Time Sensitive Application Transport · Introduction Time sensitive applications are becoming more and more demanded The demand of TSAs has introduced discussions in the network community

Time Sensitive Application TransportMohammad Shafahi

University of Amsterdam Faculty of Science

IntroductionTime sensitive applications are becoming more and more demanded

The demand of TSAs has introduced discussions in the network community specially the NRENS community

The NRENS main question is “What transport technology best suites time sensitive applications?”

Research Question(s)

What are the sources of delay and jitter in technologies?

What are the magnitudes of each source of delay and jitter?

What are the requirements for measuring delay and jitter?

What are the suitable methods and tools for measuring delay and jitter?

What are TSAs?

Jitter requirements of TSAs

Video Audio Application jitter ✔ Overlay image 240ms

✔ ✔ lip synchronization 80ms

✔ ✔ Music Script 5ms

✔ Dialog 120ms

✔ Background music 500ms

✔ Stereo 5µs

What are the sources of delay and jitter in

technologies?

Sources of delay in a network node

dealyit = RDt +QD1t + PCDt +QD2t + TDt + PPDt

Sources of delay in a network node

Propagation PropagationReception Transmission

Queuing

Processing

Queuing

dealyit = RDt +QD1t + PCDt +QD2t + TDt + PPDt

Delay in a network path

S N1 N2 RNn

NX

i=1

(RDit +QD1it + PCDi

t +QD2it + TDit + PPDi

t)� PDNt

delayt =

Delay in a network path

S N1 N2 RNn

NX

i=1

(RDit +QD1it + PCDi

t +QD2it + TDit + PPDi

t)� PDNt

delayt =

Definition of jitter

Jitteri = delayi � delayi�1

Jitter(�t) =

NPi=1

|jitteri|

N

S

N1 N2

R

Nn

(1)

Definition of jitter

Jitteri = delayi � delayi�1

Jitter(�t) =

NPi=1

|jitteri|

N

S

N1 N2

R

Nn

(1)

Sources of delayTech/Delay Propagation Transmission/

Reception Processing Queuing

TDM(D)WDM

SONET/SDHOTN

OpenflowMPLS-TPPBB-TEOpticalDiffserv

✔

✔

✔

✔

✔

✔

✔

✔

✔

What are the magnitudes of each source of delay and jitter?

Magnitudes of delay

Source of Delay Magnitude

Propagation 4.9 µs/km

Transmission 0.01 µs/kb*

Processing 2 µs/kb**

Queuing Used MemoryService Speed

* For a 100Gb interface** Could be much less

What are the requirements for measuring delay and

jitter?

One Way Delay and jitter

S RN

TSTS = Send Time Registered TS = Actual Send TimeTRTS = Receive Time Registered TR = Actual Receive Time


S RN



S RN

TSTS1

TS1

, TSTS2

, TS2 TRTS1

TR1

, TRTS2

, TR2


Round Trip Time and jitter

S RN



S RN



S RN

TSTS1

TS1

, TSTS2

, TS2

TRTS1

TR1

, TRTS2

, TR2TSTS = Send Time Registered TS = Actual Send Time

TRTS = Receive Time Registered TR = Actual Receive Time

Calculating delay and jitter

delayni = TRi � TS

i

delaymi = TSi � TSTS

i + TRTSi � TR

i

delayoi

= delaymi

+ delayni

Dela

yJitt

er jitterni = delayni � delayni�1

jittermi = delaymi � delaymi�1

jitteroi

= delayoi

� delayoi�1

jitterm(�t) + jittern(�t) =

NPi=1

|jittermi

|

N+

NPi=1

|jitterni

|

N

=

NPi=1

|jittermi

|+ |jitterni

|

N

�

NPi=1

|jitteroi

|

N= Jittero(�t)


delaym(�t) + delayn(�t) =

NPi=1

|delaymi

|

N+

NPi=1

|delayni

|

N

=

NPi=1

|delaymi

|+ |delayni

|

N

�

NPi=1

|delayoi

|

N= delayo(�t)


Measuring Delay and jitter

One way delay measurement (OWD)

requires synchronous clock for measuring delay (Using NTP + GPS)

Works fine without synchronous clock for jitter

Round Trip Time measurement (RTT)

Assumes your out going and return path and delay are the same/equal (Use the same!)

What are the suitable methods and tools for

measuring delay and jitter?

Tools for measuringdelay and jitter

Hardware Solutions

Expensive

Higher accuracy

Software Solutions

Cheep and many open source

Lower accuracy

Tools for measurementHardware Solutions

Custom hardware

Passive

Active

Network devices with OAM support

Software

Libraries

Applications

Supports OWD and RTT measurement

Supports multiple flows at the same time

Supports multiple senders and receivers

Supports Custom traffic patterns

Supports a verity of protocols

D-ITG

Measurement accuracy setup

Pentium D 3GHz 2 cores8GB ram

1 Gbit Ethernet

Cat5e x-connect 8m

Pentium Xeon 3GHz 8 cores

16GB ram1 Gbit Ethernet

0 10 20 30 40

0.0

0.1

0.2

0.3

Density function of Jitter for vanillaloop_voip

Jitter(us)

Density

Jitter density function of Setup

Measurement accuracy setup 2

Pentium D 3GHz 2 cores8GB ram

1 Gbit Ethernet



DellPowerConnect

6248

Jitter density function of Setup

0 10 20 30

0.00

0.05

0.10

0.15

0.20

0.25

Density function of Jitter for vanilla_voip

Jitter(us)

Density

Estimation of delay and jitter

Central Limit theorem:

The mean of a sufficiently large number of independent random variables each with finite mean and variance will approximately have a normal distribution

POC measurement setup

AMD Athlon 64 3.4GHz 1 cores




int.

SUT University,Iran

UvA University,Netherlands

60 80 100 120 140 160

0.000

0.010

0.020

0.030

Jitter(us)

Density

Jitter density function of setup

SD 14.3Mean 96.8

N 12000

Conclusion Classified the sources of delay and provide a magnitude for them

Provided a framework for discussion about delay and jitter

We have to be careful with arithmetics

Showed that software solutions provide accuracies of microseconds in jitter measurements

Estimate that hardware is more accurate

Further Work

Studying hardware solutions

Looking into different implementations of OAM in Network devices

Adding queueing theory and system compression theories to the framework

Thanks

Cees de laat for his great guidance

The OS3 Research group

My wife, fahime for her patience

[email protected]

[email protected]

mailto:[email protected]




Documents

Time Sensitive Application Transport · Introduction Time sensitive applications are becoming more and more demanded The demand of TSAs has introduced discussions in the network community