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Network Sharing Issues Lecture 15 Aditya Akella
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Is this the biggest problem in cloud resource allocation? Why? Why not? How does the problem differ wrt allocating other resources? FairCloud: Sharing the Network in Cloud Computing, Sigcomm 2012 What are the assumptions? Drawbacks?
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Motivation Network?
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Context Networks are more difficult to share than other resources X
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Context Several proposals that share network differently, e.g.: – proportional to # source VMs (Seawall [NSDI11]) – statically reserve bandwidth (Oktopus [Sigcomm12]) –…–… Provide specific types of sharing policies Characterize solution space and relate policies to each other?
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FairCloud Paper 1.Framework for understanding network sharing in cloud computing – Goals, tradeoffs, properties 2.Solutions for sharing the network – Existing policies in this framework – New policies representing different points in the design space
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Goals 1.Minimum Bandwidth Guarantees – Provides predictable performance – Example: file transfer finishes within time limit A1A1 A2A2 Time max = Size / B min B min
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Goals 1.Minimum Bandwidth Guarantees 2.High Utilization – Do not leave useful resources unutilized – Requires both work-conservation and proper incentives A BBB Both tenants activeNon work-conservingWork-conserving
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Goals 1.Minimum Bandwidth Guarantees 2.High Utilization 3.Network Proportionality – As with other services, network should be shared proportional to payment – Currently, tenants pay a flat rate per VM network share should be proportional to #VMs (assuming identical VMs)
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Goals 1.Minimum Bandwidth Guarantees 2.High Utilization 3.Network Proportionality – Example: A has 2 VMs, B has 3 VMs A1A1 A2A2 Bw A B1B1 B3B3 B2B2 Bw B Bw A = 2 3 When exact sharing is not possible use max-min
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Goals 1.Minimum Bandwidth Guarantees 2.High Utilization 3.Network Proportionality Not all goals are achievable simultaneously!
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Tradeoffs Min Guarantee High Utilization Network Proportionality Not all goals are achievable simultaneously!
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Tradeoffs Min Guarantee Network Proportionality
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Tradeoffs Bw B Bw A AB Access Link L Capacity C Bw B = 11/13 C Bw A = 2/13 C 10 VMs Network Proportionality Bw A ≈ C/N T 0 #VMs in the network Bw B = 1/2 C Bw A = 1/2 C Minimum Guarantee Min Guarantee Network Proportionality
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Tradeoffs High Utilization Network Proportionality
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Tradeoffs L B1B1 B3B3 B2B2 B4B4 A1A1 A3A3 A2A2 A4A4 High Utilization Network Proportionality
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Tradeoffs L B1B1 B3B3 B2B2 B4B4 A1A1 A3A3 A2A2 A4A4 Bw B = 1/2 C Bw A = 1/2 C Network Proportionality High Utilization Network Proportionality
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Tradeoffs L B1B1 B3B3 B2B2 B4B4 A1A1 A3A3 A2A2 A4A4 P High Utilization Network Proportionality Uncongested path
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Tradeoffs L B1B1 B3B3 B2B2 B4B4 A1A1 A3A3 A2A2 A4A4 Bw B Bw A < Network Proportionality L L Tenants can be disincentivized to use free resources If A values A 1 A 2 or A 3 A 4 more than A 1 A 3 Bw A +Bw A = Bw B L L P P High Utilization Network Proportionality Uncongested path
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Network Proportionality Tradeoffs L B1B1 B3B3 B2B2 B4B4 A1A1 A3A3 A2A2 A4A4 P Network proportionality applied only for flows traversing congested links shared by multiple tenants High Utilization Uncongested path Congestion Proportionality
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Network Proportionality Tradeoffs L B1B1 B3B3 B2B2 B4B4 A1A1 A3A3 A2A2 A4A4 Uncongested path P Bw B Bw A = Congestion Proportionality L L High Utilization Congestion Proportionality
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Network Proportionality Tradeoffs Still conflicts with high utilization High Utilization Congestion Proportionality
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Tradeoffs B1B1 B3B3 A1A1 A3A3 B2B2 B4B4 A2A2 A4A4 L2L2 C 1 = C 2 = C Network Proportionality High Utilization L1L1 Congestion Proportionality
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Tradeoffs B1B1 B3B3 A1A1 A3A3 B2B2 B4B4 A2A2 A4A4 L1L1 L2L2 Bw B Bw A = Congestion Proportionality L1 Bw B Bw A = L2 Network Proportionality High Utilization C 1 = C 2 = C Congestion Proportionality
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Tradeoffs B1B1 B3B3 A1A1 A3A3 B2B2 B4B4 A2A2 A4A4 L1L1 L2L2 Demand drops to ε Network Proportionality High Utilization C 1 = C 2 = C Congestion Proportionality
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Tradeoffs B1B1 B3B3 A1A1 A3A3 B2B2 B4B4 A2A2 A4A4 ε C - ε ε Tenants incentivized to not fully utilize resources Network Proportionality High Utilization C 1 = C 2 = C Congestion Proportionality L1L1 L2L2
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Tradeoffs B1B1 B3B3 A1A1 A3A3 B2B2 B4B4 A2A2 A4A4 ε C - 2 ε Uncongested ε C - ε L1L1 L2L2 C 1 = C 2 = C Network Proportionality High Utilization Tenants incentivized to not fully utilize resources Congestion Proportionality
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L2L2 Tradeoffs B1B1 B3B3 A1A1 A3A3 B2B2 B4B4 A2A2 A4A4 ε C - 2 ε C/2 Uncongested C 1 = C 2 = C Network Proportionality High Utilization Congestion Proportionality Tenants incentivized to not fully utilize resources L1L1
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Tradeoffs Proportionality applied to each link independently Congestion Proportionality Link Proportionality Network Proportionality High Utilization L2L2 B1B1 B3B3 A1A1 A3A3 B2B2 B4B4 A2A2 A4A4 L1L1
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L2L2 Tradeoffs B1B1 B3B3 A1A1 A3A3 B2B2 B4B4 A2A2 A4A4 Full incentives for high utilization Congestion Proportionality Link Proportionality Network Proportionality High Utilization L1L1
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Goals and Tradeoffs Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality
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Guiding Properties Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Break down goals into lower-level necessary properties
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Properties Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality
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Work Conservation Bottleneck links are fully utilized Static reservations do not have this property
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Properties Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation
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Utilization Incentives Tenants are not incentivized to lie about demand to leave links underutilized Network and congestion proportionality do not have this property Allocating links independently provides this property
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Properties Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives
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Communication-pattern Independence Allocation does not depend on communication pattern Per flow allocation does not have this property – (per flow = give equal shares to each flow) Same Bw
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Properties Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives Comm-Pattern Independence
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Symmetry Swapping demand directions preserves allocation Per source allocation lacks this property – (per source = give equal shares to each source) Same Bw
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Goals, Tradeoffs, Properties Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives Comm-Pattern Independence Symmetry
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Outline 1.Framework for understanding network sharing in cloud computing – Goals, tradeoffs, properties 2.Solutions for sharing the network – Existing policies in this framework – New policies representing different points in the design space
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Per Flow (e.g. today) Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives Comm-Pattern Independence Symmetry
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Per Source (e.g., Seawall [NSDI’11]) Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives Comm-Pattern Independence Symmetry
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Static Reservation (e.g., Oktopus [Sigcomm’11]) Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives Comm-Pattern Independence Symmetry
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New Allocation Policies 3 new allocation policies that take different stands on tradeoffs
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Proportional Sharing at Link-level (PS-L) Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives Comm-Pattern Independence Symmetry
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Proportional Sharing at Link-level (PS-L) Per tenant WFQ where weight = # tenant’s VMs on link A B WQ A = #VMs A on L Bw B Bw A = #VMs A on L #VMs B on L Can easily be extended to use heterogeneous VMs (by using VM weights)
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Proportional Sharing at Network-level (PS-N) Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives Comm-Pattern Independence Symmetry
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Proportional Sharing at Network-level (PS-N) Congestion proportionality in severely restricted context Per source-destination WFQ, total tenant weight = # VMs
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Proportional Sharing at Network-level (PS-N) WQ A1 A2 = 1/N A1 + 1/N A2 A1A1 A2A2 N A2 N A1 Total WQ A = #VMs A Congestion proportionality in severely restricted context Per source-destination WFQ, total tenant weight = # VMs
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Proportional Sharing at Network-level (PS-N) WQ B WQ A = #VMs A #VMs B Congestion proportionality in severely restricted context Per source-destination WFQ, total tenant weight = # VMs
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Proportional Sharing on Proximate Links (PS-P) Min Guarantee Link Proportionality High Utilization Congestion Proportionality Network Proportionality Work Conservation Utilization Incentives Comm-Pattern Independence Symmetry
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Assumes a tree-based topology: traditional, fat-tree, VL2 (currently working on removing this assumption) Proportional Sharing on Proximate Links (PS-P)
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Assumes a tree-based topology: traditional, fat-tree, VL2 (currently working on removing this assumption) Min guarantees – Hose model – Admission control Proportional Sharing on Proximate Links (PS-P) A1A1 Bw A1 A2A2 Bw A2 AnAn Bw An …
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Assumes a tree-based topology: traditional, fat-tree, VL2 (currently working on removing this assumption) Min guarantees – Hose model – Admission control High Utilization – Per source fair sharing towards tree root Proportional Sharing on Proximate Links (PS-P)
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Assumes a tree-based topology: traditional, fat-tree, VL2 (currently working on removing this assumption) Min guarantees – Hose model – Admission control High Utilization – Per source fair sharing towards tree root – Per destination fair sharing from tree root Proportional Sharing on Proximate Links (PS-P)
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Deploying PS-L, PS-N and PS-P Full Switch Support – All allocations can use hardware queues (per tenant, per VM or per source-destination) Partial Switch Support – PS-N and PS-P can be deployed using CSFQ [Sigcomm’98] No Switch Support – PS-N can be deployed using only hypervisors – PS-P could be deployed using only hypervisors, we are currently working on it
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Evaluation Small Testbed + Click Modular Router – 15 servers, 1Gbps links Simulation + Real Traces – 3200 nodes, flow level simulator, Facebook MapReduce traces
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Many to one Bw B Bw A AB N One link, testbed PS-P offers guarantees Bw A N
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MapReduce One link, testbed Bw B Bw A 5 R5 M M+R = 10 M Bw B (Mbps) PS-L offers link proportionality
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MapReduce Network, simulation, Facebook trace
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MapReduce Network, simulation, Facebook trace PS-N is close to network proportionality
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MapReduce Network, simulation, Facebook trace PS-N and PS-P reduce shuffle time of small jobs by 10-15X
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Summary Sharing cloud networks is not trivial First step towards a framework to analyze network sharing in cloud computing – Key goals (min guarantees, high utilization and proportionality), tradeoffs and properties New allocation policies, superset properties from past work – PS-L: link proportionality + high utilization – PS-N: restricted network proportional – PS-P: min guarantees + high utilization What are the assumptions, drawbacks?
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