Destination Peer Research Articles

Mediation of Lazy Update Propagation in a Replicated Database over a Decentralized P2P Architecture

While replicating data over a decentralized Peer-to- Peer (P2P) network, transactions broadcasting updates arising from different peers run simultaneously so that a destination peer replica can be updated concurrently, that always causes transaction and data conflicts. Moreover, during data migration, connectivity interruption and network overload corrupt running transactions so that destination peers can experience duplicated data or improper data or missing data, hence replicas remain inconsistent. Different methodological approaches have been combined to solve these problems: the audit log technique to capture the changes made to data; the algorithmic method to design and analyse algorithms and the statistical method to analyse the performance of new algorithms and to design prediction models of the execution time based on other parameters. A Graphical User Interface software as prototype, have been designed with C #, to implement these new algorithms to obtain a database synchronizer-mediator. A stream of experiments, showed that the new algorithms were effective. So, the hypothesis according to which “The execution time of replication and reconciliation transactions totally depends on independent factors.” has been confirmed.

Place matters: The impact of place of residency on racial attitudes among regional and urban migrants

Scholars have debated whether racial attitudes are socialized early in life and persist throughout one’s lifetime or are open to influences from one’s environment as an adult. This study introduces another approach that holds that place, as opposed to the timing of socialization, is an important consideration for the socialization of racial attitudes. Using data from the American National Election Study, we consider the effect of region and urban residency on racial attitudes by comparing lifelong residents of these locations to those who migrate into and out of them. Using improved measures of early life socialization and region of residency, we conclude that a place-based model can be used to explain the socialization of racial resentment. For regional migrants, those moving into and out of the non-South maintain levels of racial resentment similar to non-Southern stayers. For urban migrants, the lifelong openness model of socialization was most appropriate. These migrants were more likely to change and adopt the level of racial resentment similar to that of their destination peers. These findings generally persist across time.

An Effective Scheme for Performance Improvement of P2P Live Streaming Systems

To solve the problems of long start-up latency, low playback continuity and data distribution rate in P2P live streaming system, this paper proposes two optimization strategies. One is an adaptive peer selection algorithm based on peers' real-time service ability. In the algorithm, a simple but effective method is proposed to calculate the peers' ability. And source peer adjusts the amount of requested data and the priority of destination peers according to the destination peers' abilities and the limit of out-degree. Thus a load balance and efficiently system can be constructed. The other one is a push-pull combination data distribution mechanism. This mechanism adaptively chooses push or pull model to distribute data fast and efficiently. The results show that the strategies have a significant effect on reducing start-up latency and control message overhead and improving the playback continuity and data distribution rate.

A Routing Scheme Considering Mobility in Mobile Peer-to-peer Networks

Recently, with the development of wireless communication technology and the wide usage of mobile devices such as PDAs, netbooks, and smart phones, interests on mobile P2P networks have been increased. Location based routing schemes considering the mobility of mobile devices in order to provide mobile P2P services were proposed. However, the existing schemes cause high communication costs since they broadcast the messages to a whole network to create routing paths. In this paper, we propose a new location based routing scheme to efficiently create routing paths along with the mobility of mobile devices. The proposed scheme maintains the information of peers within 2-hop in order to reduce the costs of routing path searches. The proposed scheme searches the routing path considering the directionality of the destination peer and maintains it using the connectivity of peers. It was shown through performance evaluation that the proposed scheme outperforms the existing schemes.

3D P2P overlay over MANETs

We study the challenging problems of the mismatch between the overlay and the physical network and the resilience of the overlay structure in peer-to-peer (P2P) protocols over a mobile ad hoc network (MANET). Existing P2P protocols have used inflexible overlay structures to arrange peers and do not consider intra-neighbor relationships of peers when assigning logical identifiers. The intra-neighbor relationships of peers are crucial to exactly interpret the physical proximity of peers in an overlay and to avoid the mismatch between the overlay and the physical network that causes extensive routing overhead, larger average file discovery delay, increased false-negative ratio, and high average path-stretch. In this paper, we present a novel P2P overlay over MANETs that exploits a 3-dimensional overlay and 3D space that takes into account the physical intra-neighbor relationship of a peer and exploits a 3D-overlay to interpret that relationship. In the proposed protocol, each peer runs a distributed algorithm that exploits a 3D-overlay to calculate a consecutive logical identifier to a peer. Moreover, the protocol utilizes the 3D-overlay to maintain multi-paths to a destination peer that provides resilience against a node/link failure. Simulation results show that the proposed 3D-overlay outperforms the existing P2P overlay protocol in terms of routing overhead, average file-discovery delay, false-negative ratio, and average path-stretch.

P2P Networks Considering Sybil-Proof with the Reputation of Social Link

In P2P networks, malice peers forge identity to interrupt routing, called Sybil attack. To avoid it, methods in related works consider routing as random walk. Since the destination of random walk is hard to predict, Sybil-proof P2P networks need large routing information to support routing. However, a large size routing table constrains the scalability of the system. Therefore, we aim to develop a routing algorithm to satisfy the requirement of P2P networks which has a good performance at Sybil-Proof by using a reasonable size of routing table. Social links are useful to prevent a Sybil attack because friend peers have little chance to be a Sybil peer. In this proposed method, reputation of social link is useful for achieving this objective. Considering the distance to destination peers can help for routing efficiency and considering the reputation can make routing to have better performance resisting Sybil-attacks.

Securing Information in PeertoPeer Environment

emerging model of communication and computation, Peer-to-Peer(P2P) networking has recently gained significant acceptance in today's internet computing, Suffers from the problem of securing information while transferring from one peer to other peer. In existing direct path was established between source and destination peer to secure the data. We analyzed the problem of security and constructing direct path between source and destination peer which led p2p systems might compromise user privacy. To overcome the above issue we proposed an algorithm to find out the optimal path among the existing paths, through which the information can be sent and received. To enhance the system performance by implementing security measures we compared two asymmetric cryptographic algorithm with our application model(ICRQR),which is decentralized and unstructured and proved that p2p reputation model is more secured and hence increases the system performance.

Expertise-based peer selection in Peer-to-Peer networks

Peer-to-Peer systems have proven to be an effective way of sharing data. Modern protocols are able to efficiently route a message to a given peer. However, determining the destination peer in the first place is not always trivial. We propose a model in which peers advertise their expertise in the Peer-to-Peer network. The knowledge about the expertise of other peers forms a semantic topology. Based on the semantic similarity between the subject of a query and the expertise of other peers, a peer can select appropriate peers to forward queries to, instead of broadcasting the query or sending it to a random set of peers. To calculate our semantic similarity measure, we make the simplifying assumption that the peers share the same ontology. We evaluate the model in a bibliographic scenario, where peers share bibliographic descriptions of publications among each other. In simulation experiments complemented with a real-world field experiment, we show how expertise-based peer selection improves the performance of a Peer-to-Peer system with respect to precision, recall and the number of messages.

순수 P2P 네트워크 환경에서 에이전트 이주를 위한 자원 예약 기반 동적 부하 균형 기법

이동 에이전트는 자율성을 가지고 비동기적으로 수행이 가능한 개체로, 네트워크상의 여러 호스트들을 이동하면서 사용자를 대신해 특정한 작업을 수행하고 다른 에이전트들과 상호 협력할 수 있는 프로세스로 정의된다. 현재 이동 에이전트는 전자 상거래, 이동 통신, 병렬처리, 정보의 검색 및 복구 둥 여러 분야에서 사용된다. 그러나 순수 P2P 환경에서 컴퓨팅 자원을 사용하고자 하는 이동 에이전트들이 이주할 피어의 가용한 자원을 고려하지 않고 이주할 경우, 이주된 에이전트로 인해 해당 시스템의 부하가 증가 된다는 문제점이 발생하게 된다. 이러한 문제점을 해결하기 위해 본 논문에서는 각 피어들에 상주하는 자원 관리 에이전트를 이용하여 부하 정보를 모니터링 하고 이주할 에이전트와 목적지 피어를 결정하게 된다. 이동 에이전트가 이주하는 과정에서 특정 피어의 자원이 예약 선점 되었을 경우 해당 자원이 다른 에이전트에게 할당되는 것을 방지하는 자원 예약 기법을 기반으로 피어들 간의 균형 있는 이주 기법을 제안한다. Mobile agents are defined as processes which can be autonomously delegated or transferred among the hosts in a network in order to perform some computations on behalf of the user and co-operate with other agents. Currently, mobile agents are used in various fields, such as electronic commerce, mobile communication, parallel processing, search of information, recovery, and so on. In pure P2P network environment, if mobile agents that require computing resources rashly migrate to another peers without consideration on the peer's capacity of resources, the peer may have a problem that the performance of the peer is degraded due to lack of resources. To solve this problem, we propose resource reservation based load balancing scheme of using RMA(Resource Management Agent) that monitors workload information of the peers and that decides migrating agents and destination peers. In mobile agent migrating procedure, if the resource of specific peer is already reserved, our resource reservation scheme prevents other mobile agents from allocating the resource.