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Thesis Proposal . Data Consistency in DHTs. Background. Peer-to-peer systems have become increasingly popular Lots of P2P applications around us File sharing, file storage, Real time broadcasting, … Advantages of P2P system Scalable load balance, fault-tolerant, low-cost deployment
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Thesis Proposal Data Consistency in DHTs
Background • Peer-to-peer systems have become increasingly popular • Lots of P2P applications around us • File sharing, file storage, Real time broadcasting, … • Advantages of P2P system • Scalable • load balance, • fault-tolerant, • low-cost deployment • Why is it so magic?
Core of P2P • Each peer is a server and a client • DHT • Every peer can find each other and cooperate • A hashed ID maps to a peer or an object • The object would be stored on the closest peer
Usages of DHT • Directory service • Very little amount of information, such as URI, metadata, … • Don’t need to modified • Storage • Data, such as files, … • Immutable, only for downloading and uploading • What is the next?
Mutable DHT • Most of DHT are for immutable data • Immutable • Data wouldn’t be modified • Operations of DHT • ping, search, publish • Mutable • Data would be modified • Operations of DHT • ping, search, publish, delete, modified
What is the challenge? • Churn • Peer join, leave, fail randomly • Replica • Fault-tolerant • Problem • Object consistency • Replicas are consistent on different nodes
What is the challenge? • Network dynamic • Partial unreachability • Problem • Key consistency • Only one node is the root of a key
Related work • Consensus system • Primary data maintainer • Clients modify the data on primary one • Do consensus algorithm • After data modified • After churn happened • Quorum system • No primary one • Clients try to lock every replica before modifying
Related work • Authorization • Contact the original closest one • Get Authorized token of the closer partition • Be the root of the partition
Questions • Is key consistency really a big assumption on realistic environment? • For what kind of churn and mutability, do we need a strong consistency mechanism? • The importance of key and data consistency mechanisms • If we can guarantee only one of them, than what is the result on different situations?
Experimental Plan • Create a realistic network environment for simulation • Result of data consistency on different churn and mutability • DHT without any mechanism • DHT with key consistency mechanism • DHT with data consistency mechanism • DHT with key and data consistency mechanisms
Network Environment for Simulation • Partial unreachability • Path outage probability of internet • Path outage duration and inter-duration • Distribution of Node up and down • Statistics of real p2p network • Topology • Hierarchical topology (few depth of AS’) • BRITE
References • Non-Transitive Connectivity and DHTs • Key consistency in DHTs • Toward Fault-tolerant Atomic Data Access in Mutable Distributed Hash Tables • Etna: a Fault-tolerant Algorithm for Atomic Mutable DHT Data • PaxonDHT: Achieving Consensus in Distributed Hash Tables • MUREX: A Mutable Replica Control Scheme for Structured Peer-to-Peer Storage Systems • A Practical Distributed Mutual Exclusion Protocol in Dynamic Peer-to-Peer Systems • An Experimental Study of the Skype Peer-to-Peer VoIP System • Actively Monitoring Peers in KAD • An Analysis of Network Reachability Using BGP Data • PlanetSeeer: Internet Path Failure Monitoring and Characterization in Wide-Area services • Quantifying the Effects of Routing dynamics on End-to-End Internet Path Failures