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