1. All rights reserved © 2006, Alcatel Accelerating TCP Traffic on Broadband Access Networks  Ing-Jyh Tsang  02-05-2006

2. All rights reserved © 2006, Alcatel Page 2 Overview  Why and what is the TCP accelerator  Experimental setups  Measurement results  Demonstrators

3. 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

4. All rights reserved © 2006, Alcatel Page 4 What is the TCP Accelerator ClientServer 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

5. 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. ClientServer TCP Accelerator WS = 17520 WS = 65535 Intercept packets

6. 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. Client Server ACK Intercept packets TCP Accelerator

7. All rights reserved © 2006, Alcatel Page 7 Standalone Configuration Client Server Line Characteristics Network Emulator Network Characteristics US & DS: Delay ± Jitter Packetloss Management Host TCP US & DS: Delay ± Jitter Packetloss

8. All rights reserved © 2006, Alcatel Page 8 Integrated Configuration Client Server Core Network Characteristics Management Host TCP Client DSL Network with Same characteristics CPE

9. All rights reserved © 2006, Alcatel Page 9 Interleaved TCP RTT= 40ms 0,0% PL 0,0% PL A straight line is the maximum limit of the DS throughput

10. All rights reserved © 2006, Alcatel Page 10 Interleaved TCP RTT= 40ms 0,0% PL 0,2% PL TCP accelerator performs as with no packet loss at core

11. All rights reserved © 2006, Alcatel Page 11 Interleaved TCP RTT= 40ms 0,0% PL 0,4% PL Results above the WS 65Kbytes (orange line) indicates that throughput is better than increasing WS at client

12. All rights reserved © 2006, Alcatel Page 12 Fast TCP RTT= 4ms 0,2% PL 0,0% PL

13. All rights reserved © 2006, Alcatel Page 13 Fast TCP RTT= 4ms 0,2% PL 0,2% PL

14. All rights reserved © 2006, Alcatel Page 14 Fast TCP RTT= 4ms 0,2% PL 0,4% PL

15. All rights reserved © 2006, Alcatel Page 15 Interleaved – IPDSLAM

16. All rights reserved © 2006, Alcatel Page 16 Fast – IPDSLAM

17. 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

18. All rights reserved © 2006, Alcatel Page 18 Internet file download demo Client Server Core Network Characteristics Management Host TCP CPE Internet

19. All rights reserved © 2006, Alcatel Questions?  02-05-2006