Showing papers on "Equal-cost multi-path routing published in 2003"

Performance of multihop wireless networks: shortest path is not enough

Abstract: Existing wireless ad hoc routing protocols typically find routes with the minimum hop-count. This paper presents experimental evidence from two wireless test-beds which shows that there are usually multiple minimum hop-count paths, many of which have poor throughput. As a result, minimum-hop-count routing often chooses routes that have significantly less capacity than the best paths that exist in the network. Much of the reason for this is that many of the radio links between nodes have loss rates low enough that the routing protocol is willing to use them, but high enough that much of the capacity is consumed by retransmissions. These observations suggest that more attention be paid to link quality when choosing ad hoc routes; the paper presents measured link characteristics likely to be useful in devising a better path quality metric.

Making intra-domain routing robust to changing and uncertain traffic demands: understanding fundamental tradeoffs

Abstract: Intra-domain traffic engineering can significantly enhance the performance of large IP backbone networks. Two important components of traffic engineering are understanding the traffic demandsand configuring the routing protocols. These two components are inter-linked, as it is widely believed that an accurate view of traffic is important for optimizing the configuration of routing protocols and through that, the utilization of the network.This basic premise, however, never seems to have been quantified --How important is accurate knowledge of traffic demands for obtaining good utilization of the network? Since traffic demand values are dynamic and illusive, is it possible to obtain a routing that is "robust" to variations in demands? Armed with enhanced recent algorithmic tools we explore these questions on a diverse collection of ISP networks. We arrive at a surprising conclusion: it is possible to obtain a robust routing that guarantees a nearly optimal utilization with a fairly limited knowledge of the applicable traffic demands.

Performance analysis of reactive shortest path and multi-path routing mechanism with load balance

Abstract: Research on multipath routing protocols to provide improved throughput and route resilience as compared with single-path routing has been explored in details in the context of wired networks. However, multipath routing mechanism has not been explored thoroughly in the domain of ad hoc networks. In this paper, we analyze and compare reactive single-path and multipath routing with load balance mechanisms in ad hoc networks, in terms of overhead, traffic distribution and connection throughput. The results reveals that in comparison with general single-path routing protocol, multipath routing mechanism creates more overheads but provides better performance in congestion and capacity provided that the route length is within a certain upper bound which is derivable. The analytical results are further confirmed by simulation.

Performance analysis of reactive shortest path and multipath routing mechanism with load balance

Abstract: Research on multipath routing protocols to provide improved throughput and route resilience as compared with single-path routing has been explored in details in the context of wired networks. However, multipath routing mechanism has not been explored thoroughly in the domain of ad hoc networks. In this paper, we analyze and compare reactive single-path and multipath routing with load balance mechanisms in ad hoc networks, in terms of overhead, traffic distribution and connection throughput. The results reveals that in comparison with general single-path routing protocol, multipath routing mechanism creates more overheads but provides better performance in congestion and capacity provided that the route length is within a certain upper bound which is derivable. The analytical results are further confirmed by simulation.

On selfish routing in internet-like environments

Abstract: A recent trend in routing research is to avoid inefficiencies in network-level routing by allowing hosts to either choose routes themselves (e.g., source routing) or use overlay routing networks (e.g., Detour or RON). Such approaches result in selfish routing, because routing decisions are no longer based on system-wide criteria but are instead designed to optimize host-based or overlay-based metrics. A series of theoretical results showing that selfish routing can result in suboptimal system behavior have cast doubts on this approach. In this paper, we use a game-theoretic approach to investigate the performance of selfish routing in Internet-like environments. We focus on intra-domain network environments and use realistic topologies and traffic demands in our simulations. We show that in contrast to theoretical worst cases, selfish routing achieves close to optimal average latency in such environments. However, such performance benefit comes at the expense of significantly increased congestion on certain links. Moreover, the adaptive nature of selfish overlays can significantly reduce the effectiveness of traffic engineering by making network traffic less predictable.

Data funneling: routing with aggregation and compression for wireless sensor networks

Abstract: This paper considers the problem of minimizing the amount of communication needed to send readings from a set of sensors to a single destination in energy constrained wireless networks. Substantial gains can be obtained using packet aggregation techniques while routing. The proposed routing algorithm, called Data Funneling, allows the network to considerably reduce the amount of energy spent on communication setup and control, an important concern in low data-rate communication. This is achieved by sending only one data stream from a group of sensors to the destination instead of having an individual data stream from each sensor to the destination. Doing so also reduces the probability of packet collisions in the wireless medium because the same amount of information can be transmitted by having fewer nodes send longer packets. Additional gains can be realized by efficient compression of data. This is achieved by losslessly compressing the data by encoding information in the ordering of the sensors' packets. This "coding by ordering" scheme compresses data by suppressing certain readings and encoding their values in the ordering of the remaining packets. Using these techniques together can more than halve the energy spent in communication.

Preemptive routing in ad hoc networks

Abstract: Routing in ad hoc networks is a challenging problem because nodes are mobile and links are continuously being created and broken. Existing on-demand ad hoc routing algorithms initiate route discovery only after a path breaks, incurring a significant cost in detecting the disconnection and establishing a new route. In this work, we investigate adding proactive route selection and maintenance to on-demand ad hoc routing algorithms. More specifically, when a path is likely to be broken, a warning is sent to the source indicating the likelihood of a disconnection. The source can then initiate path discovery early, potentially avoiding the disconnection altogether. A path is considered likely to break when the received packet power becomes close to the minimum detectable power (other approaches are possible). Care must be taken to avoid initiating false route warnings due to fluctuations in received power caused by fading, multipath effects and similar random transient phenomena. Experiments demonstrate that adding proactive route selection and maintenance to DSR and AODV (on-demand ad hoc routing protocols) significantly reduces the number of broken paths, with a small increase in protocol overhead. Packet latency and jitter go down in most cases. Because preemptive routing reduces the number of broken paths, it also has a secondary effect on TCP performance--unnecessary congestion handling measures are avoided. This is observed for TCP traffic under different traffic patterns (telnet, ftp and http). Additionally, we outline some problems in TCP performance in ad hoc environments.

A fault-tolerant and deadlock-free routing protocol in 2D meshes based on odd-even turn model

Abstract: We propose a deterministic fault-tolerant and deadlock-free routing protocol in two-dimensional (2D) meshes based on dimension-order routing and the odd-even turn model. The proposed protocol, called extended X-Y routing, does not use any virtual channels by prohibiting certain locations of faults and destinations. Faults are contained in a set of disjointed rectangular regions called faulty blocks. The number of faults to be tolerated is unbounded as long as nodes outside faulty blocks are connected in the 2D mesh network. The extended X-Y routing can also be used under a special convex fault region called an orthogonal faulty block, which can be derived from a given faulty block by activating some nonfaulty nodes in the block. Extensions to partially adaptive routing, traffic and adaptivity-balancing using virtual networks, and routing without constraints using virtual channels and virtual networks are also discussed.

Quality of service routing in ad-hoc networks using OLSR

Abstract: In an ad-hoc network, all communication is done over wireless media, without the help of wired base stations. While many routing protocols have been developed to find and maintain routes based on a best-effort service model, quality-of-service (QoS) routing in an ad-hoc network is difficult because the network topology may change constantly and the available state information for routing is inherently imprecise. In this paper, we discuss how to support QoS routing in OLSR (optimized link state routing protocol, one of the routing protocols under study by the IETF MANET Working Group). We develop heuristics that allow OLSR to find the maximum bandwidth path, show through simulation that these heuristics do improve OLSR in the static network case, and finally, we prove that for our ad-hoc network model, two of the heuristics are indeed optimal (i.e., guarantee that the highest-bandwidth path between any two nodes is found).

Network routing with path vector protocols: theory and applications

Abstract: Path vector protocols are currently in the limelight, mainly because the inter-domain routing protocol of the Internet, BGP (Border Gateway Protocol), belongs to this class. In this paper, we cast the operation of path vector protocols into a broad algebraic framework and relate the convergence of the protocol, and the characteristics of the paths to which it converges, with the monotonicity and isotonicity properties of its path compositional operation. Here, monotonicity means that the weight of a path cannot decrease when it is extended, and isotonicity means that the relationship between the weights of any two paths with the same origin is preserved when both are extended to the same node. We show that path vector protocols can be made to converge for every network if and only if the algebra is monotone, and that the resulting paths selected by the nodes are optimal if and only if the algebra is isotone as well.Many practical conclusions can be drawn from instances of the generic algebra. For performance-oriented routing, typical in intra-domain routing, we conclude that path vector protocols can be made to converge to widest or widest-shortest paths, but that the composite metric of IGRP (Interior Gateway Protocol), for example, does not guarantee convergence to optimal paths. For policy-based routing, typical in inter-domain routing, we formulate existing guidelines as instances of the generic algebra and we propose new ones. We also show how a particular instance of the algebra yields a sufficient condition for signaling correctness of internal BGP.

Diverse routing in optical mesh networks

Abstract: We study the diverse routing problem in optical mesh networks. We use a general framework based on shared risk link groups to model the problem. We prove that the diverse routing problem is indeed NP-complete, a result that has been conjectured by several researchers previously. In fact, we show that even the fiber-span-disjoint paths problem, a special case of the diverse routing problem, is also NP-complete. We then develop an integer linear programming formulation and show through numerical results that it is a very viable method to solve the diverse routing problem for most optical networks found in many applications which typically have no more than a few hundred nodes and fiber spans.

Detecting network intrusions via sampling: a game theoretic approach

Abstract: In this paper, we consider the problem of detecting an intruding packet in a communication network. Detection is accomplished by sampling a portion of the packets transiting selected network links (or router interfaces). Since sampling entails incurring network costs for real-time packet sampling and packet examination hardware, we would like to develop a network packet sampling strategy to effectively detect network intrusions while not exceeding a given total sampling budget. We consider this problem in a game theoretic framework, where the intruder picks paths (or the network ingress point if only shortest path routing is possible) to minimize chances of detection and where the network operator chooses a sampling strategy to maximize the chances of detection. We formulate the game theoretic problem, and develop sampling schemes that are optimal in this game theoretic setting.

Best-path vs. multi-path overlay routing

Abstract: Time-varying congestion on Internet paths and failures due to software, hardware, and configuration errors often disrupt packet delivery on the Internet.Many aproaches to avoiding these problems use multiple paths between two network locations. These approaches rely on a path-independence assumption in order to work well; i.e., they work best when the problems on different paths between two locations are uncorrelated in time.This paper examines the extent to which this assumption holds on the Internet by analyzing 14 days of data collected from 30 nodes in the RON testbed. We examine two problems that manifest themselves---congestion-triggered loss and path failures---and find that the chances of losing two packets between the same hosts is nearly as high when those packets are sent through an intermediate node (60%) as when they are sent back-to-back on the same path (70%). In so doing, we also compare two different ways of taking advantage of path redundancy proposed in the literature: mesh routing based on packet replication, and reactive routing based on adaptive path selection.

Cooperative packet caching and shortest multipath routing in mobile ad hoc networks

Abstract: A mobile ad hoc network is an autonomous system of infrastructureless, multihop wireless mobile nodes. Reactive routing protocols perform well in such an environment due to their ability to cope quickly against topological changes. In this paper, we propose a new routing protocol called Caching and Multipath (CHAMP) Routing Protocol. CHAMP uses cooperative packet caching and shortest multipath routing to reduce packet loss due to frequent route breakdowns. Simulation results reveal that by using a five-packet data cache, CHAMP exhibits excellent improvement in packet delivery, outperforming AODV and DSR by at most 30% in stressful scenarios. Furthermore, end-to-end delay is significantly reduced while routing overhead is lower at high mobility rates.

GOAL: a load-balanced adaptive routing algorithm for torus networks

Abstract: We introduce a load-balanced adaptive routing algorithm for torus networks, GOAL - Globally Oblivious Adaptive Locally - that provides high throughput on adversarial traffic patterns, matching or exceeding fully randomized routing and exceeding the worst-case performance of Chaos [2], RLB [14], and minimal routing [8] by more than 40%. GOAL also preserves locality to provide up to 4.6× the throughput of fully randomized routing [19] on local traffic. GOAL achieves global load balance by randomly choosing the direction to route in each dimension. Local load balance is then achieved by routing in the selected directions adaptively. We compare the throughput, latency, stability and hot-spot performance of GOAL to six previously published routing algorithms on six specific traffic patterns and 1,000 randomly generated permutations.

Method, apparatus and system for optimizing routing of mobile IP packets

Abstract: Network devices on mobile networks may be configured to improve and optimize packet processing and routing. Specifically, a home agent device may be decomposed into its major functionality, namely processing and routing. Various processors on the device are assigned to specific tasks and each processor may be optimized for its specific tasks, thus improving packet processing and routing. The home agent device may comprise one or more physical components.

Secure traceroute to detect faulty or malicious routing

Abstract: Network routing is vulnerable to disruptions caused by malfunctioning or malicious routers that draw traffic towards themselves but fail to correctly forward the traffic. The existing approach to addressing this problem is to secure the routing protocol by having it validate routing updates, i.e., verify their authenticity, accuracy, and/or consistency. In this paper, we argue that it is also important to ensure the robustness of packet forwarding itself. To this end, we propose a different approach, the central idea of which is a secure traceroute protocol that enables end hosts or routers to detect and locate the source of (arbitrarily severe) routing misbehaviors, so that appropriate action can be taken.

Dynamic routing of restorable bandwidth-guaranteed tunnels using aggregated network resource usage information

Abstract: This paper presents new algorithms for dynamic routing of restorable bandwidth-guaranteed paths. We assume that connection requests one-by-one and have to be routed with no a priori knowledge of future arrivals. In order to guarantee restorability, in addition to determining an active path to route each request, an alternate link (node) disjoint backup (restoration) path has to be determined for the request at the time of connection initiation. This joint on-line routing problem is becoming particularly important in optical networks and in multiprotocol label switching (MPLS)-based networks due to the trend in backbone networks toward dynamic provisioning of bandwidth-guaranteed or wavelength paths. A straightforward solution for the restoration problem is to find two disjoint paths. However, this results in excessive resource usage. Given a restoration objective, such as protection against single-link failures, backup path bandwidth usage can be reduced by judicious sharing of backup paths amongst certain active paths while still maintaining restorability. The best sharing performance is achieved if the routing of every path in progress in the network is known to the routing algorithm at the time of a new path setup. We give an integer programming formulation for this problem which is new. Complete path routing knowledge is a reasonable assumption for a centralized routing algorithm. However, it is not often desirable, particularly when distributed routing is preferred. We show that an aggregate information scenario which uses only aggregated and not per-path information provides sufficient information for a suitably developed algorithm to be able to perform almost as well as the complete information scenario. Disseminating this aggregate information is feasible using proposed traffic engineering extensions to routing protocols. We formulate the dynamic restorable bandwidth routing problem in this aggregate information scenario and develop efficient routing algorithms. We show that the performance of our aggregate information-based algorithm is close to the complete information bound.

An approach to alleviate link overload as observed on an IP backbone

Abstract: Shortest path routing protocols may suffer from congestion due to the use of a single shortest path between a source and a destination. The goal of our work is to first understand how links become overloaded in an IP backbone, and then to explore if the routing protocol, -either in its existing form, or in some enhanced form could be made to respond immediately to overload and reduce the likelihood of its occurrence. Our method is to use extensive measurements of Sprint's backbone network, measuring 138 links between September 2000 and June 2001. We find that since the backbone is designed to be overprovisioned, link overload is rare, and when it occurs, 80% of the time it is caused due to link failures. Furthermore, we find that when a link is overloaded, few (if any) other links in the network are also overloaded. This suggests that deflecting packets to less utilized alternate paths could be an effective method for tackling overload. We analytically derive the condition that a network, which has multiple equal length shortest paths between every pair of nodes (as is common in the highly meshed backbone networks) can provide for loop-free deflection paths if all the link weights are within a ratio 1 + 1/(d- I) of each other; where d is the diameter of the network. Based on our measurements, the nature of the backbone topology and the careful use of link weights, we propose a deflection routing algorithm to tackle link overload where each node makes local decisions. Simulations suggest that this can be a simple and efficient way to overcome link overload, without requiring any changes to the routing protocol.

Routing using potentials: a dynamic traffic-aware routing algorithm

Abstract: We present a routing paradigm called PBR that utilizes steepest gradient search methods to route data packets. More specifically, the PBR paradigm assigns scalar potentials to network elements and forwards packets in the direction of maximum positive force. We show that the family of PBR schemes are loop free and that the standard shortest path routing algorithms are a special case of the PBR paradigm. We then show how to design a potential function that accounts for traffic conditions at a node. The resulting routing algorithm routes around congested areas while preserving the key desirable properties of IP routing mechanisms including hop-by-hop routing, local route computations and statistical multiplexing. Our simulations using the ns simulator indicate that the traffic aware routing algorithm shows significant improvements in end-to-end delay and jitter when compared to standard shortest path routing algorithms. The simulations also indicate that our algorithm does not incur too much control overheads and is fairly stable even when traffic conditions are dynamic.

Achieving near-optimal traffic engineering solutions for current OSPF/IS-IS networks

Abstract: Traffic engineering is aimed at distributing traffic so as to "optimize" a given performance criterion. The ability to carry out such an optimal distribution depends on both the routing protocol and the forwarding mechanisms in use in the network. In IP networks running the OSPF or IS-IS protocols, routing is over shortest paths, and forwarding mechanisms are constrained to distributing traffic uniformly over equal cost shortest paths. These constraints often make achieving an optimal distribution of traffic impossible. In this paper, we propose and evaluate an approach, based on manipulating the set of next hops for routing prefixes, that is capable of realizing near optimal traffic distribution without any change to existing routing protocols and forwarding mechanisms. In addition, we explore the tradeoff that exists between performance and the overhead associated with the additional configuration steps that our solution requires. The paper's contributions are in formulating and evaluating an approach to traffic engineering for existing IP networks that achieves performance levels comparable to that offered when deploying other forwarding technologies such as MPLS.

HIERAS: a DHT based hierarchical P2P routing algorithm

Abstract: Routing algorithm has great influence on system overall performance in peer-to-peer (P2P) applications. In current DHT based routing algorithms, routing tasks are distributed across all system peers. However, a routing hop could happen between two widely separated peers with high network link latency which greatly increases system routing overheads. We propose a new P2P routing algorithm - HIERAS to relieve this problem, it keeps scalability property of current DHT algorithms and improves system routing performance by the introduction of hierarchical structure. In HIERAS, we create several lower level P2P rings besides the highest level P2P ring. A P2P ring is a subset of the overall P2P overlay network. We create P2P rings in such a strategy that the average link latency between two peers in lower level rings is much smaller than higher level rings. Routing tasks are first executed in lower level rings before they go up to higher level rings, a large portion of routing hops previously executed in the global P2P ring are now replaced by hops in lower level rings, thus routing overheads can be reduced. The simulation results show HIERAS routing algorithm can significantly improve P2P system routing performance

Constraint-based routing in the internet: Basic principles and recent research

Abstract: Novel routing paradigms based on policies, quality of service (QoS) requirements, and packet content have been proposed for the Internet over the last decade. Constraint-based routing algorithms select a routing path satisfying constraints that are either administrative-oriented (policy routing) or service-oriented (QoS routing). The routes, in addition to satisfying constraints, are selected to reduce costs, balance network load, or increase security. In this article, we discuss several constraint-based routing approaches and explain their requirements, complexity, and recent research proposals. In addition, we illustrate how these approaches can be integrated with Internet label switching and QoS architectures. We also discuss examples of application-level routing techniques used in today's Internet.

Three power-aware routing algorithms for sensor networks

Abstract: Summary This paper discusses online power-aware routing in large wireless ad hoc networks (especially sensor networks) for applications in which the message sequence is not known. We seek to optimize the lifetime of the network. We show that online power-aware routing does not have a constant competitive ratio to the off-line optimal algorithm. We develop an approximation algorithm called max –min zPmin that has a good empirical competitive ratio. To ensure scalability, we introduce a second online algorithm for power-aware routing. This hierarchical algorithm is called zone-based routing. Our experiments show that its performance is quite good. Finally, we describe a distributed version of this algorithm that does not depend on any centralization. Copyright  2003 John Wiley & Sons, Ltd.

Energy efficient routing with guaranteed delivery in wireless sensor networks

Abstract: High delivery ratio with low energy consumption is one of design challenges for wireless sensor network routing protocols. In this paper, we identify the drawbacks of pure single path routing scheme and multipath routing scheme, in terms of guaranteed delivery with low energy consumption. Accordingly, we describe a scheme, in which data is forwarded along a pre-established single path to save energy, and a high delivery ratio is achieved by path repair whenever a break is detected. We propose a simple, quick, local path repairing approach, whereby a pivot node can skip over path break by only using the already existing routing information in its neighborhood. We implement this scheme and compare its performance with those of pure single path without repair and two multipath routing schemes. Simulation results show that in the same network topology with the same failed nodes, our single-path with repair routing scheme (SWR) has the highest delivery ratio among all the compared schemes in almost all the test cases. The energy consumed by SWR for one data delivery test is relatively low compared with the other schemes.

System and method for distributed multicast routing

Abstract: A distributed router composed of individual units connected by links in a routing fabric which appears to be a single network entity routes multicast packets by bridging to the final unit in the fabric At the final unit the packet is replicated as necessary and routed The scheme avoids multiple transmission of the same packet across the fabric

TCP performance over multipath routing in mobile ad hoc networks

Abstract: In this paper, we investigate TCP performance over a multipath routing protocol. Multipath routing can improve the path availability in mobile environment. Thus, it has a great potential to improve TCP performance in ad hoc networks under mobility. Previous research on multipath routing mostly used UDP traffic for performance evaluation. When TCP is used, we find that most times, using multiple paths simultaneously may actually degrade TCP performance. This is partly due to frequent out-of-order packet delivery via different paths. We then test another multipath routing strategy called backup path routing. Under the backup path routing scheme, TCP is able to gain improvements against mobility. We then further study related issues to backup path routing, which can affect TCP performance. Some important discoveries are reported in the paper and simulation results show that by careful selection of the multipath routing strategies, we can improve TCP performance by more than 30% even under very high mobility.

Link-disjoint paths for reliable QoS routing

Abstract: SUMMARY The problem of finding link/node-disjoint paths between a pair of nodes in a network has received much attention in the past. This problem is fairly well understood when the links in a network are only specified by a single link weight. However, in the context of quality of service routing, links are specified by multiple link weights and restricted by multiple constraints. Unfortunately, the problem of finding link/node disjoint paths in multiple dimensions faces different conceptual problems. This paper presents a first step to understanding these conceptual problems in link-disjoint quality of service routing and proposes a heuristic link-disjoint QoS algorithm that circumvents these problems. Copyright # 2003 John Wiley & Sons, Ltd.

Method and apparatus for multimedia interaction routing according to agent capacity sets

Abstract: A routing software application for predicting a best routing destination from a pool of considered routing destinations for an incoming event into a communications routing system has a detection module for detecting the arrival of the event for routing; at least one instance of an information gathering routine for gathering and compiling information about the considered destinations; at least one reporting module for organizing and reporting the gathered information; and a processing module for computing values from the gathered information and selecting the best routing destination based on isolation of the best computed value. In a preferred embodiment scalar load information per media type and per destination and agent skill information related to at least media skills per type of media per destination is processed by the processing module, which isolates, identifies, and selects at least the best destination for routing.