Peer Connections Research Articles

Dynamic Transmission Scheduling for Streaming Applications via P2P Overlay

In current Peer-to-Peer streaming applications, a lot of research attempts to provide timely stream services to the end users. Most of them focus on how to organize the peer connections into an efficient overlay network. Due to the variation in the network, a lot of overhead is generated when the overlay structure adapts to the changes. In order to minimize the impact of network fluctuation, we proposed a scheduling algorithm which helps to distribute stream data efficiently through the fluctuating networks. It needs only partial information about overlay structure and provides the services to satisfy most number of users. The global latency experienced by peers in the system is thus minimized. To alleviate the problem of packet loss along the overlay, we introduce retransmission requests into our scheduling algorithm. Requests for much needed data are treated with higher priority. Parent peers which receive the request will re-send the missing data to minimize the loss impact. The missing data which are needed by more peers will have a larger cumulative impact through the tree overlay and these are thus scheduled and sent earlier. Simulation results showed that our prioritization and scheduling algorithm minimizes the negative impact of fluctuation and data loss in a dynamic network environment.

Content and overlay-aware scheduling for peer-to-peer streaming in fluctuating networks

Due to the scalability of peer-to-peer structure, it is widely applied in multimedia streaming applications to provide services for large number of clients concurrently. A lot of research work has been done on improving the data distribution efficiency by adapting the overlay structure to the dynamically changing networks. Instead of changing overlay structure, we propose a data packet scheduling algorithm to improve transmission efficiency of the streaming system. Our scheduling algorithm distributedly prioritizes the data packets and sends the most important data to the whole system first. It avoids wasting network resources while frequently switching peer connections. The algorithm serves to provide an optimal ordering solution to minimize overall latency based on overlay structure information. With the help of content-aware weighting scheme, the scheduling algorithm also improves the streaming quality at the peers. Our algorithm shows good performance even under a dynamic and challenging network environment with negligible algorithm overhead.

Improving peer connectivity in wide-area overlays of virtual workstations

Self-configuring virtual networks rely on structured P2P routing to provide seamless connectivity among nodes through overlay routing of virtual IP packets, support decentralized hole-punching to establish bi-directional communication links among nodes behind network address translators, and dynamic configuration of virtual IP addresses. Our experiences with deployments of virtual networks in support of wide-area overlays of virtual workstations (WOWs) reveal that connectivity constraints imposed by symmetric NATs and by Internet route outages often hinder P2P overlay structure maintenance and routability, subsequently limiting the ability of WOWs to deliver high-throughput computing through aggregation of resources in different domains.In this paper, we describe and evaluate two novel approaches which are generally applicable and fully decentralized, and show that they improve routability of structured P2P networks in such connectivity constrained environments: (1) a fault-tolerant routing algorithm based on simulated annealing from optimization theory, and (2) tunneling of connections between adjacent nodes (in the P2P identifier space) over common neighbors when direct communication is not possible. Simulation-based analyses show that (1) when pairs of nodes only have 70% chance of being able to communicate directly, the described approaches improve all-to-all routability of the network from 90% to 99%, and (2) even when only 70% of the nodes are behind NATs that include symmetric NATs, these techniques improve the all-to-all connectivity of the network from less than 95% to more than 99%. We have implemented these techniques in the IP-over-P2P (IPOP) virtual network and have conducted experiments with a 180-node WOW Condor pool, demonstrating that, at 81% probability of establishing a pair-wise connection, annealing and tunneling combined allow all nodes to be connected to the pool, compared to only 160 nodes in the absence of these techniques.

SELF‐ORGANIZING PEER‐TO‐PEER SOCIAL NETWORKS

Peer‐to‐peer (P2P) systems provide a new solution to distributed information and resource sharing because of its outstanding properties in decentralization, dynamics, flexibility, autonomy, and cooperation, summarized as DDFAC in this paper. After a detailed analysis of the current P2P literature, this paper suggests to better exploit peer social relationships and peer autonomy to achieve efficient P2P structure design. Accordingly, this paper proposes Self‐organizing peer‐to‐peer social networks (SoPPSoNs) to self‐organize distributed peers in a decentralized way, in which neuron‐like agents following extended Hebbian rules found in the brain activity represent peers to discover useful peer connections. The self‐organized networks capture social associations of peers in resource sharing, and hence are called P2P social networks. SoPPSoNs have improved search speed and success rate as peer social networks are correctly formed. This has been verified through tests on real data collected from the Gnutella system. Analysis on the Gnutella data has verified that social associations of peers in reality are directed, asymmetric and weighted, validating the design of SoPPSoN. The tests presented in this paper have also evaluated the scalability of SoPPSoN, its performance under varied initial network connectivity and the effects of different learning rules.

Families, Urban Neighborhood Youth Centers, and Peers as Contexts for Development

Abstract: Three social contexts—family, neighborhood youth centers, and peer relationships—were examined in relation to several measures of adjustment among 1,406 mostly minority, inner‐city adolescents. Family and center involvement were directly related to 3 of the 4 adjustment measures (i.e., achievement orientation, emotion regulation, attitudes toward school). Peer connections interacted with family and center involvement to also predict these variables. Substance use, the fourth adjustment measure, was related only to family involvement. Significant 3‐way interactions suggested that within urban settings, favorable attitudes toward school may best be achieved when family, neighborhood youth center, and peer involvement are all strong. The combined effects of these 3 contexts appear to be greater among younger adolescents. Implications for promoting urban youth development programs are discussed.

Peer Play Interventions To Support the Social Competence of Children with Autism Spectrum Disorders

Children with autism spectrum disorders (ASD) have difficulty connecting with others because they often lack the communication, social interaction, and play skills necessary for developing relationships with their peers. This article highlights the characteristics of four peer intervention programs described in the literature that have been successful in facilitating the social connections between children with ASD and their typical peers. The environments established for intervention, the role of the typical peer, and the role of the adult are described across the four programs. A fifth peer intervention program is introduced that focuses on establishing peer connections in the home of the child with ASD while facilitating bids and responses for behavior regulation, social interaction, and joint attention in the child with ASD and his or her typical peer in the context of play. Implications for practice are provided as clinicians consider the role peer mediation has in intervention planning and implementation for children with ASD.

Practicing What We Preach: Creating Groups for Ourselves

ABSTRACT This article focuses on the professional isolation faced by social group work practitioners and educators. It identifies the need for peer support and connection in an environment of limited opportunities for professional development. The paper describes and assesses long-term peer support groups initiated and developed by each of the authors, one for group work educators and the other for practitioners. It discusses the potential for expanding the development of such groups, which could benefit individual group workers as well as strengthen efforts to ensure the survival of group work.

Managing distributed objects in peer-to-peer systems

Peer-to-peer systems that dynamically organize, interact and share resources are increasingly being deployed in large-scale environments. The location, intermittent connectivity, and organization of the peers have significant impact on meeting the quality of service requirements of distributed applications. This article presents the design, implementation, and empirical evaluation of a middleware architecture for managing distributed objects in peer-to-peer systems. The architecture consists of a self-organizing infrastructure that uses only local knowledge to dynamically form overlays of multiple peers and respond to changing processing and networking conditions; and a management layer that monitors the behavior of the applications transparently, schedules object invocations over multiple machines, and obtains accurate resource projections. The system works in a two-level feedback loop structure that uses measurements of elapsed time and resource loads to refine the initial estimates and revise the peer connections. Our empirical evaluation shows that the system manipulates the peer connections dynamically in response to changes in resource utilization to meet application end-to-end soft real-time requirements.

Emotional resilience: risk and protective factors for depression among alternative education students in New Zealand.

A total of 268 alternative education students from New Zealand were surveyed to examine risk and protective factors for depression within the social environment. Twenty-eight (35.4%) of the girls and 31 (21.1%) of the boys had cut-off scores that indicated a high likelihood of significant psychopathology from depression. Multivariate analysis demonstrated that family and peer connections were protective against depression. High levels of poverty, witnessing violence at home, and experiencing bullying at school were significant risk factors for depression.

Assessing the Reliability and Validity of Student Self-Reports of Campus Violence

Responses of adolescents who failed reliability and/or validity checks on a school climate and violence questionnaire (n = 109) were compared with a randomly selected matched group of students (n = 109) who answered consistently and accurately. Results indicated significant differences between the two groups on indexes of school violence victimization, perceived danger at school, peer connections, and course grades. The most critical finding was that students with invalid and/or unreliable responses reported significantly more violence victimizations than the comparison group. The need for research addressing the accuracy of school violence self-reports and concerns about the accuracy of existing school violence prevalence information are discussed.

Mothers' personal social networks and child maltreatment.

The social networks of 32 mothers in families being treated in a hospital-based program for indicated cases of child abuse and neglect were compared to the networks of a demographically comparable control group of 24 mothers whose children were not subject to maltreatment. The clinic mothers were found to be more isolated and more insulated from other people in their -networks. Their isolation reflected a deficiency primarily in their peer connections, and their insularity served to separate their immediate families from their peer connections and from the rest of their families. Child and adolescent maltreatment has become more noticeable to the public in recent years as our information-gathering systems have become more efficient and reports issued have revealed its deleterious effects on children (American Health Association, 1976; American Humane Association, 1978; Konopka, 1975; Straus, Gelles, & Steinmetz, 1980; Child Protective Services, Note 1). Severe maltreatment of children by members of their families is unsanctioned by all social communities. There are cultural differences in disciplinary child-rearing practices that share some of the attributes of violence, as described in Erlanger's (1974) review, but nevertheless, there are limits and standards set by all social groups regulating such behavior and specifying the contexts in which and the extent to which it is permitted. The behavior we are concerned with, child maltreatment severe enough to be indicated by Child Protective Services, falls outside these limits and is considered a problem in every social group. Its persistence within the

Developments in the Presidency and the Conception of Political Leadership

leader groups and their superiors was, for the most part, amorphous. When the leaders' immediate superiors were excluded from the field, the upper status group displayed greater competitive predilection, but these data were not conclusive. Since there was no exploration of the caste barrier existing between commissioned and non-commissioned officers, these findings should be interpreted with caution. In the main sample, as leaders ascended the noncommissioned hierarchy, their behavior more closely approached commissioned group expectancies, while quite the opposite was true of the old and presumably less promotable sergeants in the age-controlled experimental test group. Statistics on relative vertical mobility by rank were not available, but one might conjecture that if rigid controls were employed in sample selection, a mere definition of the parameters of each group's interaction universe might lead to findings substantially similar to those revealed in this study. With further refinement, a set of measures gauging the leader's subordinate and peer connections might assist in determining leadership effectiveness. They might further serve as rough predictors of probable leadership success.