1
QoS on Best-effort IP Networks
Les Cottrell – SLACwww.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
2
Overview• Measurement methodology
• Delay
• Loss
• Jitter
• Availability
• Summary
3
PingER• Measurements from
– 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
4
RTT from ESnet to Groups of Sites
ITU G.114 300 ms RTT limit for voice
20%/year
RTT ~ distance/(0.6*c) + hops * router delayRouter delay = queuing + clocking in & out + processing
5
RTT Region to Region
OKWhite 0-64msGreen 64-128msYellow 128-256ms
NOT OKPink 256-512msRed > 512ms
OK within regions, N. America OK with Europe, Japan
6
RTT from California to world
Longitude (degrees)
300ms
300ms
RTT (ms.)
Fre
quen
cy
RT
T (
ms)
Source = Palo Alto CA, W. Coast
E. C
oast
US
W. C
oast
US
Eur
ope
& S
. Am
eric
a
Europe
3*0.6c
Bra
zil
E. C
oast
Data from CAIDA Skitter project
7
Loss seen from US to groups of Sites
ETSI DTR/TIPHON-05001 V1.2.5 threshold for good speech
50% improvement / year
8
Loss to world from US
Using year 2000, fraction of world’s population/country fromwww.nua.ie/surveys/how_many_online/
9
Losses between Regions
10
“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
11
“Jitter” between regions
75ms=Good 125ms=Med 225ms=Poor
ETSI: DTR/TIPHON-05001 V1.2.5 (1998-09)
Jitter varies with loading
12
SLAC-CERNJitter
IQR(ipdv) between CERN & SLAC from Surveyor measurements (12/15/98 & medians for Dec-98)
0.1
1
10
100
0 5 10 15 20 25
Time since midnight (GMT)
IQR
(IP
DV
) in
ms
ec
.
IQR(ipdv) CERN>SLAC IQR(ipdv) SLAC>CERN
Monthly IQR(ipdv) CERN>SLAC Monthly IQR(ipdv) SLAC>CERN
ETSI/TIPHON delayjitter threshold
(75 ms)
13
Availability – Outage ProbabilitySurveyor probes randomly 2/secondMeasure time (Outage length) consecutive probes don’t getthroughHeavy tailed outage lengths (packet loss not Poisson)
http://www-iepm.slac.stanford.edu/monitoring/surveyor/outage.html
14
More Information• This talk:
– www.slac.stanford.edu/grp/scs/net/talk/qos-itu-apr01/
• IEPM/PingER home site– www-iepm.slac.stanford.edu/