Availability Simulation of Peer-to-Peer Architectural Styles Simon - PowerPoint PPT Presentation

Availability Simulation of Peer-to-Peer Architectural Styles Simon Giesecke, Timo Warns, Wilhelm Hasselbring Referee: Timo Warns

Motivation  Evaluation of availability of P2P services  Specifics of P2P context impacting availability  Failure distribution of peers  Means of handling failures  Dynamic architecture / topology  How to integrate these aspects?  Focus: Architectural Style 2 Availability Simulation of Peer-to-Peer Architectural Styles

Approach  Conceptual framework  P2P styles Architectural Style Fault  P2P architectures Characteristics  P2P systems Architecture  Evaluation by simulation Real-World Simulated  “most real-world systems are System System too complex to allow realistic models to be evaluated analytically” Predicted Actual Availability Law and Kelton, 2000 Availability  Flexible 3 Availability Simulation of Peer-to-Peer Architectural Styles

Peer-to-Peer Styles  Classification scheme Server Peer  Type of decentralization Peer  Decentralized, hybrid, super-peer Peer Peer  Type of communication  Direct, Indirect, Mediated Peer Peer Peer  Structural Characteristics Super Super  Ring, Tree, Small-World Network Peer Peer  Rules for evolution Peer Peer Super  Joining / leaving of peers Peer Peer  No formalisation yet Peer 4 Availability Simulation of Peer-to-Peer Architectural Styles

Architecture Description Model  Graph-based formalism A = (N, C, ν, λ, τ)  N, C – Sets of nodes and connections  ν: C →{{n 1 , n 2 } | n 1 ≠ n 2 and n 1 , n 2 in N} – Node function  λ: N → L – Labelling function  L is a set of node labels (e.g., “Peer”, “Server”, ...)  τ: T → NC T – Time mapping  τ describes evolution over time  E.g., peer p participates at system from t n to t m => p is in image of τ for t in [t n , t m [ 5 Availability Simulation of Peer-to-Peer Architectural Styles

Example Description Model [t 0 , t 1 [  N = {p 1 , ..., p 4 } Peer p 1 c 1 c 2  C = {c 1 , ..., c 5 } c 3 Peer Peer p 3 p 2  λ(n) = Peer for all n in N [t 1 , t 2 [ Peer Peer  τ:  ν: p 1 c 1 p 4 c 2 c 4 c ν(c) T NC T c 3 Peer Peer c 1 {p 1 , p 3 } p 3 p 2 [t 0 , t 1 [ p 1 , ..., p 3 , c 1 , ..., c 3 c 2 {p 1 , p 2 } [t 1 , t 2 [ p 1 , ..., p 4 , c 1 , ..., c 4 c 5 c 3 {p 2 , p 3 } [t 2 , t 3 [ [t 2 , t 3 [ p 1 , ..., p 4 , c 1 , ..., c 5 Peer Peer p 1 c 4 {p 3 , p 4 } c 1 p 4 c 2 c 4 c 5 {p 1 , p 4 } c 3 Peer Peer p 3 p 2 6 Availability Simulation of Peer-to-Peer Architectural Styles

Simulation  Prototype of simulator 4,50 ROWA 4,25  Based on graph formalism 4,00 Majority Consensus 3,75  Peer model 3,50 3,25 3,00 Relative Change in %  Derived from real-world 2,75 2,50 2,25 system 2,00 1,75  Enhanced by classic 1,50 1,25 replication strategies 1,00 0,75  Evaluation of availability of 0,50 0,25 0,00 replicated resources -0,25 1 2 3 4 5 6 7 8 9 10 11 12 Scenario Class 7 Availability Simulation of Peer-to-Peer Architectural Styles

Conclusions  Conceptual framework  Evaluation of availability of P2P services  Architectural styles, architectures, systems  Classification scheme for architectural styles  Description model for P2P architectures  Simulator prototype 8 Availability Simulation of Peer-to-Peer Architectural Styles

Future Work  Formalisation of architectural styles  Graph grammars?  Benefit: Automated creation of architectures  Formalisation of peer model  Add peer model to input for simulation  UML?  Development of improved simulator  Prototype used manually created architectures and one fixed peer model 9 Availability Simulation of Peer-to-Peer Architectural Styles