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Deep Space Network Emulation

Shaun Endres and Behnam MalakootiCase Western Reserve University

Department of Electrical Engineering and Computer Science{Shaun.Endres, Behnam.Malakooti}@case.edu

Kul Bhasin and Allen HoltzNASA Glenn Research Center

Space Communications{Kul.B.Bhasin, Allen.P.Holtz}@grc.nasa.gov

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Introduction

Presentation Outline

• Motivation

• Application

• Definition

• Overview

• Design

• Configuration

• Testing & Results

• Conclusions

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Motivation

Network Analysis Motivation

• Performance assessment

• Risk assessment

Deep Space Emulation Motivation

• No known tools for evaluating deep space networks

– Space Based Internet Emulator (University of Kansas)

– The Network Simulator (ns-2)

• Active Networking

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Application

Deep Space Network Nodes (Earth, Moon, Mars, and beyond)

• Ground stations

• Satellites

• Space shuttles

• Anything that the Satellite Tool Kit (STK) can handle

Researchable Issues

• Protocols

• Routing algorithms

• Communication architectures

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Network Emulation

Definition• Emulation refers to the ability to introduce a simulator into

a live network.

Comparison• Simulation is _____ than emulation

– Less Expensive– Faster (depending on the complexity)– Less Accurate

• A real hardware test-bed is _____ than emulation– Significantly more expensive– More accurate– Less controllable

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Emulator Overview

Emulator Features

• Completely in user space

• Any network, transport, or application layer protocol possible

• Strict cutoff between emulator and user

Emulator Usage

• Emulator is transparent to the end user

}User

}Emulator

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Emulator Design (Control & Emulation Network)

Control Network

• Star Topology• Sends ‘Physical’ Information• TCP/IP Used• Link Always Available• Error Free Link

Emulation Network

• Fully Connected Network• Sends ‘Networking’ Information• Researched Protocol Used• Link Availability Based on

‘Physical’ Information• Error Prone Link

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Emulator Design (Information Flow)

Control Network

• Communicates with STK [7] to determine position and link information

• Updates all nodes’ link tables periodicallyEmulation Network

• Applies information contained in link tables to all out going packets

Physical and Data Link Layers

• Modeled within the emulator codeNetwork, Transport, and Application Layers

• Actual implementation (left up to the researcher to implement)

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Emulator (Physical Setup)

Hardware

• Cisco Catalyst 2900 series XL switch

• Intel Pentium III 600MHz processor computer with 128MB of RAM

• Fast EthernetSoftware

• STK 5.0.4

• Microsoft Windows XP Professional

• Microsoft Visual Studio .NET 2002Programming Language

• C#

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Results

Delay Verification

Delay Accuracy gets better as the delay increases• With a 30s delay, there is about a 0.1% error

Bit Error Rate Verification• Bit error rate application has about a 0.25% error

0

10

20

30

40

50

1 2 3 4 5 6 7 8 9 10 11

Packet Number

De

lay

(m

s)

Measured

Target

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Conclusions and Future Work

Conclusions• Deep Space Network Emulation is Possible

Without Kernel Modifications• Great Flexibility Can Be Given to the User• OS Interrupt Timer Is Limiting Factor

Future Work• Multiple Nodes• Bandwidth Restriction• Deep Space Mission Scenario Analysis• Protocol Testing for Deep Space Missions

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Thank You

Thank You for Your Time and Attention

Any Questions?

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Selected References

[1] http://www.isi.edu/nsnam/ns/ns-emulation.html[2] Bateman, M., Allison, C., and Ruddle, A., “A Scenario Driven Emulator for Wireless, Fixed and Ad Hoc Networks,” 2003.[3] Zheng, P., and Ni, L. M., “EMPOWER: A Network Emulator for Wireline and Wireless Networks,” IEEE INFOCOM, 2003.[4] Zheng, P., and Ni, L. M., “EMPOWER: A Scalable Framework for Network Emulation.”[5] Zheng, P., and Ni, L. M., “Experiences in Building a Scalable Distributed Network Emulation System.”[6] Ingham, D. and Parrington, G., “Delayline: A Wide-Area Network Emulation Tool.”[7] www.stk.com[8] Rallapalli, S., “Emulation of a Space Based Internet Communication Link: Design and Implementation,” University of Kansas, 2000.[9] Baliga, S. R., “Design of a Space Based Internet Emulation System,” University of Kansas, 2002.[10] Endres, S., Griffith, M., Malakooti, B., Bhasin, K., and Holtz, A., “Space Based Internet Network Emulation for Deep Space Mission Applications,” AIAA ICSSC, May, 2004.[11] Sklar, B., “Digital Communications: Fundamentals and Applications,” Prentice Hall, 2001.[12] Herrscher, D., and Rothermel, K., “A Dynamic Scenario Emulation Tool.”[13] Carson, M., and Santay, D., “NIST Net – A Linux-based Network Emulation Tool.”[14] Yeom, I., and Reddy, A. L., “ENDE: An End-to-end Network Delay Emulator.”[15] Hu, Y., and Li, V. O. K., “Satellite-Based Internet: A Tutorial,” IEEE Communications Magazine, 2001.

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Additional Slides

Additional Slides Begin Here

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Improvements to Existing Tools

Improvements to the Space Based Internet Emulator

• Any transport and network layer protocol

• No kernel modifications

• Deep space objects

• Header errorsImprovements to The Network Simulator (ns-2)

• Deep space objects

• Highly dynamic link changes

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Satellite Tool Kit (STK)

Satellite Orbit Propagation

• Detailed satellite propagation

• Orbits around any planetary bodyReal time information

• STK/Connect can provide an application with real time information

Link Budget Report

• STK/Communication can provide a detailed link budget report

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Results (1 of 2)

Worst Case Delay

Measured Target Difference Error

5.00675 4 1.00675 25.17%

10.0135 8 2.0135 25.17%

15.02025 12 3.02025 25.17%

15.02025 16 0.97975 6.12%

15.02025 20 4.97975 24.90%

25.03375 24 1.03375 4.31%

25.03375 28 2.96625 10.59%

35.04725 32 3.04725 9.52%

35.04725 36 0.95275 2.65%

35.04725 40 4.95275 12.38%

45.06075 44 1.06075 2.41%

0

10

20

30

40

50

1 2 3 4 5 6 7 8 9 10 11

Packet Number

De

lay

(m

s)

Measured

Target

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Results (2 of 2)Average Case Delay

Bit Error Rate Measured Target Difference Error

1 1 0 0.00%

0.317118333 0.316228 0.000891 0.28%

0.099778333 0.1 0.000222 0.22%

0.03181 0.031623 0.000187 0.59%

0.010053333 0.01 5.33E-05 0.53%

0.003131667 0.003162 3.06E-05 0.97%

Measured Target Difference Error

30030.49 30000 30.4865 0.10%

30050.51 30000 50.5135 0.17%

30035.49 30000 35.49325 0.12%

30035.49 30000 35.49325 0.12%

30020.47 30000 20.473 0.07%

30040.5 30000 40.5 0.14%

30020.47 30000 20.473 0.07%

30015.47 30000 15.46625 0.05%

30030.49 30000 30.4865 0.10%

30035.49 30000 35.49325 0.12%