A Distributed Algorithm for the
Replica Placement Problem
Caching and replication of popular data objects contribute significantly to the reduction of the network bandwidth usage and the overall access time to data. Our focus is to improve the efficiency of object replication within a given distributed replication group.
Such a group consists of servers that dedicate certain amount of memory for replicating objects requested by their clients. The content replication problem we are solving is defined as follows: Given the request rates for the objects and the server capacities, find the replica allocation that minimizes the access time over all servers and objects. We design a distributed approximation algorithm that solves this problem and prove that it provides a 2-approximation solution. We also show that the communication and computational complexity of the algorithm is polynomial with respect to the number of servers, the number of objects, and the sum of the capacities of all servers. Finally, we perform simulation experiments to investigate the performance of our algorithm. The experiments show that our algorithm outperforms the best existing distributed algorithm that solves the replica placement problem.
EXISTING SYSTEM
- REPLICATION of popular data objects at a server closer to the users can improve the access time for the users and reduce the network bandwidth usage as well.
- Several methods have been proposed for preserving consistency of data operations on replicas in MANETs.
- In the existing systems authors proposed methods in which the consistency is maintained by employing a strategy based on the quorum system that has been proposed for distributed databases.
- In existing system, the authors extended the methods proposed in by applying probabilistic quorum system.
- Their methods are considered similar to ours because consistency of data operations is maintained based on the quorum system. However, the authors aimed to roughly keep the consistency in the entire network. Therefore, the locality in MANETs was not taken into account.
PROPOSED SYSTEM
- Details of the system model are given as follows:
- Each mobile host (peer) knows its current location by using some device such as GPS and moves around in the given area.
- The MANET consists of two kinds of mobile hosts; proxies and peers. A proxy is a specially designated peer who manages other peers in a specific region in the MANET.
- Each proxy and peer knows all proxies in the entire network. This assumption is easy to find in many real situations.
- If proxies are not within direct communication range of their neighboring proxies, communication packets are forwarded via other peers in a multihop manner.
HARDWARE SPECIFICATION
Processor Type : Pentium -IV
Speed : 2.4 GHZ
Ram : 128 MB RAM
Hard disk : 20 GB HD
SOFTWARE SPECIFICATION
Operating system : Windows - XP
Tools : OMNET ++
REFERENCE:
Sharrukh Zaman and Daniel Grosu, “A Distributed Algorithm for the Replica Placement Problem”, IEEE Transactions on Parallel and Distributed Systems, Vol.22, 2011.
