QoS on Best-effort IP Networks
Les Cottrell – SLAC
www.slac.stanford.edu/grp/scs/net/talk/qos-itu-apr01/
Presented at the Joint SG13/SG16 Workshop Panel Session: "Achieving Multimedia
QOS over IP-Based Networks" part of the ITU-T SG13/SG16 Workshop on IP
Networking and Mediacom 2004, Geneva, Switzerland, April 25-27, 2001
Partially funded by DOE/MICS Field Work Proposal on Internet End-to-end
Performance Monitoring (IEPM), also supported by IUPAP
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Overview
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Measurement methodology
Delay
Loss
Jitter
Availability
Summary
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PingER
• Measurements from
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32 monitors in 14 countries
Over 600 remote hosts
Over 72 countries
Over 3300 monitor-remote site pairs
Measurements go back to Jan-95
Reports on RTT, loss, reachability, jitter, reorders,
duplicates …
• Uses ubiquitous “ping” facility of TCP/IP
• Countries monitored
– Contain 78% of world population
– 99% of online users of Internet
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RTT from ESnet to Groups of Sites
RTT ~ distance/(0.6*c) + hops * router delay
Router delay = queuing + clocking in & out + processing
ITU G.114 300 ms RTT limit for voice
20%/year
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RTT Region to Region
OK
White 0-64ms
Green 64-128ms
Yellow 128-256ms
NOT OK
Pink 256-512ms
Red > 512ms
OK within regions, N. America OK with Europe, Japan
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Brazil
300ms
E. Coast
Europe & S. America
RTT (ms)
Frequency
RTT from California to world
Europe
3*0.6c
300ms
RTT (ms.)
Longitude (degrees)
Data from CAIDA Skitter project6
Loss seen from US to groups of Sites
ETSI DTR/TIPHON-05001 V1.2.5 threshold for good speech
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Loss to world from US
Using year 2000, fraction of world’s
population/country from
www.nua.ie/surveys/how_many_online/
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Losses between Regions
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“Jitter” from N. America to W. Europe
“Jitter” = IQR(ipdv), where ipdv(i) =RTT(i) – RTT(i-1)
214 pairs
ETSI: DTR/TIPHON-05001 V1.2.5 (1998-09) good speech < 75ms jitter
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“Jitter” between regions
ETSI: DTR/TIPHON-05001 V1.2.5 (1998-09)
75ms=Good
125ms=Med
Jitter varies with loading
225ms=Poor
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SLAC-CERN
Jitter
ETSI/TIPHON delay
jitter threshold
(75 ms)
IQR(IPDV) in msec.
IQR(ipdv) between CERN & SLAC from Surveyor measurements
(12/15/98 & medians for Dec-98)
100
IQR(ipdv) CERN>SLAC
IQR(ipdv) SLAC>CERN
Monthly IQR(ipdv) CERN>SLAC
Monthly IQR(ipdv) SLAC>CERN
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1
0.1
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5
10
15
Time since midnight (GMT)
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25
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Availability – Outage Probability
Surveyor probes randomly 2/second
Measure time (Outage length) consecutive probes don’t get
through
Heavy tailed outage lengths (packet loss not Poisson)
http://www-iepm.slac.stanford.edu/monitoring/surveyor/outage.html
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More Information
• This talk:
– www.slac.stanford.edu/grp/scs/net/talk/qos-itu-apr01/
• IEPM/PingER home site
– www-iepm.slac.stanford.edu/
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