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Network Simulation

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Network Components

Router/Switch Switch/Hub Client Computers

Server

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Simulation Goals

• To predict system behavior under various traffic loading conditions

• To evaluate failure performance

• To evaluate design options

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Simple Laboratory LAN

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Simulation Software - Comnet III

• Complete dynamic network simulation system

• Supplies frames/packets according to specified ransom distribution

• Simulates randomly distributed service times

• Records data and generates reports

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Workspace

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Toolbar

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Insert Network Object

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Define Properties

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Edit Default Values

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Expand Network

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Add Sources and Responses

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Edit Source Properties

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Edit Multiconnect Properties

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Edit Response Properties

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Select Distribution Function

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Select Report Items

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Specify Simulation Parameters

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Set Animation Parameters

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Start Simulation

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Read Simulation Report

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Basic LAN with Sources

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Preparing Subnet for Routing

• Delete server and server response

• Add network device - hub or switch

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Deletion of Server and Source

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Adding Hub/Switch

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Selecting Switch Type

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Updating Switch Parameters

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Resulting Subnet Form

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Creating the Top Level

• Add a server and response source

• Add a router

• Add link to server

• Add link to subnet

• Add subnet symbol (do not link yet!)

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Resulting Top Level

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Creating the Subnet Link

• Get copy of subnet on clipboard

• Descend into subnet from subnet symbol on top (router) level

• Intermodel Paste subnet to blank sheet

• Add access point and link to subnet switch

• Make router link to subnet

• Save all

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Select Subnet for Capture

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Selected Subnet

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Put Copy in Clipboard

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Adding the Subnet Link

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Insert Subnet

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Subnet with Access Point Added

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Connect Subnet to Router

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Selecting a Router

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Selecting a Subnet Switch

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Select Simulation Reports

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Simulated Channel Utilization

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Simulated Client Delays

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Questions to Follow Up

• How can channel utilization be reduced?

• How can client delays be reduced?

• What are the effects of various choices of network components?

• What would be the effect of changing the network interconnections from 10BaseT to 100BaseT

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Steps

• Expand the top level

• Expand each subnet– Subnet 1: 5 computers– Subnet 2: 14 computers– Subnet 3: 8 computers

• Simulate all

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Previous Subnet

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Clone the Subnets

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New Server Layer

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Laboratory Subnet

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Classroom Subnet

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Classroom Computer Group

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Editing Group Parameters

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Computer Group Parameters

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Laboratory Group Parameters

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Lab Subnet Properties

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Specify Link Properties

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Channel Utilizations

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Transit Delays

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Increasing Link Speeds

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100BaseT Utilization

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100BaseT Transit Delays

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Importing Topology and Traffic

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Comnet Baseliner™

• Used to import topology– extracts node and link information– generates Comnet topology file

• Used to import traffic models– uses network analyzer output (Ethernet, Token

Ring, FDDI ring or Point-to-point links)– transforms captured network traffic– provides load characteristics for Comnet

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Supported Network Management Systems (NMS)

• HP OpenView

• IBM NetView for AIX

• Digital PolyCenter

• Castlerock SNMPc

• Cabletron SPECTRUM

• NAC Mind

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Topology Import Steps

• Export topology from NMS (*.top, *.csv, *.ncb)

• Import topology via COMNET Baseliner

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Importing Example Topology

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Select File for Import

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Define Topology File

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View the Topology

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Another Sample

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Select Topology and Import

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Result

End

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