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/