Presentation on theme: "SCALABLESCALABLE Ankit Singla, P. Brighten Godfrey Kevin Fall, Sylvia Ratnasamy, Gianluca Iannaccone ON."— Presentation transcript:
SCALABLESCALABLE Ankit Singla, P. Brighten Godfrey Kevin Fall, Sylvia Ratnasamy, Gianluca Iannaccone ON
Scalable Routing N UMBER OF N ODES = n N OT V ERY S CALABLE ! S HORTEST -P ATH R OUTING ? R OUTING S TATE /N ODE
Scalable Routing S TRUCTURED T OPOLOGIES 3 4, 11 6, 20 But, what about general topologies?
Scalable Routing H IERARCHY Inefficient Location-dependent addressing s t 4
Why Not DNS/DHTs? Arbitrarily long paths! 5 W HERE IS A? A R IGHT N EXT TO Y OU, S ILLY !
Local Name Resolution Why local name-resolution matters – Google: 400ms delay = 0.59% searches/user – Time for name-resolution is a significant fraction of latency for short flows (which are the majority) – Fate sharing property 6
Address Dissemination Predecessor, successor and small O(1) number of fingers Distance-vector style dissemination of addresses 23 Increasing h()
1: Overlay Topology Predecessor, successor and small O(1) number of fingers – Fault tolerance: Use landmarks to fix overlay when broken – Miserly messaging: each node hears each address O(1) times – We don’t care about routing, only diameter, which is small! Increasing h() 24
2: Dissemination Protocol Disseminate new addresses learnt to overlay neighbors Record where each address was learnt from (distance vector-like) Always forward away from the direction received from – Avoids count-to-infinity problem because of ordered space Increasing h() 25
Handling Failures: Example No soft-state required! Update only on changes Increasing h() G ET N EW N EIGHBOR F ROM L ANDMARK W ITHDRAW A DDRESSES L EARNT FROM X 26 X
Routing in Disco 27 w(t) s computes h(t) w(t) = Longest-prefix match for h(t) in Vicinity(s) First : s w(t) L(t) t Later: s L(t) t s t L(t)
Protocol Messages Estimating ‘n’: synopses exchanged with neighbors Landmark and Vicinity updates: path vector style Sloppy-group bootstrap through landmarks Address-dissemination: distance-vector style 28 s
Evaluation Protocols – Disco – NDDisco – S4 [Mao et al ‘07] – VRR [Caesar et al ‘06] refer to paper Topologies – Router-level Internet topology (n = 192,244) – AS-level Internet topology (n = 30,610) – Geometric random graphs, mean degree 8 – G(n, m), mean degree 8 30
State S HORTEST P ATH P ROTOCOL 31 NDD ISCO S4 G EOMETRIC R ANDOM G RAPHS OF I NCREASING S IZE
State 32 L ONG T AIL S4 D ISCO NDD ISCO R OUTER -L EVEL I NTERNET T OPOLOGY
First-Packet Stretch G EOMETRIC RANDOM GRAPH 16384- NODES R OUTER -L EVEL I NTERNET T OPOLOGY 33 72 L ARGE F IRST -P ACKET S TRETCH D ISCO S4 D ISCO L IMITED BY S MALL P ATH - LENGTHS IN T OPOLOGY
Later-Packets Stretch G EOMETRIC RANDOM GRAPH 16384- NODES R OUTER -L EVEL I NTERNET T OPOLOGY 34 D ISCO < 1.2 N EAR -I DENTICAL S4 D ISCO
Are the Landmarks Clobbered? AS-L EVEL I NTERNET T OPOLOGY 35 ~4 IN EVERY 10,000 EDGES SEE MORE CONGESTION D ISCO
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