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Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
TCP behavior
on
Trans-Atlantic lambda’s
Wim Sjouw, Antony Antony, Hans Blom, Cees de Laat, Jason Lee
EU - IST DataTag project, WP3
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
LFNT
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Long:
RTT > 50 msec
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
FAT
B > 622 Mbps
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Surprise Surprise
Surprise Surprise
TCPthroughput
90 Mbps
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
UDPmon
Probe the network with trains of UDP packets
Packets are: numbered & time stamped
• variable number of packets• varable packet length• variable inter packet delay
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
UDPmon
Probe the network with trains of UDP packets
Very precise timing with Pentium proc. clock
Packets are: numbered & time stamped
• number of packets: 5000• packet length: 1000 Bytes• inter packet delay: 0 μsec
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
UDPmon
Probe the network with trains of UDP packets
Timing: 10 ns
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
UDPmon
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Nb = 1500 Nd = 0 l = 1000
f = 1 Gbps s = 622 Mbps
then M = 0.5 MB
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
R = 100 ms
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Back to TCP
TCP is bursty due to:
• sliding window protocol • slow start algorithm
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
W= sent segments
Y= advertised window
G= ACK’s
R= retransmits
P= SACK’s
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
512 packets in 4 ms
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
So overall pick from this menu:
• flow control
• traffic shaping
• RED (Random Early Discard)
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Receiver:
• buffer capacity of NIC
• interupt latency & coalescence
• interupt overhead
• PCI bus width and PCI bus speed
• TCP stack overhead & complexity
• OS overhead
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
< Mac OS
< Linux
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Conclusions:
• ‘old’ TCP does not perform in a “Long Fat Network”
• UDP does perform, but unacceptable
• End system(s) dictate overall performance:
o O.S
o Memory
o NIC
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
beware of
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Thanks!
http://www.science.uva.nl/research/air/
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
Advanced Internet Research Wim Sjouw Santiago de Compostela 14 February 2003
UDPmon:
www.hep.man.ac.uk/~rich/net
Richard Hughes Johnes
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