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

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

2nd OMNeT++ Community Summit 2015, 03. – 04.09.2015, IBM Research - Zurich, Switzerland

Artur Scussel, Christoph Brandauer, Georg Panholzer, Ferdinand von Tüllenburg

Performance Evaluation

• Question:
• How precise Is communication quality emulation (part. delay)?

2 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg

Test 2: Ping over emulated Link Test 1: Ping to local Standard Host

1 Gbps 10 ms delay (bidirectional)

OMNeT++ Env. INET/ExtClient Ping App Peer Local Host

ext0 10.1.1.1 Ping to 10.1.1.1

Problem Evaluation - Results

03.09.2015 3

Ping local (Test 1)

• Ping local test:
• RTT range: [0.7,22.1] ms
• Average (Mean): ~11 ms
• Test w/o emulation:
• Ping to eth1 (Host1)
• RTT < 1 ms (all time)

Ping remote (Test 2)

• Ping remote test:
• RTT range: [31.4, 60.8] ms
• Average (Mean): ~44 ms
• Expected RTT (Mean) : ~21 ms
• Test w/o emulation:
• Ping to Host 3 w/o emulation.
• RTT < 1 ms (all time)

Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg

Demo I – Unmodified Version

03.09.2015 4

Ping App Virtual Machine

Ping Reply Ping Request Peer 10.1.1.1

INET/ExtClient ExtClient Example without Modification OMNeT++ Environment

Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg

Problem Analysis & First Enhancements

• 1. Issue: Incorrect Timeout Computation
• RT Scheduler synchronizes event processing

with wall-clock

• Incoming / Outgoing Packets are induced in

FES

• Timeout Computation corrected and code
• ptimized by A. Vargas and R. Hornig (by

themselves)

03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg 5

t_0 Packet Send Event in FES with target time t_0 + 2. t_0+2 t_0+11 t_0+1 Call receiveUntil(ts) Call receiveWithTimout(10)

Wait 10ms: ts is missed and delayed unitl ts’

Delay

• 2. Issue: Kernel pcap Buffering
• Pcap Default:
• Kernel buffers packets before passing to

OMNeT++

• Work around:
• pcap immediate mode
• Risk of increased packet loss

Enhancements were integrated in INET 3.0 (actually INET 2.99.1)

Results

6 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg

Ping local (Test 1)

• Ping local test:
• RTT range [0.8,1.3] ms
• Average (Mean): ~1ms

Ping remote (Test 2)

• Ping remote test:
• RTT range [21.1, 22.2] ms
• Average (Mean): ~21ms
• But Packet Loss increases
• Test: 10Mbit/s; packet size 100 Bytes (125 packets/s)
• With immediate mode: 3.4% loss
• Without immediate mode 1.6%

Further studies needed

Demo 2

03.09.2015 7

Ping App Virtual Machine

Ping Reply Ping Request Peer 10.1.1.1

EctClient Sim. ExtClient Example with Modification OMNeT++ Environment

Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg

Summary & Future Work

• Starting Situation exhibits
• High Delays,
• High Delay Variation
• Issues found
• Incorrect Timeout Computation
• Bugs in RTScheduler
• Kernel pcap Buffering
• 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

8 03.09.2015 Improvement of Real-Time Scheduler for Emulation Mode, Ferdinand von Tüllenburg

Starting Situation Current Situation