Showing papers on "Link-state routing protocol published in 1997"

A highly adaptive distributed routing algorithm for mobile wireless networks

Abstract: We present a new distributed routing protocol for mobile, multihop, wireless networks. The protocol is one of a family of protocols which we term "link reversal" algorithms. The protocol's reaction is structured as a temporally-ordered sequence of diffusing computations; each computation consisting of a sequence of directed link reversals. The protocol is highly adaptive, efficient and scalable; being best-suited for use in large, dense, mobile networks. In these networks, the protocol's reaction to link failures typically involves only a localized "single pass" of the distributed algorithm. This capability is unique among protocols which are stable in the face of network partitions, and results in the protocol's high degree of adaptivity. This desirable behavior is achieved through the novel use of a "physical or logical clock" to establish the "temporal order" of topological change events which is used to structure (or order) the algorithm's reaction to topological changes. We refer to the protocol as the temporally-ordered routing algorithm (TORA).

Associativity-Based Routing for Ad Hoc Mobile Networks

Abstract: This paper presents a new, simple and bandwidth-efficient distributed routing protocol to support mobile computing in a conference size ad-hoc mobile network environment. Unlike the conventional approaches such as link-state and distance-vector distributed routing algorithms, our protocol does not attempt to consistently maintain routing information in every node. In an ad-hoc mobile network where mobile hosts (MHs) are acting as routers and where routes are made inconsistent by MHs‘ movement, we employ an associativity-based routing scheme where a route is selected based on nodes having associativity states that imply periods of stability. In this manner, the routes selected are likely to be long-lived and hence there is no need to restart frequently, resulting in higher attainable throughput. Route requests are broadcast on a per need basis. The association property also allows the integration of ad-hoc routing into a BS-oriented Wireless LAN (WLAN) environment, providing the fault tolerance in times of base stations (BSs) failures. To discover shorter routes and to shorten the route recovery time when the association property is violated, the localised-query and quick-abort mechanisms are respectively incorporated into the protocol. To further increase cell capacity and lower transmission power requirements, a dynamic cell size adjustment scheme is introduced. The protocol is free from loops, deadlock and packet duplicates and has scalable memory requirements. Simulation results obtained reveal that shorter and better routes can be discovered during route re-constructions.

A new routing protocol for the reconfigurable wireless networks

Abstract: We propose a new routing protocol, the Zone Routing Protocol (ZRP), for the reconfigurable wireless networks, a large scale, highly mobile ad-hoc networking environment. The novelty of the ZRP protocol is that it is applicable to large flat-routed networks. Furthermore, through the use of the zone radius parameter, the scheme exhibits the adjustable hybrid behavior of proactive and reactive routing schemes. We evaluate the performance of the protocol, showing the reduction in the number of control messages, as compared with other reactive schemes, such as flooding.

Small forwarding tables for fast routing lookups

Abstract: For some time, the networking community has assumed that it is impossible to do IP routing lookups in software fast enough to support gigabit speeds. IP routing lookups must find the routing entry with the longest matching prefix, a task that has been thought to require hardware support at lookup frequencies of millions per second.We present a forwarding table data structure designed for quick routing lookups. Forwarding tables are small enough to fit in the cache of a conventional general purpose processor. With the table in cache, a 200 MHz Pentium Pro or a 333 MHz Alpha 21164 can perform a few million lookups per second. This means that it is feasible to do a full routing lookup for each IP packet at gigabit speeds without special hardware.The forwarding tables are very small, a large routing table with 40,000 routing entries can be compacted to a forwarding table of 150-160 Kbytes. A lookup typically requires less than 100 instructions on an Alpha, using eight memory references accessing a total of 14 bytes.

An Engineering Approach to Computer Networking: ATM Networks, the Internet, and the Telephone Network

Abstract: (Most chapters contain a Summary.) Preface xiii. SECTION II. INTRODUCTION. 1. Atoms, Bits, and Networks. Introduction. Common Network Technologies. Networking Concepts and Techniques. Engineering Computer Networks. In Closing. 2. The Telephone Network: Concepts, History, and Challenges. Concepts. End-Systems. Transmission. Switching. Signaling. Cellular Communications. Historical Sketch. Challenges. Summary. 3. The Internet: Concepts, History, and Challenges. Concepts. Basic Internet Technology. Addressing. Routing. Endpoint Control. History. Challenges. Summary. 4. Atm Networks: Concepts, History, and Challenges. Virtual Circuits. Fixed-Size Packets. Small Packet Size. Statistical Multiplexing. Integrated Service. History. Challenges. Summary. SECTION II. TOOLS AND TECHNIQUES. 5. Protocol Layering. Protocols and Protocol Layering. Importance of Layering. Problems With Layering. Iso-Osi Reference Model. The Seven Layers. Summary. 6. System Design. Introduction. Resource Constraints and Their Metrics. Common Design Techniques. Performance Analysis and Tuning. Summary. 7. Multiple Access. Introduction. Choices and Constraints. Base Technologies. Centralized Access Schemes. Distributed Schemes. Summary. 8. Switching. Introduction. Circuit Switching. Packet Switching. Switch Fabrics. Buffering. Multicasting. Summary. 9. Scheduling. Introduction. Requirements. Fundamental Choices. Scheduling Best-Effort Connections. Scheduling Guaranteed-Service Connections. Comparison. Packet Dropping. Summary. 10. Naming and Addressing. Introduction. Naming and Addressing. Hierarchical Naming. Addressing. Addressing in the Telephone Network. Addressing in the Internet. Nsaps: Addressing in ATM Networks. Name Resolution. Datalink Layer Addressing. Finding Datalink Layer Addresses. Summary. 11. Routing. Introduction. Routing Protocol Requirements. Choices. Routing in the Telephone Network. Distance-Vector Routing. Link-State Routing. Choosing Link Costs. Hierarchical Routing. Internet Routing Protocols. Routing Within a Broadcast Lan. Multicast Routing. Routing With Policy Constraints. Routing for Mobile Hosts. Summary. 12. Error Control. Causes of Bit Errors. Bit-Error Detection and Correction. Causes of Packet Errors. Packet-Error Detection and Correction. Summary. 13. Flow Control. Model. Classification. Open-Loop Flow Control. Closed-Loop Flow Control. Hybrid Flow Control. Summary. 14. Traffic Management. Introduction. An Economic Framework for Traffic Management. Traffic Models. Traffic Classes. Time Scales of Traffic Management. Scheduling. Renegotiation. Signaling. Admission Control. Peak-Load Pricing. Capacity Planning. Summary. SECTION III. PRACTICE. 15. Common Protocols. Introduction. Telephone Network Protocols. Internet Protocols. Atm Network Protocols. Ip Over Atm. Summary. 16. Protocol Implementation. Introduction. Factors Affecting Protocol Stack Performance. Common Protocol Stack Procedures. Partitioning Strategies. Interface Among Protocol Layers. Protocol Implementation. Some Rules of Thumb. Summary. References. Glossary. Answers to Review Questions and Selected Exercises. Index. 0201634422T04062001

A cluster-based approach for routing in dynamic networks

Abstract: The design and analysis of routing protocols is an important issue in dynamic networks such as packet radio and ad-hoc wireless networks Most conventional protocols exhibit their least desirable behavior for highly dynamic interconnection topologies We propose a new methodology for routing and topology information maintenance in dynamic networks The basic idea behind the protocol is to divide the graph into a number of overlapping clusters A change in the network topology corresponds to a change in cluster membership We present algorithms for creation of clusters, as well as algorithms to maintain them in the presence of various network events Compared to existing and conventional routing protocols, the proposed cluster-based approach incurs lower overhead during topology updates and also has quicker reconvergence The effectiveness of this approach also lies in the fact that existing routing protocols can be directly applied to the network --- replacing the nodes by clusters

QoS routing mechanisms and OSPF extensions

Abstract: This paper presents and discusses path selection algorithms to support QoS routes in IP networks. The work is carried out in the context of extensions to the OSPF protocol, and the initial focus is on unicast flows, although some of the proposed extensions are also applicable to multicast flows. We first review the metrics required to support QoS, and then present and compare several path selection algorithms, which represent different trade-offs between accuracy and computational complexity. We also describe and discuss the associated link advertisement mechanisms, and investigate some options in balancing the requirements for accurate and timely information with the associated control overhead. The overall goal of this study is to identify a framework and possible approaches to allow deployment of QoS routing capabilities with the minimum possible impact to the existing routing infrastructure.

On path selection for traffic with bandwidth guarantees

Abstract: Transmission of multimedia streams imposes a minimum-bandwidth requirement on the path being used to ensure end-to-end Quality-of-Service (QoS) guarantees. While any shortest-path algorithm can be used to select a feasible path, additional constraints that limit resource consumption and balance the network load are needed to achieve efficient resource utilization. We present a systematic evaluation of four routing algorithms that offer different tradeoffs between limiting the path hop count and balancing the network load. Our evaluation considers not only the call blocking rate but also the fairness to requests for different bandwidths, robustness to inaccurate routing information, and sensitivity to the routing information update frequency. It evaluates not only the performance of these algorithms for the sessions with bandwidth guarantees, but also their impact on the lower priority best-effort sessions. Our results show that a routing algorithm that gives preference to limiting the hop count performs better when the network load is heavy, while an algorithm that gives preference to balancing the network load performs slightly better when the network load is light. We also show that the performance of using pre-computed paths with a few discrete bandwidth requests is comparable to that of computing paths on-demand, which implies feasibility of class-based routing. We observe that the routing information update interval can be set reasonably large to reduce routing overhead without sacrificing the overall performance, although an increased number of sessions can be misrouted.

Internet routing instability

Abstract: This paper examines the network inter-domain routing information exchanged between backbone service providers at the major U.S. public Internet exchange points. Internet routing instability, or the rapid fluctuation of network reachability information, is an important problem currently facing the Internet engineering community. High levels of network instability can lead to packet loss, increased network latency and time to convergence. At the extreme, high levels of routing instability have lead to the loss of internal connectivity in wide-area, national networks. In this paper, we describe several unexpected trends in routing instability, and examine a number of anomalies and pathologies observed in the exchange of inter-domain routing information. The analysis in this paper is based on data collected from BGP routing messages generated by border routers at five of the Internet core's public exchange points during a nine month period. We show that the volume of these routing updates is several orders of magnitude more than expected and that the majority of this routing information is redundant, or pathological. Furthermore, our analysis reveals several unexpected trends and ill-behaved systematic properties in Internet routing. We finally posit a number of explanations for these anomalies and evaluate their potential impact on the Internet infrastructure.

Ant-like agents for load balancing in telecommunications networks

Abstract: This paper describes a novel method of achieving load balancing in telecommunications networks. A simulated network models a typical distribution of calls between arbitrary nodes; nodes carrying an excess of traffic can become congested , causing calls to fail. In addition to calls, the network also supports a population of simple mobile agents with behaviours modelled on the trail laying abilities of ants. The agents move across the network between arbitrary pairs of nodes, selecting their path at each intermediate node according to the distribution of simulated pheromones at each node. As they move they deposit simulated pheromones as a function of their distance from their source node, and the congestion encountered on their journey. Calls between nodes are routed as a function of the pheromone distributions at each intermediate node. The performance of the network is measured by the proportion of calls which fail. The results are compared with those achieved by using fixed shortest-path routes, and also by using an alternative algorithmically-based type of mobile agent. The ant-based system is shown to drop fewer calls than the other methods, while exhibiting many attractive features of distributed control.

QoS based routing in networks with inaccurate information: theory and algorithms

Abstract: We investigate the problem of routing connections with QoS requirements across one or more networks, when the information available for making routing decisions is inaccurate and expressed in some probabilistic manner. This uncertainty about the actual state of a node or network arises naturally in a number of different environments, that are reviewed in the paper. The main focus is to determine the impact of such inaccuracies on the path selection process, whose goal is then to identify the path that is most likely to satisfy the QoS requirements.

Ants and reinforcement learning: a case study in routing in dynamic networks

Abstract: We investigate two new distributed routing algorithms for data networks based on simple biological "ants" that explore the network and rapidly learn good routes, using a novel variation of reinforcement learning. These two algorithms are fully adaptive to topology changes and changes in link costs in the network, and have space and computational overheads that are competitive with traditional packet routing algorithms: although they can generate more routing traffic when the rate of failures in a network is low, they perform much better under higher failure rates. Both algorithms are more resilient than traditional algorithms, in the sense that random corruption of routing state has limited impact on the computation of paths. We present convergence theorems for both of our algorithms drawing on the theory of non-stationary and stationary discrete-time Markov chains over the reals. We present an extensive empirical evaluation of our algorithms on a simulator that is widely used in the computer networks community for validating and testing protocols. We present comparative results on data delivery performance, aggregate routing traffic (algorithm overhead), as well as the degree of resilience for our new algorithms and two traditional routing algorithms in current use. We also show that the performance of our algorithms scale well with increase in network size-using a realistic topology.

Quality-of-Service Routing for Traffic with Performance Guarantees

Abstract: Quality-of-Service (QoS) routing tries to select a path that satisfies a set of QoS constraints, while also achieving overall network resource efficiency. We present initial results on QoS path selection for traffic requiring bandwidth and delay guarantees. For traffic with bandwidth guarantees, we found that several routing algorithms that favor paths with fewer hops perform well. For traffic with delay guarantees, we show that for a broad class of WFQ-like scheduling algorithms, the problem of finding a path satisfying bandwidth, delay, delay-jitter, and/or buffer space constraints while at the same time deriving the bandwidth that has to be reserved to meet these constraints, is solvable by a modified version of the Bellman-Ford shortest-path algorithm in polynomial time.

Performance of alternate routing methods in all-optical switching networks

Abstract: We study routing methods in all-optical switching networks. In all-optical switching networks, the connection with more hops encounters more call blocking, and it is especially true in optical networks with no wavelength conversions. We therefore consider an alternate routing method with limited trunk reservation in which connections with more hops are prepared more alternate routes. Through developing an approximate analytic approach, we show that our method keeps good performance when compared with the existing alternate routing methods, and also that the fairness among connections can be improved. Further performance improvement is investigated by introducing a wavelength assignment policy and a dynamic routing method. An effectiveness of the proposed method is investigated through simulation.

A protocol for scalable loop-free multicast routing

Abstract: In network multimedia applications such as multiparty teleconferencing, users often need to send the same information to several (but not necessarily all) other users. To manage such one-to-many or many-to-many communication efficiently in wide-area internetworks, it is imperative to support and perform multicast routing. Multicast routing sends a single copy of a message from a source to multiple receivers over a communication link that is shared by the paths to the receivers. Loop-freedom is an especially important consideration in multicasting because applications using multicasting tend to be multimedia and bandwidth intensive, and loops in multicast routing duplicate looping packets. We present and verify a new multicast routing protocol, called multicast Internet protocol (MIP), which offers a simple and flexible approach to constructing both group-shared and shortest-paths multicast trees. MIP can be sender-initiated or receiver-initiated or both; therefore, it can be tailored to the particular nature of an application's group dynamics and size. MIP is independent of the underlying unicast routing algorithms used. MIP is robust and adapts under dynamic network conditions (topology or link cost changes) to maintain loop-free multicast routing. Under stable network conditions, MIP has no maintenance or control message overhead. We prove that MIP is loop-free at every instant, and that it is deadlock-free and obtains multicast routing trees within a finite time after the occurrence of an arbitrary sequence of topology or unicast changes.

Securing distance-vector routing protocols

Abstract: We analyze the security requirements of distance-vector routing protocols, identify their vulnerabilities, and propose countermeasures to these vulnerabilities. The innovation we propose involves the use of mechanisms from the path-finding class of distance-vector protocols as a solution to the security problems of distance-vector protocols. The result is a proposal that effectively and efficiently secures distance-vector protocols in constant space.

An efficient message authentication scheme for link state routing

Abstract: We study methods for reducing the cost of secure link state routing. In secure link state routing, routers may need to verify the authenticity of many routing updates, and some routers such as border routers may need to sign many routing updates. Previous work such as public-key based schemes are very expensive computationally or have certain limitations. This paper presents an efficient solution, based on a detection-diagnosis-recovery approach, for the link state routing update authentication problem. Our scheme is scalable to handle large networks, applicable to routing protocols that use multiple-valued cost metrics, and applicable even, when link states change frequently.

A system and traffic dependent adaptive routing algorithm for ad hoc networks

Abstract: An ad hoc network consists of a number of mobile hosts who communicate with each other over a wireless channel without any centralized control. The basic problem is to obtain a distributed routing scheme so that under the network connectivity assumption any mobile host can transmit/receive data from any other host in the network. In this paper we propose a new routing algorithm for ad hoc networks. The proposed algorithm uses a more appropriate distance measure given by the expected delay along a path, instead of the number of hops used in most of the existing algorithms. This metric allows the algorithm to adapt to changes not only in the topology of the network, but also in the traffic intensity. The algorithm uses a novel technique for estimating the path delays without requiring the links to be bidirectional or the clocks at the nodes in the network to be synchronized. The proposed algorithm is able to perform both reliable and good routing with low communication overhead and computational requirements.

Dual Reinforcement Q-Routing: An On-Line Adaptive Routing Algorithm

Abstract: This paper describes and evaluates the Dual Reinforcement Q-Routing algorithm (DRQ-Routing) for adaptive packet routing in communication networks. Each node in the network has a routing decision maker that adapts, on-line, to learn routing policies that can sustain high network loads and have low average packet delivery time. These decision makers learn based on the information they get back from their neighboring nodes as they send packets to them (forward exploration similar to Q-Routing) and the information appended to the packets they receive from their neighboring nodes (backward exploration unique to DRQ-Routing). Experiments over several network topologies have shown that at low loads, DRQ-Routing learns the optimal policy more than twice as fast as Q-Routing, and at high loads, it learns routing policies that are more than twice as good as Q-Routing in terms of average packet delivery time. Further, DRQ-Routing is able to sustain higher network loads than Q-Routing and non-adaptive shortest-path routing.

Reducing the cost of security in link-state routing

Abstract: Security in link-state routing protocols is a feature that is both desirable and costly. This paper examines the cost of security and presents two techniques for efficient and secure processing of link state updates. The first technique is geared towards a relatively stable internetwork environment while the second is designed with a more volatile environment in mind.

Compressionless routing: a framework for adaptive and fault-tolerant routing

Abstract: Compressionless routing (CR) is an adaptive routing framework which provides a unified framework for efficient deadlock free adaptive routing and fault tolerance. CR exploits the tight coupling between wormhole routers for flow control to detect and recover from potential deadlock situations. Fault tolerant compressionless routing (FCR) extends CR to support end to end fault tolerant delivery. Detailed routing algorithms, implementation complexity, and performance simulation results for CR and FCR are presented. These results show that the hardware for CR and FCR networks is modest. Further, CR and FCR networks can achieve superior performance to alternatives such as dimension order routing. Compressionless routing has several key advantages: deadlock free adaptive routing in toroidal networks with no virtual channels, simple router designs, order preserving message transmission, applicability to a wide variety of network topologies, and elimination of the need for buffer allocation messages. Fault tolerant compressionless routing has several additional advantages: data integrity in the presence of transient faults (nonstop fault tolerance), permanent fault tolerance, and elimination of the need for software buffering and retry for reliability. The advantages of CR and FCR not only simplify hardware support for adaptive routing and fault tolerance, they also can simplify software communication layers.

Selection of routing paths in data communications networks to satisfy multiple requirements

Abstract: Methods, systems and computer program products which identify network routing paths having a first performance characteristic less than a first specified limit and a second performance characteristic less than a second specified limit from a plurality of routing paths. These routing paths are identified by combining both the first performance characteristic and the second performance characteristic for one of the plurality of routing paths to provide a third performance characteristic which differs from both the first and the second performance characteristic and which operates as a proxy for the first and second performance characteristic. It is then determined if the third performance characteristic of the routing path is less than a third performance limit associated with the third performance characteristic.

Dynamic global packet routing in wireless networks

Abstract: We consider schemes for reuse-efficient packet access in wireless data networks. We show that computing the maximum ergodic packet arrival rate is NP-hard. We give an upper bound on the maximum ergodic throughput in terms of the eigenvalues of matrices related to the path-gain matrix. We present simple, practical heuristic algorithms which exhibit good throughput and packet delay and report on results of preliminary simulations. More sophisticated algorithms that yield optimal throughput are also presented. A recent result of McKeown, Anantharam and Walrand (1996) on scheduling of input-queued switches is obtained as a by-product.

QoS based routing algorithm in integrated services packet networks

Abstract: In this paper we study QoS based routing algorithm for supporting resource reservation in high-speed Integrated Services Packet Network (ISPN). Recently, this problem was proved to be NP-complete. However, when the considered QoS constraints are bandwidth, delay, delay jitter, and loss free, we have shown that by employing Weighted Fair Queueing (WFQ) service discipline, the complexity of the problem could be reduced to that of shortest path routing without any QoS constraints. Then such a multiple QoS constrained route could be searched in polynomial time. We also present the routing algorithm (called "QoSR/sub BF/"), which is a modified version of Bellman-Ford shortest path algorithm. Simulation results show that QoSR/sub BF/ has better performance compared to the existing QoS routing algorithms.

On deadlocks in interconnection networks

Abstract: Deadlock avoidance-based and deadlock recovery-based routing algorithms have been proposed in recent years without full understanding of the likelihood and characteristics of actual deadlocks in interconnection networks. This work models the interrelationships between routing freedom, message blocking, correlated resource dependencies and deadlock formation. We empirically show that increasing routing freedom, as achieved by allowing unrestricted routing over multiple virtual channels, makes deadlocks highly improbable and reduces the likelihood of other types of correlated message blocking behavior that can degrade performance. Our results further substantiate that recovery-based routing algorithms have a higher potential performance advantage over deadlock avoidance-based routing algorithms which, inherently, allow less routing freedom.

Dynamic wavelength allocation in all-optical ring networks

Abstract: We focus on wavelength allocation schemes for all-optical WDM ring networks. For an N node network we characterize the traffic by its load L/sub max/ (the maximum number of lightpaths that share a link) and do not assume knowledge of the arrival/departure processes. We prove that shortest path routing produces a routing which has at most twice the load of the optimal solution. We show that at least 0.5 L/sub max/ log/sub 2/N+L/sub max/ wavelengths are required by any algorithm in the worst case, and develop an algorithm which requires up to 3 L/sub max/ log/sub 2/N wavelengths. For the case when the load is high and blocking is necessary we present an improved algorithm.

On two-step routing for FPGAS

Abstract: We present results which show that a separate global and detailed routing strategy can be competitive with a combined routing process. Under restricted architectural assumptions, we compute a new lower bound for detailed routing and show that our detailed router typically requires no more than two extra routing tracks above this computed limit. Also, experimental results show that the Mapping Anomaly presented in [20], which suggests that separated routing may yield arbitrarily poor results in certain instances, is a concern only if nets are restricted to a single track domain. Finally, to motivate future work, we show the latest two-step routing results that we have achieved with the VPR global router and SEGA detailed router tools on the largest CBL benchmark circuits.

Path switching-a quasi-static routing scheme for large-scale ATM packet switches

Abstract: A quasi-static routing scheme called path switching for large-scale ATM packet switch systems is proposed. Previously the Clos network has been used as the model for many large-scale ATM switch architectures, in which the most difficult issue is path and bandwidth assignment for each connection request. The static routing scheme, such as multirate circuit switching, does not fully exploit the statistical multiplexing gain. In contrast, the dynamic routing scheme, such as straight matching, requires slot-by-slot computation of route assignment. Path switching is a compromise of these two routing schemes. It uses a predetermined periodical connection pattern in the central stage, look-ahead selection in the input stage, and output queueing in the last stage. The scheduling of path switching consists of capacity assignment and route assignment. The capacity assignment is constrained by the quality of service of connection requests. The route assignment is based on the timespace interleaving of the coloring of bipartite multigraphs. We show that path switching can handle multirate and multimedia traffic effectively in the Clos network.

Improving the efficiency of adaptive routing in networks with irregular topology

Abstract: Networks of workstations are emerging as a cost-effective alternative to parallel computers. The interconnection between workstations usually relies on switch-based networks with irregular topologies. This irregularity makes routing and deadlock avoidance quite complicated. Current proposals avoid deadlock by removing cyclic dependencies between channels and therefore, many messages are routed along non-minimal paths, increasing latency and wasting resources. We propose a general methodology for the design of adaptive routing algorithms for networks with irregular topology that improves a previously proposed one by reducing the probability of routing over non-minimal paths. The resulting routing algorithms allow messages to follow minimal paths in most cases, reducing message latency and increasing network throughput. As an example of application, we propose an improved adaptive routing algorithm for Autonet.