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Lookup Service for Peer-to-Peer Systems in Mobile Ad-hoc Networks M. Tech Project Presentation By, Kalpesh Patel 02329027 Guided By, Dr. Sridhar Iyer, Dr. Krishna Paul. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 1 Outline • • • • • • • • Introduction Motivation Problem Definition Related Work RINGS : Lookup Service Analysis and Comparison Simulation Results Directions for Future Work and Conclusion 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 2 Introduction • Peer-to-Peer Systems • Nodes share files and services among other nodes in P2P network. • Mostly focuse on wired network. • Mobile Ad-hoc Networks • MANET is an autonomous system for mobile hosts over wireless links. • Multi-hop scenario. • Mobility. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 3 Motivation • Why P2P in MANET? • What happens if existing P2P protocols are deployed in MANET? – Neighbours at application layer may not necessarily be neighbours at network layer. • Problems with existing MANET protocols 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 4 Problem Definition • The overall objective is to efficiently deploy P2P applications in Mobile Ad-hoc Networks. • Specifically, need of a network layer protocol which optimizes query lookup service. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 5 Related Work • Mobile Peer-to-Peer Protocol (MPP) : Recent work on P2P in mobile environment. • Reference : Rudiger Schollmeier, Ingo Gruber, Michael Finkenzeller, Protocol for Peer-to-Peer Networking in Mobile Environments. • The problem is, MPP still relies on flooding at network layer. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 6 RINGS : Lookup Service • Basic Protocol - Advertisement • • • • Network layer gets index from application layer. Node broadcasts its data index into the network. Every K-hop nodes keep index for a given node. This process is followed by every node in the network. • Basic Protocol – Query lookup • Node forwards the query to its neighbors. • Due to equal distribution of indices throughout the network, query is answered within K/2 hops. • So, Upper bound for query lookup is K/2 hops. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 7 RINGS : Cont… • Basic protocol makes a set of imaginary circles for a given source node as shown in Fig.1. • Fig. 2 shows an example of 2-hop (K=2) scenario. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 8 RINGS : Cont… • Route Maintenance – Advertise packet maintains route to the source node. – This is accomplished by maintaining reverse route on the path. – A node, which stores the index, keeps this route along with other information. – If a query comes to this node, it responds with query result as well as route to the source. – An optimal route. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 9 RINGS : Cont… • Mobility – Mobility has none or little impact on the performance of the protocol. – In average, number of neighbors per node in mobile network can be taken as log(N). – So, even if as much as log(N) -1 nodes moves away from the network, node gets at least one node for query result. – Thus, a node gets at least one node which can satisfy its query even if L number of nodes from nearest circle leave the network, where L is, L (log( N ) 1) K / 2 Where K = 2, 4, 6, … 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 10 RINGS : Cont… • Optimization – Data Updates • Updates are sent to only those nodes which have stored indices for the source node. – Node Joining • Whenever a new node joins the network, it gets some share of indices from its neighbors. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 11 RINGS : Cont… • Node Deletion – Neighbors of leaving node search for an alternative route. – After getting alternative route, indices are reallocated according to index-hop (K) value. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 12 Analysis • Goal • Count the ‘actual’ query lookup cost for P2P protocol like ‘Chord’ in MANET. • The average distance d between any two nodes at the network layer can be taken as, d 2 N / • Now, query lookup cost for Chord in application layer is log(N). • Actual cost = App. Layer cost + Network layer cost. • So, effective lookup cost Lchord for chord protocol is, Lchord d * log( N ) 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 13 Analysis (Cont…) • For RINGS, – Query lookup cost at first hop is, LRINGS log( N ) • In turn, each of these log(N) nodes forwards query to its neighbors. • Continuing this way, query lookup cost at the nearest K-hop is, LRINGS log( N ) * (1 (log( N ) 1) (log( N ) 1) 2 ... ... (log( N ) 1) K / 21 ) 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 14 Simulation Results • An important measure is, how average number of remote indices stored per node increases as the value of K increases. • Result indicates that, as value of K increases, average number of remote indices per node increases very fast. • Value K = 4 balances both the metrics. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 15 Simulation Results (Cont…) • Graph shows comparison between query lookup costs Lchord and LRINGS • For the value of K = 4, RINGS performs better than Chord in terms of query lookup cost. • For the value of K = 6, as the number of nodes increases beyond a certain number, RINGS performs better than Chord. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 16 Comparison • Why RINGS? – Most recent work still relies on network layer flooding for query lookup. – Most adopted MANET protocols like AODV, DSR uses broadcast technique, results in flooding the whole network every-time when a search for a node requires. – P2P protocols • Gnutella uses broadcast. • Chord assigns every node a virtual identifier independent of actual locations, which is not preferable at network layer. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 17 Directions for Future Work • RINGS assumes enough storage space available at the node. There is a scope of improvement to reduce this overhead. • Effective mobility handling. • Practical applications. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 18 Conclusion • There is a need to combine P2P applications and Ad-hoc systems to share data among mobile users. • Current P2P protocols fail to perform well with this combination. • An initial step to this problem is RINGS, which focuses on query lookup cost optimization. 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 19 Thank You 09/07/2004 Peer-to-Peer Systems in Mobile Ad-hoc Networks 20