Link State Information Research Articles

EOBDBR: an Efficient Optimum Branching-Based Distributed Broadcast Routing protocol for wireless ad hoc networks

Wireless ad hoc networks are in general characterized by dynamic topologies that do not have a fixed infrastructure. In addition, connectivity is maintained in a decentralized fashion through a form of multi-hop radio network. To this effect, wireless ad hoc networks with asymmetric link costs have been advocated as more realistic ones from a network modeling perspective. In this paper, we propose an Efficient Optimum Branching-based Distributed Broadcast Routing (EOBDBR) protocol for wireless ad hoc networks with asymmetric link costs, which makes use of local information exchange only. The proposed protocol contrasts with centralized routing protocols, in which link state and other relevant information are kept in the routing table of each node. It involves setting up link states, finding minimum in-edge, detecting cycles, re-weighting and breaking cycles. Through extensive simulations, our protocol is compared against four distributed broadcast routing protocols chosen as benchmarks. The performance metrics used are message overhead, total energy consumption, number of rebroadcasting nodes, network lifetime, and broadcast time. The superiority of EOBDBR against the studied benchmark protocols is established with respect to the above-mentioned metrics.

Experiences on implementing a QoS-aware architecture on a DHT based broker overlay

The new scale of the distributed systems due to the evolution of the Internet and new emergent technologies has given rise to applications based on the dissemination of high volumes of information. Future software systems must be responsive to events and must be able to adapt the software to enhance business processes. In this context, the publish/subscribe paradigm has taken special relevance. Event Broker Networks are a scalable incarnation of the publish-subscribe paradigm for building asynchronous systems. These take the form of overlays of broker nodes and various routing schemes and filter mechanisms exist that deliver events from publishers to subscribers efficiently on different overlay structures. While a number of principles on which such architectures ride have been well established, and research efforts were concentrated in areas related to information dissemination, efficient routing algorithms, optimal composition and location of filters, optimization of resources use, reconfigurability and fail tolerance, etc., in last years, the attention has turned to exploring non-functional attributes of such systems. Several commercial products (JMS, MSMQ, Corba Event Service, Corba Notification Service) and research projects (Siena, Hermes, Rebecca) implements notification services that considerably differ each other in features and QoS that they provide. The specific nature of the notification services distributed, large scale, big amount of concurrent messages processed, etc., as well as the diversity and complexity of the facets involved in their implementations, impact negatively on the analysis and evaluation of their behavior while they are in execution. This paper proposes a distributed and scalable publish-subscribe broker with support for QoS named QoSEvBroker. The broker leverages on existing mechanisms to reserve resources in the underlying network and on an overlay network of peer-to-peer rendezvous nodes, to automatically select QoS capable paths. By avoiding flooding of either QoS reservations or link-state information, our solution is able to scale with respect to network size and number of reservations. Some experimental results show the validity of our approach.

Design and Implementation of High Availability OSPF Router

In this paper, we propose a High Availability Open Shortest Path First (HA-OSPF) router which consists of two OSPF router modules, active and standby, to support a high availability network. First, we used the continuous-time Markov chain (CTMC) to analyze the steady-state availability of an HA-OSPF router with one active router and N standby routers (1 + N redundancy model). Then, with the failure detection and recovery rate considered, from analytic results, we show that the HA-OSPF router with 1 + 1 redundancy model, one active and one standby, is the preferred model for enhancing router availability. We also show that the carrier-grade HA-OSPF router availability (i.e., five-nine availability) can be achieved under an appropriate combination of the router module failure rate (λ), repair rate (μ), and the failure detection and recovery rate (δ). Since there is a lack of research on the integration of the redundancy model, link state information backup, and failure detection and recovery, we propose a high availability management middleware (HAM middleware) framework to integrate these three elements. The HAM middleware consists of Availability Management Framework (AMF) service, Checkpoint service, and Failure Manager. It supports health check, state information exchange, and failure detection and recovery. Each HA-OSPF router was designed to have a Linux operating system, HAM middleware, and OSPF process. We have implemented the HA-OSPF router on a PC-based system. Experimental results show that the failure detection and recovery times of the proposed PC-based HA-OSPF router were reduced by 98.76% and 91.45% compared to those of an industry standard approach, VRRP (Virtual Router Redundancy Protocol), for a software failure and a hardware failure, respectively. In addition, we have also implemented the HA-OSPF router on an ATCA (Advanced Telecom Computing Architecture) platform, which can provide an industrial standardized modular architecture for an efficient, flexible, and reliable router design. Based on our ATCA-based platform with 1/δ=217 ms for a software failure and 1/δ=1066 ms for a hardware failure, along with the router module data, 1/λ = 7 years and 1/μ = 4 hours, obtained from Cisco, the availabilities of the proposed ATCA-based HA-OSPF router are 99.99999905% for a software failure and 99.99999867% for a hardware failure. Therefore, the experimental results have shown that both our proposed ATCA-based and PC-based HA-OSPF routers with 1 + 1 redundancy model can easily meet the requirement of carrier-grade availabilities with five-nine.

A cross-layer stability-based routing mechanism for ultra wideband networks

Ultra wideband (UWB) radio is emerging as an attractive physical layer for mobile ad hoc network (MANET). Routing in MANET is a challenge owing to the dynamic nature of network topology and resource constraints. A stable routing mechanism is proposed for UWB network in this paper, focusing on the instability problem derived from communication gray zone. This mechanism is a cross-layer enhancement of ad hoc on-demand vector (AODV) routing protocol, which is named as CLS_AODV. The routing discovery algorithm is extended by introducing the notion of source routing and ad hoc on-demand multipath distance vector (AOMDV) routing. A computing model is established to map received signal strengths into link stability factor and route stability factor which serves as a routing metric for path selection. In contrast to the reactive way in AODV, the received signal strength can be used to reveal the link state information for gray zone prediction, as well as for route state monitoring. A HELLO-based preemptive local route repair algorithm is presented to prevent the occurrence of link breakage. HELLO message is extended not only for neighbor sensing and neighborhood information exchanging, but also as an ON/OFF command to control the position location scheme and HELLO scheme of neighbor nodes. The simulation results show the improvements of CLS_AODV in terms of packet loss ratio and average end-to-end delay without compromising the throughput performance compared with AODV.

Enhanced crankback signaling for multi-domain IP/MPLS networks

Multi-domain traffic engineering is a very challenging problem area and crankback signaling offers a very promising solutions framework herein. Although some initial crankback studies have been done, there is still significant latitude for improving multi-domain crankback performance. Along these lines, this paper studies realistic IP/MPLS multi-domain networks and proposes a novel solution for joint intra/inter-domain signaling crankback. Namely, dynamic intra-domain link-state routing information is coupled with available inter-domain path/distance vector routing state to improve the overall search process. Mechanisms are also introduced to limit crankback overheads and delays. The performance of the proposed solution is then analyzed using simulation and compared against hierarchical inter-domain routing strategies as well as another crankback scheme.

EA-HD: a novel link state update mechanism for ASON

When a connection request comes in a mesh optical network, the routers automatically choose the suitable routing paths and wavelength to it according to the network topology and link-state information saved in its global link-state database. Because some of these wavelengths may be released or occupied at any time, the global state database is always out of date and need update by some update policy. A suitable link-state update policy is critical, since a high-frequency update policy imposes heavy burden on the network, while a low-frequency update would increase the inaccurate of the global link-state database. In this paper, we propose a link-state update policy, named the EA-HD policy, which considers two index of a link, one is the Hamming distance between the local link-state database and the global link-state database, and the other is the used ratio of its wavelengths. The proposed update policy gets a trade-off between the accurate of link-state information and its update cost. Simulation results prove that our scheme achieves a good performance in traffic blocking probability while maintaining moderate volume of update traffic.

Dynamic Multi Constraint Multi Path QOS Routing Algorithm (DMCMPRA)

Novel routing paradigms, based on policies and quality of service (QoS) requirements, have been proposed for the Internet over the last decade. Constraint-based path selection algorithm is of utmost importance in the field of QoS routing. An Internet service provider wants to find paths for QoS flows that optimize the network resources and satisfy the user requirements. But, unfortunately the problem of finding a path with multiple constraints such as delay, jitter, bandwidth, and packet loss is a Nondeterministic polynomial (NP)-complete problem. Hence, various heuristics have been proposed to find a path that satisfies more than one constraint. All these heuristics find feasible path using link-state information, which are considered to be static throughout. These heuristics do not consider the dynamic parameter such as the queuing situation at a given node. Hence, in this paper, a heuristic called dynamic multi constraint multi path routing algorithm (DMCMPRA), which incorporates a better cost model using dynamic variables (viz., buffer occupancy at a node to estimate the link cost) to compute the best path for the QoS flow and to balance the load among alternate feasible paths to the destination, is proposed. DMCMPRA uses the self-adaptive multi-constrained routing algorithm (SAMCRA) to find the k QoS aware paths. Then the link-disjoint multiple constraints routing algorithm (DIMCRA) is used to find all the n link disjoint paths among these k paths. The proposed new cost model is used to select the best path from the n link disjoint paths. On congestion notification, load balancing is achieved by selecting an alternate feasible path from the n-1 link disjoint path using the same cost model. Computer simulations show that the performance of DMCMPRA is better than SAMCRA in terms of the metrics such as percentage of successfully received packets, average delay, etc.

Optimal Transmission Rate Control Policies in a Wireless Link Under Partial State Information

We consider the problem of PHY layer transmission rate control for maximum throughput on a wireless link over a finite time horizon. For each link state there exists a most advantageous transmission rate for the controller. The controller needs to rely on incomplete link state information in the form of positive acknowledgements (ACKs) and negative acknowledgements (NACKs) for transmitted packets. We cast the problem as a partially observed Markov decision processes (POMDP). We focus on the special case of time-invariant or slowly time varying link quality with two states and two control options. In that case, the optimal control problem is a state estimation one and the optimal strategy is of threshold structure, where the thresholds are certain values of the belief of being in one of the two states. The policy admits a simple interpretation: increase rate when the number of successive ACKs exceeds a threshold, and decrease rate when the number of successive NACKs exceeds a threshold.

Selective Precomputation of Alternate Routes Using Link-State Information for IP Fast Restoration

The availability of IP networks has increased its importance due to the evolving use of real-time and mission-critical applications on IP networks. Methods for preparing alternate routing tables that can be used for fast restoration from link failures have been investigated. In such methods, each node has to compute a number of alternate routing tables in advance since they have to prepare for each potential failure. The resulting huge number of alternate routing tables has prevented these methods from being deployed. In this paper, we propose a method for reducing the number of alternate routing tables for link failure. It analyzes three types of shortest path trees on the basis of link-state information. We show that the number of alternate routing tables can be reduced to 1/100, on average, from that with the conventional method, and that they are small enough to be stored in the memory of IP routers. key words: IP fast restoration, link-state routing

An analysis of the lifetime of OLSR networks

The Optimized Link State Routing (OLSR) protocol is a well-known route discovery protocol for ad hoc networks. OLSR optimizes the flooding of link state information through the network using multipoint relays (MPRs). Only nodes selected as MPRs are responsible for forwarding control traffic. Many research papers aim to optimize the selection of MPRs with a specific purpose in mind: e.g., to minimize their number, to keep paths with high Quality of Service or to maximize the network lifetime (the time until the first node runs out of energy). In such analyzes often the effects of the network structure on the MPR selection are not taken into account. In this paper we show that the structure of the network can have a large impact on the MPR selection. In highly regular structures (such as grids) there is even no variation in the MPR sets that result from various MPR selection mechanisms. Furthermore, we study the influence of the network structure on the network lifetime problem in a setting where at regular intervals messages are broadcasted using MPRs. We introduce the ‘maximum forcedness ratio’, as a key parameter of the network to describe how much variation there is in the lifetime results of various MPR selection heuristics. Although we focus our attention to OLSR, a widely implemented protocol, on a more abstract level our results describe the structure of connected sets dominating the 2-hop neighborhood of a node.

A protocol for piggy-backing on Markov based wavelength reservation in WDM optical networks

During lightpath establishment in WDM optical networks, two important steps, other than routing, are: wavelength selection and wavelength reservation. If two or more lightpaths select the same wavelength, wavelength collision occurs. The basic reason for collision is the non-availability of the updated wavelength usage information. Markov based wavelength selection guesses a unique wavelength in advance, where each node periodically broadcasts its adjoining link usage information at a regular interval T . But, at any intermediate time t ( 0 < t < T ) , all nodes use the old update which is already outdated by time t . If T is large, the problem becomes severe. To get around this problem without introducing any extra overhead, we propose a novel technique where the normal control packets, passing through the relevant nodes during [ 0 , T ] , can be leveraged to carry the desired link state information. This may allow us even to increase the value of T (thereby reducing broadcast overhead), when control packets are frequent in the network. We apply the proposed modification to our previous work on Markov selection Split Reservation Protocol (MSRP) and call the modified protocol Fast updated MSRP (FMSRP). In fast update, we “piggy-back” normal control packets with link usage information, in addition to the usual periodic broadcasting of the same at every T . It obviously increases the chance for the nodes to get the latest information of link usage. We have simulated FMSRP and compared it with MSRP and also with another current best protocol (i.e., Markov based Backward Reservation Protocol) to show that the blocking probability for FMSRP improves considerably over them in some regions of offered load.

Effects of Outdated Control Information in Control-Plane-Enabled Optical Networks With Path Protection

New signaling suites for a distributed control plane in wavelength division multiplexing (WDM) networks, such as generalized multiprotocol label switching (GMPLS) and automatic switched optical networks (ASON), allow one to cope with the increasing variability of traffic patterns to be suppor ted by operators by providing a means to dynamically set up and release connections. The dissemination of link-state information [usually provided by routing protocols such as open-shortest-path-first traffic engineering (OSPF-TE)] is essential in this kind of control-plane enabled network: in particular, this information has to be continuously updated to allow routing algorithms to efficiently carry out the path computation. Most of the studies on dynamic traffic routing tend to neglect the effect of delays in control-information distribution on routing performance: in particular, even when the control plane is considered as in testbeds, emulators, or some simulations, the analysis of the effects of control plane delays is limited to a small range of values, applicable to well-specified contexts. Applying a very general control-delay representation, we are able to provide a wide-range simulative study to quantify the effect of sig naling on routing performance, mainly by using the blocking probability metric. We are able to evaluate the effect of outdated information (1) for a wide interval of control delay values, (2) for a large set of routing scenarios, considering, e.g., unprotected, dedica ted, and shared path protection routing, and (3) quan tifying the different delay effects in the absence or in the presence of wavelength conversion capabilities.

Constraint-Based Anycasting Over Optical Burst Switched Networks

We present a communication paradigm called “anycasting,” which is defined as delivering traffic from a source node to any one destination among a set of recipients in the network. An anycasting message finds an appropriate server that can meet the service requirements of the client effectively. We discuss the mathematical framework to provide quality of service (QoS) for anycasting over optical burst switched networks. These QoS parameters include resource availability, reliability, propagation delay, and quality of transmission. With the help of link-state information available at each network element (NE), the bursts are scheduled to their next link. This decentralized way of routing helps to provide optimal QoS and hence decreases the loss of grid jobs due to multiple constraints. We compare the performance of our proposed algorithm with the shortest-path algorithm. Using simulation results performed on different network topologies, we show that the service-aware anycasting paradigm introduced decreases the number of bursts lost.

A load‐based reflection routing protocol with resource pre‐allocation for contention resolution in OBS networks

AbstractWe introduce and evaluate a novel reflection routing protocol to reduce burst losses in emerging optical burst switching (OBS) networks. The proposed solution selects the reflection neighbour based on current link state information. To keep pace with OBS traffic dynamics, we propose link state information to be propagated downstream in the burst control packet. As the result, accurate state information of the return links coming from each adjacent neighbour can be maintained, thus improving reflection neighbour selection. Simulation results show up to 98% improvement against classic reflection routing, also outperforming standard deflection routing (DR) especially for medium‐sized burst lengths. Copyright © 2008 John Wiley &amp; Sons, Ltd.

On the performance of distributed lightpath provisioning with dynamic routing and wavelength assignment

Distributed lightpath provisioning in wavelength-division multiplexing (WDM) networks has gained wide research interests. In this article, we study the performance of distributed lightpath provisioning in WDM networks with dynamic routing and wavelength assignment (RWA). Specifically, we consider the case where routing of each lightpath is calculated based on globally flooded link-state information, and wavelength assignment is decided through local information exchanges. Simulation results show that such schemes steadily outperform those schemes with only global flooding or only local information exchanges. More significantly, the impacts of various factors on the proposed scheme, including RWA algorithm, network topology, number of wavelengths per fiber, global flooding interval, and traffic load, have been evaluated. Such evaluations help to achieve some insights useful for the future developments of efficient lightpath provisioning schemes.

Routing-oriented update schEme (ROSE) for link state updating

Few works have been reported to address the issue of updating link state information in order to effectively facilitate quality-of-service (QoS) routing. The idea of modeling the QoS link state information as random variables has been reported, but none of the existing works have provided a comprehensive probabilistic approach to link state update that takes the probability density functions of both the user's QoS requirements and the network's QoS measurements into account. We propose the routing-oriented update scheme (ROSE) that utilizes the knowledge of the history of network operations and user's QoS requirements to improve the efficiency of link state update without increasing the network overhead. ROSE is a new class-based link state update scheme which intelligently determines class sizes to minimize the impact of inaccurate link state information. Through theoretical analysis and extensive simulations, we demonstrate that ROSE outperforms other class- based link state update policies.

Impact of routing and wavelength selection strategies on GMPLS-controlled distributed restoration

The restorability problem in wavelength-routed networks without wavelength converters is investigated. A distributed control plane based on the generalized multiprotocol label switching (GMPLS) suite is considered for disseminating link-state information and reserving network resources. Different routing and wavelength selection strategies are proposed and a detailed performance analysis is carried out during restoration. Simulation results evaluate the blocking probability due to both lack of available resources (i.e., forward blocking) and resource contentions (i.e., backward blocking). Performance comparison provides some insightful suggestions to be applied to GMPLS-controlled wavelength-routed networks without wavelength converters. First, it is recommended to perform routing and wavelength selection separately at the lightpath source and destination, respectively. Second, routing can be computed on link-state information advertised during provisioning, without the need of flooding link-state information during restoration. In fact, during restoration, the resource contention among concurrent signaling instances is the dominant cause of blocking (i.e., backward blocking overcomes forward blocking). For this reason, intelligent routing and wavelength selection strategies aiming at avoiding or limiting resource contentions can help to improve restorability. In particular, among those strategies, the proposed wavelength selection has a better ability to reduce resource contentions than the routing strategies.

Multidomain shared protection with limited information via MPP and p-cycles

The Internet consists of a collection of more than 21,000 domains called autonomous systems operated mostly under different authorities (operators-providers) that, although they cooperate over different geographical areas, compete in a country or other area. Recently, the path computation element concept has been proposed to generalized multiprotocol label switching controlled optical borne networks to make routing decisions for interdomain connections taking into account traffic engineering, quality of service, and resilience considerations. Still the question of protection shareability emerges. For dedicated protection it is enough to know the topology of the network to be able to calculate disjoint paths. However, to reduce network resource usage by sharing of protection resources (e.g., end-to-end shared protection) it is also mandatory to know the exact working and protection path pairs for all the demands. This can be checked within a domain where not only the full topology and link-state information is flooded but also the working and protection paths are known for each connection; however; over the domain boundaries for security and scalability reasons no such information is being spread. We propose using two techniques that do not require flooding the information on working and protection paths while still allowing the sharing of resources. These two techniques are the multidomain p-cycles and the multidomain multipath routing with protection. After explaining the principles of these methods we evaluate the trade-off between the resource requirement and availability of these techniques by simulations.

Adaptive QoS provisioning by pricing incentive QoS routing for next generation networks

In this paper, we present an integrated solution for enabling the next generation Internet to achieve the differentiated service and availability guarantee. In particular, we utilize a recent proposed service architecture, referred to as Service Vector (SV), to enhance the QoS granularity and flexibility offered in the Diffserv network model and improve both the network resource utilization and user benefits. In order to efficiently and effectively use network resources, we investigate the issue of integrating pricing into QoS routing and propose a PRicing InCEntive QoS Routing (PRICER) mechanism. PRICER consists of two components: a novel routing-oriented state update (ROSE) scheme and an efficient Pricing Incentive Routing Algorithm (PIRA). ROSE performs the task of exchanging link state information throughout the network, and PIRA is a routing algorithm used to find paths meeting the QoS requirements of applications. By theoretical analysis and extensive simulations, we show that ROSE greatly outperforms the state of the arts in terms of both protocol overhead and the accuracy of link state information, and PIRA can guarantee finding the QoS constrained path with fairly low average computational complexity. The most distinguished property of PIRA is its progressive property, which is very useful in practice: it can self-adaptively minimize its computational complexity without sacrificing its performance. Another contribution of this paper is the introduction of a method to numerically evaluate the staleness of link state information.

Boundary Mapping and Boundary-State Routing (BSR) in Ad Hoc Networks

This paper presents a geographic routing protocol, boundary state routing (BSR), which consists of two components. The first is an improved forwarding strategy, greedy-bounded compass, which can forward packets around concave boundaries, where the packet moves away from the destination without looping. The second component is a boundary mapping protocol (BMP), which is used to maintain link state information for boundaries containing concave vertices. The proposed forwarding strategy greedy-bounded compass is shown to produce a higher rate of path completion than Greedy forwarding and significantly improves the performance of greedy perimeter state routing (GPSR) in sparse networks when used in place of greedy forwarding. The proposed geographic routing protocol BSR is shown to produce significant improvements in performance in comparison to GPSR in sparse networks due to informed decisions regarding the direction of boundary traversal at local minima.