all rights reserved © 2006, alcatel accelerating tcp traffic on broadband access networks ing-jyh...

All rights reserved © 2006, Alcatel

Accelerating TCP Traffic on Broadband Access Networks

Ing-Jyh Tsang

02-05-2006


Overview

Why and what is the TCP acceleratorExperimental setupsMeasurement resultsDemonstrators


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


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


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


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


Standalone Configuration

ClientServer

Line Characteristics Network Emulator

Network Characteristics

US & DS:Delay ± JitterPacketloss

ManagementHost

TCP

US & DS:Delay ± JitterPacketloss


Integrated Configuration

Client

Server

Core Network Characteristics

ManagementHost

TCP

Client

DSL Network with Same characteristics

CPE

CPE


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



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


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



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


DS T

hro

ughput (K

bps)

Measured 65535 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


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


DS T

hro

ughput (K

bps)

MAWS 65535 Bytes

MAWS 17520 Bytes

With TCPAccelerator


Fast TCP

RTT= 4ms 0,2% PL 0,2%

PL


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


DS T

hro

ughput (K

bps)



With TCPAccelerator


Fast TCP

RTT= 4ms 0,2% PL 0,4%

PL


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


DS T

hro

ughput (K

bps)



With TCPAccelerator


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


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




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


DS T

hro

ughput (K

bps)

0,0% Core PL - WS 17520

0,2% Core PL - WS 17520

0,4% Core PL - WS 17520





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


Internet file download demo

Client

ServerCore Network Characteristics

ManagementHost

TCPCPE

Internet


Questions?

02-05-2006

all rights reserved © 2006, alcatel accelerating tcp traffic on broadband access networks ing-jyh...

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