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  1. Providing Guaranteed Services Without Per Flow Management By: Ion Stoica, Hui Zhang Presented by: Sanjeev R. Kulkarni Advanced Computer Networks

  2. Outline • Problems with the current QoS architectures • Stateless Core Architecture(SCORE) • Dynamic Packet State • Core Jitter Virtual Clock Algorithm • Admission Control • Implementation details • Extensions to IPv6 Advanced Computer Networks

  3. Current QoS architectures • Integrated Services • Differentiated Services Advanced Computer Networks

  4. Integrated Services • All Routers maintain per-flow state • State • Control Plane • Admission Control: per flow signaling • Data Plane • Classifier: per flow flow-ids • scheduler: per flow scheduling algorithm parameters Advanced Computer Networks

  5. Integrated Services • All Routers maintain per-flow state • State • Control Plane • Admission Control: per flow signaling • Data Plane • Classifier: per flow flow-ids • scheduler: per flow scheduling algorithm parameters • Scalability?? Advanced Computer Networks

  6. Jitter Virtual Clock • For each packet • eligible time • deadline • Scheduling done in the order of the deadline • e1i,j = a1i,j • eki,j = max ( aki,j + gki,j-1, dk-1i,j) • dki,j = eki,j + lki/ri Advanced Computer Networks

  7. Core-routers and Edge routers Advanced Computer Networks

  8. Differentiated Services • A small number of traffic classes • Only Edge routers maintain per flow state • Control Plane • Admission Control: per flow signaling • Data Plane • Classifier: per class classification • Scheduler: per class scheduling Advanced Computer Networks

  9. Differentiated Services • A small number of traffic classes • Only Edge routers maintain per flow state • Control Plane • Admission Control: per flow signaling • Data Plane • Classifier: per class classification • Scheduler: per class scheduling • Quality of QoS?? Advanced Computer Networks

  10. Stateless Core Solution • Idea similar to DiffServ • Only Edge Routers maintain per flow state • Dynamic Packet State (DPS) is inserted into each packet by edge routers • Core routers update DPS and schedule packets accordingly Advanced Computer Networks

  11. DPS Ingress Egress Advanced Computer Networks

  12. How it works a b c d Advanced Computer Networks

  13. How it works a b c d Advanced Computer Networks

  14. How it works a b c d Advanced Computer Networks

  15. How it works a b c d Advanced Computer Networks

  16. How it works a b c d Advanced Computer Networks

  17. How it works a b c d Advanced Computer Networks

  18. How it differs from DiffServ • DPS versus Per Hop Behavior (PHB) • DPS is dynamic • Routers change DPS and schedule packets based on the DPS state • DPS change mirrors a Core-Jitter Virtual Clock scheduling Advanced Computer Networks

  19. Core Jitter Virtual Clock • eki,j = max ( aki,j + gki,j-1, dk-1i,j) • The main culprit is dk-1i,j • Introduce a slack variable such that • aki,j + gki,j-1 + > dk-1i,j ik =max (0, ik-1 + (lik-1 - lik)/ri - (ei,1k - ei,1k-1 - lik-1/ri)/(h-1) ) Advanced Computer Networks

  20. Example a b Advanced Computer Networks

  21. Example a ea1 da1 b Advanced Computer Networks

  22. Example ga1 a ea1 da1 b Advanced Computer Networks

  23. Example ga1 a ea1 da1 eb1 db1 b ga1 Advanced Computer Networks

  24. Example a ea1 da1 eb1 db1 b Advanced Computer Networks

  25. Example a ea1 ea2 da2 eb1 db1 b Advanced Computer Networks

  26. Example a ea2 da2 eb1 db1 b Advanced Computer Networks

  27. Example a ea2 da2 gb1 eb1 b db1 ga1 Advanced Computer Networks

  28. The algorithm • Parameter Initialization by Ingress Routers • Core routers examine the parameters and modify g • Egress Routers strip the packet of these labels Advanced Computer Networks

  29. Admission Control r s d a c b Advanced Computer Networks

  30. Admission Control Resv r s d a c b Advanced Computer Networks

  31. Admission Control r s d 1 a c b Advanced Computer Networks

  32. Admission Control r s d a c b Advanced Computer Networks

  33. Admission Control r s d a c b Advanced Computer Networks

  34. Admission Control r s d a c b Advanced Computer Networks

  35. Admission Control r s d 3 a c b Advanced Computer Networks

  36. Admission Control Resv r s d a c b Advanced Computer Networks

  37. Admission Control • Each core router maintains an upper bound R on the Total Bandwidth reserved • Local Admission Control • Accept if R + ri < C • Periodically they run an algorithm that contains the deviation between the actual B/w reserved and R. Advanced Computer Networks

  38. Recalibration Algorithm • Packet state b • Add all b values on each packet arrival • Periodically they update based on R = min ( R, RD/(1-f) + Rnew ) Advanced Computer Networks

  39. Implementation 0 7 11 15 31 TOS IPv4 Header Frag Offset 18 Advanced Computer Networks

  40. Implementation 0 7 11 15 31 18 Flag F1 F2 F3 2 5 9 16 Advanced Computer Networks

  41. Extension to Ipv6 0 7 11 31 Flow Label Flag F1 F2 F3 6 11 19 2 Advanced Computer Networks

  42. Summary • SCORE Network • Is Scalable • Gives a QoS similar to Jitter Virtual Clock • Extensible to Ipv6 • Transparent to the outside network Advanced Computer Networks