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TCP-FIT: An Improved TCP Congestion Control Algorithm and its Performance
Dr. Jingyuan Wang
Beihang University
Background
Transport Control Protocol– More than 80% traffic over the Internet use TCP
Internet traffic
TCP
user
• Network Congestion
– Speed of packets sending > network capacity• Congestion collapse: Throughput -> 0 B/S !!!
• TCP Congestion Control
– Control the packets sending speed to avoid network congestion
Background
TCPpacket
TCPSender
TCPpacket
Network
TCPReceiver
ACK
TCPpacket
TCPpacket
TCPpacket
Challenge of TCP over wireless links
• Traditional TCP congestion control algorithms are found to
perform poorly over wireless networks
– Traditional TCP: Packet loss = Congestion
– Wireless networks: Packet loss ≠ Congestion
t
TCP throughput
TCP over wired networks
Congestion losses
Networkcapacity
t
TCP throughput
TCP over wireless networks
Networkcapacity
Random losses
Main Challenge of wireless links: random losses
TCP performance over wireless links
0.1% Loss Rate (WiFi Networks)
0% Loss Rate (Wired Networks)
1% Loss Rate (3G Networks)
Random packet losses lead a serious TCP throughput degradation
Our solution: TCP-FIT
• Run MULTIPLE virtual TCP flows to fully use network capacity
TCPSender
Network
TCPReceiver
1234567
TCPSender
TCPReceiver
1357
246
Network
Traditional TCP:
TCP-FIT :
Virtual flow
Virtual flow
Use queuing delay to adjust N
Performance of TCP-FIT
• 3G networks (5mbps, 1% Loss , 100 ms RTT)
Experiments
• 245 cities over the Internet
Experiments
TCP-FIT in USTREAM.tv
Improvement to other algorithms
• Ustream.tv
Comparing algorithm Average improvement
bic 51.27%
highspeed 99.74%
htcp 60.80%
hybla 96.91%
illinois 285.33%
scalable 110.58%
TCP-FIT + HTTP Streaming
• Ustream.tv
Customer and Partners
Thank you !
Video Demo
• http://v.youku.com/v_show/id_XMTQ5NzI0ODEy.html
Improvement to other algorithms
• SAMSUNG
TCP-FIT + HTTP Streaming
• 56.com
Average Re-buffer times during 3 days
TCP-FIT
TCP BIC
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