Showing papers on "Routing table published in 1989"

A trade-off between space and efficiency for routing tables

Abstract: Two conflicting goals play a crucial role in the design of routing schemes for communication networks. A routing scheme should use paths that are as short as possible for routing messages in the network, while keeping the routing information stored in the processors' local memory as succinct as possible. The efficiency of a routing scheme is measured in terms of its stretch factor-the maximum ratio between the length of a route computed by the scheme and that of a shortest path connecting the same pair of vertices.Most previous work has concentrated on finding good routing schemes (with a small fixed stretch factor) for special classes of network topologies. In this paper the problem for general networks is studied, and the entire range of possible stretch factors is examined. The results exhibit a trade-off between the efficiency of a routing scheme and its space requirements. Almost tight upper and lower bounds for this trade-off are presented. Specifically, it is proved that any routing scheme for general n-vertex networks that achieves a stretch factor k ≥ 1 must use a total of O(n1+1/(2k+4)) bits of routing information in the networks. This lower bound is complemented by a family K(k) of hierarchical routing schemes (for every k ≥ l) for unit-cost general networks, which guarantee a stretch factor of O(k), require storing a total of O(k3n1+(1/h)logn)- bits of routing information in the network, name the vertices with O(log2n)-bit names and use O(logn)-bit headers.

Method for routing packets in a packet communication network

Abstract: A packet network routing method and system based on geographic coordinate identifiers is described. Each node in a network is uniquely identified by absolute geographical coordinates or by a code indicating absolute location in an external coordinate-based reference system (node coordinates), and such absolute geographical coordinates or the equivalent are employed as part of a packet identifier for each packet generated for use in making routing decisions. The node coordinates of a local node and its neighboring nodes and the packet coordinates are used by means at each node through which a packet is routed for determining a desired forwarding route of a data packet. The routing may be prioritized according to preselected criteria, preferably achieving maximum forward progress using the least amount of power. The packet routing protocol according to the invention requires no routing directory or table to perform data routing. Each node of the network collects in a table or is otherwise provided with information about the quality of communication between itself and its neighboring nodes. When a data packet has been received at a node, it is routed further through the network based on criteria derived from the history of communication between the local node and its neighbors.

Comparison of deflection and store-and-forward techniques in the Manhattan Street and Shuffle-Exchange Networks

Abstract: The Manhattan Street Network (MS-Net) and Shuffle-Exchange Network (SX-Net) are two-connected networks with significantly different topologies. Fixed-size packets are transmitted between nodes in these networks. The nodes are synchronized so that all of the packets that are received by a node within a slot transmission time arrive at a switching point simultaneously. Instead of storing large numbers of packets at intermediate nodes, a deflection strategy similar to hot-potato routing is used. There are characteristics of the MS-Net that make it well suited for deflection routing. With no buffer, 55-70% of the throughput with an infinite number of buffers has been obtained; with a single buffer per node, the throughput increases to 80-90%. With uniform load the throughput does not decrease significantly as the network utilization increases. Therefore, additional flow control mechanisms are not required to achieve the highest network throughput. The SX-Net does not have the above characteristics of the MS-Net. However, deflection routing still provides a significant portion of the available throughput. In the SX-Net, more buffers are required than in the MS-Net, and a flow control mechanism must be used to achieve the greatest throughput. >

High Performance Communications In Processor Networks

Abstract: In order to provide an arbitrary and fully dynamic connectivity in a network of processors, transport mechanisms must be implemented, which provide the propagation of data from processor to processor, based on addresses contained within a packet of data. Such data transport mechanisms must satisfy a number of requirements - deadlock and livelock freedom, good hot-spot performance, high throughput and low latency. This paper proposes a solution to these problems, which allows deadlock free, adaptive, high throughput packet routing to be implemented on networks of processors. Examples are given which illustrate the technique for 2-D array and toroidal networks. An implementation of this scheme on arrays of transputers is described. The scheme also serves as a basis for a very low latency routing strategy named the mad postman, a detailed implementation of which is described here as well.

Expanders might be practical: fast algorithms for routing around faults on multibutterflies

Abstract: Simple deterministic O(log N)-step algorithms for routing packets on a multibutterfly are described. The algorithms are shown to be robust against faults, even in the worst case, and to be efficient from a practical point of view. As a consequence, the multibutterfly is shown to be an excellent candidate for a high-bandwidth, low-diameter switching network underlying a distributed-memory machine. >

Method and apparatus for providing a local area network bridge

Abstract: A communication bridge interconnecting two or more local area networks. Input buffers forward packet headers of received data packets through to a routing engine. The routing engine contains one or more routing tables each having a plurality of table locations containing table data in the form of station addresses and routing data. The table is accessed by applying a hashing algorithm to a received destination address contained in the data packet to determine the table location and then checking that the station address retrieved from the table location corresponds with the destination address in the received data packet.

An optimal shortest-path routing policy for network computers with regular mesh-connected topologies

Abstract: A probabilistic routing policy, the Z/sup 2/ (zigzag) routing policy, is presented within the class of nonadaptive, shortest-path routing policies for regular mesh-connected topologies such as n-dimensional toroids and hypercubes. The focus of the research is routing in networks of computers in a distributed computing environment, where constituent subcomputers are organized in a mesh-connected topology and communication among individual computers takes places by some form of message exchange. The authors prove the optimality of this policy with respect to two criteria: (1) maximizing the probability of reaching the destination from a given source without delays at intermediate nodes; and (2) minimizing the expected lifetime of a message. >

Efficient message routing in planar networks

Abstract: The problem of routing messages along near-shortest paths in a distributed network without using complete routing tables is considered It is assumed that the nodes of the network can be assigned suitable short names at the time the network is established Two space-efficient near-shortest-path routing schemes are given for the class of planar networks Both schemes use the separator property of planar networks in assigning the node names and performing the routings For an n-node network, the first scheme uses $O(\log n)$-bit names and a total of $O(n^{{4 / 3}} )$ items of routing information, each $O(\log n)$ bits long, to generate routings that are only three times longer than corresponding shortest routings in worst cases For any constant $\epsilon ,0 < \epsilon < 1/3$, the second scheme achieves the better space bound of $O(n^{1 + \epsilon } )$ items, each $O(({1 / \epsilon })\log n)$ bits long, but at the expense of $O(({1 / \epsilon })\log n)$-bit node names and a worst-case bound of 7 on the rout

Compact distributed data structures for adaptive routing

Abstract: In designing a routing scheme for a communication network it is desirable to use as short as possible paths for routing messages, while keeping the routing information stored in the processors' local memory as succinct as possible. The efficiency of a routing scheme is measured in terms of its stretch factor - the maximum ratio between the cost of a route computed by the scheme and that of a cheapest path connecting the same pair of vertices.This paper presents a family of adaptive routing schemes for general networks. The hierarchical schemes H Sk (for every fixed k ≥ 1) guarantee a stretch factor of O (k2 · 3k) and require storing at most O (knk log n) bits of routing information per vertex. The new important features, that make the schemes appropriate for adaptive use, are applicability to networks with arbitrary edge costs;name-independence, i.e., usage of original names;a balanced distribution of the memory;an efficient on-line distributed preprocessing.

Flood-and-forward routing for broadcast packets in packet switching networks

Abstract: A routing algorithm for broadcast packets in packet switching networks, utilizing a "flood-and-forward" technique. In such networks, data are often transmitted in grat quantities from a sensor node to all other nodes in the network, or in a subnetwork, over point-to-point links. Existing broadcast routing algorithms, including multidestination addressing, constrained flooding, minimum spanning tree forwarding, and reverse path forwarding, suffer from an excessive use of bandwidth, a poor choice of routes, or a costly need for memory or computing power. In flood-and-forward routing, periodically a data packet is designated as a Scout packet and is transmitted in a constrained flood broadcast transmission. The Scout packet is identified by a Source Id and a Scout Label. Each receiving node sends a Ack Scout packet to the node from which it first receives a particular Scout packet, acknowledging receipt of that packet. Each relaying node keeps a log of nodes from which it has received Ack Scout packets and sends subsequent, non-scout packets to those same nodes. This flood-and-forward broadcast routing algorithm thus offers the best selection of routes, as in constrained flooding, and the least consumption of bandwidth, as in minimum spanning tree forwarding, while keeping the overhead cost of storage and processing to a low level. With the support of a reliable link service, the algorithm performs well in delivering critical data to all reachable destinations despite to-be-expected losses of packets, links, or nodes.

The Arc Oriented Location Routing Problem

Abstract: The location routing problem is concerned with locating depots and creating routes to service customers. In particular, location-allocation-routing (LAR) algorithms are designed to locate facilities, allocate customers to facilities and design the routes through these customers. In the literature, the typical location routing problem is a node oriented problem, where depots and customers are all represented by nodes and the routing is a node routing problem. In this paper, an Arc Oriented Location Routing Problem (AOLRP) is described, where the customers to be serviced are represented by arcs. Therefore, the allocation of customers to depots is an arc oriented problem as well as the resulting routing problem. An algorithm is presented for solving the AOLRP and computational results are given regarding parameter settings and performance of this algorithm.

Automatic call distribution system

Abstract: An automatic call distribution system includes a network switch (11) having a plurality of pilot extensions (P1, P2), a plurality of agents (A, B, C) being split into a plurality of agent groups, trunks (17, 18) provided for each of the pilot extensions, and line circuits (22, 23) provided for each of the agents. The system also includes a memory (16) which stores a route table provided for each of the pilot extensions. The route table defines some agent groups among the plurality of agent groups. The defined agent groups are to be connected to the related one of pilot extensions. A control circuit (12 - 15) seeks an idle agent relating to the agent groups defined by the related one of the route tables, and establishes a route between the call and the sought idle agent through the related trunk, network switch, and line circuit.

Upper and lower bounds for routing schemes in dynamic networks

Abstract: An algorithm and two lower bounds are presented for the problem of constructing and maintaining routing schemes in dynamic networks. The algorithm distributively assigns addresses to nodes and constructs routing tables in a dynamically growing tree. The resulting scheme routes data messages over the shortest path between any source and destination, assigns addresses of O(log/sup 2/n) bits to each node, and uses in its routing table O(log/sup 3/n) bits of memory per incident link, where n is the final number of nodes in the tree. The amortized communication cost of the algorithm is O(log n) messages per node. Also given are two lower bounds on the tradeoff between the quality of routing schemes (i.e. their stretch factor) and their amortized communication cost in general dynamic networks. >

A distributed routing algorithm for mobile radio networks

Abstract: The authors present a distributed routing protocol intended for use in networks where the rate of topological change is not so fast as to make 'flooding' the only possible routing method but not so slow as to make one of the existing protocols for a static topology applicable. The routing algorithm adapts asynchronously in a distributed fashion to arbitrary changes in topology in the absence of global topological knowledge. The protocol maintains a set of loop-free routes to each destination from any node that desires a route. The protocol's performance, measured in terms of end-to-end packet delay and throughput, is compared with that of pure flooding and an alternative algorithm that is well suited to the medium-rate topological change environment envisioned here. The results show that, when the rate of topological change becomes very high, flooding is preferable to the other alternatives. For lower rate of change, it appears that, when the effects of channel access are accounted for, the performance of the new algorithm is encouraging in that it has been generally superior to that of the alternative protocols. >

Robust algorithms for packet routing in a mesh

Abstract: This paper considers the problem of permutation packet routing on a √n×√n mesh-connected array of processors. Each node in the array is assumed to be independently faulty with a probability bounded above by a valuep. This paper gives a routing algorithm which, ifp⩽ 0.29, will with very high probability route every packet that can be routed inO(√n logn) steps with queue lengths that areO(log2n). Extensions to higher-dimensional meshes are given.

Multi-packet-routing on mesh connected arrays

Abstract: In this paper we study the problem of routing packets on an r-dimensional mesh-connected array of processors. The focus of this paper lies on routing with each processor containing exactly k packets, k > 2, initially and finally (so-called k-k-routing). For two-dimensional n x n grids the number of transport steps is at most ~kn + O(kn/f(n)) with a buffersize of O(kf(n)). In the special case of a sequence of k permutation routing problems this step count can be reduced to kn + O(kn/f(n)). For an r-dimensional cube, r > 3, with side length n the same technique yields an algorithm with step count [~] ( 2 r 2)n + O(kn/f(n) 1/(r-1)) and a buffer size of O(kf(n)). Furthermore it is shown that splitting large packets into smaller ones has benefits for permutation routing problems. 1 I n t r o d u c t i o n The performance of parallel computation is heavily influenced by the existence of fast data movement algorithms [AJP86]. In this area especially mesh connected processor arrays have drawn attention because of their simple interconnection and their easy scalability. A nl x . . . x n~ mesh connected array is a set mesh(n1,..., n~)of N = n l . . . n~ identical processors where each processor P = (pl,...,p~),O _< Pi _< ni 1, is directly connected to all its nearPermission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and /o r specific permission. @ t989 A C M 0 8 9 7 9 1 3 2 3 X / 8 9 / 0 0 0 6 / 0 3 3 6 $1.50 est neighbours only. A processor Q = ( q l , . . . , q r ) is called nearest neighbour of P iff the manhattan distance between P and Q is 1 (d(P,Q) = Eir=l IPi -qi[)" The control structure of the grid of processors is assumed to be of the MIMD type (Multiple Instruction Multiple Data). That is, each processor has its own program memory, different processors can perform different instructions at the same clock period, there is a global clock, and each processor can send data only to its nearest neighbours during one clock period. Bidirectional communication can occur with all nearest neighbours in one clock cycle. Furthermore, each processor has only a limited number of registers for data (e.g. the buffer size is constant or log N). D e f i n i t i o n I (k -k p a c k e t r o u t i n g ) A k-k pakket routing problem is the problem of transporting k packets from each processor in the mesh to k destination processors. Each processor in the mesh sends and finally receives k packets. More formally a k-k routing problem is described by a (k+l) tuple (mesh, address],..., addressk ) where each addressi is a map from mesh to mesh and for all processors P in the mesh we have k Ei=~ ]address~-l(P)l = k. All the packets in address~-l(mesh) are said to lie in layer i. In the case of k = 1 address1 is a bijective func tion by definition and the problem is then called a permutation routing problem. This basic problem has been extensively studied in the literature. For n × n meshes some algorithms based on sorting only need 3n+O(low order) steps and a buffer*This research was supported by SIEMENS AG, Mfinchen, and by the Deutsche Forschungsgemeinschaft, Grant No. Ku 658/1-1.

A new responsive distributed shortest-path rounting algorithm

Abstract: Distributed shortest-path routing algorithms based on the Ford-Fulkerson method are simple to implement but they suffer from the cost-dependent looping problem: when link costs increase, routing table loops may form and convergence to correct paths may be too slow, depending on link costs. This problem can be eliminated if constraints are imposed on the order in which routing tables are updated at different nodes but the resulting internode protocols tend to be relatively complex. Furthermore, update constraints may restrict a node's ability to obtain alternate paths quickly in an environment where topology changes are frequent. In this paper, a new distributed shortest-path routing scheme based on the Ford-Fulkerson method is presented. Under the new scheme, each node uses partial topology information to eliminate the cost-dependent looping problem. No update constraints are imposed and no assumptions are made regarding link costs. In the worst case, the new scheme responds to link cost changes in O(D) update steps, where D is the diameter of the network after the occurrence of the changes.

Routing management in computer networks

Abstract: A communication system includes a plurality of machines 21-24, 30, 33-35, etc) having unique identifiers and interconnected by a network of message switching nodes (10-14, 40, etc). Each node includes a dynamic routing table containing a plurality of machine identifiers and, for each, the next place in the network where a message to that machine should be directed to. The system includes a Directory Information Base (DIB) which includes a machine listing. For each machine, the listing has an entry including attributes of the machine. The attributes include updating and routing information. The former identifies the parts of the system need to be be updated to maintain consistency if some part of the entry is changed, including in particular information as to which nodes require their dynamic routing tables to be updated in response to a change in that entry (as if the routing tables were part of the DIB). The latter gives node identifications and routes from those nodes to the potential receiving machines. The DIB includes updating means which, on a change in an entry, use the updating attribute of that entry to transmit updating information to the rest of the DIB, in a format defined for the whole of the DIB. Such information is thus also sent to the relevant nodes. Each node includes means for updating the routing table in response to such transmissions from the updating means, including format conversion means for converting such transmissions to the format of the routing table.

Convergence of gradient projection routing methods in an asynchronous stochastic quasi-static virtual circuit network

Abstract: The convergence of the gradient projection algorithms for optimal routing in virtual circuit data networks proposed by D.P. Bertsekas (1982) is studied. The routing model explicitly takes into account stochastic generation and termination of virtual circuits, distributed asynchronous routing updates, inaccurate flow measurement, and delays in forwarding control packets. The problem of assigning paths for incoming sessions (or virtual circuits) to implement the gradient projection algorithms is also studied. A metering rule based on deficiency in a desired number of virtual circuits is proposed and analyzed. It is shown that the proposed metering rule is better than a randomized rule in some sense. The gradient projection routing algorithms implemented either by the metering rule or the randomized rule are shown to converge to a neighborhood of a long-term optimal routing. >

Method for accessing data in a table and its application to the routing of data between remote stations

Abstract: The present invention relates to the accessing data in tables and its application to apparatus for providing a communication bridge interconnecting two or more local area networks (LAN). A LAN (1) is connected to another LAN 2 by means of a bridge generally designated by the numeral (3). Input buffers (11, 21) forward packet headers of received data packets through to a routing engine (5). The routing engine (5) contains one or more routing tables each having a plurality of table locations containing table data in the form of station addresses and routing data. The table is accessed by applying a hashing algorithm to a received destination address contained in the data packet to determine the table location and then checking that the station address retrieved from the table location corresponds with the destination address in the received data packet. If the table location is empty or the destination address does not match the station address, the data packet is forwarded to all interconnected LANs. Otherwise, the data packet is forwarded according to the retrieved routing data. Embodiments are described wherein the table locations are over-written by applying the hashing algorithm to the source address of a received data packet and writing in at the resultant table location the source address and routing information of the received data packet. A time stamp can also be written at this time so that obsolete data entries are not employed for routing.

Internet routing

Abstract: Comprising an estimated 60,000 hosts, the DARPA Internet is the largest existing internet. This paper traces the routing information protocols used by Internet gateways to build routing tables that define the paths datagrams traverse as they travel between end systems. We articulate the weaknesses and limitations of the most commonly used routing protocols, including RIP, GGP, and HELLO and examine how the protocols interact with each other and with EGP. Finally, we trace the evolution of routing as the Internet has grown from a single backbone (ARPANET) to its present inclusion of the ARPANET, Milnet, and NSFnet cross-country networks.

Wiretap: an experimental multiple-path routing algorithm

Abstract: This paper introduces Wiretap, an experimental routing algorithm which computes maximum-likelihood diversity routes for packet-radio stations sharing a common broadcast channel, but with some stations hidden from others. The wiretapper observes the paths (source routes) used by other stations sending traffic on the channel and, using a heuristic set of factors and weights, constructs speculative paths for its own traffic. The algorithm is presented as an example of maximum-likelihood routing and database management techniques useful for richly connected networks of mobile stations. Of particular interest are the mechanisms to compute, select, rank and cache a potentially large number of speculative routes when only limited computational resources are available.A prototype implementation has been constructed and tested for the AX.25 packet-radio channel now in widespread use in the amateur-radio community. Its design is similar in many respects to the SPF algorithm used in the ARPANET and NSFNET backbone networks, and is in fact a variation of the Viterbi algorithm, which constructs maximum-likelihood paths on a graph according to a weighted sum of factors assigned to the nodes and edges.

Insensitivity with age-dependent routing

Abstract: The theory of insensitivity is extended to include processes where some of the routing probabilities of the process are made dependent upon the length of time the generally distributed variables have been alive. Examples of such systems are given, including networks of queues with age-dependent routing. PARTIAL BALANCE; PRODUCT-FORM QUEUEING NETWORKS; AGE-DEPENDENT ROUTING

An efficient near-optimal algorithm for the joint traffic and trunk routing problem in self-planning networks

Abstract: The configuration and routing problem (or the joint trunk and traffic routing problem) is first formulated as a mixed integer nonlinear minimization problem. Then certain properties are proved about the problem structure. These properties lead to an efficient algorithm that determines near-optimal configurations and routing assignments. A lower bound is also computed in order to evaluate the quality of the solution. The algorithm was coded and tested on several networks. Present computational experiments clearly show that the performance of a self-planning network is always better than that of the same network without the trunk routing capability. The reduction in average packet delay is as much as 67%. >

Analysis and design of a highly reliable transport architecture for ISDN frame-relay networks

Abstract: The authors explore control strategies in the design of a high-performance transport architecture for integrated services digital network (ISDN) frame-relay networks. For real-time congestion control, buffer management, priority queueing, adaptive windowing, and selective frame, discard policies are described that can effectively maximize network efficiency while preventing unfair usage of shared network resources. Virtual-circuit routing strategies are proposed that ensure an efficient distribution of traffic loads across the network despite variations in traffic patterns and topology changes. It is shown that source routing provides significant performance benefits over link-by-link routing, particularly in large networks that are not so densely connected. Routing table update and call acceptance mechanisms are described that provide for efficient bandwidth management in the network. Fault-tolerant strategies are described that include fast failure detection and local reroute. These strategies are capable of restoring affected virtual circuits in less than 10 s, which is adequate for session maintenance under most application scenarios. >

Routing table learning system

Abstract: PURPOSE:To change a routing table into a state after terminal movement in a short time even if a terminal moves among subordinate networks by deciding whether or not a transmitting origin terminal is a terminal included newly in a subordinate network connected to its node station even if the terminal address of the transmitting origin terminal is registered in the routing table. CONSTITUTION:When a terminal included in a subordinate network is moved to another subordinate network and the terminal sends a packet for the 1st time, a node station which contains the subordinate network at the movement destination receives it and decided whether or not its terminal address is registered in the routing table. When it is decided that the address is already registered, it is decided whether or not the node address registered corresponding to the terminal address is coincident with the node address of its node station; when not the node address registered corresponding to the terminal address of the terminal is changed into the node address of its node station and then the terminal address of a terminal registered in the routing table corresponding to its node address is reported to another node station with a broadcast information packet.

Datagram authentication in internet gateways: implications of fragmentation and dynamic routing

Abstract: The implications of fragmentation and dynamic routing for datagram authentication at the gateway level are discussed. Two protocols are presented that permit varying degrees of fragmentation and dynamic routing, while allowing the gateways to authenticate successive packets belonging to authorized connections. The first adapts to changing paths and fragmentation by keeping state information on a per-packet basis, while the second restricts fragmentation but incurs little state overhead. The two methods vary in implementation complexity, overhead, number of extra packets sent, and host modification requirements. They were designed with different network characteristics in mind, and, since they are not mutually exclusive, both can be incorporated and used depending on the nature of communication. >

Routing using a pyramid data structure

Abstract: A general-purpose routing algorithm is proposed. Ideas behind both the maze-running algorithm and the hierarchical routing algorithm are combined into a hybrid routing algorithm. The new algorithm demonstrates a speed compatible to a hierarchical router and produces routings with quality equivalent to that by a maze router. Hybrid routing is based on the maze-running method with a third search dimension added. The extra search space is built by recursively constructing a hierarchy of coarser grid meshes. A user-given parameter can turn this algorithm into a pure maze router, a pure hierarchical router, or a wide spectrum of hybrid routers with different speed/quality characteristics between the extremes. With this approach, it is possible to handle easily a routing of large size, such as those encountered in the sea-of-gate layout. >