Last Week: Requirement Analysis

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Last Week Requirement Analysis

• The Network Analysis Process
• Requirement Analysis
• Gather Requirements
• Develop Service Metrics to Measure Performance
• Characterizing behaviour
• Develop Performance Thresholds
• Distinguishing Between Service Requirements
• Flow Analysis
• Establish Flow Boundaries
• Identify Backbone/Composite Flow
• Develop Flowspec
• Capacity Plan
• Service Plan

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Requirement Analysis
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Flow Analysis

• Concepts
• Guidelines

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Flow Analysis
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Flow Analysis Concepts

• Background
• Flows
• Data Sources and Sinks
• Flow Models
• Flow Boundaries
• Flow Distributions
• The Flow Specification

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Flow Analysis Concepts

• Background
• We have established the user, application, host
  and the network requirements, established
  requirements specifications
• Further analyse these requirements based on their
  end-to-end characteristics
• We will discuss the concepts of flow and flow
  specification
• Use with best effort service for capacity
  planning
• Use with specified services for service planning

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Flow Analysis Concepts

• Background
• Introduce flow concepts
• Data sources and sinks
• Flow models
• Flow distributions
• To identify, size, and choose flows
• Develop cumulative performance specifications for
  each flow

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Flow Analysis Concepts

• Flows
• A flow is
• A set of application and protocol information
  that has some common attributes, such as
• Source address
• Destination address
• Information type
• Options
• Routing etc.
• And is transmitted during a single session of an
  application.

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Flow Analysis Concepts

• Flows
• End-to-end, source-to destination (between
  applications/hosts)
• Can also be examined on
• a link-by-link or
• Network-by-network basis
• Flow analysis help to choose
• Technology and
• Protocol

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Flow Analysis Concepts

• Flows
• Flow analysis provides
• An end-to-end perspective on requirements
• Some insight to the degree of hierarchy and
  redundancy needed
• Useful information for choosing an
  interconnection strategy
• Switching
• Routing, or
• Hybrid mechanisms

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Flow Analysis Concepts

• Flows
• Three types
• Individual flow
• Composite flow
• Backbone flow

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Flow Analysis Concepts

• An individual flow is the flow for a single
  session of an application
• Derived from the requirements specification or
• Estimated
• A composite flow is the combination of individual
  flows that share the same path, link or network
• Used in capacity planning of the network

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Flow Analysis Concepts

• A backbone flow is formed by composite flows when
  the network achieves a certain degree of
  hierarchy
• Has implications on capacity planning
• Useful for
• routing and
• addressing plans

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Flow Analysis Concepts

• Data Sources and Sinks
• A data source is a device or group of devices
  that primarily produces data that the network
  will carry
• A data sink primarily accepts data from the
  network, acting as a data repository.
• Almost all devices on a network will both produce
  and accept data
• Some devices will act as either sources or sinks

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Flow Analysis Concepts

• Data Sources and Sinks
• Data sources
• Computing servers
• Mainframes
• Parallel systems
• Computing clusters
• Data sinks
• Groups of disks/tape devices
• Video editing or display devices

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Flow Analysis Concepts

• Data Sources and Sinks
• Gives an indication of where flows are
  consolidated or generated
• Create flow models to help with the design process

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Flow Analysis Concepts

• Flow models
• Map flows to general, well known flow models
• Flow models are characterized by their
• Directionality and
• Hierarchy
• Many flows have different requirements in each
  direction

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Flow Analysis Concepts

• Flow models
• Most flows are asymmetrical
• Access and transmission technologies can be
  optimised for asymmetrical flows
• Digital Subscriber Loop (xDSL), ATM
• Hierarchy describes the degree of concentration
  of flows
• Hierarchy, is a result of the logical grouping of
  users, hosts, network, names, addresses etc.

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Flow Analysis Concepts

• Flow Models - well known models
• Peer-to-peer
• Client-server
• Cooperative computing
• Distributed computing

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Flow Analysis Concepts

• Flow models
• Determine the directionality and hierarchy of
  flows
• Identify critical flows the most important ones
  to determine the backbone flows

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Hierarchical Design
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Flow Analysis Concepts

• Flows
• Peer-to-peer
• Users and applications are roughly similar
• No obvious directionality
• No obvious hierarchy
• Example early Internet where FTP and telnet were
  primarily used to transfer information

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Peer-to-peer
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Flow Analysis Concepts

• Peer-to-peer flows
• Default model
• All users need equal access to each other for an
  application
• Example A tele-services application (e.g.
  teleconferencing)
• Most likely to be best effort
• Used in the capacity planning

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Flow Analysis Concepts

• The client-server model
• The most generally applicable model
• Has flow directionality and hierarchy
• Two way communications
• Request small
• Response bigger
• Asymmetric, mainly towards the client
• May even be considered unidirectional
• Hierarchical

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Client-server flow model
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Flow Analysis Concepts

• Client-server
• Multicast at some layer in the network should be
  considered to optimize the flows
• Example The Internet has evolved to become a
  client-server model ftp servers, gopher, Archie

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Flow Analysis Concepts

• Cooperative Computing Flow Model
• More hierarchical
• Multiple applications work together and share
  information to accomplish a task or
• Multiple client-server applications are managed
  by a higher-level application
• Critical flows server-to-server,
  server-to-manager, server-to-client
• Server source or sink? - More information about
  application needed to decide
• Example A climate modeling problem (McCabe)

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Cooperative Computing Flow
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Flow Analysis Concepts

• Distributed Computing Flow Model
• The most specialized flow model
• Flows may be primarily
• Between a task manager and its computing nodes or
• Between the computing nodes
• Computing nodes
• Loosely coupled little or no information
  transfer between nodes
• Closely coupled frequent information transfer
  between nodes

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Flow Analysis Concepts

• Distributed Computing Flow Model
• Tasks
• Having a coarse granularity
• Each task dedicated to a single computing node
• Having a fine granularity
• A task is subdivided between several computing
  nodes and computing is done concurrently

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Flow Analysis Concepts

• When a task has a coarse granularity and nodes
  are loosely coupled
• Computing cluster
• Asymmetric flow, mainly node to task manager
• Flows are not synchronized (independent of each
  other)
• Critical flows node to server

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Flow Analysis Concepts

• When a task has a fine granularity and nodes are
  closely coupled
• Simplified parallel processing system
• Each task is subdivided between several computing
  nodes
• Nodes work concurrently exchanging information
  with neighbour nodes
• Flows may have the most stringent performance
  characteristics of any of the models
• Critical flow between nodes

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Distributed Computing Flow Model
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Flow Analysis Concepts

• Distributed computing model
• Critical flow between computing nodes
• Muticasting should be considered for optimizing
  flow performance
• Flow characteristics will vary between the
  computing cluster and parallel system models
• The degree of granularity and degree of coupling
  is important in determining the flow.

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Flow Analysis Concepts

• Flow Boundaries
• Separations between large portions of the system,
  used to indicate where flow consolidations and
  hierarchies occur
• Usually applied to separate geographic areas
• LAN/WAN
• LAN/MAN
• MAN/MAN
• Campus/Campus
• Building/Building
• Floor/Floor

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Flow Analysis Concepts

• Flow Boundaries
• Most frequently used boundaries
• LAN/WAN
• Campus/Campus
• Building/Building

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Flow Analysis Concepts

• Flow Boundaries
• Logical boundaries can be used to separate
  between
• Backbones
• Flow concentration points (e.g. a network access
  point in the Internet)
• WANs, where service providers are likely to be
  used
• Specialized areas having specific requirements

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Flow Analysis Concepts

• Flow Distributions
• Used to determine where backbone flows are
  located in the design
• Show when flows stay in one region of the network
  or transit one or more regions of the network
• Regions for flow distributions
• LANs, MANs and WANs
• Flow distribution within a LAN/between LANs

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Flow Analysis Concepts

• Flow distributions
• 80/20 rule
• 80 of the flow of traffic stays within a LAN
• 20 is across a WAN
• Therefore, WAN capacity is approximately 25 of
  LAN
• 10 Mbps Ethernet LANs connected through
  1.544/2.048 Mbps T1/E1 circuits
• Today, 80/20 rule is less applicable
• 80/20, 50/50, 20/80 All possible

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Flow distributions
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Flow Analysis Concepts

• The flow specification
• When we have
• Flows identified
• Each applications requirements listed
• We can then determine how to combine the
  requirements for each flow

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Flow Analysis Concepts

• The flow specification three forms
• A one-part (unitary) flowspec, used for capacity
  planning of best-effort flows when there are no
  specified flows
• A two-part flowspec containing both best-effort
  and specified flows
• A multipart flowspec, providing more detail on
  individual components of the specified flows

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Flow Analysis Concepts

• The flowspec algorithm
• To develop the flowspec algorithm
• List the characteristics of each of the flows
• Apply an algorithm to bring these characteristics
  together into a specification for the combined
  flows
• Combines
• Reliability
• Capacity and
• Delay characteristics for each of the flows to
  describe the expected overall performance required

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Flow Analysis Concepts

• The flowspec algorithm conditions
• Only capacity requirements are used in
  best-effort calculations
• Use all characteristics (if available) in
  calculations for specified flows
• When guaranteed delay and/or reliability
  requirements are indicated, they will be used
  individually in the calculations for the flowspec
• Capacities generated by the unitary, two-part,
  and multipart flowspecs are base line capacities
  only, and not the performance modifiers

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Flow Analysis Concepts

• Unitary flowspec
• Capacity planning
• Best-effort (BE) environment

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Flow Analysis Concepts

• Two-part flowspec
• Capacity and Service Planning
• Specified Environment
• RDET, DDET,
• Best-effort environment

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Flow Analysis Concepts

• Multipart flowspec
• Capacity and Service Planning
• Guaranteed Environment
• Ci, Ri, Di
• Specified Environment
• RDET, DDET,
• Best-effort environment

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Flow Analysis Guidelines
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Flow Analysis Guidelines

• Applying the flow models
• Establishing flow boundaries
• Applying flow distributions
• Combining flow models, boundaries, and
  distributions
• Developing the flow specification
• Prioritizing Flows

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Flow Analysis Guidelines

• Applying the flow models
• Application map done
• Flow model done
• The locations of data sources and sinks
  identified
• Therefore, flows and flow directions are
  identified
• See example 6.1 (McCabe)

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Flow Analysis Guidelines

• Establishing flow boundaries
• Identify data sources and sinks
• Determine the flow model
• Place the flow boundaries
• Identify flows crossing these boundaries
• For flows crossing boundaries, determine whether
  they are critical flows
• If step 5 applies give special consideration to
  critical flows crossing boundaries

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Flow Analysis Guidelines

• Applying flow distributions
• Flow distributions tell us the expected relative
  traffic volumes of a flow when it crosses flow
  boundaries (e.g. 80/20)
• Guidelines
• Peer-to-peer no particular flow distribution
• Client-server 50/50 when clients must cross a
  boundary to get a server, otherwise 80/20
• Cooperative computing - 50/50 when traffic from
  different servers must cross a boundary to get a
  server, otherwise 80/20

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Flow Analysis Guidelines

• Distributed computing flow distributions
• Computing cluster and computing nodes are remote
  from the task manager 50/50
• Parallel computing and the traffic between
  computing nodes is across flow boundaries 20/80
• These are only guidelines to indicate starting
  points and will be changed according to
• Applications requirements
• The distribution of users
• The user behaviour patterns
• Flow distributions are used to determine whether
  a backbone flow will be generated or not

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Flow Analysis Guidelines

• Combining flow models, boundaries, and
  distributions
• Indicates the possibility and location of
  backbone flows
• Backbone flows imply hierarchy in a network

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Flow Analysis Guidelines

• Developing the flow specification
• Helps in making technology choices
• Helps in requesting, configuring, and verifying
  services
• Provides capacity and service plans
• Used to generate a service plan (capacity delay
  reliability requirements)
• Helps to determine how to meet delay and
  reliability requirements

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Flow Analysis Guidelines

• To developing the flow specification we need
• A listing of applications (applications
  portfolio) and their requirements
• Category of each application low/high
  performance, specified, or best effort
• The applications map
• Potential user and application modifiers for
  performance
• Flow models, boundaries, distributions, and data
  sources and sinks for our environment

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Flow Analysis Guidelines

• Prioritizing flows
• Flowspec enables us to prioritize flows
• This can be done according to
• Number of users affected by each flow
• The performance characteristics of each flow
• Distances and locations