Fundamentals of network performance engineering

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Selected highlights from our public network performance engineering workshop.

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Fundamentals of network performance engineering

  1. 1. Fundamentals ofNetwork Performance EngineeringDr Neil DaviesPredictable Network Solutions LtdPeter ThompsonPredictable Network Solutions LtdMartin GeddesMartin Geddes Consulting Ltd© 2013 All Rights ReservedPREDICTABLENETWORKSOLUTIONS
  2. 2. Dr Neil DaviesCo-founder, Predictable Network Solutions LtdEx: University of Bristol (23 years).Former technical head of joint university/research institute (SRF/PACT).Peter ThompsonCTO, Predictable Network Solutions LtdEx: 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 LtdEx: BT, Telco 2.0, Sprint, Oracle, Oxford University.Thought leader on future of telecommunications industry.PREDICTABLENETWORKSOLUTIONS
  3. 3. Dr Neil DaviesCo-founder, Predictable Network Solutions LtdEx: University of Bristol (23 years).Former technical head of joint university/research institute (SRF/PACT).Peter ThompsonCTO, Predictable Network Solutions LtdEx: 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 LtdEx: BT, Telco 2.0, Sprint, Oracle, Oxford University.Thought leader on future of telecommunications industry.PREDICTABLENETWORKSOLUTIONSThe only ex-ante network performanceengineering company in the world.• New mathematical performance techniques.• Performance assessment methodology.• World’s first network contention managementsolution.Consultancy on the future oftelecoms and the Internet.• Business model innovation.• Technology & product ideation.• Organisation development.• Public & private workshops.
  4. 4. This presentation is taken from the content forFundamentals of NetworkPerformance WorkshopFor information on locations andtiming of public events visitwww.sustainablebroadband.comPREDICTABLENETWORKSOLUTIONS
  5. 5. OverviewWhat is“NetworkPerformanceEngineering”?3 BasicConceptsG, S and VImplications:Broadband,LTE, SDN, NFVPREDICTABLENETWORKSOLUTIONS
  6. 6. What isnetworking?• Networking is inter-processcommunications– What matters is enabling computation• We only care about the effectsvisible to the computation processes– We don’t per se care abouttechnologies, mechanisms or policies.• The only visible effect of thenetwork to the computationprocesses is (paradoxically)to lose and delay data!
  7. 7. Networking is astatistical“game of chance”• We’re sharing a fixed and finitetransmission resource throughstatistical multiplexing• Good outcomes come from– many “good coincidences”– few “bad coincidences”• In the game of chance, networkshave some choices over what to loseand delayPREDICTABLENETWORKSOLUTIONS
  8. 8. What is“Network Performance Engineering?”• Network performance engineering is aboutdelivering good enough outcomes…– Acceptable quality of experience (QoE) to user– Low cost to network operator• …and managing the trade-offs in achievingthese…• …by tipping the odds in the game of chance infavour of lower cost and higher QoEPREDICTABLENETWORKSOLUTIONS
  9. 9. OverviewWhat is“NetworkPerformanceEngineering”?3 BasicConceptsG, S and VImplications:Broadband,LTE, SDN, NFVPREDICTABLENETWORKSOLUTIONS
  10. 10. Three essential concepts ofnetwork performance engineering1. Loss and delay accumulate along a pathPREDICTABLENETWORKSOLUTIONS
  11. 11. The raw data we want to work with isend-to-end path delay, because that’s whatthe computation processes experience.
  12. 12. Three essential concepts ofnetwork performance engineering1. Loss and delay accumulates along a path2. What matters is the distribution of loss anddelayPREDICTABLENETWORKSOLUTIONS
  13. 13. This is the simplest viewof the probabilitydistribution, but it is oflimited use formanaging performance
  14. 14. Cumulative view allows(de)composition of lossand delay along the path:can isolate performanceissues to specific networkelements and links.
  15. 15. We are most interestedin the “tails” and theirstructure: these arewhat cause applicationQoE failure, and whosemitigation drives cost.
  16. 16. Three essential concepts ofnetwork performance engineering1. Loss and delay accumulates along a path2. What matters is the distribution of loss anddelay3. A model of causality: decompose and predictPREDICTABLENETWORKSOLUTIONSHow can you know what kind of intervention will address yourQoE or cost issue, and what its effect will be?
  17. 17. Is there another way of looking at this datathat will help us to select the rightintervention and predict its effect?
  18. 18. OverviewWhat is“NetworkPerformanceEngineering”?3 BasicConceptsG, S and VImplications:Broadband,LTE, SDN, NFVPREDICTABLENETWORKSOLUTIONS
  19. 19. Sort by packet size:a clear structureemerges
  20. 20. Example packetdelay: what is itcomprised of?
  21. 21. Transit time ofhypothetical zerolength packetLook at how there is thisboundary line. Packets on the lineexperienced a network where allbuffers were empty; those abovehad to wait for other traffic inbuffers. Note that the differencein delay along this dotted line isrelated only to packet size.
  22. 22. Geographic delayGEvery packet experienced astructural delay due to thespeed of light, routinglookup overheads.
  23. 23. Serialisation delaySPackets with bigger payloads experience more delay:as they are being duplicated by each network element it takes longerto turn the packet into a bitstream, and back again into a packet.
  24. 24. Variable contentiondelayVThe remainder of the delay isnot structural, but is inducedby applying a demand load tothe shared transmissionsupply. We have choices overhow we allocate this delay.
  25. 25. Geographic delaySerialisation delayVariable contentiondelayGSVAll delay is (everywhere andalways) comprised of thesethree basic elements.
  26. 26. Network technologyor designLink rateSchedulingGSVOnce we understand theircontribution to QoE and cost, we canmeasure and manage the right thing!
  27. 27. Ideas like “jitter” conflate delayfrom V and S, along with loss.Measure the wrong thing, andyou manage the wrong thing.Packets whose delay is on this lineare experiencing no contention,even though their delays arevarying due to packet size.
  28. 28. Summary (thus far)1. Measure paths… not points.2. Analyse distributions… not averages.3. Extract structure… for understandingand prediction.PREDICTABLENETWORKSOLUTIONSNote that these simple principles are not common practise innetwork performance engineering today.(That’s why you should do business with us.)
  29. 29. OverviewWhat is“NetworkPerformanceEngineering”?3 BasicConceptsG, S and VImplications:Broadband,LTE, SDN, NFVPREDICTABLENETWORKSOLUTIONS
  30. 30. So what? BroadbandMegabits/second are an insufficient measure: G and V matter too.The broadband market is not being regulated correctly!PREDICTABLENETWORKSOLUTIONSExample: Two different ADSL providers in the same location, with same measured “speed”Great for gaming Useless for gaming
  31. 31. So what? LTE• Cellular will never be as goodas low-spec ADSL– G and V are too high– Has implications for real-timemedia, gaming• Nothing in 3G/4G standardsand networks supportsconsistent loss and delay– Yet this is needed for real-timevalue added servicesPREDICTABLENETWORKSOLUTIONSDownstream delay over a 3G connectionToo much variability forTCP to work well.
  32. 32. So what? SDN and NFVSoftware DefinedNetworking (SDN)resource model isrestricted to the arbitraryconcept of “bandwidth”.– So can’t ask for the rightG, S and V loss and delaycharacteristics.PREDICTABLENETWORKSOLUTIONSDelays measured across UK Internet exchangeBad virtualisation is likely to be the result!“Bandwidth” is too weaka proxy for what mattersin network performance
  33. 33. For further information onnetwork performance engineeringdownload white papers atwww.pnsol.com/publications.htmlPREDICTABLENETWORKSOLUTIONS
  34. 34. For further insight, webinarsand workshopssign up forFuture of Communicationsemail newsletterwww.martingeddes.com
  35. 35. Neil DaviesNeil.Davies@pnsol.comPeter ThompsonPeter.Thompson@pnsol.comMartin Geddesmail@martingeddes.comPREDICTABLENETWORKSOLUTIONS

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