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CIS679: Anycast

CIS679: Anycast. Review of Last lecture Anycast. Review of Last Lecture. H.323. Anycast. Unicast, multicast and anycast. Usage of Anycast. Providing Service transparency DNS server, and mirrored Web site Improving network performance load balance at application and network layers.

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CIS679: Anycast

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  1. CIS679: Anycast • Review of Last lecture • Anycast

  2. Review of Last Lecture • H.323

  3. Anycast • Unicast, multicast and anycast

  4. Usage of Anycast • Providing Service transparency • DNS server, and mirrored Web site • Improving network performance • load balance at application and network layers

  5. An Example for Ancast Usage R1 R2 R3 1 mbs 1 mbs 1 mbs R4 R6 1 mbs 1 mbs R5 3 mbs R7 core R8 R9 R10 R11 R12 R13 A traffic flow with SP-To-Core method

  6. Anycast at Different Layers • Network-layer anycast • Anycast address • Anycast membership management • Anycast routing • Application-layer anycast

  7. Anycast Address • Shares with unicast • Advantage: compatible to unicast • Disadvantage: too like unicast, some benefit of anycast lost • Separate from unicast, just like multicast • Advantage: easy to make full use of anycast semantics • Disadvantage: difficult to deploy

  8. Anycast Membership Management • Similar to multicast -- IGMP • But, there is more freedom

  9. Anycast Routing • Single-path Routing The path from the source to the destination is time invariant. • Multi-path Routing The traffic from the source to the destination is split into different paths.

  10. Multi-Path Routing for Anycast Messages • Two issues • Loop free routing • How to select multi-path?

  11. Dest Dest Dest Dest Dist Dist Dist Dist hop hop hop hop A, H15 A, H15 A, H15 A, H15 8 5 10 7 R9 R9 R11 R7 A, H16 A, H16 A, H16 A, H16 6 9 9 4 R9 R12 R12 R16 R10 R13 R10 R7 A, H17 A, H17 A, H17 A, H17 13 8 10 13 8 3 8 5 R10 R10 R7 R14 A, H18 A, H18 A, H18 A, H18 Routing table at R9 Routing table at R12 Routing table at R7 Routing table at R10 1 R16 H3 Hi H8 H16 H15 H5 H2 H1 H18 H7 H17 H6 H4 Ri Host Router H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} Link with distance 2 1 Link in a loop Loop in Anycast Routing 1 1 1 1 R3 R1 R2 R4 4 2 3 1 1 1 1 1 1 1 1 R7 R6 R8 R5 2 1 2 3 R9 R10 4 6 1 3 4 2 5 R13 R11 R12 R14 7 6 3 1 3 1 1 1 1 R17 R18 R15

  12. Loop-free Routing • Ordered routing A router with a higher order can send anycast message to a lower order router. • Methods to order the routers • SSPF method • MIN_D method • SBT method • CBT method

  13. The SSPF Method • SSP order: X>SSPY if Y is the next hop of X on Pssp(X, G(A)). • An anycast packet is routed to the nearest member of the anycast group.

  14. Dest Dest Dest Dest Dist Dist Dist Dist hop hop hop hop A, H15 A, H15 A, H15 A, H15 7 2 1 6 R11 R5 H15 R11 A, H16 A, H16 A, H16 A, H16 10 9 12 12 R11 R9 R5 R2 R11 R12 R9 R5 A, H17 A, H17 A, H17 A, H17 16 17 19 20 1 1 1 1 R3 R1 R2 R4 14 11 12 15 R2 R11 R2 R5 A, H18 A, H18 A, H18 A, H18 4 2 3 Routing table at R11 1 1 * 1 1 Ri * 1 1 1 1 R7 R6 R8 R5 2 1 2 3 Routing table at R1 Routing table at R5 R9 R10 4 6 1 3 4 2 5 * * R13 R11 R12 R14 7 6 1 3 1 3 1 R16 H15 H4 H7 H6 H17 H18 H8 H2 H1 Hi H3 H5 H16 1 1 1 R17 R18 R15 Routing table at R15 Host Router H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} 1 Link with distance 2 1 Congested link Link on DBTs The SSPF Method

  15. The MIN-D Method • Function min_d() • MIN_D order X >MIN_DY if min_d(X, A) > min_d(Y, A). • An anycast packet is routed to the nearer member of the anycast group.

  16. Dest Dest Dest Dest Dist Dist Dist Dist hop hop hop hop A, H15 A, H15 A, H15 A, H15 5 7 10 6 R9 R11 R9 R7 1 1 1 1 A, H16 A, H16 A, H16 A, H16 7 6 7 6 9 7 4 R16 R12 R12 R9 6 R3 R1 R2 R4 R13 R10 R10 R7 A, H17 A, H17 A, H17 A, H17 13 13 14 8 * * 4 2 3 1 1 1 1 8 8 3 9 R7 R10 R14 R10 A, H18 A, H18 A, H18 A, H18 * 1 1 1 1 5 6 6 Routing table at R9 R7 5 Routing table at R6 Routing table at R12 Routing table at R10 R6 R8 R5 Ri 2 1 2 3 5 3 R9 R10 4 6 1 3 4 2 * 5 * 2 R13 R11 R12 R14 4 4 2 * 7 6 1 1 3 3 * * 1 1 1 R17 R18 R15 1 1 1 1 1 R16 H7 Hi H2 H6 H8 H15 H16 H17 H18 H5 H4 H3 H1 2 Host Router with MIN-D H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} Link with distance 1 2 1 Link on a general graph Congested link The MIN-D Method

  17. The SBT Method • SBT order: X>SBTY if X is the father of Y on the source-based tree of Source S • An anycast packet is routed along the source-based tree rooted at the source of the packet.

  18. Dest Dest Dest Dest Dist Dist Dist Dist hop hop hop hop A, H15 A, H15 A, H15 A, H15 8 9 6 5 R6 R11 R9 R9 1 1 1 1 A, H16 A, H16 A, H16 A, H16 6 7 10 9 R9 R6 R9 R12 R3 R1 R2 R4 R7 R7 R10 R10 A, H17 A, H17 A, H17 A, H17 13 11 10 14 4 2 3 * * 1 1 1 1 5 9 6 8 R7 R7 R10 R10 A, H18 A, H18 A, H18 A, H18 * * 1 1 1 1 Routing table at R9 R7 Routing table at R6 Routing table at R3 Routing table at R7 R6 R8 R5 * Ri 2 * 1 2 3 R9 R10 4 6 1 3 4 2 5 R13 R11 R12 R14 7 * * 6 1 1 3 3 * * 1 1 1 R17 R18 R15 1 R16 H8 H15 H4 H17 H5 H16 H1 H7 H6 H2 H18 Hi H3 Router Host H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} Link with distance 2 1 Link on a SBT tree rooted at R3 The SBT Method

  19. The CBT Method • CBT order: X>CBTY if X is the father of Y on the core-based tree. • For an anycast packet: • at the on-CBT router, it is routed following CBT order. • at the off-CBT router, it is routed following SSP order

  20. Dest Dest Dest Dest Dist Dist Dist Dist hop hop hop hop A, H15 A, H15 A, H15 A, H15 10 8 7 5 R11 R9 R9 R7 A, H16 A, H16 A, H16 A, H16 1 1 1 1 4 9 9 6 R12 R12 R9 R16 R3 R1 R2 R4 R10 R13 R7 R10 A, H17 A, H17 A, H17 A, H17 13 10 8 13 4 2 3 1 1 * * 1 1 5 8 3 8 R14 R7 R10 R10 A, H18 A, H18 A, H18 A, H18 * * 1 1 1 1 Routing table at R9 Routing table at R7 Routing table at R10 Routing table at R12 R7 R6 R8 R5 Ri * 2 1 * 2 3 R9 R10 4 6 1 3 4 2 5 R13 R11 R12 R14 * 7 6 * 1 1 3 3 1 1 1 * R17 R18 R15 1 R16 H5 H16 H3 H1 H18 Hi H6 H8 H4 H7 H2 H15 H17 Router Host H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} Link with distance 2 2 1 Link on the truncated DBTs Link on a CBT tree rooted at R7 The CBT Method

  21. Summary of Router-ordering Methods • The number of loop-free paths SSPF < MIN_D < SBT = CBT • Overhead in terms of the memory storage SSPF < MIN_D < CBT << SBT

  22. Multiple Path Selection • Weight Random Selection (WRS) A path with high weight has higher probability to be selected than the path with low weight. • A rule of thumb • the weight should be inversely proportionally to the distance of the route, i.e, W~ 1/D • when r = 0, Wi = 1/K • when r = , Wi = 1/Di if Di < Dj for any j, o.w. 0

  23. Dest Dest Dest Dest Dist Dist Dist Dist hop hop hop hop A, H15 A, H15 A, H15 A, H15 7 6 10 5 R11 R9 R7 R9 A, H16 A, H16 A, H16 A, H16 9 4 6 7 R12 R12 R16 R9 R13 R10 R7 R10 A, H17 A, H17 A, H17 A, H17 13 8 13 14 8 8 3 9 R10 R10 R14 R7 A, H18 A, H18 A, H18 A, H18 Routing table at R9 Routing table at R12 Routing table at R10 Routing table at R6 Ri 1 1 1 1 7 6 7 6 R3 R1 R2 R4 * * 4 2 3 1 1 1 1 * 1 1 1 1 5 6 6 R7 5 R6 R8 R5 2 1 2 3 5 3 R9 R10 4 6 1 3 4 2 * 5 1 * R16 H2 H17 H4 H15 H8 H6 H7 H1 H5 Hi H16 H3 H18 2 R13 R11 R12 R14 4 4 2 2 Host Router with MIN-D H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} * 7 6 1 1 3 3 * * 1 1 1 R17 R18 R15 1 1 1 1 Link with distance 2 1 Link on a general graph Weight Assignment • Consider R12 with r=1 W15 = 0.24, W16 = 0.42, W17 = 0.13, and W18 = 0.21

  24. Performance Evaluation • Metrics: the average end-to-end delay • Evaluated systems: <α, β, γ> • α {SSP, MIN_D, SBT, CBT} • β {fixed, adaptive} • γ {independent, flow} • Network: ARPANET, one group with 5 members • Traffic: Poisson

  25. 0.040 0.040 SSP SSP MIN-D 0.035 GO 0.035 CBT SBT CBT DOR SBT 0.030 0.030 DOR 0.025 0.025 0.020 0.020 0.015 0.015 0.010 0.010 0.005 0.005 0.000 0.000 0.00 0.50 1.00 1.50 2.00 0.00 0.50 1.00 1.50 2.00 Throughput Throughput (b) <*, Fixed, Flow> (a) <*, Fixed, Non-Flow> 0.040 0.040 SSP SSP MIN-D 0.035 MIN-D CBT 0.035 CBT SBT SBT DOR 0.030 DOR 0.030 0.025 0.025 0.020 0.020 0.015 0.015 0.010 0.010 0.005 0.005 0.000 0.000 0.00 0.50 1.00 1.50 2.00 0.00 0.50 1.00 1.50 2.00 Throughput Throughput (c) <*, Adaptive, Non-Flow> (d) <*, Adaptive, Flow> Evaluation Results

  26. Conclusion • Anycast motivation • Anycast address • Anycast membership management • Anycast routing • Multi-routing • loop-free routing methods • multiple path selection

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