network available bandwidth measurements

Network Available Bandwidth Measurements

XiaoLong HE

04/19/23 XiaoLong He Network Available Bandwidth Measurements

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Outline of the Talk Problems Related Work Traffic Design Our Approach (SimProbe) Analysis of Simulation Results SMRT Implementation Lessons Learned Future Work


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Why measurement?

Measurement is critical to network control. Measurement for selecting server/ISP Measurement for verifying network configuration Measurement for designing real-time applications Measurement for load balancing in WAN Measurement for accounting


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Taxonomy of Internet Network Measurement Approaches

Sender-based vs. Receiver-based Passive Watch vs. Active Probe Layer of Protocol used


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Measurement Problems

Route Fluttering Packet Loss Out of Order packet delivery Clocks Synchronization Routers reject ICMP due to denial of

series attacks.


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Bottleneck Bandwidth

Bottleneck bandwidth: the maximal rate at which data can be sent along a connection, determined by the slowest element in the entire chain.


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Available Bandwidth

Available Bandwidth:how fast can the data in fact be transmitted over the connection.

[PacketSize/(PacketSize+CompetitorPacketSize)] * Bottleneck Bandwidth


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Related Works

Bprobe/Cprobe - Robert L. Carter and Mark E. Crovella, Boston University, 1996

Ping - M. Muuss, U.S.Army Ballistic Research Laboratory, 1983

Traceroute - Van Jacobson, Berkeley, Univeristy of California, 1997

Treno - M. Mathis and J. Mahdavi, Proceedings of INET’96, Montreal, 1996


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Bprobe/Cprobe Bottleneck Bandwidth = (PacketSize/Time) Available Bandwidth = (S2+…+Sn)/(Tn-T1)


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SimProbe Simulator

To carry the thesis out, we build a Java-based discrete event simulator.

Swing, Java2D and AWT packets for GUI design

Thread for comparing different probing methods

Port it to Unix (without GUI) for long time simulation


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How traffic is generated in SimProbe Simulator


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Traffic Patterns supported by SimProbe

Flat/Static Slope Web (modifed code by Arthur Blais)

– Time between requests: Pareto Distribution

– Number of embedded references: Pareto Distribution

– Time between references: Weibull Distribution

– File Size: Body (Lognormal Distribution) Tail (Pareto Distribution)


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Network Topology Used in This Simulation Study


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Our Approaches Sending as few packets as possible. Using round trip time

measurements for network available bandwidth. Trip Time Measurement Formula:

TripTime*MeasuredAvailableBandwidth = MinimalTripTime*MaximalAvailableBandwidth

– Round Trip Time Measurement SMRT MMRT

– Unidirectional Trip Time Measurement SMUT MMUT

Time Gap between packets– ACB (Adaptive Cprobe)


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SMRT(Single Msg Round Trip Time Measurement)

Using multiple packets to find minimum of the round trip time of a connection

Using Bprobe to get the maximal available bandwidth of a connection

Sending single probing packet Using round trip time to estimate the available

bandwidth of the connection


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MMRT

Use Bprobe to get the maximal available bandwidth of a connection

Using multiple packets to find minimum of the round trip time of a connection

Sending multiple packets Round trip time for estimating ABW


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SMUT


Using multiple packets to find minimum of the unidirectional trip time of a connection

Sending single probing packet Using unidirectional trip time for estimating

available bandwidth


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MMUT


Using multiple packets to find minimum of the unidirectional trip time of a connection

Sending multiple probing packets Using unidirectional trip time for estimating

available bandwidth


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Simulation result analysis

Difference Metric:|AvailableBandwidth - MeasuredAvailableBandwidth|

AvailableBandwidth– AvailableBandwidth = [PacketSize/(PacketSize+QueuingSize)]*

Bottleneck Bandwidth

– MeasuredAvailableBandwidth =

(MinimalTripTime*MaximalAvailableBandwidth)/ TripTime

DelayTime:TripTime - MinimalTripTime


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SMRT Random Characteristics

Problem: Dependent on the arrival time of probing packet on bottleneck link

Three Scenarios:

1) no queuing time, yields bottleneck available bandwidth.

2) yields the lower bound of bottleneck available bandwidth

3) yields average bottleneck

available bandwidth


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Impact of Packet Size on SMRT DelayTime rises when probing

packets size increases. Smaller packet size gets

worse results RoundTripTime =

MinimalRoundTripTime + DelayTime

Examples:

– T1 / (T1+T)– T2 / (T2+T)

PacketSize impact on Difference

0

0.5

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PacketSize (Bytes)

Dif

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ce

PackeSize impact on DelayTime

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PacketSize (Bytes)

Dela

yT

ime (

Sec)


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Impact of Link Length on SMRT The result accuracy is

worse with the length increasing

Delay Time dominates RoundTrip Time at shorter link length

Propagation time dominates RoundTrip Time at longer link length

LinkLength/Difference

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1

2

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5

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100 1000 10000 100000 1000000

Link Length (meters)

Dif

fere

nce


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Impact of Router Speed on SMRT

No apparent difference for 1GBps or 10GBps

Router Speed affects the time gap between packets

Slow router speed enlarges the time gap between packets

Router Speed must be faster than link speed

RouterSpeed impact on Difference

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0.2

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1 2

1GBps

10GBps


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Impact of Bottleneck Link Bandwidth on SMRT

SMRT results follow the available bandwidth trend

SMRT performance is similar to the performance trend by SMRT performance with 10MBps bottleneck link bandwidth

SMRT result with 200MBps Bottleneck Bandwidth

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100000000

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Time

Ban

dw

idth

(B

ps) AvailableBandwidth

MeasuredABandwidth

SMRT Performance with 200MBps Bottleneck Bandwidth

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10152025303540

Available Bandwidth (Bps)

Dif

feren

ce


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MMRT Try to alleviate the

random characteristic of SMRT

Small time gap between probing packets may experience big traffic difference in Slope traffic pattern

Obvious improvement on SMRT performance in web traffic

MMRT Performance

00.5

11.5

22.5

33.5

44.5

5

Available Bandwidth

Dif

fere

nce

Difference Comparison of SMRT and MMRT

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0.05

0.1

0.15

0.2

0.25

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SMRT MMRT

Dif

feren

ce


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SMUT

Measure the available bandwidth on unidirectional route.

SMUT has the same random characteristics as SMRT.

SMUT

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Times

Ban

dw

idth

Available Bandw idth

Measured AvailableBandw idth


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MMUT Try to alleviate the

random characteristic of SMUT

Small time gap between probing packets may experience big traffic difference with slope traffic pattern

MMUT has Better performance than SMUT with web traffic pattern

Difference Comparison of SMUT and MMUT

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0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

SMUT MMUT

Dif

fere

nce


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ACB Using the last

measured available bandwidth

Send two packets once a time

Reprobing in Cprobe if time gap between packets is inside of a range

Not better than Cprobe

Adaptive Cprobe

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1 2 3 4 5 6 7 8 9 10 11 12 13 14

Times

Availab

le B

an

dw

idth

Available Band

MAvailable Band

Cprobe

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Times

Availab

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an

dw

idth

Available Band

MAvailable Band


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Summary of Simulation AnalysisSummary of Simulation Analysis

0

2000000

4000000

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10000000

12000000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31Times

Bn

ad

wid

th

Cprobe Available Band

Cprobe Measured AvailableBandwidth

SMRT AvailabeBandwidth

SMRT Measured AvailableBandwidth

SMUT Available Bandwidth

SMUT Measured AvailableBandwidth


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Implementation of SMRT SMRT is implemented in C Maintain a host file, which specifies the list of sites to be probed Bprobe is used to measure the largest bottleneck available

bandwidth Ping is used to measure the smallest round trip time of a

connection Using Bprobe and Ping to collect the history information for

each host in the file, at offpeak and over a long period Probed host must be contained in the host file Round trip time of the probing message is used to measure the

instant available bandwidth


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Implementation results of SMRT

We probed a list of mirror sites for popular software packages such as perl, linux and netscape


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Orst is good choice for us to download software

DownLoadTimes (seconds)

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100

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700

Times

Do

wn

Lo

ad

Tim

es

UncDownloadTime

gatechDownloadTime

buffaloDownloadTime

orstDownloadTime


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Orst gives us relative short round trip time

RoundTripTime (ms)

0

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Times

Ro

un

dT

rip

Tim

e (

ms)

UncPing

gatechPing

buffaloPing

orstPing


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Lessons Learned Impact of router speed on traffic generation

– Problem: When router speed is lower than the bottleneck link speed, we can not get expected traffic?

– Solution: Make sure the router speed in our connection is greater than the bottleneck link speed, especially for the large bottleneck link bandwidth


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Lessons Learned (Cont) Cprobe Limitations

– Probing returned packets interfere with later probing packets

– Queuing time is not the only results from connection competition

Examined factors:– Router Speed– Hop Number– Message Size– Message Number


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Lessons Learned (Cont)

OOP design in Java– Problem: Chart can not be updated when we call the chart in

a thread directly.– Solution: Using SwingUtilities.invokeLater Class

Double data type precision problem– Problem: The round trip time with traffic pattern is even

shorter than the time without any traffic– Reason: machine double type data has a precision problem

in representing a value exactly– Solution: Because difference is small, so ignore it


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Future Works

How to measure available bandwidth of a host whose history information is not available.

How to find a better available bandwidth estimation formula to improve the accuracy of SMRT

Convert MMRT, SMUT and MMUT simulation code from Java to C

More traffic route to test the reliability of SMRT and other methods

network available bandwidth measurements

Documents

network control

trip time measurement

long time simulationxiaolong

pareto distributiontime

awt packets

simulation studyxiaolong

simprobe simulatorxiaolong

gui designthread