Peer-to-Peer SIP for Mobile Computing

Due to the increasing popularity of Peer-to-Peer (P2P) computing, the information technology industry and standardization organizations have started to direct their efforts on standardizing P2P algorithms and protocols. The Internet Engineering Task Force (IETF) has recently formed the Peer-to-Peer SIP (P2PSIP) working group for enabling serverless operation of Session Initiation Protocol (SIP). This chapter introduces the P2PSIP by presenting its background and purpose, operational principles, current status, and application areas. The focus is on the challenges and problem areas from the viewpoint of standardization and related research. The mobile- and heterogeneous environments are considered with special care. The authors provide a glance to the existing and emerging solutions that may be used in tackling the mentioned challenges and thus paving the way for successful deployment of P2PSIP in mobile environments.

Incentives for Resource Sharing in Ad Hoc Networks

The goal of this chapter is to analyze the incentive issues that arise in multi-hop ad hoc networks when their nodes are potentially mobile devices controlled by independent self-interested end-users. The author decomposes the problem into its economic and technological dimensions according to which he categorizes the numerous proposed solutions. He then analyzes certain drawbacks of the economics oriented approach and argues for the need to go beyond the rationality assumption. This is to exploit a variety of powerful more intrinsic, social, human motivations for encouraging participation and resource sharing in ad hoc networks. Existing successful online communities provide a good starting point for designing social software that can provide cross-layer social incentives for resource sharing. In this chapter, the author motivates this novel but challenging approach and provides some insights toward coming closer to its ambitious objective.

Cooperation Strategies for P2P Content Distribution in Cellular Mobile Networks

The performance of P2P content distribution in cellular networks depends highly on the cooperation and coordination of heterogeneous and often selfish mobile users. The major challenges are the identification of problems arising specifically in cellular mobile networks and the development of new cooperation strategies to overcome these problems. In the coherent previous chapter, the authors focused on the selfishness of users in such heterogeneous environments. This discussion is now extended by emphasizing the impact of mobility and vertical handover between different wireless access technologies. An abstract mobility model is required to allow the performance evaluation in feasible computational time. As a result, the performance in today’s and future cellular networks is predicted and new approaches to master heterogeneity in cellular networks are derived.

Wireless Peer-to-Peer Media Streaming

The widespread deployment of competing wireless technologies has created new research opportunities. In particular, the authors consider media streaming in hybrid wireless networks where each mobile device is equipped with two wireless network interfaces: server interface and peer interface. The server interface connects wireless clients to the server while the peer interface allows neighboring clients to communicate with one another. The two interfaces have different energy characteristics. In this chapter, the authors first give a brief account of P2P media streaming in wireless operating environments. They then survey and analyze the current state-of-the-art in tackling the security and performance issues in P2P media streaming systems. In view of the deficiencies of the existing approaches, they introduce new approaches based on game theoretic concepts. Specifically, the authors propose two collaborating relationships in which neighboring clients utilize both interfaces to share the energy cost of retrieving media content from the server. Their results show that the proposed relationships improve the streaming performance of peers without violating their energy consumption constraints. Moreover, both relationships are stable when clients neither unilaterally deviate nor voluntarily leave as a group.

P2P over MANETs

Both Mobile Ad hoc Networks (MANETs) and Peer-to-Peer (P2P) networks are decentralized self-organizing networks with a dynamic topology, used to route queries in a distributed environment. However, whilst MANETs are composed of resource-constrained devices susceptible to faults, P2P networks are popular for their resilience and fault-tolerance. This makes P2P networks the ideal data sharing system for MANETs. This chapter focuses on the integration of these networks. More specifically, the authors evaluate routing strategies of both the network layer and the application layer. Their results indicate that the performance of the protocols depends greatly on the environment and point out the need for new approaches.

Mobility Support in a P2P System for Publish/Subscribe Applications

Peer-to-Peer computing is a popular, relatively new, distributed computing paradigm. It allows for a flexible set of participants to coordinate their resources with little overhead or reliance on central servers/ services and is becoming particularly relevant in mobile computing environments, where peers come and go. Communication between an (unknown) number of peers, which may or may not be online at the same time, is greatly facilitated by the publish/subscribe model. In this chapter, the authors review the stateof- the-art in publish/subscribe systems, focusing on the support for mobile peers in infrastructure-based networks. They propose a novel handoff approach that proactively distributes pub/sub-related information to brokers/superpeers ahead of a peer’s movement. They show through extensive experiments in a small testbed that the new approach has significant performance benefits, compared to the more typical reactive approach, in which pub/sub context is only established after a handoff event occurred.

Context-Aware P2P Over Opportunistic Networks

Recently, the popularity of p2p computing paradigm has been increasing, especially in the mobile environments, due to the large use of mobile devices as tools to generate and share content among users. Several works have been proposed in ad hoc networks literature to optimize legacy p2p systems over a mobile environment, mainly relying on the necessity of a stable path between pairs of nodes wishing to communicate. However, in the last few years, resources limitations and high mobility of users have introduced a new networking paradigm characterized by intermittent connectivity and frequent partitioning: the opportunistic networks. In such a dynamic environment, where systems must exploit all communication opportunities to enable the users to get in touch and exchange data, the authors propose a novel definition of mobile p2p, which exploits context information to enhance distributed services. In addition, they present a Context-aware opportunistic File Sharing application as a practical example of an optimized p2p service over opportunistic networks.

Peer-Based Collaborative Caching and Prefetching in Mobile Broadcast

Caching and prefetching are two effective ways for mobile peers to improve access latency in mobile environments. With short-range communication such as IEEE 802.11 and Bluetooth, a mobile peer can communicate with neighboring peers and share cached or prefetched data objects. This kind of cooperation improves data availability and access latency. In this chapter the authors review several cooperative caching and prefetching schemes in a mobile environment that supports broadcasting. They present two schemes in detail: CPIX (Cooperative PIX) and ACP (Announcement-based Cooperative Prefetching). CPIX is suitable for mobile peers that have limited power and access the broadcast channel in a demand-driven fashion. ACP is designed for mobile peers that have sufficient power and prefetch from the broadcast channel. They both consider the data availability in local cache, neighbors’ cache, and on the broadcast channel. Moreover, these schemes are simple enough so that they do not incur much information exchange among peers and each peer can make autonomous caching and prefetching decisions.

Peer-to-Peer Networking Platform and Its Applications for Mobile Phones

Compared with traditional Internet technologies, peer-to-peer technologies has functions to realize resource discovery, resource sharing, and load balancing in a highly distributed manner. In addition to the Internet, new networks such as home network, ad-hoc network and sensor network are emerging. An easy prediction is the emergence of a new environment in which many sensors, people, and many different kinds of devices coexist, move, and communicate with one another over such heterogeneous networks. Peer-to-peer technology is one of the most important and suitable technologies for such ubiquitous networking since it supports discovery mechanisms, simple one-to-one communication, free and extensible distribution of resources, and distributed search to handle the enormous number of resources. The authors have designed and implemented a peer-to-peer networking platform for realizing applications, which include various applications for mobile phones. This chapter presents their peer-to-peer networking architecture, protocols, and applications for mobile phones.

Overlay Construction in Mobile Peer-to-Peer Networks

With the evolution of wireless technologies, mobile networks can provide much more interesting services and resources to users than before. Consequently storing, sharing and delivering resources efficiently have become popular topics in the field of mobile networks. Mobile Peer-to-Peer (the authors use mobile P2P for short hereinafter) networks, which are inspired by the great success of P2P networks, have been proposed to efficiently share the network resources among the peers in mobile networks. However, due to the characteristics of mobile networks and stringent constraints of applications, it is fairly difficult to construct mobile P2P networks. In this chapter, the authors present a survey of overlay construction in mobile P2P networks. First, they outline the design issues of running P2P networks on top of mobile networks. The authors then present a survey of existing overlay construction techniques for mobile P2P networks. They highlight the advantages and disadvantages of various overlay construction techniques for mobile P2P networks and further compare these methods. They also point out the open research issues in each sub-area and conclude with possible future research directions in mobile P2P overlay construction.