Introduction to NS-3

Transcription

1 Introduction to NS-3 Konstantinos Katsaros surrey.ac.uk Centre for Communications System Research University of Surrey System Level Simulations - Technical Club

2 Outline 1 Introduction 2 NS-3 Modules 3 LTE Module 4 WiFi Example K. Katsaros Introduction to NS-3 04/07/13 2 / 33

3 Introduction ns-3 is written in C++, with bindings available for Python simulation programs are C++ executables or Python programs 300,000 lines of mostly C++ (estimate based on cloc source code analysis) ns-3 is a GNU GPLv2-licensed project ns-3 is mainly supported for Linux, OS X, and FreeBSD ns-3 is not backwards-compatible with ns-2 K. Katsaros Introduction to NS-3 04/07/13 3 / 33

4 Where to get it Where do I get ns-3? - Where do I get today s code? Download the latest release: - wget - tar xjf ns-allinone-3.17.tar.bz2 Clone the latest development code 1 : - hg clone 1 Mercurial is used as source code control tool K. Katsaros Introduction to NS-3 04/07/13 4 / 33

5 Current Modules in main NS-3 tree Network: Node, Sockets, Queues, Packet, etc Core: Smart Pointers, Callbacks, Event, Scheduler, Logging, Tracing, etc K. Katsaros Introduction to NS-3 04/07/13 5 / 33

6 Module Organization model/ contains source code for main part of module helper/ contains code for helper classes examples/ tests/ bindings/ files related to python doc/ wscript the Makefile" equivalent K. Katsaros Introduction to NS-3 04/07/13 6 / 33

7 Helper API The ns-3 helper API" provides a set of classes and methods that make common operations easier than using the low-level API Consists of: - container objects - helper classes The helper API is implemented using the low-level API Users are encouraged to contribute or propose improvements to the ns-3 helper API K. Katsaros Introduction to NS-3 04/07/13 7 / 33

8 Building NS-3 Waf is a Python-based framework for configuring, compiling and installing applications. It is a replacement for other tools such as Autotools, CMake or Ant For those familiar with autotools: configure./waf configure make./waf build K. Katsaros Introduction to NS-3 04/07/13 8 / 33

9 Discrete-event simulations Simulation time moves in discrete jumps from event to event C++ functions schedule events to occur at specific simulation times A simulation scheduler orders the event execution Simulator::Run() gets it all started Simulation stops at specific time or when events end K. Katsaros Introduction to NS-3 04/07/13 9 / 33

10 Time in NS-3 Time is stored as a large integer in ns-3 - Avoid floating point discrepancies across platforms Special Time classes are provided to manipulate time (such as standard operators) Default time resolution is nanoseconds, but can be set to other resolutions Time objects can be set by floating-point values and can export floating-point: double timedouble = t.getseconds(); K. Katsaros Introduction to NS-3 04/07/13 10 / 33

11 NS-3 API Most of the ns-3 API is documented with Doxygen ( K. Katsaros Introduction to NS-3 04/07/13 11 / 33

12 Scalability Distributed simulation in ns-3 allows a user to run a single simulation in parallel on multiple processors By assigning a different rank to nodes and connecting these nodes with point-to-point links, simulator boundaries are created Simulator boundaries divide Logical Processes (LPs), and each LP can be executed by a different processor Distributed simulation in ns-3 offers solid performance gains in time of execution for large topologies Simulation on a HPC cluster at the U.S. Mobile Network Modeling Institute (2011) cores, 3 TB of memory - 360,448,000 simulated nodes - 413, packet receive events per second [wall-clock] 2 K. Renard et al, A Performance and Scalability Evaluation of the NS-3 Distributed Scheduler. Proceedings of WNS K. Katsaros Introduction to NS-3 04/07/13 12 / 33

13 Attribute System Problem: Researchers want to identify all of the values affecting the results of their simulations and configure them easily ns-3 solution: Each ns-3 object has a set of attributes: - A name, help text - A type - An initial value Control all simulation parameters for static objects Dump and read them all in configuration files Visualize them in a GUI Makes it easy to verify the parameters of a simulation List of all attributes in the API: attribute_list.html K. Katsaros Introduction to NS-3 04/07/13 13 / 33

14 Tracing System Simulator provides a set of pre-configured trace sources - Users may edit the core to add their own Users provide trace sinks and attach to the trace source -Simulator core provides a few examples for common cases Multiple trace sources can connect to a trace sink List of all trace sources in the API: trace_source_list.html K. Katsaros Introduction to NS-3 04/07/13 14 / 33

15 FlowMonitor Network monitoring framework found in src/flow-monitor/ Goals: - detect all flows passing through network - stores metrics for analysis such as throughput, duration, delays, packet sizes, packet loss ratios Currently works ONLY on IPv4 packets. K. Katsaros Introduction to NS-3 04/07/13 15 / 33

16 NetAnim Animate packets over wired-links and wireless- links - limited support for LTE traces Packet timeline with regex filter on packet meta-data. Node position statistics with node trajectory plotting (path of a mobile node). Print brief packet meta-data on packets K. Katsaros Introduction to NS-3 04/07/13 16 / 33

17 LTE module - Design FemtoForum LTE MAC Scheduler API Radio signal model granularity: Resource Block - Symbol-level model not affordable - Simplified Channel PHY model Realistic Data Plane Protocol stack model - Realistic RLC, PDCP, S1-U, X2-U - Allow proper interaction with IP networking - Allow end-to-end QoE evaluations Hybrid Control Plane model: - Realistic RRC model - Simplified S1-C, X2-C and S11 models Simplified EPC - One MME and one SGW - SGW and PGW in the same node (no S5/S8 interface) Focus on connected mode - RRC connected, EMM Registered, ECM connected K. Katsaros Introduction to NS-3 04/07/13 17 / 33

18 Model Overview K. Katsaros Introduction to NS-3 04/07/13 18 / 33

19 Propagation Models Buildings model - Add buildings to network topology Path loss model - Okumura Hata (outdoor) - ITU-R P1411 LOS & NLOS (outdoor) - ITU-R P1238 (indoor) - External & internal wall losses - Log-normal shadowing - Pathloss logic chooses correct model depending on node position Fast fading model - Trace-based - Freq. and time dependent Antenna models - Isotropic - Sectorial (cosine & parabolic shape) K. Katsaros Introduction to NS-3 04/07/13 19 / 33

20 PHY model Only FDD is modelled Freq domain granularity: RB Time domain granularity: 1 TTI, further divided into - DL: ctrl, data - UL: ctrl+data, SRS Gaussian Interference model CQI feedback Signal processing not modelled accurately use error model SISO propagation model MIMO modeled as SINR gain over SISO - different gains for different TX modes Supports different freqs and bandwidths per enb - leveraging on the ns-3 Spectrum module K. Katsaros Introduction to NS-3 04/07/13 20 / 33

21 MAC Scheduler model Resource allocation model: - allocation type 0 - RBs grouped into RBGs - localized mapping approach Adaptive Modulation and Coding - two algorithms working on reported CQI feedback - Piro" model: based on analytical BER (very conservative) - Vienna" model: aim at max 10% BLER based on error model curves - Dynamic TX mode selection supported but no adaptive algorithm currently implemented Transport Block model - Mimics 3GPP structure mux RLC PDU onto MAC PDU - Virtual MAC Headers and CEs (no real bits) MAC overhead not modeled Consistent with requirements (scheduler neglects MAC OH) K. Katsaros Introduction to NS-3 04/07/13 21 / 33

22 MAC Scheduler Round Robin (RR) Proportional Fair (PF) Maximum Throughput (MT) Throughput to Average (TTA) Blind Average Throughput (BET) Token Bank Fair Queue (TBFQ) Priority Set Scheduler (PSS) All implementations based on the FemtoForum API The above algorithms are for downlink only For uplink, all current implementations use the same Round Robin algorithm K. Katsaros Introduction to NS-3 04/07/13 22 / 33

23 Simulation Output Lots of KPIs available at different levels: Channel - SINR maps - pathloss matrices PHY - TB tx / rx traces - RSRP/RSRQ traces MAC - UL/DL scheduling traces RLC and PDCP - Time-averaged PDU tx / rx stats IP and application stats - Can be obtained with usual ns-3 means - FlowMonitor, PCAP traces, get stats directly from app, etc. K. Katsaros Introduction to NS-3 04/07/13 23 / 33

24 Features Highlighted K. Katsaros Introduction to NS-3 04/07/13 24 / 33

25 Simulation Time 5s sim time, 1 UE per enb, full traffic K. Katsaros Introduction to NS-3 04/07/13 25 / 33

26 Walkthrough of WiFi Internet example K. Katsaros Introduction to NS-3 04/07/13 26 / 33

27 NS-3 Implementation of WiFi Example K. Katsaros Introduction to NS-3 04/07/13 27 / 33

28 Structure of NS-3 program int main (int argc, char *argv[]) { // Set default attribute values // Parse command-line arguments // Configure the topology; nodes, channels, devices, mobility // Add (Internet) stack to nodes // Configure IP addressing and routing // Add and configure applications // Configure tracing // Run simulation } K. Katsaros Introduction to NS-3 04/07/13 28 / 33

29 Source Code for P2P example Starting your script with this line ensures that emacs editor will be able to indent your code correctly. The following lines ensure that your code is licensed under the GPLv2. /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */ // GPLv2 Licence Include the proper header files. For simulation scripts, you can aggregate them with modules, but when developing your module, you have to include the specific header file (not the aggregated) include ns3/core-module.h" include ns3/network-module.h" include ns3/internet-module.h" include ns3/point-to-point-module.h" include ns3/applications-module.h"... Use the ns3 project namespace using namespace ns3; K. Katsaros Introduction to NS-3 04/07/13 29 / 33

30 example cont. Enable and disable console message logging by reference to the name NS_LOG_COMPONENT_DEFINE ( FirstScriptExample"); int main (int argc, char *argv[]) LogComponentEnable ( UdpEchoClientApplication", LOG_LEVEL_INFO); LogComponentEnable ( UdpEchoServerApplication", LOG_LEVEL_INFO); Topology Configuration NodeContainer nodes; nodes.create (2); PointToPointHelper pointtopoint; pointtopoint.setdeviceattribute ("DataRate", StringValue ("5Mbps")); pointtopoint.setchannelattribute ("Delay", StringValue ("2ms")); NetDeviceContainer devices; devices = pointtopoint.install (nodes); K. Katsaros Introduction to NS-3 04/07/13 30 / 33

31 example cont. Set up Internet Stack InternetStackHelper stack; stack.install (nodes); Ipv4AddressHelper address; address.setbase (" ", " "); Ipv4InterfaceContainer interfaces = address.assign (devices); Set up applications UdpEchoServerHelper echoserver (9); ApplicationContainer serverapps = echoserver.install (nodes.get (1)); serverapps.start (Seconds (1.0)); serverapps.stop (Seconds (10.0)); UdpEchoClientHelper echoclient (interfaces.getaddress (1), 9); echoclient.setattribute ("MaxPackets", UintegerValue (1)); echoclient.setattribute ("Interval", TimeValue (Seconds (1.0))); echoclient.setattribute ("PacketSize", UintegerValue (1024)); ApplicationContainer clientapps = echoclient.install (nodes.get (0)); clientapps.start (Seconds (2.0)); clientapps.stop (Seconds (10.0)); Run your scenario Simulator::Run (); Simulator::Destroy (); K. Katsaros Introduction to NS-3 04/07/13 31 / 33

32 Resources Web site: Mailing list: ns-3-users IRC: ns-3 at freenode.net Tutorial: Code server: Wiki: For LENA project: http: //iptechwiki.cttc.es/lte-epc_network_simulator_(lena) K. Katsaros Introduction to NS-3 04/07/13 32 / 33

33 Acknowledgments Special Thanks to: Tom Henderson Mathieu Lacage Nicola Baldo for borrowing material from their presenations K. Katsaros Introduction to NS-3 04/07/13 33 / 33