Showing papers on "Routing table published in 1997"

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.

Scalable high speed IP routing lookups

Abstract: Internet address lookup is a challenging problem because of increasing routing table sizes, increased traffic, higher speed links, and the migration to 128 bit IPv6 addresses. IP routing lookup requires computing the best matching prefix, for which standard solutions like hashing were believed to be inapplicable. The best existing solution we know of, BSD radix tries, scales badly as IP moves to 128 bit addresses. Our paper describes a new algorithm for best matching prefix using binary search on hash tables organized by prefix lengths. Our scheme scales very well as address and routing table sizes increase: independent of the table size, it requires a worst case time of log2(address bits) hash lookups. Thus only 5 hash lookups are needed for IPv4 and 7 for IPv6. We also introduce Mutating Binary Search and other optimizations that, for a typical IPv4 backbone router with over 33,000 entries, considerably reduce the average number of hashes to less than 2, of which one hash can be simplified to an indexed array access. We expect similar average case behavior for IPv6.

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.

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

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.

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.

ATM-based routing in LEO/MEO satellite networks with intersatellite links

Abstract: An asynchronous transfer mode (ATM)-based concept for the routing of information in a low Earth orbit/medium Earth orbit (LEO/MEO) satellite system including intersatellite links (ISLs) is proposed. Specific emphasis is laid on the design of an ATM-based routing scheme for the ISL part of the system. The approach is to prepare a virtual topology by means of virtual path connections (VPCs) connecting all pairs of end nodes in the ISL subnetwork for a complete period in advance, similar to implementing a set of (time dependent) routing tables. The search for available end-to-end routes within the ISL network is based on a modified Dijkstra (1959) shortest path algorithm (M-DSPA) capable of coping with the time-variant topology. With respect to the deterministic time variance of the considered ISL topologies, an analysis of optimization aspects for the selection of a path at call setup time is presented. The performance of the path search in combination with a specific optimization procedure is-by means of extensive simulations-evaluated for example LEO and MEO ISL topologies, respectively.

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.

Scalable high speed IP routing lookups

Abstract: Internet address lookup is a challenging problem because of increasing routing table sizes, increased traffic, higher speed links, and the migration to 128 bit IPv6 addresses. IP routing lookup req...

Distributed route server

Abstract: A design for a network route server in which network routing functions are distributed throughout the processing elements that constitute a switching node, while maintaining the global identity and routing information exchange functions of a route server element (RSE). Intelligent line-cards are provided having the ability to route independently of the RSE. This removes the RSE as a bottleneck resource and ensures that the capacity of the switching node is limited only by the switching capacity of its switch fabric. The RSE serves the functions of network topology discovery and routing table construction using a network topology database and an optimal routing algorithm. Copies of the dynamically maintained routing tables are distributed to the intelligent line-cards on a periodic basis governed by predetermined criteria. Wider geographical distribution of the RSE is enabled and most efficient utilization of the switch fabric is ensured. Scaling of distributed switching architectures is also enabled. The advantage is a significant increase in switching capacity as well as an increased degree of network connectivity.

Mapping of routing traffic to switching networks

Abstract: IP based networks use a number of different IP routing protocols to determine how packets ought to be routed. However, due to the rapid growth of the Internet, there is a great need for higher packet forwarding performance. This invention describes a way to map IP routing information onto a technology that uses label switching and swapping, such as ATM, without the need to change the network paradigm. This allows a network to continue to function and appear as a standard IP network, but with much higher performance. In this invention, an Integrated Switch Router (ISR), is a switch that has been augmented with standard IP routing support. The ISR at an entry point to the switching environment performs standard IP forwarding of datagrams, but the "next hop" of the IP forwarding table has been extended to include a reference to a switched path (for example, the VCC in ATM technology). Each switched path may have an endpoint at a neighboring router (comparable to existing IP next hops on conventional routers), or may traverse a series of ISRs along the best IP forwarding path, to an ISR endpoint. This allows datagrams to be switched at hardware speeds through an entire ISR network.

Responsive routing control method and apparatus

Abstract: A method and apparatus for controlling routing within a communication system (10) modifies (258) routing tables (220, 230, 232, 234, 236) located within nodes (150) so that received data packets are not returned directly to their sending nodes. In response to detection (352) of a failed link, a node (150) modifies (354) its routing tables (220, 230, 232, 234, 236) to avoid the failed link. After notification (402) of the failed link, a control facility (28) responds by creating (404) commands that compensate for the failed link. The control facility (28) sends (404) the commands to at least the node (150) that detected the failed link. If not already performed by the control facility (28), the node (150) then modifies (364, 366) its routing tables (220, 230, 232, 234, 236) so that data packets are not returned to their sending nodes, and to avoid the failed link.

Router for high-speed packet communication between terminal apparatuses in different LANs

Abstract: In a router having a routing section for performing routing on the basis of a routing table and an ARP (address resolution protocol) table to transmit a received packet to a destination, and adapted to connect a plurality of local area networks (LANs), to realize high-speed routing, the IP addresses and MAC addresses of the terminal apparatuses in the LANs directly connected to the router are stored in a memory table in correspondence with the interfaces information to which the LANs are connected, together with the IP addresses of the terminal apparatuses in a LAN connected to the router through another router, the MAC address of another router, and the interfaces information to which another router is connected, which are stored in correspondence with each other. When a packet determination section determines that a received packet satisfies predetermined conditions, and a registration determination section determines that destination IP address of the packet is registered in the memory table, a second routing section specially designed for packets satisfying the predetermined conditions reads out information corresponding to the IP address from the memory table, updates the MAC address of the received packet with the information, and outputs the packet.

Technique for handling forwarding transients with link state routing protocol

Abstract: A detection technique detects inconsistencies in forwarding databases of a router and its neighbor, i.e., a next-hop router, during routing transients in a computer network. The technique enables the router to detect when its view of a computed path to a destination station is inconsistent with the view of its neighbor along that path. Upon detecting such an inconsistent state, the router invokes one of a plurality of forwarding mechanisms with respect to a packet intended for the destination station in an attempt to suppress forwarding loops that may arise during the transients.

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.

Method and apparatus for routing emergency services calls in an intelligent network

Abstract: Emergency services calls may be alternate-routed in an intelligent network having at least one Service Control Point (SCP) with access to a routing table, a plurality of Service Switching Points (SSP) equipped with point-in-call triggers and one or more emergency services stations (PSAP). The routing table lists a routing number for each of the emergency services stations. The alternate routing involves presetting a point-in-call trigger at a Service Switching Point to operate at a predetermined point in a call for emergency services. During subsequent processing of an emergency services call, the trigger interrupts processing of the call and and prompts transmission to the SCP of a query signalling message requesting routing information. Upon receipt, the SCP accesses the routing table in dependence upon parameters in the query signalling message and obtains a routing number for a selected emergency services operator station, forms a response signalling message including the routing number and returns such response signalling message to the SSP. Upon receipt of the response signalling message, the SSP detects the routing number, and routes the call to the emergency services operator station. There is also provided a method of translating signalling message parameters from a mobile protocol to an intelligent network protocol, and vice versa, to enable emergency services calls from mobile users to be routed to one or more PSAPs in the intelligent network.

A method for routing data packets within a wireless, packet-hopping network and a wireless network and node for implementing the same

Abstract: A random multiple path tabular routing method for routing data packets within a wireless, packet-hopping network, e.g., an intelligent lighting control system, which includes the steps of programming a plurality of the individual nodes to each serve as a repeater node for a least one other individual node, the reapeater nodes forming multiple programmed communication paths between the central node and each of at least selected ones of the individual nodes, and randomly hopping the data packets along the programmed communication paths. The repeater nodes are preferably programmed on the basis of nodal connectivity information obtained during a network initialization process. The repeater nodes are preferably programmed by storing compact partial routing tables in a memory portion of each of these repeater nodes. This routing method is partially deterministic or tabular in that routing tables are used to preprogram the multiple communication paths, and partially random, in that the data packets are randomly hopped along these preprogrammed multiple paths, rather than being hopped along preprogrammed singular paths.

Apparatus and method for querying replicated databases

Abstract: The apparatus and method of the present invention provides even loadsharing of round-robin querying of replicated databases in a network architecture which responds to network conditions. The network architecture utilizes a round-robin routing table that includes correlated index numbers, point codes and addresses of the replicated databases. The network architecture responds to incoming queries with searching of the round-robin routing table by incrementing to a successor index number and an associated point code. The network architecture may further determine whether the database at the address pointed by the point code is accessible. If not, the network architecture increments to another successor index number to locate an accessible database. When an accessible database is found, the point code is set to the address of the accessible database and the query is forwarded to that address.

Information dissemination system with central and distributed caches

Abstract: A system for disseminating information over a wide area network includes a central caching unit for storing data to be made available over the wide area network Local access give users access to the wide area network Distributed caching units associated with the local access nodes for store cacheable material A satellite communications system establishes satellite communications between the central caching unit and the local caching units for the transfer of cacheable material from the central caching unit to the local units A router at the local access nodes routes packets from users to a destination address The router includes local routing tables containing the addresses of material cached at the associated local node and responds to routing requests for locally cached material by directing the requests to the local cache

Tag switching architecture overview

Abstract: Tag switching is a way to combine the label-swapping forwarding paradigm with network-layer routing with particular application to the Internet. This has several advantages. Tags can have a wide spectrum of forwarding granularities, so at one end of the spectrum a tag could be associated with a group of destinations, while at the other end, a tag could be associated with a single application flow. At the same time, forwarding based on tag switching, due to its simplicity, is well suited to high-performance forwarding. These factors facilitate the development of a routing system that is both functionally rich and scalable. Last, tag switching simplifies the integration of routers and asynchronous transfer mode switches by employing common addressing, routing, and management procedures.

System for maintaining multiple loop free paths between source node and destination node in computer network

Abstract: A system for maintaining routing tables at each router in a computer network The system is based on (a) a feasibility condition that provides multiple loop-free paths through a computer network and that minimizes the amount of synchronization among routers necessary for the correct operation of a routing algorithm, and (b) a method that manages the set of successors during the time it synchronizes its routing-table update activity with other routers, in order to efficiently compute multiple loop-free paths, including the shortest path, through a computer network

System for routing packet switched traffic

Abstract: The system of the invention uses ATM switches as high performance Internet routers by using standard ATM signaling to set up cut-through paths. The cut-through paths are Switched Virtual Paths which are shared with similar flows toward the same destination and a similar Quality of Service (QOS). The concurrency of multiple flows is achieved by using a different Virtual Channel Identification (VCI) for each flow. The cut-through paths are reused to minimize the overhead associated with setting up and tearing down the paths. Depending on the needs of the traffic, different SVCs having different QOS and different bandwidths can be used. Customer service needs and traffic measurements data are used to identify potential cut-through paths. Once a cut-through path is set up, IP mechanisms are used to update the routing tables of related routers and ATM hosts. Specifically, IP protocols' adjacency bring-up procedures and reachability exchanges are used to update routers' routing tables, and ICMP redirect messages are used to update ATM hosts' routing tables. All ATM QOS are available for the cut-through paths.

Method and apparatus for determining a routing table for each node in a distributed nodal system

Abstract: A method enables each node in a multi-nodal network to construct a routing table to all other nodes in the network. Each "home" or originating node performs a method which includes the steps of: transmitting a query to all immediate neighbor nodes and recording in a routing table, responses received which identify the neighbor node at the terminus of each link; transferring to each neighbor node, home node routing table entries and receiving routing table entries from each neighbor node; and, for each routing table entry to a node that is received from a neighbor node, if the route indicator is already present in the home node routing table, ignoring the entry; if the new entry indicates a route to a new node, entering the new node and a route identifier; and if the entry indicates a route to a node for which there is already an entry in the home node routing table, noting the new entry as a lower priority route to the node. Once the aforementioned procedure is repeated a number of times, each node in the multi-nodal network includes routes to all nodes in the network, with the routes having automatically been prioritized in accordance by sequence of receipt.

Providing number portability by means of enhanced routing tables

Abstract: A method of providing number portability for the treatment of calls from a calling party to a specific number of a ported called party is disclosed. Once the dialed digits are received at a switching office serving the calling party, a determination is made of whether the call is a number that has been ported. If the number has been ported, the new routing information is obtained from an enhanced directory number table resident at the originating office. In the event that the originating office is unable to offer LRN service, information is obtained at an alternate office. Routing information is updated automatically and directly from a network Service Management System (SMS) to each telephone exchange.

Method and apparatus for routing data using router identification information

Abstract: A system for routing data through a network determines whether router identification information is associated with the data. The system then identifies a next hop router from a router table if router identification information is associated with the data. Otherwise, the system identifies a next hop router from a routing table if router identification information is not associated with the data. When identifying a next hop router from the router table, the system determines whether a match exists between entries in the router table and the router identification information. The system may set a switch tag in the data packet, in which the switch tag corresponds to a destination router identification. The router table used by the system contains information regarding how to reach all known routers.

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.

Method and apparatus for implementing forwarding decision shortcuts at a network switch

Abstract: A shortcut technique implements forwarding decision shortcuts at a switch for frames routed between subnetworks of a computer network. The switch monitors the flow of a first frame of a particular type to and from the router, which renders a forwarding decision for routing the frame. The switch records information stored in network layer header of a packet encapsulated within the first frame, and then compares that information with the information stored in network layer headers of packets contained within subsequent frames of that particular type. Forwarding decisions for these subsequent frames are then rendered by hardware logic circuits of the switch rather than by the router.

Packet switching architecture in cellular radio

Abstract: Improved performance is achieved for cellular systems with an arrangement where mobile units transmit information in packet format. A base station routes received packets to switching agents identified by the packets, and the switching agents forward the information contained in the packets to a wired network. The switching agent thus forms the interface between the packet switched portion of the cellular system and the wired network, which may be a circuit switched network. The routing of packets to switching agents allows the system to dedicate one agent to each mobile unit known to the system. It also allows a mobile unit's switching agent to remain wherever it is hosted even when the mobile unit moves from cell to cell, causing different base stations to receive the mobile unit's packets. The routing of packets is achieved with a routing network, which preferably is immune to single failures. In one illustrative embodiment, the routing network comprises a mesh network that interfaces a multiply connected routing 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.