Improvements in OMNeT++/INET Real-Time Scheduler for Emulation Mode - PowerPoint PPT Presentation

Artur Scussel, Christoph Brandauer, Georg Panholzer, Ferdinand von Tüllenburg Improvements in OMNeT++/INET Real-Time Scheduler for Emulation Mode 2nd OMNeT++ Community Summit 2015, 03. – 04.09.2015, IBM Research - Zurich, Switzerland

Performance Evaluation  Question:  How precise Is communication quality emulation (part. delay)? Test 1: Ping to local Standard Host Test 2: Ping over emulated Link INET/ExtClient 10.1.1.1 Ping Peer App ext0 Ping to OMNeT++ Env. 10.1.1.1 1 Gbps Local Host 10 ms delay (bidirectional ) 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg 2

Problem Evaluation - Results Ping local (Test 1) Ping remote (Test 2)  Ping local test:  Ping remote test:  RTT range: [0.7,22.1] ms  RTT range: [31.4, 60.8] ms  Average (Mean): ~11 ms  Average (Mean): ~44 ms  Test w/o emulation:  Expected RTT (Mean) : ~21 ms  Ping to eth1 (Host1)  Test w/o emulation:  RTT < 1 ms (all time)  Ping to Host 3 w/o emulation.  RTT < 1 ms (all time) 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg 3

Demo I – Unmodified Version INET/ExtClient Ping Reply Ping App Ping Request Peer 10.1.1.1 OMNeT++ Environment Virtual Machine ExtClient Example without Modification 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg 4

Problem Analysis & First Enhancements t_0 Packet Send Event in FES with target time t_0 + 2. Call receiveUntil(ts ) t_0+1  1. Issue: Incorrect Timeout Computation Call receiveWithTimout(10)  RT Scheduler synchronizes event processing with wall-clock Wait 10ms: t_0+2  Incoming / Outgoing Packets are induced in ts is missed and FES delayed unitl ts’ Delay  Timeout Computation corrected and code optimized by A. Vargas and R. Hornig (by t_0+11 themselves)  2. Issue: Kernel pcap Buffering  Pcap Default:  Kernel buffers packets before passing to Enhancements were integrated in OMNeT++ INET 3.0  Work around: (actually INET 2.99.1)  pcap immediate mode  Risk of increased packet loss 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg 5

Results Ping remote (Test 2) Ping local (Test 1)  Ping remote test:  Ping local test:  RTT range [21.1, 22.2] ms  RTT range [0.8,1.3] ms  Average (Mean): ~21ms  Average (Mean): ~1ms  But Packet Loss increases  Test: 10Mbit/s; packet size 100 Bytes (125 packets/s) Further studies  With immediate mode: 3.4% loss needed  Without immediate mode 1.6% 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg 6

Demo 2 EctClient Sim. Ping Reply Ping App Ping Request Peer 10.1.1.1 OMNeT++ Environment Virtual Machine ExtClient Example with Modification 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg 7

Summary & Future Work  Starting Situation exhibits  High Delays,  High Delay Variation  Issues found  Incorrect Timeout Computation  Bugs in RTScheduler  Kernel pcap Buffering Starting Situation  Correcting these issues  Enhances delay precision, responsiveness  Increases packet loss  Future Work  Investigation of packet loss issue  Check other packet capturing mechanisms (e. g., PF_RING)  Multi-threading Current Situation 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg 8