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Capacity Dimensioning Based on Traffic Capacity Dimensioning Based on Traffic Measurement in the InternetMeasurement in the Internet

Capacity Dimensioning Based on Traffic Capacity Dimensioning Based on Traffic Measurement in the InternetMeasurement in the Internet

Kazumine Matoba(k-matoba@jp.fujitsu.com)

Osaka UniversityShingo Ata (Osaka City Univ.)

Masayuki Murata (Osaka Univ.)Now in Fujitsu Laboratories

Kazumine Matoba(k-matoba@jp.fujitsu.com)

Osaka UniversityShingo Ata (Osaka City Univ.)

Masayuki Murata (Osaka Univ.)Now in Fujitsu Laboratories

*

*

2

Measuring Networks

ISPs need to offer stable QoS (Quality of Service)

for redesigning current ISP’s network,for redesigning current ISP’s network,

end-to-end network characteristics is neededend-to-end network characteristics is needed

propose network planning framework

based on current end-to-end network characteristics

propose network planning framework

based on current end-to-end network characteristics

Important QoS metric is measured only by end users

e.g. Web document download time

measurement from end user measurement from end user measurement from end user measurement from end user

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Capacity Dimensioning

Active Traffic Measurement

Analysis of the measurement result

Internet

UserUserServerServerBottleneck Link

1. find the bottleneck area between end hosts2. measure the bottleneck link utilization

3. propose the design framework for determining link capacity Network Capacity Dimensioning

4

Contents

Capacity Dimensioning1. Measurement Based Identification Method of

Performance Bottleneck

2. Measurement Method of Bottleneck Link Utilization

3. Capacity Dimensioning Based on Traffic Measurement

Conclusion

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Bottleneck Classification

Three kinds of bottlenecks in the end-to-end communication

Sender Side Configuration Sender Side Configuration

collect information about TCP communication

UserUserTarget PathTarget Path ServerServer

Receiver Side Configuration (Buffer size) Receiver Side Configuration (Buffer size)

Network Condition (Congestion) Network Condition (Congestion)

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How to Detect Each Bottleneck?

TCP throughput (estimated value)*take no thought of sender side configuration

* J.Padhye, V.Firoiu, D.Toesley.,and J.Kurose, “Modeling TCP throughput: A simple model and its empirical validation”, Proceedings of ACM SIGCOMM’98, pp.303-314, September 1998.

expected window size of TCP connection

actual throughput << estimated throughput

① sender side configuration

② check buffer size (receiver side)

b ： duplicate ACK numberp ： packet loss rate

2

32

3)1(8

32

][

bb

bpp

bb

WE 2

32

3)1(8

32

][

bb

bpp

bb

WE

buffer size of receiver hostexpected window size

:: ][

maxWWE

maxWE[W ] maxWE[W ]

③ check network congestion (network condition)

congested router queue and/or drop packets

large RTT and high packet loss rate

*

bottleneck is sender!

buffer size is insufficient!

network is congested!

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- buffer size is insufficient

- when buffer size is increased, TCP throughput becomes high

Bottleneck Classification Process　 measure RTT, Packet Loss Rate, and TCP throughput

check socket buffer size of receiver host

repeat measurement, changing socket buffer size

- sufficient size of buffer

- high packet loss rate

- large RTT

- no relationship between buffer size and throughput- actual throughput << estimated throughput

① sender side configuration

② buffer size (receiver side)

③ network congestion (network condition)

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Server 2Server 1

Classification Experimens in the Internet

0

10

20

30

40

8 16 24 32 40 48 56 64

Buffer Size (KByte)

Th

rou

gh

pu

t (M

bp

s)

0

10

20

30

40

8 16 24 32 40 48 56 64

Buffer Size (KByte)

Th

rou

gh

pu

t (M

bp

s)

0

10

20

30

40

8 16 24 32 40 48 56 64

Buffer Size (KByte)

Th

rou

gh

pu

t (M

bp

s)

Estimated throughputActual throughput

No special feature

buffer increase

⇒Throughput increase

Larger than Actual throughput

Buffer size is insufficient

Network Condition

Receiver SideSender Side

05

10152025303540

8 16 24 32 40 48 56 64

Buffer Size (KByte)R

ou

nd

Tri

p T

ime (

ms)

0

0.05

0.1

0.15

0.2

0.25

0.3

Pac

ket

Lo

ss R

ate

(%

)

Packet Loss Rate

Round Trip Time

Large RTT

High Packet Loss Rate

For each bottleneck,

their characteristics can be found

For each bottleneck,

their characteristics can be found

Server 3

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Contents

Capacity Dimensioning1. Measurement Based Identification Method of

Performance Bottleneck

2. Measurement Method of Bottleneck Link Utilization

3. Capacity Dimensioning Based on Traffic Measurement

Conclusion

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Estimate Link Utilization

measure and estimate capacity of bottleneck linkPathchar, Pchar, Clink, etc.

ccrr

bb

rrbb

uu cc

estimate bottleneck link utilization

measure the amount of cross traffic passing through the bottleneck link

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need these items!

Estimate Throughput of Cross Traffic

assume probe packets are queued at router n

cross trafficcr

probe packet

Bottleneck Router n Router n+1

Bottleneck Link

n+1lnl

sb llr nnc 1the amount of

cross traffics :size of probe packet

b :capacity of link n+1

throughput of cross trafficn

nc

l

sb lr

1

client host send ICMP ECHO packet continuously

router n and n+1 return reply packets

observe returned packet and calculate interval of arrival time

client host send ICMP ECHO packet continuously

router n and n+1 return reply packets

observe returned packet and calculate interval of arrival time nnll n+1n+1ll

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Estimation Results of Link Utilization

measure bottleneck link between two universities

Estimation error is under 10% in link utilization

link utilization

(cross traffic)

estimation

15.9% (0.95 Mbps) 22.8%

27.9% (1.7 Mbps) 27.8%

38.5% (2.3 Mbps) 32.1%

69.5% (4.1 Mbps) 60.3%

77.6% (4.6Mbps) 81.6%

Bottleneck link 6MbpsBottleneck link 6Mbps

Osaka City Univ.Osaka Univ.

Measurement HostMeasurement Host

Router nRouter nRouter n+1Router n+1

Target HostTarget Host

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Contents

Capacity Dimensioning1. Measurement Based Identification Method of

Performance Bottleneck

2. Measurement Method of Bottleneck Link Utilization

3. Capacity Dimensioning Based on Traffic Measurement

Conclusion

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Capacity Dimensioning

from user’s viewpointfulfill a demand of user

Designing network for each bottleneck1. sender or receiver side configuration

2. network configuration (link bandwidth)

based on end-to-end network characteristicsbased on end-to-end network characteristics

propose a design framework

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Capacity Dimensioning 1:Bottleneck Resides in the End Host

Sender side configurationremove the cause of bottleneck

• Ex. configure rate shaping, upgrade hardwares, etc.

Receiver side configuration (buffer size)increase buffer size to ff

RTTRTTttff '''' tt ''： throughput which user needs： throughput which user needs

： Round Trip Time： Round Trip TimeRTTRTT

''

Bottleneck may shift to another areaBottleneck may shift to another area

need to upgrade link capacity?

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Designing Link Capacity:Bottleneck Resides in the End Host

most thin available bandwidth link

timetime

cross trafficcross traffic

user’s trafficuser’s trafficCC

ttCCAA

tt

CC))11((

link utilization

tt

ttttAACC ''

lower bound of new link capacity

lower bound of new link capacity

link capacitylink capacity

determine new link capacity

C ： link capacity

A ： throughput of cross traffict ： throughput of user’s traffic

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user traffic

both of the user and cross traffic

Capacity Dimensioning 2:Bottleneck Resides in Network

timetime

send data

timetime

cross trafficcross traffic

user’s traffic tuser’s traffic t

timetime

cross trafficcross traffic

timetime

cross trafficcross traffic

user’s trafficuser’s trafficsend data

cross traffic Across traffic Alink capacitylink capacity

link capacitylink capacity

same as the former

capacity decision

ttAC '

predict amount of future cross traffic

upgrade

cross traffic may increase

cross traffic may increase

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Designing Link Capacity:Bottleneck Resides in Network

assume and simplify the situationbottleneck router is M/M/1 queueing system

current link capacity C will increase to C’ =a C

choose following user traffic will increase to t’

aaTTbpbptt

TT

2233

''11

T　： packet service time at bottleneck router

b ： the number of arrival packets notified one ACK

p ： packet loss rate

Ta ： constant (=RTT-T)

T　： packet service time at bottleneck router

b ： the number of arrival packets notified one ACK

p ： packet loss rate

Ta ： constant (=RTT-T)

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Conclusion

Capacity dimensioning based on traffic measurement in the Internet

Identification method of performance bottleneck• classify into 3 kinds of bottlenecks

Measurement method of link utilization• focused on the bottleneck link

Capacity dimensioning• Modeling the router as an M/M/1 queueing system

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The End

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Available BandwidthAvailable Bandwidth

Existing Method to EstimateLink Utilization

Bottleneck linkBottleneck link

packet pair

packet stream

probe packet affects measurement resultbut not take into consideration

only focus on the end-to-end performance

UserUser ServerServer

- capacity of bottleneck link

- available bandwidth in end-to-end communication