Field Test Results of F-RTO

The 63rd IETF Meeting

1

Field Test Results of F-RTO

Kazunori YamamotoNTT DoCoMo

[email protected]

William GilliamHewlett-Packard Company

[email protected]

Paris, August 2, 2005


2

Purpose

Algorithm Implemented Functions

Detection F-RTOImplement F-RTO based on ID except for the SACK enhancement function.

Response Eifel ResponseImplement the function to recover congestion control state after STO based on RFC4015.

Implement F-RTO with Eifel response on the HP-UX 11i prototype. Conduct tests in the commercial 3G mobile communication network. The service is known as “FOMA” and provided by NTT DoCoMo in Japan.

Validate the effectiveness of F-RTO with Eifel response throughthe field test

Unnecessary retransmission Throughput Detection rate of Spurious Timeout (STO)


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Test Environment

Internet

3G Mobile Communication Network (FOMA)

100Mbps Access Network

Location: Yokosuka Research park

HP-UX11i 　 Prototype

Without F-RTO

UE

Fixed point, Low speed

High speed (Bullet Train)

Middle speed (Car)

UE: User Equipment

With F-RTO


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Test Parameters

Environment Condition Contents Size Client TCP Setting

Fixed Point

Good wireless quality

6Kbyte

18Kbyte

300Kbyte

2Mbye

Window Size:64KB

RTO: default

SACK: enable

Timestamp: ON

Bad wireless quality

Low Speed

(Walk)Downtown

Medium Speed

(Car)

Urban district,

Mountainous lands

High Speed

(Bullet Train)Lots of tunnels 518Mbyte


5

0.34

0.190.23 0.23

0.34

0

0.1

0.2

0.3

0.4

High Middle Low Fixed(Bad)

Fixed(Good)

No.

ST

O/1

MB

Dat

a T

rans

fer

Frequency of STO

STO occurred 0.26 times for 1MB data transfer on average. STO occurred most frequently at high speed and fixed point with good wireless condition. (Once per 3MB data transfer)

Passing many tunnelsHigh frequency of handover

Channelswitch


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Reduction in Unnecessary Retransmission (1/3)

Unnecessary retransmissioncaused by STO 0.34%

Necessary retransmission 0.76%

Original Data 98.9%

Unnecessary retransmissioncaused by STO

Necessary retransmission

31.2%

68.8%

Total Retransmitted Data1.1%

Without F-RTO


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92.9%


Unnecessary retransmissioncaused by STO 0.06%

Necessary retransmission 0.79%

Original Data 99.15%

Unnecessary retransmissioncaused by STO

Necessary retransmission

Total Retransmitted Data0.85%

With F-RTO

7.1%


8

90

100

80

70

Red

ucti

on R

ate

in

Unn

eces

sary

Ret

rans

mis

sion

(%

)

0.99

0.100.21

0.34

0.170.030.030.020.020.05

0

0.2

0.4

0.6

0.8

1

1.2

High Middle Low Fixed(Bad)

Fixed(Good)

Unn

eces

sary

Ret

rans

mis

sion

/D

ata

Tra

nsm

issi

on (

%)


Without F-RTO, unnecessarily retransmitted data due to STO accounts for 0.99% of the whole transmitted data at high speed. With F-RTO, unnecessarily retransmitted data due to STO is reduced by over 80% in every environment.

Without F-RTO

With F-RTO


9

0

50

100

150

200

250

300

Without F-RTO With F-RTO

Thr

ough

put (

kbps

)Throughput

277.7264

6% Up

With F-RTO, the throughput is increased by 6% for the connections that suffered STO more than once and transferred at least 2MB data.


10

28%

Detection Rate of F-RTO

71%

STO detected

STO occurred after FIN sent.

Receive window restricted new data transmission after STO.

Duplicate ACKs were received after STO.

STO not detected29%

0.7% 0.3%


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Experimental Environment

Parameter Value

Bandwidth (DL/UL)

14Mbps/384kbps

RTT 300ms

Receive Buffer 512KB

Timer

(min/default/max)0.5/0.5/64sec

Delay Spike 1sec

Content Size 2MB

Con

gest

ion

Win

dow

Siz

e (K

B)

After reaching MaxWin

Mid. stage of slow start

Early stage of slow start


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Experimental ResultsU

nnec

essa

ry R

etra

nsm

issi

on (

segm

ent)

Early Mid. MaxWin

0

100

200

300

400

500

0

100

200

300

2

4

6

8

10

12

Thr

ough

put (

Mbp

s)

Incr

ease

Rat

e in

Thr

ough

put

0

Early Mid. MaxWin

5

227

377

1 1 1

9.7 10.1 10

2.7

5.2

7.3

Unnecessary Retransmission Throughput

The effects of F-RTO, in terms of unnecessary retransmission and throughput, become large with higher wireless speed. Throughput is increased by a maximum of 262%.

Without F-RTO

With F-RTO


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Conclusions

Unnecessary Retransmission Without F-RTO, unnecessary retransmission due to

STO accounts for 31% of the total retransmission. F-RTO can reduce unnecessary retransmission to 7%.

Throughput F-RTO can increase throughput by 6% in the 3G

mobile communications network. F-RTO can increase throughput by 262% in higher

speed mobile communication network (HSDPA). Detection Rate

F-RTO can detect 71% of STO.

Good enough to become Proposed Standard?


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Papers

K. Yamamoto, et. al., “Effects of F-RTO and Eifel Response Algorithms for W-CDMA and HSDPA networks,” Wireless Personal Multimedia Communications(WPMC)’05, Sept. 2005.

A. Hokamura, et. al., “Performance Evaluation of F-RTO and Eifel Response Algorithms over W-CDMA packet network,” Wireless Personal Multimedia Communications(WPMC)’05, Sept. 2005.

Field Test Results of F-RTO

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