The 25 papers in this special issue focus on simple wireless sensor networking solutions.

The twenty-one papers in this special issue are devoted to peer-to-peer communications and their applications. Covers such topics as: overlay networks, searching, video streaming, files and servers, and theories and applications.

Multihop mobile wireless networks, characterized by volatile state and limited resources, present a challenging environment for effective and efficient route selection. In such networks, nodes may be restricted in their use of resources for obtaining state information and making routing decisions and often may have to base their decisions on incomplete or out-of-date information. In this paper, we compare six variants of well-known routing algorithms with respect to their communication, computation, and memory demands and the characteristics of the routes they produce. We show that algorithms that probabilistically select routes based upon locally-available state information derived through dynamic programming techniques result in efficient use of transmission capacity and hence hold promise for use in highly-dynamic networks with limited resources.

As networks grow in scale and heterogeneity, hierarchical organization is inevitable. We present the case for optimal self-organization of network hierarchies. We provide a graph partitioning formulation relevant to networking but different from extant graph partitioning literature. In particular, we require that the resultant partitions be connected, a constraint that changes the character of the problem significantly. We devise a solution that consists of distinct phases for initial partitioning, refinement and post-processing, propose efficient heuristics for each phase, and evaluate them extensively on internetwork-like graphs through simulation. The results suggest that vertex trading techniques, in vogue for a number of decades in graph partitioning, are highly applicable, but multilevel techniques favored by conventional graph partitioning research may be of limited value for internetwork-like graphs. This solution can be implemented in practical networks to automatically generate Internet OSPF areas or ATM PNNI clusters.

Multihop mobile wireless networks offer a means for providing a rapidly-deployable and fluid network infrastructure that enables "on-the-move" communications among nodes that may be widely-dispersed over a large area. These networks experience frequent changes in node interconnectivity and link characteristics, resulting from node movements and environmental changes. Such volatility in network state presents challenges in maintaining a desired quality of service over the life of a session, particularly if the session involves many participants. We have developed, simulated, and tested a network architecture designed to support distributed multimedia sessions in a multihop mobile wireless network. In this paper, we focus on the functions of construction, maintenance, and use of multipoint virtual circuits for transporting session traffic among mobile nodes.

Internetworks that are global in scale, contain multiple administrative domains, and support a range of services present special requirements for routing. Multiple administrative domains introduce the need for policy-sensitive routing. Service heterogeneity intensifies the requirement for type of service (TOS) routing, as well as other protocol support for handling a range of services, from datagrams to multimedia streams. Key concepts and protocols developed as part of the interdomain policy routing (IDPR) architecture are summarized. Emphasis is placed on the route installation and packet forwarding mechanisms because they are critical to protocol performance and differ significantly from current practice in datagram wide area networks.>