The 63rd IETF Meeting
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Field Test Results of F-RTO
Kazunori YamamotoNTT DoCoMo
William GilliamHewlett-Packard Company
Paris, August 2, 2005
The 63rd IETF Meeting
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Purpose
Algorithm Implemented Functions
Detection F-RTO Implement 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
6Kbyte18Kbyte300Kbyte2Mbye
Window Size:64KBRTO: defaultSACK: enableTimestamp: ON
Bad wireless quality
Low Speed(Walk)
Downtown
Medium Speed(Car)
Urban district,Mountainous lands
High Speed(Bullet Train)
Lots of tunnels 518Mbyte
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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.
STO
/1M
B D
ata
Tran
sfer
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%
Reduction in Unnecessary Retransmission (2/3)
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%
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90
100
80
70
Red
uctio
n R
ate
in
Unn
eces
sary
Ret
rans
mis
sion
(%)
0.99
0.100.21
0.340.17
0.030.030.020.020.050
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
Tran
smis
sion
(%)
Reduction in Unnecessary Retransmission (3/3)
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-RTOWith F-RTO
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0
50
100
150
200
250
300
Without F-RTO With F-RTO
Thro
ughp
ut (k
bps)Throughput
277.72646% 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.
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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 (s
egm
ent)
Early Mid. MaxWin0
100
200
300
400
500
0
100
200
300
2
4
6
8
10
12
Thro
ughp
ut (M
bps)
Incr
ease
Rat
e in
Thr
ough
put
0Early 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-RTOWith 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.