Introduction to NS-3 Part - 2

1. Introduction to NS-3Part - 2 Katsaros Konstantinos PhD Student PGSDP Workshop on NS-3 2 April 2012

2. Overview • FlowMonitor • Smart Pointers • Packet Tags • Debugging • Visualization • Creating a new Module • Advanced Simulation with NS-3 • NSC (Network Simulator Cradle) • MPI (Message Passing Interface) • EMU (Emulation) 2 Konstantinos Katsaros

3. Flow Monitor • A common problem was identified • “how to easily extract flow metrics from arbitrary simulations?” • Existing solutions do not solve this problem effectively • The Flow Monitor solves the problem • Requires significant less programming time than NS-3 callback based tracing • A lot more efficient than ascii tracing • More data output methods (e.g. database and binary file) • More options to control level of detail stored in memory • Monitor multicast/broadcast flows 3 Konstantinos Katsaros

4. Flow Monitor Measurements • timeFirstTxPacket, timeLastTxPacketbegin and end times of the flow from the point of view of the receiver • timeFirstRxPacket, timeLastRxPacketbegin and end times of the flow from the point of view of the receiver • delaySum, jitterSumsum of delay and jitter values • txBytes, txPacketsnumber of transmitted bytes and packets • rxBytes, rxPacketsnumber of received bytes and packets • lostPacketsnumber of definitely lost packets • timesForwardedthe number of times a packet has been reportedly forwarded, summed for all packets in the flow • delayHistogram, jitterHistogram, packetSizeHistogramHistogram versions for the delay, jitter, and packet sizes, respectively • packetsDropped, bytesDroppeddiscriminates the losses by a reason code • DROP NO ROUTE no IPv4 route found for a packet • DROP TTL EXPIRE a packet was dropped due to an IPv4 TTL field decremented and reaching zero • DROP BAD CHECKSUM a packet had a bad IPv4 header checksum and had to be dropped 4 Konstantinos Katsaros

5. Flow Monitor Example Create a FlowMonitorHelper object FlowMonirtorHelperflowmon; Create a pointer to FlowMonirot class and install probes to all nodes Ptr<FlowMonitor> monitor = flowmon.InstallAll(); Configure histogram parameters Monitor->SetAttribute (”DelayBinWidth”, DoubleValue(0.001)); Monitor->SetAttribute (”JitterBinWidth”,DoubleValue (0.001)); Run simulation Simulator::Run (); Write results into an XML file monitor->SerializeToXmlFile (”results.xml”,True,True); 5 Konstantinos Katsaros

6. Smart Pointer • NS3 uses reference-counting smart pointers at its APIs to limit memory leaks • Or “pass by value” or “pass by reference to const” where appropriate • A “smart pointer” behaves like a normal pointer (syntax) but does not lose memory when reference count goes to zero • Use them like built-in pointers: Ptr<MyClass> p = CreateObject<MyClass> (); p->method (); 6 Konstantinos Katsaros

7. Packet Tags • Small chunks of information • Any number of tags can be attached a packet • Tags are keyed by the a structure type itself E.g.: Ptr<Packet> p; MyTag tag; p->AddTag (tag); p->PeekTag (tag); • New tag types are defined similarly to header types • Tags can be used to: • Attach context information to a packet • Example: NetDevice attaches destination MAC address when queueing, retrieves it when dequeuing for transmission • Convey additional information across layers 7 Konstantinos Katsaros

8. Debugging (1) • Assertions: NS_ASSERT (expression); • Aborts the program if expression evaluates to false • Includes source file name and line number • Unconditional Breakpoints: NS_BREAKPOINT (); • Forces an unconditional breakpoint, compiled in • Debug Logging (not to be confused with tracing!) • Purpose • Used to trace code execution logic • For debugging, not to extract results! • Properties • NS_LOG* macros work with C++ IO streams • E.g.: NS_LOG_UNCOND (”I have received ” << p->GetSize () << ” bytes”); • NS_LOG macros evaluate to nothing in optimized builds • When debugging is done, logging does not get in the way of execution performance 8 Konstantinos Katsaros

9. Debugging (2) • Logging levels: • NS_LOG_ERROR (...): serious error messages only • NS_LOG_WARN (...): warning messages • NS_LOG_DEBUG (...): rare ad-hoc debug messages • NS_LOG_INFO (...): informational messages (eg. banners) • NS_LOG_FUNCTION (...):function tracing • NS_LOG_PARAM (...): parameters to functions • NS_LOG_LOGIC (...): control flow tracing within functions • Logging ”components” • Logging messages organized by components • Usually one component is one .cc source file • NS_LOG_COMPONENT_DEFINE ("OlsrAgent"); • Displaying log messages. Two ways: • Programatically: • LogComponentEnable("OlsrAgent", LOG_LEVEL_ALL); • From the environment: • NS_LOG="OlsrAgent" ./my-program 9 Konstantinos Katsaros

10. Visualization • Not integrated (directly) with ns-3 • Ns-3 creates “animation” file, visualizers use this as input and create the animation. • netanim, pyviz, and nam for ns-3 10 Konstantinos Katsaros

11. NetAnim 3.0 Features • Animate wired-links and wireless-links based simulations. • LTE-packets cannot be animated, but topology will be shown • Complete redesign using the QGraphics framework • Packet statistics with filter • Node position statistics with node trajectory (path of a mobile node) plotting • Improved window re-sizing and zooming http://www.nsnam.org/wiki/index.php/NetAnim 11 Konstantinos Katsaros

12. Adding New Module • In order to create a new module in the NS3, just run the create-module.py script that will create the basic structure of the module (examples, helper, test, model and the appropriate wscript ). • As of ns-3.13 there is no need to add the module in ns3 wscript, it is done automatically. Usage: ./create-module.py [options] modulename Then clean the project, configure and re-build it %./wafdistclean %./waf configure %./waf 12 Konstantinos Katsaros

13. NSC • The Network Simulation Cradle (NSC) is a framework which allows real world TCP/IP network stacks to be used inside a network simulator http://www.nsnam.org/wiki/index.php/Network_Simulation_Cradle_Integration 13 Konstantinos Katsaros

14. Distributed Simulation with MPI • MPI: Message Passing Interface • Library (and protocol) for distributed applications • MPI simulator (as of ns-3.8) • Nodes in the simulation assigned different System Ids • Nodes with different System Ids run on different cluster machines • Nodes on different machines may communication using p2p links only Node 0 SystemId 1 Node 3 SystemId 2 Point-to-point Link (simulation and real world) Node 2 SystemId 1 Node 1 SystemId 1 Node 4 SystemId 2 Node 5 SystemId 2 14 Konstantinos Katsaros

15. Emulation • Support moving between simulation and testbeds or live systems • A real-time scheduler, and support for two modes of emulation • GlobalValue::Bind (“SimulatorImplementationType”, StringValue(“ns3::RealTimeSimulatorImpl”)); 15 Konstantinos Katsaros

16. Acknowledgements • Special thanks to: • Mathieu Lacage • Tom Henderson • Gustavo Carneiro For borrowing parts of their slides 16 Konstantinos Katsaros