Three applications for mobile epidemic algorithms

This paper presents a framework for the pervasive sharing of data using wireless networks. 'FarCry' uses the mobility of users to carry files between separated networks. Through a mix of ad-hoc and infrastructure-based wireless networking, files are transferred between users without their direct involvement. As users move to different locations, files are then transmitted on to other users, spreading and sharing information. We examine three applications of this framework. Each of these exploits the physically proximate nature of social gatherings. As people group together in, for example, business meetings and cafés, this can be taken as an indication of similar interests, e.g. in the same presentation or in a type of music. MediaNet affords sharing of media files between strangers or friends, MeetingNet shares business documents in meetings, and NewsNet shares RSS feeds between mobile users. NewsNet also develops the use of pre-emptive caching: collecting information from others not for oneself, but for the predicted later sharing with others. We offer observations on developing this system for a mobile, multi-user, multi-device environment

Domino: exploring mobile collaborative software adaptation

Social Proximity Applications (SPAs) are a promising new area for ubicomp software that exploits the everyday changes in the proximity of mobile users. While a number of applications facilitate simple file sharing between co–present users, this paper explores opportunities for recommending and sharing software between users. We describe an architecture that allows the recommendation of new system components from systems with similar histories of use. Software components and usage histories are exchanged between mobile users who are in proximity with each other. We apply this architecture in a mobile strategy game in which players adapt and upgrade their game using components from other players, progressing through the game through sharing tools and history. More broadly, we discuss the general application of this technique as well as the security and privacy challenges to such an approach

Epidemic Dissemination of Presence Information in Mobile Instant Messaging Systems

This paper presents an approach for exchanging presence information between users of an instant messaging system in a mobile ad hoc network. As major feature, presence information is transferred when mobile users get in direct contact, similar to the spread of an infections disease. By exploiting node mobility, presence information is epidemically distributed throughout the network, effectively overcoming network partitions. We show how to apply the Passive Distributed Indexing Protocol, which implements a general-purpose lookup service for mobile applications building upon epidemic data dissemination, for implementing the exchange of presence information. The effectiveness of the approach is illustrated in a simulation study using the network simulator ns-2. Building upon the results, we present the architecture of a mobile instant messaging system that supports the widely adopted Extensible Messaging and Presence Protocol (XMPP), an IETF standardized protocol for instant messaging

Updated Data Dissemination for Applications with Time Constraints in Mobile Ad Hoc Networks

In our previous work, we proposed few updated data dissemination methods to refresh old replicas efficiently in mobile ad hoc networks. These methods disseminate updated data items every time when owners of original data items update the items or every time two mobile hosts are newly connected with each other and this causes heavy traffic in the entire network. In this paper, we assume applications that periodically execute read operations with strict deadlines to data items and propose few alternative updated data dissemination methods. These methods reduces the traffic for data dissemination while keeping a high success ratio for read operations

Diffusion of Digital Products in Peer-to-Peer Networks

Peer-to-peer (P2P) networks are fast emerging as a viable and cost effective alternative for content delivery on the Internet. By offering rebates to users who share content with others, incentives can be provided to address the well-documented problem of free riding. A primary value proposition of P2P networks is their ability to scale well and facilitate fast distribution of digital products. While the fast diffusion of products in P2P networks has generated substantial interest in P2P, rigorous theoretical studies of the diffusion process have been in absence. Our paper provides one of the first analytical studies of the diffusion process in P2P networks. Starting with an analogy between P2P diffusion and epidemic diffusion, we develop a stochastic diffusion model for flat P2P networks. We find that product diffusion, in P2P networks is likely to follow classic S-shaped processes. Next, we develop a deterministic approximation that is computationally efficient. The model allows a content publisher to analyze the diffusion process, evaluate the impact of offering rebates on product diffusion and also determine the optimal rebate to offer by trading off the reduced margins with the faster diffusion of the product. Finally, we expand our study to account for generation of multiple requests and forwarding of requests in P2P networks. The analytical models presented in this paper serve as a starting point for rigorous modeling and study of content diffusion in P2P networks

Consistency mechanisms for a distributed lookup service supporting mobile applications

This paper presents a general-purpose distributed lookup service, denoted Passive Distributed Indexing (PDI). PDI stores entries in form of (key, value) pairs in index caches located in each mobile device. Index caches are filled by epidemic dissemination of popular index entries. By exploiting node mobility, PDI can resolve most queries locally without sending messages outside the radio coverage of the inquiring node. Thus, PDI reduces network traffic for the resolution of keys to values. For keeping index caches coherent, configurable value timeouts implementing implicit invalidation and lazy invalidation caches implementing explicit invalidation are introduced. Inconsistency in index caches due to weak connectivity or node failure is handled by value timeouts. Lazy invalidation caches reduce the fraction of stale index entries due to modified data at the origin node. Similar to index caches, invalidation caches are filled by epidemic distributions of invalidation messages. Simulation results show that with the suitable integration of both invalidation mechanisms, more than 95% of results delivered by PDI index caches are up-to-date for the considered scenario

Exploiting epidemic data dissemination for consistent lookup operations in mobile applications

This paper presents a general-purpose distributed lookup service, denoted Passive Distributed Indexing (PDI). PDI stores entries in form of (key, value) pairs in index caches located at mobile devices. Index caches are filled by epidemic dissemination of popular index entries. By exploiting node mobility, PDI can resolve most queries locally without sending messages outside the radio coverage of the inquiring node. For keeping index caches coherent, configurable value timeouts implementing implicit invalidation and lazy invalidation caches implementing explicit invalidation are introduced. Inconsistency in index caches due to weak connectivity or node failure is handled by value timeouts. Lazy invalidation caches reduce the fraction of stale index entries due to modified data at the origin node. Similar to index caches, invalidation caches are filled by epidemic distributions of invalidation messages. We evaluate the performance of PDI for a mobile P2P file sharing a mobile instant messaging application. Simulation results show that with the suitable integration of both invalidation mechanisms, up to 80% of the lookup operations return correct results and more than 90% of results delivered by PDI index caches are up-to-date

Diffusion Models for Peer-to-Peer (P2P) Media Distribution: On the Impact of Decentralized, Constrained Supply

In Peer-to-Peer (P2P) media distribution, users obtain content from other users who already have it. This form of decentralized product distribution demonstrates several unique features. Only a small fraction of users in the network are queried when a potential adopter seeks a file and many of these users may even free-ride i.e. not distribute the content to others. As a result, generated demand may not always be fulfilled immediately. We present mixing models for product diffusion in P2P networks that capture decentralized product distribution by current adopters, incomplete demand fulfillment and other unique aspects of P2P product diffusion. The models serve to demonstrate the important role that P2P search process and distribution referrals – payments made to users that distribute files – play in efficient P2P media distribution. We demonstrate the ability of our diffusion models to derive normative insights for P2P media distributors by studying the effectiveness of distribution referrals in speeding product diffusion and determining optimal referral policies for fully decentralized and hierarchical P2P networks