprove
PerformanceManagement
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Information Flows between Network Analysis,
Architecture, and Design
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Network Analysis and Design Methodology- Overall
Characteristics -

• Requirements (business, application, and data)
  definition is required prior to network design
  activities
• Expected compliance with requirements in a
  Request For Proposal (RFP) by both in-house
  personnel and outside consultants
• Activities from various stages often take place
  simultaneously and backtrack to previous
  activities is sometimes needed
• This methodology is an overall guideline to the
  network development process rather than
  cookbook instructions

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Network Analysis and Design Methodology-
Critical Success Factors of the NDLC (1/3) -

• Identification of all potential customers and
  constituencies
• All groups must be consulted
• Political awareness
• Corporate culture hierarchical, distributed, or
  open
• Backroom politics can play a role in systems
  design
• Find ways to ensure objectivity of the analysis
  and design process (e.g., measurable goals)
• Buy-in
• Reach consensus on the acceptability of results
  of each stage
• Approved results of one stage become the
  foundation or starting point for the next stage
• Makes the final presentation smoother

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Network Analysis and Design Methodology-
Critical Success Factors of the NDLC (2/3) -

• Communication
• With all groups
• Write memos, communicate with key people in
  person, etc.
• Detailed project documentation
• Prepare agendas
• Take meeting minutes
• Action items
• Use a project binder for all the above

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Network Analysis and Design Methodology-
Critical Success Factors of the NDLC (3/3) -

• Process/Product awareness
• Stay focused what is the process/product at each
  stage?
• Keep meeting on track no off-subject discussions
• Be honest with yourself
• Be your own harshest critic (no one else knows
  the potential weaknesses or areas for improvement
  in your proposal better than you)
• Use peer reviews
• Not all weaknesses can be corrected (e.g.,
  financial or time constraints)

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Network Analysis and Design Methodology -
Overall Guidelines -

• Start with a clearly defined problem
• Identify affected parties and representatives
• Held brainstorming sessions to define problems
  and requirements of a solution
• Understand strategic business objectives defined
  by senior management
• Collect baseline data from customer groups about
  the current status of the system and network
• This is used to measure eventual impact of the
  installed network
• Perform a feasibility study problem definition
  and associated alternative recommendations for
  further study

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Customers Requirements- Understanding the
Customer -

• A good network design must recognize the
  customers requirements - need to make sure your
  design meets THEIR needs and not just YOURS!
• The Customer may be your own firm, the who
  you are designing the network for
• Need an overview of a customers requirements
• The best designed network will fail miserably
  without the support of people

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Customers Requirements- Users Needs -

• What do the users want?
• Services
• What do the users need?
• What dont they know but they need?
• Organize and Prioritize Requirement

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Customers Requirements- How they are used -

• User Requirements ? Performance Requirements

• Timeliness
• Interactivity
• Reliability
• Quality
• Security
• Affordability
• User Numbers
• User Locations
• User Growth

Delay
Reliability
Capacity
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Analysis and Design Processes

• Set and achieve goals
• Maximizing performance
• Minimizing cost
• Optimization with trade-offs
• Recognizing trade-offs
• No single best answer
• Hierarchies
• Provide structure in the network
• Redundancy
• Provides availability reliability

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Approaches Used for Design

• Heuristic by using various algorithms
• Exact by working out mathematical solutions
  based on linear programming, etc., minimizing
  certain cost functions
• Simulation often used when no exact analytical
  form exists. Experiments are conducted on
  simplified models to see the performance of a
  network

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Design and Study of a System
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Art or Science?

• The Art of Network Design
• Technology choices
• Relations to business goals

• The Science of Network Design
• Understanding of network technologies
• Analysis of capacity, redundancy, delay

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Types of Network Design

• New network design
• Re-engineering a network design
• Network expansion design

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New Network Design

• Actually starting from scratch
• No legacy networks to accommodate
• Major driver is the budget, no compatibility
  issues to worry about
• Getting harder to find these situations

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Re-engineering a Network Design

• Modifications to an existing network to
  compensate for original design problems
• Sometimes required when network users change
  existing applications or functionality
• More of the type of problems seen today

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Network Expansion Design

• Network designs that expand network capacity
• Technology upgrades
• Adding more users or networked equipment

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This Whole Thing is Messy
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This Whole Thing is Messy

• Ambiguous Requirements
• The network will only transport IP
• The application requires Novell IPX

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This Whole Thing is Messy

• Conflicting Requirements
• Keep costs down
• High performance cost money

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This Whole Thing is Messy

• Lack of Design Tools
• Lack of Management Tools
• Lack of Vendor Interoperability

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This Whole Thing is Messy

• Lack of Documentation
• Existing network
• How things should be done (e.g., wiring)
• Vendor information

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This Whole Thing is Messy

• Network Management
• More management uses more bandwidth
• Every vendor has their own management tools
• Vendor tools may conflict with each other

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This Whole Thing is Messy

• Security
• What is enough security?
• What is too much security?
• security and management can not be dealt with as
  afterthoughts. It is not an add-on feature, it
  has to be integrated within.

10Mb/s Ethernet
10Mb/s Ethernet
T1 1.5Mb/s
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This Whole Thing is Messy

• Evolving Network Technologies
• Everything is a moving target
• Products are put onto the market before standards
  are approved
• Everyone is a computer expert

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OAMPOperations, Administration, Maintenance,
Provisioning
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Functional Flow Chart
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References

• Dr. Khalid Salah (ICS, KFUPM), CSE 550 Lecture
  Slides, Term 032
• Dr. Marwan Abu-Amara (COE, KFUPM), CSE 550
  Lecture Slides, Term 052
• P. Oppenheimer, Top-Down Network Design, Cisco
  Press, 2nd edition, 2004
• J. McCabe, Network Analysis, Architecture, and
  Design Morgan Kaufmann Publishers, Inc., 2nd
  edition, 2003
• J. E. Goldman, Applied Data Communications - A
  Business-Oriented Approach, 1998