The importance of informal communication on the Internet has been increasing in recent years. Several systems for informal communication have been developed. These systems, however, require a particular server and/or specialized 3D contents. In this paper, we propose a system, named InCom, for informal communication in a 3D virtual environment. Browsers which are component of InCom generate 3D virtual worlds from existing common 2D HTML documents. Browsers communicate in a peer-to-peer manner. Using avatars makes gaze awareness smooth. Our results show that users shared interests by gaze awareness.

Peer-to-peer complementary currencies can be powerful tools for promoting collaborations and building relationships on the Internet. i-wat is a proposed such currency based on WAT System, a polycentric complementary currency using WAT tickets as its medium of exchange. Participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. i-wat implements the tickets electronically by exchanges of messages signed in OpenPGP. This paper clarifies the trust model of i-wat, and investigates how it is related with that of PGP. To implement the model by dynamically building an appropriate web of trust (WOT), we claim that it would suffice if the behaviors of participants satisfy the following three properties: 1. mutual signing by knowing, or any two mutual acquaintances sign the public keys of each other, 2. mutual signing by participation, or the drawer and a user of an i-wat ticket sign the public keys of each other, and3. mutual full trust by participation, or the drawer and a user of an i-wat ticket fully trust each other, and a recipient fully trust the corresponding user of a ticket, in the context of PGP public key signing.Likelihood of satisfaction of these properties is supported by the (dis)incentives imposed by the semantics of i-wat. A reference implementation of i-wat has been developed in the form of a Jabber instant messaging client. We are beginning to put the currency system into practical use.

Wireless LANs (Local Area Networks) are currently spreading over diverse places such as hotels and airports, as well as offices and homes. Consequently, they provide convenient and important ways to access the Internet. Another type of communication model, Peer-to-Peer (P2P) communication on the Internet, has also attracted much attention, and P2P over wireless LANs will soon be very common. There are concerns about the capability of wireless stations (STAs) to send a large amount of traffic on an uplink. In this paper, we first clarify some issues that arise in this context by examining the feature of the Access Point(AP). Furthermore, we consider the role of the AP and propose, as a solution, ways of enabling both efficient and fair transmission over both the downlink and uplink. We evaluate the proposed schemes through simulations and show that communications over the uplink and downlink can share the wireless LAN access resource effectively. Furthermore, we show that coordinating our solution with the 802.11e Enhanced Distributed Channel Access (EDCA) can meet the different requirements of various types of traffic.

Many P2P lookup services based on distributed hash tables (DHT) have appeared recently. These schemes are built upon overlay networks and ignore distance to the target resources. As a result, P2P lookups often suffer from unnecessarily long routes in the underlay network, which we call overlay dilation. This paper proposes a new scheme for resource routing, called hybrid hierarchical overlay routing, dubbed Hyho. We introduce distance-weighted Bloom filters (dwBFs) as a concise representation of routing information for scattered resources in overlay networks. To further reduce the size of Bloom filters, so that they are linear in the number of distinct resources, Hyho splits overlay networks in accordance with DHT, where each subnetwork has a smaller set of resources and spans the entire network thinly. As a result, Hyho constructs a hierarchical overlay network and routes requests accordingly. Simulation results show that Hyho can reduce overlay dilation to one half that yielded by the Chord lookup service.

Availability of network access "anytime and anywhere" will impose new requirements to presence services - server load sharing and privacy protection. In such cases, presence services would have to deal with sensor device information with maximum consideration of user's privacy. In this paper, we propose FieldCast: peer-to-peer system architecture for presence information exchange in ubiquitous computing environment. According to our proposal, presence information is exchanged directly among user's own computing resources. We illustrate our result of evaluation that proves the feasibility of our proposal.

This paper outlines and analyses major P2P technologies currently being actively studied at various research organisations or already in use in both business and personal environments. Various technical features of P2P as well as its history and market trends are shown. P2P principles focussing on discovery and network-organisational mechanisms of major P2P systems such as JXTA, SIONet, Freenet, and Chord are first summarised. Also, other technical issues related to delivery, network control, security, digital rights management, and distributed computing are described. Then, P2P technologies to promote next-generation community networks with autonomous and intelligent characteristics are addressed. Based on these, P2P applications are analysed and some examples are shown. Studies of P2P traffic measurement, which is difficult by using traditional evaluation methods, are taken up to consider total network design in the P2P era.

Traditional Web cache servers based on HTTP and ICP infrastructure tend to have higher hardware and management cost, have difficulty in availability, automatic and dynamic reconfiguration, and may have slow links to some users. We find that peer-to-peer technology can help solve these problems. The peer cache service (PCS) we proposed here leverages each peer's local cache, similar access patterns, fully distributed coordination, and fast communication channels to enhance response time, scale of cacheable objects, and availability. Moreover, incorporating goals and strategies such as making the protocol lightweight and mutually compatible with existing cache infrastructure, supporting mobile devices, undertaking dynamic three-level caching, and exchanging cache meta-information further improve the effectiveness and differentiate our work from other similar-at-first-glance P2P Web cache systems.

Gnutella's service announcement in March 2000 stirred worldwide interest by referring to P2P model. Basically, the P2P model needs not the broker "the centralized management server" that until now has figured so importantly in prevailing business models, and offers a new approach that enables peers such as end terminals to discover out and locate other suitable peers on their own without going through an intermediary server. It seems clear that the wealth of content made available by peer-to-peer systems like Gnutella and Freenet have spurred many authors into considering how meta-data might be used to support more effective search in a distributed environment. This paper has reviewed a number of these systems and attempted to identify some common themes. At this time the major division between the different approaches is the use of a hash-based routing scheme.