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All rights reserved © 2006, Alcatel
Accelerating TCP Traffic on Broadband Access Networks
Ing-Jyh Tsang
02-05-2006
All rights reserved © 2006, Alcatel
Page 2
Overview
Why and what is the TCP acceleratorExperimental setupsMeasurement resultsDemonstrators
All rights reserved © 2006, Alcatel
Page 3
Why TCP Accelerator
Evolutions:Bandwidth will increase on Access Link ADSL2+, VDSL, PON
Video deployments would require very low packet loss Use of FEC interleaver on DSL recommended (increase of
RTT with 20-40 ms)
However:TCP has known drawbacks Maximum throughput of TCP is limited due to its control
mechanisms Throughput drops heavily with increasing RTT (Client
Server) Packet loss on wireless access links interact with
congestion control mechanisms
All rights reserved © 2006, Alcatel
Page 4
What is the TCP Accelerator
Client Server
TCP parameters X
TCP parameters Y
Intercept packets
It is an implementation residing at the network element in between the client and the server.
It intercepts the TCP connections and modifies the TCP parameters, improving the end-to-end performance.
It does not modify neither the sender or the receiver TCP protocol programs.
TCP Accelerator increases speed (throughput) of TCP connection, in case not the physical line but TCP is the bottleneck
TCP Accelerator
All rights reserved © 2006, Alcatel
Page 5
TCP ACCEL: Change Windows Size
TCP Accelerator changes advertised window-size towards the server In most of the client side (user PC) the default window size is
small. This limits the maximum throughput of the TCP connection, even if there is more available bandwidth on the network.
It improves the performance of the TCP transmission, because a bigger window size allows more packets to be transmitted in the regime were there is no congestion on the network path.
Client ServerTCP Accelerator
WS = 17520
WS = 65535
Intercept packets
All rights reserved © 2006, Alcatel
Page 6
TCP ACCEL: Send Acknowledge
Send ACK to the server according to the packets received by the TCP accelerator. Improves the throughput between the TCP accelerator and the server.
Packets received by the TCP accelerator are already acknowledged. It increases the advantage of the TCP accelerator in case of packet loss
on the DSL link. If packets are lost at the core link the buffered packets at the TCP
Accelerator will maintain an steady flow of packets to the client.
ClientServer
ACK
Intercept packets
TCP Accelerator
All rights reserved © 2006, Alcatel
Page 7
Standalone Configuration
ClientServer
Line Characteristics Network Emulator
Network Characteristics
US & DS:Delay ± JitterPacketloss
ManagementHost
TCP
US & DS:Delay ± JitterPacketloss
All rights reserved © 2006, Alcatel
Page 8
Integrated Configuration
Client
Server
Core Network Characteristics
ManagementHost
TCP
Client
DSL Network with Same characteristics
CPE
CPE
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Page 9
Interleaved with 0,0% Packetloss Core
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
RTT in Backbone (ms)
DS T
hro
ughput (K
bps)
MAWS 65535 Bytes
MAWS 17520 Bytes
With TCPAccelerator
Interleaved TCP
RTT= 40ms
0,0% PL0,0%
PL
A straight line is the maximum limit
of the DS throughput
All rights reserved © 2006, Alcatel
Page 10
Interleaved with 0,2% Packetloss Core
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
RTT in Backbone (ms)
DS T
hro
ughput (K
bps)
MAWS 65535 Bytes
MAWS 17520 Bytes
With TCPAccelerator
Interleaved TCP
RTT= 40ms
0,0% PL0,2%
PL
TCP accelerator performs as with no packet loss at
core
All rights reserved © 2006, Alcatel
Page 11
Interleaved with 0,4% Packetloss Core
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
RTT in Backbone (ms)
DS T
hro
ughput (K
bps)
Measured 65535 Bytes
Measured 17520 Bytes
With TCPAccelerator
Interleaved TCP
RTT= 40ms
0,0% PL0,4%
PL
Results above the WS 65Kbytes (orange line) indicates that
throughput is better than increasing WS
at client
All rights reserved © 2006, Alcatel
Page 12
Fast TCP
RTT= 4ms 0,2% PL 0,0%
PL
Fast Bad with 0,0% Packetloss Core
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
RTT in Backbone (ms)
DS T
hro
ughput (K
bps)
MAWS 65535 Bytes
MAWS 17520 Bytes
With TCPAccelerator
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Page 13
Fast TCP
RTT= 4ms 0,2% PL 0,2%
PL
Fast Bad with 0,2% Packetloss Core
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
RTT in Backbone (ms)
DS T
hro
ughput (K
bps)
Measured 65535 Bytes
Measured 17520 Bytes
With TCPAccelerator
All rights reserved © 2006, Alcatel
Page 14
Fast TCP
RTT= 4ms 0,2% PL 0,4%
PL
Fast Bad with 0,4% Packetloss Core
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
RTT in Backbone (ms)
DS T
hro
ughput (K
bps)
Measured 65535 Bytes
Measured 17520 Bytes
With TCPAccelerator
All rights reserved © 2006, Alcatel
Page 15
Interleaved – IPDSLAM
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
RTT in Backbone (ms)
DS T
hro
ughput (K
bps)
0,0% Core PL - WS 17520
0,2% Core PL - WS 17520
0,4% Core PL - WS 17520
0,0% TCP Accelerator
0,2% TCP Accelerator
0,4% TCP Accelerator
All rights reserved © 2006, Alcatel
Page 16
Fast – IPDSLAM
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
RTT in Backbone (ms)
DS T
hro
ughput (K
bps)
0,0% Core PL - WS 17520
0,2% Core PL - WS 17520
0,4% Core PL - WS 17520
0,0% TCP Accelerator
0,2% TCP Accelerator
0,4% TCP Accelerator
All rights reserved © 2006, Alcatel
Page 17
Video streaming over TCP demo
Server
TCP
Client B
Client A
Video streaming
Smooth video
Choppy video
Normal time between frames
Time delayed between frames
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Page 18
Internet file download demo
Client
ServerCore Network Characteristics
ManagementHost
TCPCPE
Internet
All rights reserved © 2006, Alcatel
Questions?
02-05-2006