The paper presents HiPeer, a robust resource distribution and discovery algorithm that can be used for fast and fault-tolerant location of resources in P2P network environments. HiPeer defines a concentric multi-ring overlay networking topology, whereon dynamic network management methods are deployed. In terms of performance, HiPeer delivers of number of lowest bounds. We demonstrate that for any De Bruijn digraph of degree d 2 and diameter DDB HiPeer constructs a highly reliable network, where each node maintains a routing table with at most 2d+2 entries independent of the number N of nodes in the system. Further, we show that any existing resource in the network with at most d nodes can be found within at most DHiPeer = log d(N(d-1)+d)-1 overlay hops. This result is as close to the Moore bound [1] as the query path length in other outstanding P2P proposals based on the De Bruijn digraphs. Thus, we argue that HiPeer defines a highly connected network with connectivity d and the lowest yet known lookup bound DHiPeer. Moreover, we show that any node's "join or leave" operation in HiPeer implies a constant expected reorganization cost of the magnitude order of O(d) control messages.

Application-level multicast (ALM) is a novel technology for multipoint applications, such as large scale file distribution, video and audio streaming, and video conferencing. Although many ALM mechanisms or algorithms have been proposed, all the multicast functions have been independently developed and integrated into individual applications. In such a situation, the development of ALM applications includes a lot of redundancy. Our goal is to improve the efficiency of developing ALM applications by reducing the development redundancy and to provide application developers with a middleware on which various ALM applications can be efficiently developed with minimum efforts. To this end, we develop a functional unit oriented ALM middleware, namely RelayCast. RelayCast provides a minimum but fundamental set of functionality as a functional unit, and constructs the basis on which additional and specific functions (i.e. codec, video capture, etc.) for each application are implemented. Some functional units contain several components with different algorithms, and RelayCast meets the requirements of various applications by choosing the appropriate component. In this paper, we propose RelayCast architecture, and present the implementation and experiments of a prototype.

This paper discusses effective configuration methods for peer-to-peer (P2P) network topologies within a mobile ad-hoc network. With recent progress in mobile ad-hoc network technology promoting the creation of new and attractive services, we are examining and developing P2P network systems for operation within ad-hoc networks. Our focus is on identifying methods of network-topology control that provide the best balance between performance and availability. We evaluate three methods through computer simulation and field trials from the viewpoints of resource consumption and network integrity, and clarify their domains of applicability. The results are expected to contribute to the design of future P2P networks for operation in mobile ad-hoc networks.

Application-level multicast (ALM) is a feasible alternative to IP multicast. In ALM, multicast related features, such as group membership management, multicast routing and packet replication, are implemented at end-hosts instead of routers. A multicast distribution tree is constructed in the application layer, so all nodes in this tree are end-hosts. Packet transmission between end-hosts uses conventional IP unicast service. Therefore, all end-hosts can enjoy multicast communications without IP multicast service. However, ALM has a serious problem that the multicast distribution tree is intrinsically fragile and an end-host failure causes tree partitions. In this paper, to deal with this problem, we propose a new tree construction protocol which makes outdegrees of intermediate nodes be balanced. The degree-balanced distribution tree can reduce the average number of nodes decoupled by tree partitions. To investigate performance of our protocol, it is compared with an existing ALM protocol. Our simulation results show that our protocol outperforms the existing protocol from the viewpoints of robustness, loss probability and receiver-perceived delay.

Interactive multimedia applications (IMAs) require not only adequate bandwidth to support large volume data transmission but also bounded end-to-end transmission delay between end users. This study proposes a Delay and Degree constrained Multicasting Spanning Tree (D2MST) algorithm to build an any-to-any share tree for IMAs. D2MST comprises root selection and spanning tree generation. A weighting function is defined based on the novel concept of network center and gravity to choose the root of a share tree. From the root, a spanning tree is built by incrementally connecting nodes with larger "power" to the tree so that the degree constraint is satisfied. Simulation results show that D2MST can successfully generate a Δ-constraint MST in which a high percentage of nodes can interact within the bounded delay.

Future wireless/mobile system is expected to have heterogeneous wireless overlay networks for ubiquitous multimedia communication. In a such network environment, mobile users are likely to try to get attached to higher bandwidth network as bandwidth-hungry multimedia applications are increasing. However, the users have to perform vertical handoff to lower bandwidth network, as high bandwidth network become unavailable due to various reasons (such as its limited coverage, network congestion, etc.). In this paper, we discuss the problem of vertical handoff from a user's perspective. For this purpose, we formulate user satisfaction as a function of bandwidth utility and handoff latency. Then, we investigate the effect of call holding time, user movement probability, etc. on the satisfaction that a user derives from the use of network service for multimedia applications. In addition, based on the evaluation, we present an algorithm for selecting a wireless network, which maximizes the effective user satisfaction.

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.

Connectionless data from existing network applications compose a large portion of the workload during an early ATM deployment, and are likely to make up an important portion of ATM's workload even in the long term. For providing a connectionless service over the ATM network, we compare two approaches; an indirect and a direct approaches, which are adopted by International Telecommunication Union-Telecommunication (ITU-T) as generic approaches. Our main subject of this paper is to compare network costs of two approaches by taking into account several cost factors such as transmission links, buffers, and connectionless servers in the case of the direct approach. Since the cost of the direct approach heavily depends on the configuration of a virtual connectionless overlay network, we propose a new heuristic algorithm to construct an effective connectionless overlay network topology. The proposed algorithm determines an optimal number of connectionless servers and their locations to minimize the network cost while satisfying QoS requirements such as maximum delay time and packet loss probability. Through numerical examples, we compare the indirect and direct approaches, the latter of which is constructed by means of our proposed algorithm.