Showing papers on "Multipath routing published in 2001"

On-demand multipath distance vector routing in ad hoc networks

Abstract: We develop an on-demand multipath distance vector protocol for mobile ad hoc networks. Specifically, we propose multipath extensions to a well-studied single path routing protocol known as ad hoc on-demand distance vector (AODV). The resulting protocol is referred to as ad hoc on-demand multipath distance vector (AOMDV). The protocol computes multiple loop-free and link-disjoint paths. Loop-freedom is guaranteed by using a notion of "advertised hopcount". Link-disjointness of multiple paths is achieved by using a particular property of flooding. Performance comparison of AOMDV with AODV using ns-2 simulations shows that AOMDV is able to achieve a remarkable improvement in the end-to-end delay-often more than a factor of two, and is also able to reduce routing overheads by about 20%.

Highly-resilient, energy-efficient multipath routing in wireless sensor networks

Abstract: Previously proposed sensor network data dissemination schemes require periodic low-rate flooding of data in order to allow recovery from failure. We consider constructing two kinds of multipaths to enable energy efficient recovery from failure of the shortest path between source and sink. Disjoint multipath has been studied in the literature. We propose a novel braided multipath scheme, which results in several partially disjoint multipath schemes. We find that braided multipaths are a viable alternative for energy-efficient recovery from isolated and patterned failures.

Split multipath routing with maximally disjoint paths in ad hoc networks

Abstract: In recent years, routing has been the most focused area in ad hoc networks research On-demand routing in particular, is widely developed in bandwidth constrained mobile wireless ad hoc networks because of its effectiveness and efficiency Most proposed on-demand routing protocols however, build and rely on a single route for each data session Whenever there is a link disconnection on the active route, the routing protocol must perform a route recovery process In QoS routing for wired networks, multiple path routing is popularly used Multiple routes are however, constructed using link-state or distance vector algorithms which are not well-suited for ad hoc networks We propose an on-demand routing scheme called split multipath routing (SMR) that establishes and utilizes multiple routes of maximally disjoint paths Providing multiple routes helps minimizing route recovery process and control message overhead Our protocol uses a per-packet allocation scheme to distribute data packets into multiple paths of active sessions This traffic distribution efficiently utilizes available network resources and prevents nodes of the route from being congested in heavily loaded traffic situations We evaluate the performance of our scheme using extensive simulation

Energy efficient routing in wireless sensor networks

Abstract: Wireless sensor nodes can be deployed on a battlefield and organize themselves in a large-scale ad-hoc network. Traditional routing protocols do not take into account that a node contains only a limited energy supply. Optimal routing tries to maximize the duration over which the sensing task can be performed, but requires future knowledge. As this is unrealistic, we derive a practical guideline based on the energy histogram and develop a spectrum of new techniques to enhance the routing in sensor networks. Our first approach aggregates packet streams in a robust way, resulting in energy reductions of a factor 2 to 3. Second, we argue that a more uniform resource utilization can be obtained by shaping the traffic flow. Several techniques, which rely only on localized metrics are proposed and evaluated. We show that they can increase the network lifetime up to an extra 90% beyond the gains of our first approach.

Power-aware localized routing in wireless networks

Abstract: A cost aware metric for wireless networks based on remaining battery power at nodes was proposed for shortest-cost routing algorithms, assuming constant transmission power. Power-aware metrics, where transmission power depends on distance between nodes and corresponding shortest power algorithms were also proposed. We define a power-cost metric based on the combination of both node's lifetime and distance-based power metrics. We investigate some properties of power adjusted transmissions and show that, if additional nodes can be placed at desired locations between two nodes at distance d, the transmission power can be made linear in d as opposed to d/sup /spl alpha// dependence for /spl alpha/ /spl ges/ 2. This provides basis for power, cost, and power-cost localized routing algorithms where nodes make routing decisions solely on the basis, of location of their neighbors and destination. The power-aware routing algorithm attempts to minimize the total power needed to route a message between a source and a destination. The cost-aware routing algorithm is aimed at extending the battery's worst-case lifetime at each node. The combined power-cost localized routing algorithm attempts to minimize the total power needed and to avoid nodes with a short battery's remaining lifetime. We prove that the proposed localized power, cost, and power-cost efficient routing algorithms are loop-free and show their efficiency by experiments.

The performance of query control schemes for the zone routing protocol

Abstract: In this paper, we study the performance of route query control mechanisms for the Zone Routing Protocol (ZRP) for ad hoc networks. ZRP proactively maintains routing information for a local neighborhood (routing zone), while reactively acquiring routes to destinations beyond the routing zone. This hybrid routing approach can be more efficient than traditional routing schemes. However, without proper query control techniques, the ZRP cannot provide the expected reduction in the control traffic.Our proposed query control schemes exploit the structure of the routing zone to provide enhanced detection and prevention of overlapping queries. These techniques can be applied to single- or multiple-channel ad hoc networks to improve both the delay and control traffic performance of ZRP. Our query control mechanisms allow ZRP to provide routes to all accessible network nodes, with less control traffic than purely proactive link state or purely reactive route discovery, and with less delay than conventional flood searching.

Compact routing schemes

Abstract: We describe several compact routing schemes for general weighted undirected networks. Our schemes are simple and easy to implement. The routing tables stored at the nodes of the network are all very small. The headers attached to the routed messages, including the name of the destination, are extremely short. The routing decision at each node takes constant time. Yet, the stretch of these routing schemes, i.e., the worst ratio between the cost of the path on which a packet is routed and the cost of the cheapest path from source to destination, is a small constant. Our schemes achieve a near-optimal tradeoff between the size of the routing tables used and the resulting stretch. More specifically, we obtain: A routing scheme that uses only O (n 1/2) bits of memory at each node of an n-node network that has stretch 3. The space is optimal, up to logarithmic factors, in the sense that every routing scheme with stretch n2), and every routing scheme with stretch n3/2). The headers used are only (1 + O(1)) log2> n-bits long and each routing decision takes constant time. A variant of this scheme with [log2 n] -bit headers makes routing decisions in O(log log n) time. Also, for every integer k > 2, a general handshaking based routing scheme that uses O (n1/k) bits of memory at each node that has stretch 2k - 1. A conjecture of Erdos from 1963, settled for k = 3, 5, implies that the routing tables are of near-optimal size relative to the stretch. The handshaking is similar in spirit to a DNS lookup in TCP/IP. Headers are O(log2 n) bits long and each routing decision takes constant time. Without handshaking, the stretch of the scheme increases to 4k - 5. One ingredient used to obtain the routing schemes mentioned above, may be of independent practical and theoretical interest: A shortest path routing scheme for trees of arbitrary degree and diameter that assigns each vertex of an n-node tree a (1 + O(1)) log2 n-bit label. Given the label of a source node and the label of a destination it is possible to compute, in constant time, the port number of the edge from the source that heads in the direction of the destination. The general scheme for k > 2 also uses a clustering technique introduced recently by the authors. The clusters obtained using this technique induce a sparse and low stretch tree cover of the network. This essentially reduces routing in general networks into routing problems in trees that could be solved using the above technique.

Performance of multipath routing for on-demand protocols in mobile ad hoc networks

Abstract: Mobile ad hoc networks are characterized by multi-hop wireless links, absence of any cellular infrastructure, and frequent host mobility. Design of efficient routing protocols in such networks is a challenging issue. As class of routing protocols called on-demandprotocols hs recently found attention because of their low routing overhead. The on-demand protocols depend on query floods to discover routes whenever a new route is needed. Such floods take up a substantial portion of network bandwidth. We focus on a particular on-demand protocol, called Dynamic Source Routing, and show how intelligent use of multipath techniques can reduce the frequency of query floods. We develop an analytic modeling framework to determine the relative frequency of query floods for various techniques. Our modeling effort shows that while multipath routing is significantly better than single path routing, the performance advantage is small beyond a few paths and for long paths lengths. It also shows that providing all intermediate nodes in the primary (shortest) route with alternative paths has a significantly better performance than providing only the source with alternate paths. We perform some simulation experiments which validate these findings.

Issues for routing in the optical layer

Abstract: Optical layer control planes based on MPLS and other Internet protocols hold great promise because of their proven scalability, ability to support rapid provisioning, and auto discovery and self-inventory capabilities and are under intense study in various standards bodies. To date however little attention has been paid to aspects of the optical layer which differ from those found in data networking. We study three such aspects which impact routing: network elements which are reconfigurable, but in constrained ways; transmission impairments which may make some routes unusable; and diversity. We conclude that if emerging optical technology is to be maximally exploited, heterogeneous technologies with dissimilar routing constraints are likely. Four alternative architectures for dealing with this eventuality are identified and some trade-offs between centralizing or distributing some aspects of routing are discussed.

Vehicle routing and reverse logistics: The vehicle routing problem with simultaneous delivery and pick-up

Abstract: Recently, the increasing focus on environmental protection has led to significant changes in logistics processes In addition to the distribution process to the customers, re-usable packaging and goods to be recycled or remanufactured have to be transported in the reverse direction If both tasks have to be performed simultaneously at the customers' locations which are serviced by a fleet of vehicles stationed in a depot or distribution/redistribution center, the vehicle routing problem with simultaneous delivery and pick-up arises In this paper, the relation between this problem and other vehicle routing problems is investigated A heuristic construction procedure is suggested The proposed algorithm is successfully applied to a real-life problem as well as test instances introduced in the literature earlier In addition, randomly generated instances are tackled in order to try to determine favorable settings for the parameters used in the solution approach

Geometric spanner for routing in mobile networks

Abstract: We propose a new routing graph, the Restricted Delaunay Graph (RDG), for ad hoc networks. Combined with a node clustering algorithm RDG can be used as an underlying graph for geographic routing protocols. This graph has the following attractive properties: (1) it is a planar graph; (2) between any two nodes there exists a path in the RDG whose length, whether measured in terms of topological or Euclidean distance, is only a constant times the optimum length possible; and (3) the graph can be maintained efficiently in a distributed manner when the nodes move around. Furthermore, each node only needs constant time to make routing decisions. We also show by simulation that the RDG outperforms the previously proposed routing graphs under the Greedy Perimeter Stateless Routing (GPSR) protocol. In addition, we investigate theoretical bounds on the quality of paths discovered using GPSR

Lagrange relaxation based method for the QoS routing problem

Abstract: In this paper a practically efficient QoS routing method is presented, which provides a solution to the delay constrained least cost routing problem. The algorithm uses the concept of aggregated costs and provides an efficient method to find the optimal multiplier based on Lagrange relaxation. This method is proven to be polynomial and it is also efficient in practice. The benefit of this method is that it also gives a lower bound on the theoretical optimal solution along with the result. The difference between the lower bound and the cost of the found path is very small proving the good quality of the result. Moreover, by further relaxing the optimality of paths, an easy way is provided to control the trade-off between the running time of the algorithm and the quality of the found paths. We present a comprehensive numerical evaluation of the algorithm, by comparing it to a wide range of QoS routing algorithms proposed in the literature. It is shown that the performance of the proposed polynomial time algorithm is close to the optimal solution computed by an exponential algorithm.

Methods, apparatuses and systems facilitating deployment, support and configuration of network routing policies

Abstract: Methods, apparatuses and systems relating to the control and application of policies for routing data over a computer network, such as the Internet. Some implementations of the invention facilitate the configuration, deployment and/or maintenance of network routing policies. Some implementations of the invention are particularly useful for controlling the routing of data among autonomous systems or organizations. Certain implementations allow for dynamic modification of routing policy based on such factors as current Internet performance, load sharing, user-defined parameters, and time of day.

Dynamic lightpath establishment in wavelength routed WDM networks

Abstract: In wavelength-routed WDM networks, a control mechanism is required to set up and take down all-optical connections. Upon the arrival of a connection request, this mechanism must be able to select a route, assign a wavelength to the connection, and configure the appropriate optical switches in the network. The mechanism must also be able to provide updates to reflect which wavelengths are currently being used on each link so that nodes may make informed routing decisions. In this work, we review control mechanisms proposed in the literature. We also investigate and compare two different distributed control mechanisms for establishing all-optical connections in a wavelength-routed WDM network: an approach based on link-state routing, and one based on distance-vector routing.

The impact of Internet policy and topology on delayed routing convergence

Abstract: This paper examines the role inter-domain topology and routing policy play in the process of delayed Internet routing convergence. In previous work, we showed that the Internet lacks effective inter-domain path fail-over. Unlike circuit-switched networks which exhibit fail-over on the order of milliseconds, we found Internet backbone routers may take tens of minutes to reach a consistent view of the network topology after a fault. In this paper, we expand an our earlier work by exploring the impact of specific Internet provider policies and topologies on the speed of routing convergence. Based on data from the experimental injection and measurement of several hundred thousand inter-domain routing faults, we show that the time for end-to-end Internet convergence depends on the length of the longest possible backup autonomous system path between a source and destination node. We also demonstrate significant variation in the convergence behavior of Internet service providers, with the larger providers exhibiting the fastest convergence latencies. Finally, we discuss possible modifications to BGP and provider routing policies which if deployed, would improve inter-domain routing convergence.

MP-DSR: a QoS-aware multi-path dynamic source routing protocol for wireless ad-hoc networks

Abstract: Routing in wireless ad-hoc networks has received significant attention in the literature due to the fact that the dynamic behavior of these networks poses many technical challenges on the design of an effective routing scheme. Though on-demand routing approaches have been shown to perform well, they generally lack the support for quality-of-service (QoS) with respect to data transmission. In order to select a subset of end-to-end paths to provide increased stability and reliability of routes, a new QoS metric, end-to-end reliability, is defined and emphasized. We present a distributed multi-path dynamic source routing protocol (MP-DSR)for wireless ad-hoc networks to improve QoS support with respect to end-to-end reliability. Our protocol forwards outgoing packets along multiple paths that are subject to a particular end-to-end reliability requirement. A simulation study is performed to demonstrate the effectiveness of our proposed protocol, particularly the fact that MP-DSR achieves a higher rate of successful packet delivery than existing best-effort ad-hoc routing protocols, such as the dynamic source routing (DSR).

Multipath routing in the presence of frequent topological changes

Abstract: In this article we propose a framework for multipath routing in mobile ad hoc networks and provide its analytical evaluation. The instability of the topology (e.g., failure of links) in these types of networks, due to nodal mobility and changes in wireless propagation conditions, makes transmission of time-sensitive information a challenging problem. To combat this inherent unreliability of these networks, we propose a routing scheme that uses multiple paths simultaneously by splitting the information among the multitude of paths, to increase the probability that the essential portion of the information is received at the destination without incurring excessive delay. Our scheme works by adding some overhead to each packet, which is calculated as a linear function of the original packet bits. The resulting packet (information and overhead) is fragmented into smaller blocks and distributed over the available paths. Our goal is, given the failure probabilities of the paths, to find the optimal way to fragment and then distribute the blocks to the paths so that the probability of reconstructing the original information at the destination is maximized. Our algorithm has low time complexity, which is crucial since the path failure characteristics vary with time and the optimal block distribution has to be recalculated in real time.

Dynamic routing of locally restorable bandwidth guaranteed tunnels using aggregated link usage information

Abstract: We consider a new QoS routing problem which requires the on-line routing of a bandwidth guaranteed path along with the setting up of bypass paths for every link or node traversed by the primary active path. The bypass paths are used for fast local restoration where upon a link or node failure, the first upstream node re-establishes path continuity (with bandwidth guarantees) by switching to the bypass path for the failed node or link, The routing objective is to minimize the bandwidth usage for each connection so as optimize use of network resources while protecting against single node or link failure. Bandwidth efficiency is achieved by exploiting the potential for inter-demand and intra-demand backup bandwidth sharing. We develop a new algorithm for this routing problem which only uses aggregated link usage information (total bandwidth consumed on each link by active paths, total bandwidth consumed on each link by backup paths, and the residual bandwidths) that is easily obtainable by proposed routing protocol extensions. We show that the algorithm performs well in terms of the number of rejected requests and the total bandwidth used, The main use of this algorithm is for MPLS network routing and for wavelength routing in optical networks with wavelength conversion.

The impact of routing policy on Internet paths

Abstract: The impact of routing policy on Internet paths is poorly understood. In theory, the policy can inflate shortest-router-hop paths. To our knowledge, the extent of this inflation has not been previously examined. Using a simplified model of the routing policy in the Internet, we obtain approximate indications of the impact of policy routing on Internet paths. Our findings suggest that the routing policy does impact the length of Internet paths significantly. For instance, in our model of the routing policy, some 20% of Internet paths are inflated by more than five router-level hops.

Routing in Trees

Abstract: This article focuses on routing messages along shortest paths in tree networks, using compact distributed data structures. We mainly prove that n-node trees support routing schemes with message headers, node addresses, and local memory space of size O(log n) bits, and such that every local routing decision is taken in constant time. This improves the best known routing scheme by a factor of O(log n) in term of both memory requirements and routing time. Our routing scheme requires headers and addresses of size slightly larger than log n, motivated by an inherent trade-off between address-size and memory space, i.e., any routing scheme with addresses on log n bits requires Ω(√n) bits of local memory-space. This shows that a little variation of the address size, e.g., by an additive O(log n) bits factor, has a significant impact on the local memory space.

Integrated dynamic IP and wavelength routing in IP over WDM networks

Abstract: This paper develops an algorithm for integrated dynamic routing of bandwidth guaranteed paths in IP over WDM networks. By integrated routing, we mean routing taking into account the combined topology and resource usage information at the IP and optical layers. Typically, routing in IP over WDM networks has been separated into routing at the IP layer taking only IP layer information into account, and wavelength routing at the optical layer taking only optical network information into account. The motivation for integrated routing is the potential for better network usage, and this is a topic which has not been been studied extensively. We develop an integrated routing algorithm that determines (1) whether to route an arriving request over the existing topology or whether it is better to open new wavelength paths. Sometimes it is better to open new wavelength paths even if it feasible to route the current demand over the existing IP topology due to previously set-up wavelength paths. 2) For routing over the existing IP-level topology, compute "good" routes. (3) If new wavelength paths are to be set-up, determine the routers amongst which new wavelength paths are to be set-up and compute "good" routes for these new wavelength paths. The performance objective is the accomodation of as many requests as possible without requiring any a priori knowledge regarding future arrivals. The route computations account for the presence or absence of wavelength conversion capabilities at optical crossconnects. We show that the developed scheme performs very well in terms of performance metrics such as the number of rejected demands.

Load-balancing routing for wireless access networks

Abstract: The widespread use of wireless devices presents new challenges for network operators, who need to provide service to ever larger numbers of mobile end users, while ensuring quality-of-service guarantees. We describe a new distributed routing algorithm that performs dynamic load-balancing for wireless access networks. The algorithm constructs a load-balanced backbone tree, which simplifies routing and avoids per-destination state for routing and per-flow state for QoS reservations. We evaluate the performance of the algorithm using several metrics including adaptation to mobility, degree of load-balance, bandwidth blocking rate, and convergence speed. We find that the algorithm achieves better network utilization by lowering bandwidth blocking rates than other methods.

Evaluating the impact of stale link state on quality-of-service routing

Abstract: Quality-of-service (QoS) routing satisfies application performance requirements and optimizes network resource usage by selecting paths based on connection traffic parameters and link load information. However, distributing link state imposes significant bandwidth and processing overhead on the network. This paper investigates the performance tradeoff between protocol overhead and the quality of the routing decisions in the context of the source-directed link state routing protocols proposed for IP and ATM networks. We construct a detailed model of QoS routing that parameterizes the path-selection algorithm, link-cost function, and link state update policy. Through extensive simulation experiments with several network topologies and traffic patterns, we uncover the effects of stale link state information and random fluctuations in traffic load on the routing and setup overheads. We then investigate how inaccuracy of link state information interacts with the size and connectivity of the underlying topology. Finally, we show that tuning the coarseness of the link-cost metric to the inaccuracy of underlying link state information reduces the computational complexity of the path-selection algorithm without significantly degrading performance. This work confirms and extends earlier studies, and offers new insights for designing efficient quality-of-service routing policies in large networks.

Inherently safe backup routing with BGP

Abstract: The Internet consists of a large number of autonomous systems (ASes) that exchange routing information using the border gateway protocol (BGP). Each AS applies local policies for selecting routes and propagating routes to others, with important implications for the reliability and stability of the global system. In and of itself, BGP does not ensure that every pair of hosts can communicate. In addition, routing policies are not guaranteed be safe, and may cause protocol divergence. Backup routing is often used to increase the reliability of the network under link and router failures, at the possible expense of safety. This paper presents a general model for backup routing that increases network reliability while allowing each AS to apply local routing policies that are consistent with the commercial relationships it has with its neighbors. In addition, our model is inherently safe in the sense that the global system remains safe under any combination of link and router failures. Our model and the proof of inherent safety are cast in terms of the stable paths problem, a static formalism that captures the semantics of interdomain routing policies. Then, we describe how to realize our model in BGP with locally-implementable routing policies. To simplify the specification of local policies, we propose a new BGP attribute that conveys the avoidance level of a route. We also describe how to realize these policies without modification to BGP by using the BGP community attribute.

MDVA: a distance-vector multipath routing protocol

Abstract: Routing protocols using the distributed Bellman-Ford (DBF) algorithm converge very slowly to the correct routes when link costs increase, and in the case when a set of link failures results in a network partition, DBF simply fails to converge, a problem which is commonly referred to as the count-to-infinity problem. We present the first distance-vector routing algorithm, MDVA, that uses a set of loop-free invariants to prevent the count-to-infinity problem. MDVA, in addition, computes multipaths that are loop-free at every instant. In our earlier work we shows how such loop-free multipaths can be used in traffic load-balancing and minimizing delays, which otherwise are impossible to perform in current single-path routing algorithms.

An adaptive distance vector routing algorithm for mobile, ad hoc networks

Abstract: We present a new routing algorithm called adaptive distance vector (ADV) for mobile, ad hoc networks (MANETs). ADV is a distance vector routing algorithm that exhibits some on-demand characteristics by varying the frequency and the size of the routing updates in response to the network load and mobility conditions. Using simulations we show that ADV outperforms AODV and DSR especially in high mobility cases by giving significantly higher (50% or more) peak throughputs and lower packet delays. Furthermore, ADV uses fewer routing and control overhead packets than that of AODV and DSR, especially at moderate to high loads. Our results indicate the benefits of combining both proactive and on-demand routing techniques in designing suitable routing protocols for MANETs.

Algebra and algorithms for QoS path computation and hop-by-hop routing in the Internet

Abstract: Prompted by the advent of QoS routing in the Internet, we investigate the properties that path weight functions must have so that hop-by-hop routing is possible and optimal paths can be computed with a generalized Dijsktra's (1959) algorithm. For this purpose we define an algebra of weights which contains a binary operation, for the composition of link weights into path weights, and an order relation. Isotonicity is the key property of the algebra. It states that the order relation between the weights of any two paths is preserved if both of them are either prefixed or appended by a common, third, path. We show that isotonicity is both necessary and sufficient for a generalized Dijkstra's algorithm to yield optimal paths. Likewise, isotonicity is also both necessary and sufficient for hop-by-hop routing. However, without strict isotonicity, hop by-hop routing based on optimal paths may produce routing loops. They are prevented if every node computes what we call lexicographic-optimal paths. These paths can be computed with an enhanced Dijkstra's algorithm that has the same complexity as the standard one. Our findings are extended to multipath routing as well. As special cases of the general approach, we conclude that shortest-widest paths can neither be computed with a generalized Dijkstra's algorithm nor can packets be routed hop-by-hop over those paths. In addition, loop free hop by hop routing over widest and widest-shortest paths requires that each node computes lexicographic-optimal paths, in general.

Adaptive multipath source routing in ad hoc networks

Abstract: In this paper, we propose a new multipath routing protocol for ad hoc wireless networks-multipath source routing (MSR), which is an extension of DSR (dynamic source routing). Based on the measurement of RTT, we propose a scheme to distribute load among multiple paths. The simulation results show that our approach improves the packet delivery ratio and the throughput of TCP and UDP, and reduces the end-to-end delay and the average queue size, while adding little overhead. As a result, MSR decreases the network congestion and increases the path fault tolerance quite well.