Online Routing Algorithm Research Articles

Possible Collision Avoidance with Off-line Route Selection

The paper describes the traffic flow problems in telecommunication networks based on the Internet protocol. The main aim of telecommunication network operator today is to offer an SLA (Service Level Agreement) contract to end users, with provided QoS (Quality of Service) for different classes of services. In order to achieve this, it is necessary to establish the routes between marginal network nodes meeting the network traffic requirements and optimizing the network performances free of simultaneous flows conflicts. In DiffServ/MPLS (Multi-Protocol Label Switching) networks traffic flows traverse the network simultaneously and there may come to collision of concurrent flows. They are distributed among LSPs (Labeled Switching Paths) related to service classes. In LSP creation the IGP (Interior Gateway Protocol) uses simple on-line routing algorithms based on the shortest path methodology. In highly loaded networks this becomes an insufficient technique. In this suggested approach LSP need not necessarily be the shortest path solution. It can be pre-computed much earlier, possibly during the SLA negotiation process. In that sense an effective algorithm for collision control is developed. It may find a longer but lightly loaded path, taking care of the collision possibility. It could be a very good solution for collision avoidance and for better load-balancing purpose where links are running close to capacity. The algorithm can be significantly improved through heuristic approach. Heuristic options are compared in test-examples and their application for collision control is explained. KEYWORDS: Telecommunication networks, collision avoidance, multi-constraint route selection, self-organizing systems, MPLS, QoS

Probing-based anypath forwarding routing algorithms in wireless mesh networks

Existing routing protocols for Wireless Mesh Networks (WMNs) are generally optimized with statistical link measures, without focusing on the intrinsic uncertainty of wireless links. We show evidence that, with the transient link uncertainties at PHY and MAC layers, a pseudo-deterministic routing protocol that relies on average or historic statistics can hardly explore the full potentials of a multi-hop wireless mesh.We study optimal WMN routing using probing-based anypath forwarding, with explicit consideration of transient link uncertainties. Starting from a two-state link capacity model, we show the underlying connection between WMN routing and the classic Canadian Traveller Problem (CTP) [1]. Inspired by a stochastic recoverable version of CTP (SRCTP), we develop an practical SRCTP-based online routing algorithm under link uncertainties. We study how dynamic next-hop selection can be done with low cost, and derive a systematic selection order for minimizing transmission delay. We further extend our solution to a general multi-rate link model, and present a Stopping Theory (ST) based solution, which naturally degrades to the SRCTP algorithm in the two-state link model. We conduct simulation studies to verify the effectiveness of the SRCTP and ST algorithms under diverse network configurations. In particular, compared to deterministic routing, reduction of end-to-end delay (51.15–73.02% for two-state links, 5.16% for multi-rate links) and improvement on packet delivery ratio (99.76% for two-state links, 94.44% for multi-rate links) are observed. By using RTS/CTS as the online probing tool in ns3 simulator, we observed both significant goodput improvements (29.9% than EXOR, 61.8% than HWMP) and much less packet arriving jitter (14.27 times less than EXOR, 45% less than HWMP) as compared to EXOR and HWMP routing protocols.

A coarse-grained differentiated routing algorithm in multi-protocol label switching traffic engineering

A new coarse-grained differentiated least interference routing algorithm (CDLI) with DiffServ-Aware was presented. This algorithm is composed of off-line and on-line stages, taking into account both real-time traffic and best-effort traffic. Off-line stage is to determine the shortest path set disjointed path (DP) database for real-time traffic, and to identify link critical value by traffic profile information of real-time traffic and DP database. On-line stage is at first to select route in the DP database for real-time traffic, if there is no path to meet the needs, the dynamic routing will be operated. On-line routing algorithm chooses the relatively short path for real-time traffic to meet their bandwidth requirements, and for best-effort traffic it chooses a lighter load path. The simulation results show that compared with the dynamic online routing algorithm (DORA) and constrained shortest path first (CSPF) algorithm, the new algorithm can significantly improve network throughput and reduce the average path length of real-time traffic. This guarantees quality of service (QoS) of real-time traffic while improving the utilization of network resources.

Adaptive Online Sensor Clustering and Routing Algorithms for QoS Provisioning and Energy Efficiency

Due to the limited energy supply, energy efficiency is the most important issue for wireless sensor networks. In addition, next generation networks are also expected to support QoS sensitive data services. In this paper, a new online sensor network management scheme is developed for energy efficiency and QoS provisioning. To satisfy these conflicting requirements, the proposed scheme consists of clustering and routing algorithms. Without global network information, the online control paradigm is realized in a distributed way. Therefore, the principle contributions of these algorithms are its scalability and responsiveness to current network situations. Simulation results indicate the superior performance of the proposed schemes, while other schemes cannot offer such an attractive performance balance.

Routing automorphisms of the hypercube

We present an online algorithm for routing the automorphisms (BPC permutations) of the queueless MIMD hypercube. The routing algorithm has the virtue of being executed by each node of the hypercube without knowing the state of the others nodes. The algorithm is also vertex and link-contention free. We show, using the proposed algorithm, that BPC permutations are arbitrarily routable in the considered communication model.

Energy Efficient Online Routing Algorithm for QoS-Sensitive Sensor Networks

In this letter, we propose a new energy efficient online routing algorithm for QoS-sensitive sensor networks. An important design principle underlying our algorithm is online decision making based on real time network estimation. This on-line approach gives adaptability and flexibility to solve a wide range of control tasks for efficient network performance. In addition, our distributed control paradigm is practical for real sensor network management. Simulation results indicate the superior performance of our algorithm between energy efficiency and QoS provisioning.

The Network as a Storage Device: Dynamic Routing with Bounded Buffers

We study dynamic routing in store-and-forward packet networks where each network link has bounded buffer capacity for receiving incoming packets and is capable of transmitting a fixed number of packets per unit of time. At any moment in time, packets are injected at various network nodes with each packet specifying its destination node. The goal is to maximize the throughput, defined as the number of packets delivered to their destinations. In this paper, we make some progress on throughput maximization in various network topologies. Let n and m denote the number of nodes and links in the network, respectively. For line networks, we show that Nearest-to-Go (NTG), a natural distributed greedy algorithm, is $\tilde{O}(\sqrt{n})$-competitive, essentially matching a known $\Omega(\sqrt{n})$lower bound on the performance of any greedy algorithm. We also show that if we allow the online routing algorithm to make centralized decisions, there is a randomized polylog(n)-competitive algorithm for line networks as well as for rooted tree networks, where each packet is destined for the root of the tree. For grid graphs, we show that NTG has a competitive ratio of $\tilde{\Theta}(n^{2/3})$while no greedy algorithm can achieve a ratio better than $\Omega(\sqrt{n})$. Finally, for arbitrary network topologies, we show that NTG is $\tilde{\Theta}(m)$-competitive, improving upon an earlier bound of O(mn).

Routing Bandwidth-Guaranteed Paths in MPLS Traffic Engineering: A Multiple Race Track Learning Approach

This paper presents an efficient adaptive online routing algorithm for the computation of bandwidth-guaranteed paths in multiprotocol label switching witching (MPLS)-based networks by using a learning scheme that computes an optimal ordering of routes. The contribution of this work is twofold. The first is that we propose a new class of solutions other than those available in the literature, incorporating the family of stochastic random races (RR) algorithms. The most popular previously proposed MPLS-based traffic engineering (TE) solutions attempt to find a superior path to route an incoming setup request. Our algorithm, on the other hand, tries to learn an optimal ordering of the paths through which requests can be routed according to the rank of the paths in the order learned by the algorithm. The second contribution of our work is that we have proposed a routing algorithm that has a performance superior to the important algorithms in the literature. Our conclusions are based on three important performance criteria: 1) the rejection ratio, 2) the percentage of accepted bandwidth, and 3) the average route computation time per request. Although some of the previously proposed algorithms were designed to achieve low rejection and high throughput of route requests, they are unreasonably slow. Our algorithm, on the other hand, in general attempts to reject the least number of requests, achieves the highest throughput, and computes routes in the fastest possible time when compared to the algorithms that we used as benchmarks for comparison.

Multicast Communications inAd HocNetworks Using Directional Antennas: A Lifetime-Centric Approach

We consider a wireless ad hoc network where each node employs a single-beam directional antenna and is provisioned with limited energy. We are interested in an online routing algorithm for successive multicast communication requests with the aim of maximizing the network lifetime. The beam-forming property, which is associated with single-beam directional antennas, introduces some unique problems that do not exist for omnidirectional antennas and, therefore, significantly increases the design space for routing algorithms. The contributions of this paper are twofold. First, we provide some important theoretical understanding on various multicast problems and deduce that even an offline version of this problem is NP-hard. Second, we develop a highly competitive online routing algorithm that takes the network lifetime consideration directly into iterative calculations and show that an algorithm that is designed under this methodology provides consistently better performance than the current state-of-the-art algorithm that only considers remaining energy. The theoretical results and routing algorithm in this paper offer some important insights on algorithm design for energy-constrained wireless ad hoc networks with directional antennas

On-line routing and wavelength assignment for dynamic traffic in WDM ring and torus networks

We develop on-line routing and wavelength assignment (RWA) algorithms for WDM bidirectional ring and torus networks with N nodes. The algorithms dynamically support all k-allowable traffic matrices, where k denotes an arbitrary integer vector [k/sub 1/, k/sub 2/,... k/sub N/], and node i, 1 /spl les/ i /spl les/ N, can transmit at most k/sub i/ wavelengths and receive at most k/sub i/ wavelengths. Both algorithms support the changing traffic in a rearrangeably nonblocking fashion. Our first algorithm, for a bidirectional ring, uses [(/spl Sigma//sub i=1//sup N/ k/sub i/)/3] wavelengths in each fiber and requires at most three lightpath rearrangements per new session request regardless of the number of nodes N and the amount of traffic k. When all the k/sub i/'s are equal to k, the algorithm uses [kN/3] wavelengths, which is known to be the minimum for any off-line rearrangeably nonblocking algorithm. Our second algorithm, for a torus topology, is an extension of a known off-line algorithm for the special case with all the k/sub i/'s equal to k. For an R /spl times/ C torus network with R /spl ges/ C nodes, our on-line algorithm uses [kR/2] wavelengths in each fiber, which is the same as in the off-line algorithm, and is at most two times a lower bound obtained by assuming full wavelength conversion at all nodes. In addition, the on-line algorithm requires at most C - 1 lightpath rearrangements per new session request regardless of the amount of traffic k. Finally, each RWA update requires solving a bipartite matching problem whose time complexity is only O (R), which is much smaller than the time complexity O(kCR/sup 2/) of the bipartite matching problem for an off-line algorithm.

A Routing Algorithm for Ad Hoc Networks Based on Delaunay Triangulation

Delaunay triangulation has been widely used in many fields such as computational fluid dynamics, statistics, meteorology, solid state physics, computational geometry and so on. With the development of Ad Hoc networks, some researchers proposed geometric routing protocols to guarantee the delivery of the packet between any pair of nodes in the network, and the underlying network topology is also constructed by the ways of Delaunay triangulation. In this paper, a novel online routing algorithm GLNFR (greedy and local neighbor face routing) for finding communication paths between the mobile nodes is proposed. The localized manner is used to form the local Delaunay triangulation as the underlying topology of a wireless network on which the GLNFR routing algorithm could guarantee the delivery of the packets. It has better scalability and adaptability for the change of networks. Experiment on NS (network simulator) has been conducted. The results show that the delivery success rate of packets and routing protocol overhead under such novel routing protocols performs better than others proposed

A matrix-based analytical approach to connection unavailability estimation in shared backup path protection

This letter introduces a matrix-based approach to connection unavailability estimation in shared backup path protection (SBPP). The proposed approach yields accurate results for networks of national size using simple matrix operations, being therefore suitable for online routing algorithms. The accuracy of the unavailability estimates is verified through simulations.

Source routing and scheduling in packet networks

We study routing and scheduling in packet-switched networks. We assume an adversary that controls the injection time, source, and destination for each packet injected. A set of paths for these packets is admissible if no link in the network is overloaded. We present the first on-line routing algorithm that finds a set of admissible paths whenever this is feasible. Our algorithm calculates a path for each packet as soon as it is injected at its source using a simple shortest path computation. The length of a link reflects its current congestion. We also show how our algorithm can be implemented under today's Internet routing paradigms.When the paths are known (either given by the adversary or computed as above), our goal is to schedule the packets along the given paths so that the packets experience small end-to-end delays. The best previous delay bounds for deterministic and distributed scheduling protocols were exponential in the path length. In this article, we present the first deterministic and distributed scheduling protocol that guarantees a polynomial end-to-end delay for every packet.Finally, we discuss the effects of combining routing with scheduling. We first show that some unstable scheduling protocols remain unstable no matter how the paths are chosen. However, the freedom to choose paths can make a difference. For example, we show that a ring with parallel links is stable for all greedy scheduling protocols if paths are chosen intelligently, whereas this is not the case if the adversary specifies the paths.

An online throughput-competitive algorithm for multicast routing and admission control

We present the first polylog-competitive online algorithm for the general multicast admission control and routing problem in the throughput model. The ratio of the number of requests accepted by the optimum offline algorithm to the expected number of requests accepted by our algorithm is O ( ( log n + log log M ) ( log n + log M ) log n ) , where M is the number of multicast groups and n is the number of nodes in the graph. We show that this is close to optimum by presenting an Ω ( log n log M ) lower bound on this ratio for any randomized online algorithm against an oblivious adversary, when M is much larger than the link capacities. Our lower bound applies even in the restricted case where the link capacities are much larger than bandwidth requested by a single multicast. We also present a simple proof showing that it is impossible to be competitive against an adaptive online adversary. As in the previous online routing algorithms, our algorithm uses edge-costs when deciding on which is the best path to use. In contrast to the previous competitive algorithms in the throughput model, our cost is not a direct function of the edge load. The new cost definition allows us to decouple the effects of routing and admission decisions of different multicast groups.

Competitive online routing in geometric graphs

We consider online routing algorithms for finding paths between the vertices of plane graphs. Although it has been shown in Bose et al. (Internat. J. Comput. Geom. 12(4) (2002) 283) that there exists no competitive routing scheme that works on all triangulations, we show that there exists a simple online O(1)-memory c-competitive routing strategy that approximates the shortest path in triangulations possessing the diamond property, i.e., the total distance travelled by the algorithm to route a message between two vertices is at most a constant c times the shortest path. Our results imply a competitive routing strategy for certain classical triangulations such as the Delaunay, greedy, or minimum-weight triangulation, since they all possess the diamond property. We then generalize our results to show that the O(1)-memory c-competitive routing strategy works for all plane graphs possessing both the diamond property and the good convex polygon property.

Online Routing in Triangulations

We consider online routing algorithms for routing between the vertices of embedded planar straight line graphs. Our results include (1) two deterministic memoryless routing algorithms, one that works for all Delaunay triangulations and the other that works for all regular triangulations; (2) a randomized memoryless algorithm that works for all triangulations; (3) an O(1) memory algorithm that works for all convex subdivisions; (4) an O(1) memory algorithm that approximates the shortest path in Delaunay triangulations; and (5) theoretical and experimental results on the competitiveness of these algorithms.

Robust traffic engineering

On-line routing algorithms deal with requests as they arrive without assuming any knowledge of the underlying process that generates the streams of requests. By contrast, off-line traffic engineering algorithms assume complete statistical knowledge of the request generating process. This dichotomy, however, oversimplifies many practical situations when some incomplete information on the expected demands is available, and proper utilization of the available information may improve the network performance. This paper proposes a game theoretic framework for robust traffic engineering intended to guard against the worst case scenario with respect to possible uncertainties in the external demands and link loads. The proposed framework can be interpreted as a game of the routing algorithm attempting to optimize the network performance and the adversarial environment attempting to obstruct these efforts by selecting the worst case scenario with respect to the uncertainties. Two different classes of schemes are considered: first, suitable for MPLS implementation, centralized schemes, and, second, suitable for OSPF-OMP implementation, decentralized schemes.

ONLINE ROUTING IN CONVEX SUBDIVISIONS

We consider online routing algorithms for finding paths between the vertices of plane graphs. We show (1) there exists a routing algorithm for arbitrary triangulations that has no memory and uses no randomization, (2) no equivalent result is possible for convex subdivisions, (3) there is no competitive online routing algorithm under the Euclidean distance metric in arbitrary triangulations, and (4) there is no competitive online routing algorithm under the link distance metric even when the input graph is restricted to be a Delaunay, greedy, or minimum-weight triangulation.

DORA: Efficient Routing for MPLS Traffic Engineering

This paper introduces DORA, a dynamic online routing algorithm for construction of bandwidth guaranteed paths in MPLS-enabled networks. The main objective of DORA is to place paths with reserved bandwidth evenly across the network in order to allow more future paths to be accepted into the network and to balance the traffic load. During path computation, the key operation in DORA is to avoid routing over links that (1) have high potential to be part of any other path, and (2) have low residual bandwidth available. Our simulation results based on unsuccessful path-setup ratio and successful path-reroutes upon link failure, show that DORA offers better performance than some sophisticated algorithms, while at the same time being less computationally expensive.

Minimum-interference routing based on flow maximisation

A new on-line routing algorithm based on the notion of minimum-interference is presented. The algorithm maximises the sum of residual flows of ingress–egress pairs, using a simple heuristic method. It achieves good results in terms of total bandwidth routed.