There is no quality in averages

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We are falling short in terms of the "structural engineering" for broadband because we are using the wrong resource models of the "materials" we are working with.

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There is no quality in averages

  1. 1. GEDDESV There is no quality in averages Martin Geddes September 2014
  2. 2. How to construct high-value assured services at the lowest cost
  3. 3. Structure Demand for Cluallty meaningfully about Of p the problem, Multiplexing and money Oops! There is no quality in averages Examples How to get quality and cost right — Measure, model, manipulate Digital ‘supply chain management’ Language to talk ll
  4. 4. GEDDESV DEMAND
  5. 5. ll This requires a whole digital supply chain to come together. Users pay for application outcomes, nkea working Application ‘ phone call. outcomes
  6. 6. That supply chain manufactures performance for distributed computing applications. '7?" -E” T ‘J, ‘ ll 3' I 5 l H l , .i| I111‘l11p| II| IIIgI‘1;Im’; || l]l]l i| l|l| l‘IllllllrlllllllJ| lll]l‘l| l:l| l | |Ill| l’l[lIl[llllllllllflllly -' n : -R ; ‘ 60in , _ 4 ~ _/ ,3 T’ '5}7"' T 7.. We need some way to y _ quantify performance l x ' in terms of ‘ demand and supply. «»
  7. 7. When supply meets the requirements of demand, then you enable a task substitution. For example, a reliable phone service means you don’t have to drive to a meeting. in
  8. 8. There is a risk of the application outcome not occurring. These are performance hazards. When a hazard ‘matures’ into a failure, it creates a direct cost to the user. So a failed call wastes time and could mean a lost sale. There is also a self-insurance cost (e. g. you need a second car to visit key clients).
  9. 9. We provide service assurance to reduce or eliminate these failure costs. We can only remove the self-insurance cost when we reach high levels of dependability. '1 -n i
  10. 10. Hazards depend on loss and delay (and nothing else) 1 Honest!
  11. 11. —I '-I I 3.35 .3: ~: ::: ‘;/ ::: :': ”’EE:3 ’ .5+'“'»3— : ’—i: , 7 7—— —__T”*—— — " W 9.34 To deliver on our assurance i promise, we need to keep loss and delay bounded to stay away from performance ‘cliffs’ "'—~-. ,,, ___ '8 W , , 3,91 ’”—-——, ,,, ,__7 7.5 7777’T"? -——7,___ , 13.5 ‘m 7 O —— r 5.5 7' a. a3 , :3 Loss rate
  12. 12. Cumulative Distribution 0 oo 0 an 0 3:. 0 t. ) Performance ‘budget’ This predictable region of operation defines a ‘budget’ for loss and delay along the path. 2 4 B 8 10 Outcome Response Time (Sec) 12 14
  13. 13. GEDDESV SUPPLY
  14. 14. We are moving from TDM circuits. .. No overlaps or collisions
  15. 15. .. .to packet-based statistical multiplexing Hence needing a richer characterisation
  16. 16. IPX is only part of an assurance value chain Quality is lost along the whole of this chain. ) [ ll/ l$ PSTN + VOLTE There is no perceived value to assurance that l doesn’t deliver the application outcome.
  17. 17. GEDDES FFFFF U LTI P L E I N G Where supply and X demand meet
  18. 18. Statistically shared medium
  19. 19. Networks are trees of multiplexers where the ‘game of chance’ plays out. 1 The efficiency of assurance is determined by the multiplexing gain, and 1 effectiveness by the scheduling 1
  20. 20. When we schedule the traffic we l place bets that bias us towards high efficiency and effectiveness. p
  21. 21. So let’s summarise how we make money
  22. 22. Too little multiplexing gain Sm LOW SHARING
  23. 23. Too many performance hazards mature into failure T» HIGH SHARING
  24. 24. Like Goldilocks, we 1 don’t want to run the network too hot or cold. The ideal is somewhere in the middle.
  25. 25. This delivers assurance at I — higher utilisation levels, so we make more profit.
  26. 26. I You need to have some metric goal I against which to judge ‘good’ or ‘bad’ scheduling bets.
  27. 27. IPX predictive resource model Average bandwidth + average loss + average jitter
  28. 28. GEDDES V OOPS!
  29. 29. Oops! There is Lo guality in averages
  30. 30. Would you like an
  31. 31. Here’s your apple! Sorry it’s a bit yuk, but really, on average they are very fresh.
  32. 32. Oops! There is Lo guality in averages
  33. 33. GEDDESV EXAMPLES
  34. 34. KPSN() Kent Public Service Network We| |—run UK public sector network Wants to run voice over IP Will it wor| <?
  35. 35. High average load, no QoE failure risk Breach Metric 20 100 A->C - QTA breach 5ms@99.5% + Link % util Low average load (<O.1°/ o), high QoE failure risk Util (%) The average metrics don’t + +. +.+ give you the data l. 0+ *+ _ , youneedto 3:33 3:733 3333 333 33333 Da 33 manage C05t and performance. Source: Predictable Network Solutions Ltd
  36. 36. Oops! There is Lo quality in averages I
  37. 37. IPX Specification | R.34 v9.1§6.3.4 Average Monthly Packet L ss 1 <0 1% 3 EF+AF4 Table 9: Packet loss You could in theory take a 40 minute break once a month and still be compliant. The standard doesn’t specify a working voice service!
  38. 38. Oops! There is Lo quality in averages I
  39. 39. SBC de-jittering is a bad idea Optimisations to meet local requirements on average variability mean we break the global ‘budget’ for a working service. 1 IMS + VOLTE PS TN
  40. 40. I I think you get the . idea by now. .. I
  41. 41. Current resource model 1. Is not a strong So even if you deliver the technical requirements, you’ve not necessarily delivered the application outcome.
  42. 42. Current resource model 2. Is not So you can’t decompose the overall ‘budget’ and allocate it along the supply chain.
  43. 43. Current resource model 3. Is not along the path. I! So we are too ‘slack’ in some places, I and impossibly ‘tight’ in others.
  44. 44. GEDDESV OUR FATE?
  45. 45. You can’t put the lost quality back in with IPX! I 9 A V . . ll W111 m‘I1:= ~ : .11:I1I11g 1" "lI1l1l11I 1 llllfil IV 7 S ' Lots more ways in which calls can lose ""'l l quality at the edge.
  46. 46. .. .costs rise without stat mux gain Can’t mix. .. Media & signalling Video & voice Elastic & inelastic Rea| -time & bulk
  47. 47. The consequence? Increasing unmanaged performance hazards and/ or Increasing idle resources
  48. 48. Falling profit s, $
  49. 49. GEDDESV THE PRIZE?
  50. 50. End-to-end assurance by measuring and managing hazards 4—> IPX
  51. 51. Rising profit
  52. 52. GEDDESV THE ISSUE?
  53. 53. How to manage the performance hazards whilst keeping utilisation high?
  54. 54. GEDDESV THE ANSWER?
  55. 55. The answer the demand for performance. I Using metrics that are a I strong QoE proxy
  56. 56. The answer the demand for performance. the supply of performance for each link. Using a compositional metric
  57. 57. The answer the demand for performance. the supply of performance for each link. your traffic manage performance hazards to keep within the budget. Beyond the scope of this presentation l
  58. 58. hfleasure Needto measure the right thing: quality attenuation along the path
  59. 59. I V Distribution Limited xSingIe Point predictive power Temporal and spatial predictive power
  60. 60. Stochastic Predictive Resource Model A
  61. 61. End-to-end assurance ‘budget’ Because the value is an assured supply chain, notjust a wholesale core.
  62. 62. Manage to 8.85 ’ :1, ’* * -4” ”*: :’f’1§§lft; j*—i—-, ” —”’ 9.04 7' was (How to configure scheduling r§{: ::: is out of scope here. ) Loss rate l l I 260 288 308 320 340 368 388 | Deflay
  63. 63. GEDDESV SUMMARY
  64. 64. ' . . l I . « ' 1 — ' - . .> , ' . /~ V‘ . _ , - -. s‘ 3“ 9 , ‘r V ‘ « ‘ll. w , . ‘. /V’ ‘- '1 ‘I ’ ' 7 "K1 ' , _ . . ” ‘ I . ~ / / ' « I , , » ' / " ’ l I / , / ‘if’ I ‘ / . 0 ‘ ‘I A » r , * ‘ "“ l v i K. ( «I . ‘ l l ‘ 1 V This building isn't going to fall down. That’s because the architect specified a building for a realistic load with a safety margin to account for the most extreme anticipated variation / ‘ in demand and/ or supply. W a / /A / i ,
  65. 65. ' I —- f >‘ , »- . l ‘ K‘- ; * . I V ,3; x P T I g Quantity surveyors obtained materials ; whose properties they fully understood and can model. _3r—- not‘: -‘i>. .,, ~.‘-l| &_v"". VEk: _g'. ‘~'-_’3.' 1* '7;‘: l ' _ ‘ ¥‘)“’ ' '$*, “r" 4 1‘-7‘: ‘-'-" 4 "' E‘-'~ . - 1 l‘ 9 . l“A"" -‘K195 " 4 IV.
  66. 66. Structural engineers understood how to compose those materials to meet the architect’s requirements. 7 . l
  67. 67. u--I As a result of l these capabilities, l: , ee. e____% we can reliably build skyscrapers.
  68. 68. Our models don’t reflect our materials. We're still trying to build assured telecoms services with the techniques of a previous generation. |t’s | i|<e we’re making medieval cathedrals with skilled craftspeople.
  69. 69. If we up our ‘structural engineering’ game, and move from craft to science, we can build networks whose efficiency and effectiveness exceeds what was previously thought possible.
  70. 70. Fresh thinking www. martingeddes. com/ thin| <—tank mai| @martingeddes. com

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