Notes

Outline

NS internals Velibor Markovski Communication Networks Laboratory School of Engineering Science Simon Fraser University

Software architecture Split programming model (C++ and OTcl) Simulation kernel ® C++ Simulation definition, configuration and control ® OTcl Tradeoff: performance vs. flexibility

Class mirroring OTcl class hierarchy C++ class hierarchy

Simple script Two nodes CBR traffic from source to destination UDP used as transport protocol

Simple script

Simple script - initialization

Simple script - initialization

Simple script - initialization

Simple script - initialization

Simple script - initialization

Simple script - initialization

Simple script – node creation

Simple script – link creation

Simple script – setting up source

Simple script – setting up sink

Simple script – connecting nodes

Simple script – schedule “at” events

Event scheduler

Initial events

Initial and follow-up events

Initial and follow-up events

Scheduler’s main functions Schedule events at certain time Insert events in the list Deque events from the list Dispatch dequed events Call appropriate event handler

Back to our example

Back to our example

Back to our example

Back to our example

Even more details…

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Complex software structure Approximate numbers: 27K lines of C++ code (ns-2.1b5) 12K lines of OTcl code 18K lines of test suites and examples

Why simulators at all? Inexpensive Flexible: with scenario generation with link speeds with topologies Access to ALL data

Alternatives to simulation Testbeds Emulation (testbed-simulator mix) Live Internet tests

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