Fundamentals of network performance engineering

Fundamentals of Network Performance Engineering

Dr Neil DaviesPredictable Network Solutions Ltd

Peter ThompsonPredictable Network Solutions Ltd

Martin GeddesMartin Geddes Consulting Ltd

© 2013 All Rights Reserved

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Dr Neil DaviesCo-founder, Predictable Network Solutions Ltd

Ex: University of Bristol (23 years).Former technical head of joint university/research institute (SRF/PACT).

Peter ThompsonCTO, Predictable Network Solutions Ltd

Ex: GoS Networks, U4EA, SGS-Thomson, INMOS & Universities of Bristol, Warwick and Cambridge.Authority on technical and commercial issues of converged networking.

Martin GeddesFounder, Martin Geddes Consulting Ltd

Ex: BT, Telco 2.0, Sprint, Oracle, Oxford University.Thought leader on future of telecommunications industry.

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Dr Neil DaviesCo-founder, Predictable Network Solutions Ltd

Ex: University of Bristol (23 years).Former technical head of joint university/research institute (SRF/PACT).

Peter ThompsonCTO, Predictable Network Solutions Ltd

Ex: GoS Networks, U4EA, SGS-Thomson, INMOS & Universities of Bristol, Warwick and Cambridge.Authority on technical and commercial issues of converged networking.

Martin GeddesFounder, Martin Geddes Consulting Ltd

Ex: BT, Telco 2.0, Sprint, Oracle, Oxford University.Thought leader on future of telecommunications industry.

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SOLUTIONS} The only ex-ante network performance engineering company in the world.

• New mathematical performance techniques.• Performance assessment methodology.• World’s first network contention management

solution.

} Consultancy on the future oftelecoms and the Internet.

• Business model innovation.• Technology & product ideation.• Organisation development.• Public & private workshops.

This presentation is taken from the content for

Fundamentals of Network Performance Workshop

For information on locations and timing of public events visit

www.sustainablebroadband.com

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Overview

What is “Network

Performance Engineering”?

3 Basic Concepts G, S and V

Implications: Broadband,

LTE, SDN, NFV

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What is networking?

• Networking is inter-process communications– What matters is enabling computation

• We only care about the effects visible to the computation processes– We don’t per se care about

technologies, mechanisms or policies.

• The only visible effect of the network to the computation processes is (paradoxically)to lose and delay data!

Networking is a statistical

“game of chance”

• We’re sharing a fixed and finite transmission resource through statistical multiplexing

• Good outcomes come from– many “good coincidences”– few “bad coincidences”

• In the game of chance, networks have some choices over what to lose and delay

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What is“Network Performance Engineering?”• Network performance engineering is about

delivering good enough outcomes…– Acceptable quality of experience (QoE) to user– Low cost to network operator

• …and managing the trade-offs in achieving these…

• …by tipping the odds in the game of chance in favour of lower cost and higher QoE

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Overview

What is “Network

Performance Engineering”?

3 Basic Concepts G, S and V

Implications: Broadband,

LTE, SDN, NFV

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Three essential concepts of network performance engineering

1. Loss and delay accumulate along a path

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The raw data we want to work with isend-to-end path delay, because that’s what

the computation processes experience.

Three essential concepts of network performance engineering

1. Loss and delay accumulates along a path2. What matters is the distribution of loss and

delay

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This is the simplest view of the probability

distribution, but it is of limited use for

managing performance

Cumulative view allows (de)composition of loss

and delay along the path: can isolate performance

issues to specific network elements and links.

We are most interested in the “tails” and their

structure: these are what cause application QoE failure, and whose mitigation drives cost.

Three essential concepts of network performance engineering

1. Loss and delay accumulates along a path2. What matters is the distribution of loss and

delay3. A model of causality: decompose and predict

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How can you know what kind of intervention will address your QoE or cost issue, and what its effect will be?

Is there another way of looking at this data that will help us to select the right intervention and predict its effect?

Overview

What is “Network

Performance Engineering”?

3 Basic Concepts G, S and V

Implications: Broadband,

LTE, SDN, NFV

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Sort by packet size: a clear structure

emerges

Example packet delay: what is it comprised of?

Transit time of hypothetical zero

length packet

Look at how there is this boundary line. Packets on the line experienced a network where all buffers were empty; those above

had to wait for other traffic in buffers. Note that the difference in delay along this dotted line is

related only to packet size.

Geographic delayG

Every packet experienced a structural delay due to the

speed of light, routing lookup overheads.

Serialisation delayS

Packets with bigger payloads experience more delay:as they are being duplicated by each network element it takes longer

to turn the packet into a bitstream, and back again into a packet.

Variable contentiondelayV

The remainder of the delay is not structural, but is induced by applying a demand load to

the shared transmission supply. We have choices over

how we allocate this delay.

Geographic delay

Serialisation delay

Variable contentiondelay

G

S

V

All delay is (everywhere and always) comprised of these

three basic elements.

Network technologyor design

Link rate

Scheduling

G

S

V

Once we understand their contribution to QoE and cost, we can measure and manage the right thing!

Ideas like “jitter” conflate delay from V and S, along with loss. Measure the wrong thing, and you manage the wrong thing.

Packets whose delay is on this line are experiencing no contention,

even though their delays are varying due to packet size.

Summary (thus far)1. Measure paths… not points.2. Analyse distributions… not averages.3. Extract structure… for understanding

and prediction.

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Note that these simple principles are not common practise in network performance engineering today.

(That’s why you should do business with us.)

Overview

What is “Network

Performance Engineering”?

3 Basic Concepts G, S and V

Implications: Broadband,

LTE, SDN, NFV

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So what? Broadband

Megabits/second are an insufficient measure: G and V matter too.

The broadband market is not being regulated correctly!

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Example: Two different ADSL providers in the same location, with same measured “speed”

Great for gaming Useless for gaming

So what? LTE

• Cellular will never be as good as low-spec ADSL– G and V are too high– Has implications for real-time

media, gaming

• Nothing in 3G/4G standards and networks supports consistent loss and delay– Yet this is needed for real-time

value added services

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Downstream delay over a 3G connection

Too much variability for TCP to work well.

So what? SDN and NFV

Software Defined Networking (SDN) resource model is restricted to the arbitrary concept of “bandwidth”.

– So can’t ask for the right G, S and V loss and delay characteristics.

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Delays measured across UK Internet exchange

Bad virtualisation is likely to be the result!

“Bandwidth” is too weak a proxy for what matters in network performance

For further information on network performance engineering

download white papers at

www.pnsol.com/publications.html

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For further insight, webinarsand workshops

sign up for

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www.martingeddes.com

Neil [email protected]

Peter [email protected]

Martin [email protected]

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