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

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

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

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

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

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.

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

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

Loop-free Routing Ordered routing Methods to order the routers 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

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.

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

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.

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

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.

The SBT Method R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R14 R13 R12 R11 R15 R16 Link with distance Link on a SBT tree rooted at R3 Ri Router H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} Hi Host Dest Dist hop A, H15 A, H16 A, H17 A, H18 14 9 Routing table at R6 * 13 8 Routing table at R9 10 Routing table at R7 11 Routing table at R3

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

The CBT Method R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R14 R13 R12 R11 R15 R16 Ri Router H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} Hi Host Dest Dist hop A, H15 A, H16 A, H17 A, H18 10 9 8 Routing table at R10 Routing table at R7 13 Routing table at R9 Routing table at R12 * Link with distance Link on a CBT tree rooted at R7 Link on the truncated DBTs

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

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

Weight Assignment Consider R12 with r=1 Dest Dist hop A, H15 A, H16 A, H17 A, H18 10 R7 9 R12 8 R13 3 R14 Routing table at R10 6 R9 7 14 R10 Routing table at R6 5 R11 13 Routing table at R9 4 R16 Routing table at R12 * 1 H1 H2 H6 H7 H8 H15 H4 H17 H18 H5 2 R1 R2 R3 R4 R5 R6 R8 R15 H16 R17 R18 H3 Link with distance Link on a general graph H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18} Hi Ri Router with MIN-D Host Consider R12 with r=1 W15 = 0. 24, W16 = 0.42, W17 = 0.13, and W18 = 0.21

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

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

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