Resilient multicast using overlays
We introduce Probabilistic Resilient Multicast (PRM): a multicast data recovery scheme that improves data delivery ratios while maintaining low end-to-end latencies. PRM has both a proactive and a reactive components; in this paper we describe how PRM can be used to improve the performance of application-layer multicast protocols especially when there are high packet losses and host failures. Through detailed analysis in this paper, we show that this loss recovery technique has efficient scaling properties-the overheads at each overlay node asymptotically decrease to zero with increasing group sizes. As a detailed case study, we show how PRM can be applied to the NICE application-layer multicast protocol. We present detailed simulations of the PRM-enhanced NICE protocol for 10 000 node Internet-like topologies. Simulations show that PRM achieves a high delivery ratio (>97%) with a low latency bound (600 ms) for environments with high end-to-end network losses (1%-5%) and high topology change rates (5 changes per second) while incurring very low overheads (<5%).

title: Distribution of path durations in mobile ad-hoc networks - Palm's Theorem to the rescue
abstract: We first study the distribution of path duration in multi-hop wireless networks. We show that as the number of hops along a path increases, the path duration distribution can be accurately approximated by an exponential distribution under a set of mild conditions, even when the link duration distributions are not identical. Then, we develop an approximate model for computing the distribution of link duration under a Random Waypoint (RWP) mobility model, and demonstrate that the path duration distribution converges to an exponential distribution with increasing number of hops. Simulation results obtained using ns-2 simulator are provided to validate the analysis.

title: Backbone construction in selfish wireless networks
abstract: We present a protocol to construct routing backbones in wireless networks composed of selfish participants. Backbones are inherently cooperative, so constructing them in selfish environments is particularly difficult; participants want a backbone to exist (soothers relay their packets) but do not want to join the backbone (so they do not have to relay packets for others).
 We model the wireless backbone as a public good and use impatience as an incentive for cooperation. To determine if and when to donate to this public good, each participant calculates how patient it should be in obtaining the public good. We quantify patience using the Volunteer's Timing Dilemma (VTD), which we extend to general multihop network settings. Using our generalized VTD analysis, each node individually computes as its dominant strategy the amount of time to wait before joining the backbone. We evaluate our protocol using both simulations and an implementation. Our results show that, even though participants in our system deliberately wait before volunteering, a backbone is formed quickly. Further, the quality of the backbone (such as the size and resulting network lifetime) is comparable to that of existing backbone protocols that assume altruistic behavior.

title: Efficient geographic routing in multihop wireless networks
abstract: We propose a new link metric called normalized advance (NADV) for geographic routing in multihop wireless networks. NADV selects neighbors with the optimal trade-off between proximity and link cost. Coupled with the local next hop decision in geographic routing, NADV enables an adaptive and efficient cost-aware routing strategy. Depending on the objective or message priority, applications can use the NADV framework to minimize various types of link cost.We present efficient methods for link cost estimation and perform detailed simulations in diverse scenarios. Our results show that NADV outperforms current schemes in many aspects: for example, in high noise environments with frequent packet losses, the use of NADV leads to 81% higher delivery ratio. When compared to centralized routing under certain settings, geographic routing using NADV finds paths whose cost is close to the optimum.

title: A new wireless ad hoc multicast routing protocol
abstract: An ad hoc network is a multi-hop wireless network of mobile nodes without the intervention of fixed infrastructure. Limited bandwidth and mobility require that ad hoc routing protocols be robust, simple, and energy conserving. This paper proposes a new ad hoc multicast routing protocol called neighbor-supporting multicast protocol (NSMP). NSMP adopts a mesh structure to enhance resilience against mobility. And NSMP utilizes node locality to reduce the overhead of route maintenance. NSMP also attempts to improve route efficiency and reduce data transmissions. Our simulation results show that NSMP delivers packets efficiently while substantially reducing control overhead in various environments.

title: On-Demand Multicast Routing Protocol in Multihop Wireless Mobile Networks
abstract: An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile ad hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation.

title: ARMS: An Authenticated Routing Message in Sensor Networks
abstract: In wireless sensor networks, a sensor node broadcasts its data (such as routing information, beacon messages or meta-data) to all its neighbors, which is called local broadcast. A general case for a sensor node to use a local broadcast is to advertise its routing information. Considering that sensor networks are vulnerable to a variety of attacks and current routing protocols are insecure, a sensor node's broadcast message should be authenticated by all its neighbors. Unfortunately, the previous work on broadcast authentication in sensor networks mainly concentrates on broadcast messages from a base station which has greater capabilities, not from a sensor node. Those schemes' properties are not appropriate for broadcast authentication of sensor node's routing messages. In this paper, we present ARMS, a protocol for broadcast authentication of sensor node's routing messages. It requires only a small memory space, authenticates routing messages without delay (thus, no buffering is needed), needs no time synchronization among sensor nodes, and mitigates the effect of packet loss. These ARMS' properties are suitable for a sensor node to broadcast an authenticated routing message.

title: SmartSeer: Using a DHT to Process Continuous Queries Over Peer-to-Peer Networks
abstract: As the academic world moves away from physical journals and proceedings towards online document repositories, the ability to efficiently locate work of interest among the torrent of newly-generated papers will become increasingly important. To aid in this endeavor, we designed SmartSeer, a system that allows users to register personalized continuous queries over the CiteSeer database of technical documents. Users are then alerted whenever papers that match their queries are put online. SmartSeer has two main design requirements. First, to allow effective information retrieval, it should support rich continuous queries (as opposed to simple keyword searches). Second, to make effective use of donated infrastructure, it should be capable of running on a loosely maintained group of unreliable machines spread across multiple organizations (as opposed to assuming a reliable and tightly coupled distributed system). Existing work on distributed continuous query systems fails at least one of these requirements. Our design for SmartSeer is based on Distributed Hash Tables (DHTs), and thereby leverages previous work on DHT-based query systems. A prototype of SmartSeer has been implemented and evaluated on Planetlab. Though we evaluate our design only for the SmartSeer application, we believe it also provides useful insights into other distributed and rich continuous query systems (web alerts, news alerts etc).

title: Wireless Ad Hoc Multicast Routing with Mobility Prediction
abstract: An ad hoc wireless network is an infrastructureless network composed of mobile hosts. The primary concerns in ad hoc networks are bandwidth limitations and unpredictable topology changes. Thus, efficient utilization of routing packets and immediate recovery of route breaks are critical in routing and multicasting protocols. A multicast scheme, On-Demand Multicast Routing Protocol (ODMRP), has been recently proposed for mobile ad hoc networks. ODMRP is a reactive (on-demand) protocol that delivers packets to destination(s) on a mesh topology using scoped flooding of data. We can apply a number of enhancements to improve the performance of ODMRP. In this paper, we propose a mobility prediction scheme to help select stable routes and to perform rerouting in anticipation of topology changes. We also introduce techniques to improve transmission reliability and eliminate route acquisition latency. The impact of our improvements is evaluated via simulation.

title: NCL: A common language for achieving rule-based interoperability among heterogeneous systems
abstract: For achieving interoperability among heterogeneous computing systems, the Object Management Group (OMG) has adapted the Common Object Request Broker Architecture (CORBA) and the use of an Interface Definition Language (IDL) for specifying object properties and operations which encapsulate the data and programs of heterogeneous systems. This paper describes a common language which is an enhancement of IDL to include: 1) the semantic richness of EXPRESS, an information modeling language adapted by the ISO/STEP community for achieving product model and data exchange; and 2) the extensibility features and knowledge rule specification offered by the Object-oriented Semantic Association Model (OSAM*). This common language, named the NIIIP Common Language (NCL), is a part of the R&D effort of a project entitled the National Industrial Information Infrastructure Protocols (NIIIP). The design of NCL is standards-based, incorporating the semantic features of the two standard languages, IDL and EXPRESS, and conforming to their syntaxes as much as possible. It is an extensible language which supports the addition of new class, constraint, and association types to the language and its underlying object model in order to satisfy the diverse modeling needs of virtual enterprises. The language also contains a high-level rule specification component. Rules in NCL can be used for defining and enforcing integrity and security constraints, government or enterprise policies and regulations, and other types of semantic constraints that are local or global to heterogeneous systems. In this paper, we shall show how such a modeling language and its supporting KBMS functions can be used to achieve rule-based interoperability in an active heterogeneous system as an enhancement to OMG's CORBA.