Existing multicast routing mechanisms were intended for use within regions where a group is widely represented or bandwidth is universally plentiful. When group members, and senders to those group members, are distributed sparsely across a wide area, these schemes are not efficient; data packets or membership report information are occasionally sent over many links that do not lead to receivers or senders, respectively. Wehave developed a multicast routing architecture that efficiently establishes distribution trees across wide area internets, where many groups will be sparsely represented. Efficiency is measured in terms of the state, control message processing, and data packet processing, required across the entire network in order to deliver data packets to the members of the group. Our Protocol Independent Multicast (PIM) architecture: (a) maintains the traditional IP multicast service model of receiver-initiated membership; (b) can be configured to adapt to different multicast group and network characteristics; (c) is not dependent on a specific unicast routing protocol; and (d) uses soft-state mechanisms to adapt to underlying network conditions and group dynamics. The robustness, flexibility, and scaling properties of this architecture make it well suited to large heterogeneous inter-networks.

Unlike static networks, ad-hoc networks have no spatial hierarchy and suffer from frequent link failures which prevent mobile hosts from using traditional routing schemes. Under these conditions, mobile hosts must find routes to destinations without the use of designated routers and also must dynamically adapt the routes to the current link conditions. This paper proposes a distributed adaptive routing protocol for finding and maintaining stable routes based on signal strength and location stability in an ad-hoc network and presents an architecture for its implementation. 1 Introduction Mobility is becoming increasingly important for users of computing systems. Technology has made possible wireless devices and smaller, less expensive, and more powerful computers. As a result users gain flexibility and the ability to maintain connectivity to their primary computer while roaming through a large area. The number of users with portable laptops and personal communications devices is increa...

In this paper, we study the NP-hard delay-constrained least-cost path problem, and propose a simple, distributed heuristic solution: the delay-constrained unicast routing (DCUR) algorithm. DCUR requires limited network state information to be kept at each node: a cost vector and a delay vector. We prove DCUR's correctness by showing that it is always capable of constructing a loop-free delay-constrained path within finite time, if such a path exists. The worst case message complexity of DCUR is O(|V|³) messages, where |V| is the number of nodes. However, simulation results show that,on the average, DCUR requires much fewer messages. Therefore, DCUR scales well to large networks. We also use simulation to compare DCUR to the optimal algorithm, and to the least-delay path algorithm. Our results show that DCUR's path costs are within 10% from those of the optimal solution.

This document describes a framework for Virtual Private Networks (VPNs) running across IP backbones. It discusses the various different types of VPNs, their respective requirements, and proposes specific mechanisms that could be used to implement each type of VPN using existing or proposed specifications. The objective of this document is to serve as a framework for related protocol development in order to develop the full set of specifications required for widespread deployment of interoperable VPN solutions.

Multicast services have been increasingly used in large scale continuous media applications. The quality-of-service (QoS) requirements of these continuous media applications prompt the necessity for QoS-driven, constraint-based multicast routing. This article provides a comprehensive overview of existing multicast routing algorithms, protocols, and their QoS extension. In particular, we classify multicast routing problems according to their optimization functions and performance constraints, present basic routing algorithms in each problem class, and discuss their strengths and weakness. We also categorize existing multicast routing protocols, outline the issues and challenges in providing QoS in multicast routing, and point out possible future research directions.

Internet telephony offers the opportunity to design a global multimedia communications system that may eventually replace the existing telephony infrastructure. We describe the upper-layer protocol components that are specific to Internet telephony services: the Real-Time Transport Protocol (RTP) to carry voice and video data, and the Session Initiation Protocol (SIP) for signaling. We also mention some complementary protocols, including the Real Time Streaming Protocol (RTSP) for control of streaming media, and the Wide Area Service Discovery Protocol (WASRV) for location of telephony gateways. 1

We show how to use an interactive theorem prover, HOL, together with a model checker, SPIN, to prove key properties of distance vector routing protocols. We do three case studies: correctness of the RIP standard, a sharp realtime bound on RIP stability, and preservation of loop-freedom in AODV, a distance vector protocol for wireless networks. We develop verification techniques suited to routing protocols generally. These case studies show significant benefits from automated support in reduced verification workload and assistance in finding new insights and gaps for standard specifications.

We present a solution to the denial of service problem for routing infrastructures. When a network suffers from denial of service, packets cannot reach their destinations. Existing routing protocols are not well-equipped to deal with denial of service; a misbehaving router -- which may be caused by software/hardware faults, misconfiguration, or malicious attacks -- may be able to disable entire networks. To protect network infrastructures from routers that incorrectly drop packets and misroute packets, we hypothesize failure models for routers and present protocols that detect and respond to those misbehaving routers. Based on realistic assumptions, we prove that our protocols have the following properties: (1) A well-behaved router never incorrectly claims another router as a misbehaving router; (2) If a network has misbehaving routers, one or more of them can be located; (3) Misbehaving routers will eventually be removed.

Bandwidth and power constraints are the main concerns in current wireless networks because multihop, ad hoc mobile wireless networks rely on each node in the network to act as a router and packet forwarder. This dependency places bandwidth, power, and computation demands on mobile hosts which must be taken into account when choosing the best routing protocol. In recent years, protocols that build routes based "on demand" have been proposed. The major goal of on-demand routing protocols is to minimize control traffic overhead. In this paper, we perform a simulation and performance study on some routing protocols for ad hoc networks. Distributed Bellman-Ford, a traditional table-driven routing algorithm, is simulated to evaluate its performance in multihop wireless networks. In addition, two on-demand routing protocols (Dynamic Source Routing and Associativity-Based Routing) with distinctive route selection algorithms are simulated in a common environment to quantitatively measure and co...

A loop-free path-finding algorithm (LPA) is presented; this is the first routing algorithm that eliminates the formation of temporary routing loops without the need for internodal synchronization spanning multiple hops or the specification of complete or variable-size path information. Like other previous algorithms, LPA operates by specifying the second-to-last hop and distance to each destination; this feature is used to ensure termination. In addition, LPA uses an inter-neighbor synchronization mechanism to eliminate temporary routing loops. A detailed proof of LPA's correctness and loop-freedom property is presented and its complexity is evaluated. LPA's average performance is compared by simulation with the performance of algorithms representative of the state of the art in distributed routing, namely an ideal link-state (ILS) algorithm, a loop-free algorithm that is based on internodal coordination spanning multiple hops (DUAL) and a path-finding algorithm without the inter-neigh...