Showing papers on "Routing table published in 1991"

Public telephone network including a distributed imaging system

Abstract: A public telephone network includes enhanced capabilities with a distributed imaging system. The imaging system interfaces with end users through appropriate bridges, routers and gateways to provide the user with a virtual local area network. Automatic number information (ANI) is used to automatically configure the system as required by the user. A central processing system performs text and image manipulation and transmission functions using the switched network facilities. Routing tables stored by the imaging system support automatic image and document routing functions.

A Tree-Based Packet Routing Table for Berkeley Unix.

Abstract: Packet forwarding for OSI poses strong challenges for routing lookups: the algorithm must be able to efficiently accommodate variable length, and potentially very long addresses. The 4.3 Reno release of Berkeley UNIX† uses a reduced radix tree to make decisions about forwarding packets. This data structure is general enough to encompass protocol to link layer address translation such as the Address Resolution Protocol (ARP), and the End System to Intermediate System Protocol (ES−IS), and should apply to any hierarchical routing scheme, such as source and quality-of-service routing, or choosing between multiple Datakits on a single system. The system uses a message oriented mechanism to communicate between the kernel and user processes to maintain the routing database, inform user processes of spontaneous events such as redirects, routing lookup failures, and suspected timeouts through gateways.

Another adaptive distributed shortest path algorithm

Abstract: The authors give a distributed algorithm to compute shortest paths in a network with changing topology The authors analyze its behavior The proof of correctness is discussed It does not suffer from the routing table looping behavior associated with the Ford-Bellman distributed shortest path algorithm although it uses truly distributed processing Its time and message complexities are evaluated Comparisons with other methods are given >

Routing system capable of effectively processing routing information

Abstract: In a routing system having a plurality of external input ports and a plurality of external output ports, a switch network having a plurality of internal input ports and a plurality of internal output ports, an input section between the external input ports and the internal input ports, an output section between the internal output ports and the external output ports, and a control section connected to the switch network and the input section, an input port number which may be assigned to each of the external input ports is arranged in a routing information field of a transmission path signal by an input port number setter included in the input section. The input port number is memorized in a discarded cell memory of the control section together with an internal output port number which is assigned to the internal output ports and which is derived from a routing table along with a header. On occurrence of a discarded cell, the cause of discard can be analyzed by the use of the input port number and the header. When a plurality of external input cells are multiplexed into a multiplexed input cell sequence, the input port number may be replaced by the internal output port number in the control section to effectively utilize the routing information field.

A framework for adaptive routing in multicomputer networks

Abstract: Message-passing concurrent computers, also known as multicomputers, such as the Caltech Cosmic Cube [47] and its commercial descendents, consist of many computing nodes that interact with each other by sending and receiving messages over communication channels between the nodes. The communication networks of the second-generation machines, such as the Symult Series 2010 and the Intel iPSC2 [2], employ an oblivious wormhole-routing technique that guarantees deadlock freedom. The network performance of this highly evolved oblivious technique has reached a limit of being capable of delivering, under random traffic, a stable maximum sustained throughput of ~~45 to 50% of the limit set by the network bisection bandwidth, while maintaining acceptable network latency. This thesis examines the possibility of performing adaptive routing as an approach to further improving upon the performance and reliability of these networks. In an adaptive multipath routing scheme, message trajectories are no longer deterministic, but are continuously perturbed by local message loading. Message packets will tend to follow their shortest-distance routes to destinations in normal traffic loading, but can be detoured to longer but less-loaded routes as local congestion occurs. A simple adaptive cut-through packet-switching framework is described, and a number of fundamental issues concerning the theoretical feasibility of the adaptive approach are studied. Freedom of communication deadlock is achieved by following a coherent channel protocol and by applying voluntary misrouting as needed. Packet deliveries are assured by resolving channel-access conflicts according to a priority assignment. Fairness of network access is assured either by sending round-trip packets or by having each node follow a local injection-synchronization protocol. The performance behavior of the proposed adaptive cut-through framework is studied with stochastic modeling and analysis, as well as through extensive simulation experiments for the 2D and 3D rectilinear networks. Theoretical bounds on various average network-performance metrics are derived for these rectilinear networks. These bounds provide a standard frame of reference for interpreting the performance results. In addition to the potential gain in network performance, the adaptive approach offers the potential for exploiting the inherent path redundancy found in richly connected networks in order to perform fault-tolerant routing. Two convexity-related notions are introduced to characterize the conditions under which our adaptive routing formulation is adequate to provide fault-tolerant routing, with minimal change in routing hardware, The effectiveness of these notions is studied through extensive simulations, The 2D octagonal-mesh network is suggested; this displays excellent fault-tolerant potential under the adaptive routing framework. Both performance and reliability behaviors of the octagonal mesh are studied in detail. A number of

VLSI implementation of routing tables: tries and CAMs

Abstract: Routing tables for communication networks can be designed using many different approaches, including table lookup, content-addressable memory (CAM), hashing, and tries. The authors compare these approaches in the context of custom VLSI implementation. For tables with a small number of entries and a large address space, CAMs can be very cost effective. If only RAM is available, it is shown that tries, of which simple table lookup is a special case, provide a useful architecture. Also considered is a new variation, table partitioning, which constitutes a useful compromise between the conventional CAM and a trie. >

Routing apparatus and method for high-speed mesh connected local area network

Abstract: A packet routing apparatus allows numerous packets to be routed simultaneously through a mesh connected network. The network consists of a number of interconnected switches which are coupled, in turn, to the hosts that are members of the local network. The switches are nonblocking switches that are coupled to each other and to the hosts by a multiplicity of point to point links. Each switch has a routing mechanism for automatically routing received packets toward their specified destinations. For each received packet the router generates a routing mask representing the output links that may be used to route the packet towards its destination. The routing mask includes a broadcast bit. If the broadcast bit is ON, the packet must be simultaneously routed to all of the output links specified by the routing mask. If the broadcast bit is OFF, the packet may be routed on any single one of the links specified by the routing mask. To ensure that every packet makes progress towards its destination, packets are processed in the order of their arrival by placing the corresponding routing masks in a queue. Periodically, the set of available output links is compared with all of the routing masks. Using a first come, first considered routing discipline, the first routing mask in the queue to match the available output lines is selected. A routing selection is then generated for the corresponding packet and the selected routing mask is removed from the queue.

Topological routing in SURF: Generating a rubber-band sketch

Abstract: A multi-layer topological router for generating rubberband sketches is described. The router uses hierarchical togdown partitioning to perform global routing for all nets simultaneously. I t combines this with successive refinement to help correct mistakes made before more detailed local information is discovered. Layer assignment is performed during the partitioning process to generate routing that has fewer vias and is not restricted to one-layer one-direction. The local router uses a region connectivity graph to generate shortest-path rubber-band routing.

Deadlock-free adaptive routing algorithms for multicomputers: evaluation of a new algorithm

Abstract: A new theory for the design of deadlock-free adaptive routing algorithms for wormhole and store-and-forward routing as well as two design methodologies have been proposed previously. In this paper, a new adaptive routing algorithm, obtained from the application of the former theory to the binary n-cube, is evaluated under different load conditions and compared with other algorithms. The results show that the new design methodology supplies faster routing algorithms, at least for those networks with a high connectivity. >

Fully-adaptive minimal deadlock-free packet routing in hypercubes, meshes, and other networks

Abstract: This paper deals with the problem of packet-switched routing in parallel machines. Several new routing algorithms for different interconnection networks are presented. While the new techniques apply to a wide variety of networks, routing algorithms will be shown for the bypercube, the 2-dinleusional mesh, and the shuffleexchange. The techniques presented for hypercubes and meshes are fully-adaptive and minimal. A similar technique can be devised for tori. A fully-adaptive and millimal routing is one in which all possible minimal paths bet,ween a source and a destination are of potential use at the time a message is injected into the network. Minimal paths followed by messages ultimately depend on the local congestion encountered in each node of the network. In the shuffle-exchange network, the routing scheme also exhibits adaptivity but paths could be up to 3 log N long for an N node machine. The shuflleexchange algorithm is the first adaptive and deadlockfree method that requires a small (and independent of N) number of buffers and queues in the routing nodes for that network. * ESLAI, Escuela Superior Latino Americana de Informitica, CC 3193,(1000) Buenos Aires, Argentina. t Computer Research and Advanced Applications Group, IBM Argentina, Ing. E. Bntti 275, (1300) Buenos Aires, Argentina. + Computer Science Dept., IBh’1 Almadeu Research Center, San

Channel routing by sorting

Abstract: A novel approach for the channel routing problem based on sorting is described. A router based on the bubble-sort for routing two point nets across a channel is presented. A lower and an upper bound on the channel width and an upperbound on the number of vias are given. The router is extended for handling multiterminal nets and single-sided connections. Results for multilayer channel routing are presented. The high-speed and predictable performance of these channel routing algorithms makes them valuable in assessing the difficulty of routing a particular configuration of logic blocks. This makes then suitable for use when calculating a cost metric in an iterative placement algorithm. >

Constant queue routing on a mesh

Abstract: Packet routing is an important problem in parallel computation since a single step of inter-processor communication can be thought of as a packet routing task. In this paper we present an optimal algorithm for packet routing on a mesh-connected computer.

Fully-adaptive routing: packet switching performance and wormhole algorithms

Abstract: In thts paper, a strnulatton study on the performance of some new algorithms for deadlock- and lwelock-free adaptive routing is reported. Packetswztchcd fully -adaptive minzmal routing on the mesh and the hypercube as ezplored for dt~erent tn~ection models: stattc and dynamic. The algorithms stmu lated in this paper are the jirst known to be !ivelockand deadlock-free fully -adaptive minimal that requzre a moderate amount of hardware. These techniques need only two central queues per routing node. The performance of these schemes IS measured for dtfferent irafic models: random, complement, transpose, bit-reversal and leveied permutations. Several machine sizes are trted and critical parameters indicating the performance of the routing algorithms are measured such as throughput, maximum and average latency, effective tn~ectaon, and saturation point. In the case of the mesh network, the new method w compared to an obltvzous scheme based on a simtlar routing node model. In the present versaon of thts paper, stm u!atton results are reported for hypercubes up to 16K nodes and for meshes of 11{ nodes. Ftnallyl a fu!iy-adaptwe minzmal worm-hole routing algorathm for the torus network wiil be presented. This technique is dead!ock- and hvelock-free and requuvs only 8 vzrtual channels per physzcal bzdzrectzonal link for zts implementation. Szmu!ations are currently being performed to determme the practical performance of this routing method.

A Fault-Tolerant Routing Algorithm for Star Graph Interconnection Network.

Abstract: This paper presents a fault tolerant routing algorithm for the star graph. The suggested algorithm is based on the concept of unsafety vectors, originally proposed for hypercubes. In this algorithm, each node starts by computing a first level unsafety set, composed of the set of unreachable neighbors. It then performs some exchanges with its neighbors to determine the unsafety nodes. After that, all nodes have the addresses of all faulty nodes. Based on the information gathered in each node, faulttolerant routing between a source node and a destination node is realized. We conducted a performance comparison between the star and hypercube graph using the unsafety vectors routing algorithm under different working conditions. The results obtained through simulation experiments reveal that the hypercube is of superior performance compared to the star graph in the presence of low fault rates. But its performance under high fault rates falls short of that of the star graph.

Routing method and apparatus for switching between routing and conversion tables based on selection information included in cells to be routed

Abstract: A cell routing method and apparatus in an ATM processing apparatus. The ATM processing apparatus has two or more routing tables associated with address filters of an ATM switch to store routing information for indicating the destination of cell output, and two or more conversion tables associated with VPI conversion circuits for replacing VPI (Virtual Path Identifier) or VCI conversion circuits for replacing VCI (Virtual Channel Identifier) to store information for indicating the VPI or VCI obtained after conversion. In an input interface circuit, selection information indicating which routing table and conversion table out of the above described two or more routing tables and two or more conversion tables should be selected is written into an occupied area within a cell. In a switch circuit, the selection information is read and one routing table is selected out of the above described two or more routing tables on the basis of the selection information thus read, and cell routing is thus performed based on information in the selected routing table. Further, in an output interface circuit, selection information contained in the cell is read and one conversion table is selected out of the above described two or more conversion tables on the basis of the selection information thus read, and VPI conversion or VCI conversion is thus executed based on information in the selected conversion table.

Hierarchical network routing

Abstract: A disadvantage of Link State routing schemes is that exact shortest path calculations require a complete topology, which can overload the capacity of small nodes in a large network. Area routing schemes (when destination names are structured corresponding to the network topology) allow nodes to reduce the size of routing tables, by recording only one entry for an entire region rather than one for each node in the region. A description is presented of a general hierarchical routing scheme that allows all nodes to participate in a distributed routing network, using close to optimal paths, with short routing tables, and a reduction of topology information for minor nodes. >

Reliable multiuser tree setup with local identifiers

Abstract: The authors present a reliable protocol for setting up a tree connection for the purpose of multicast communication over a high-speed packet switched network. The tree connection is based on the use of local identifiers that are swapped at every intermediate node of the tree. Local identifiers are simple to manage, provide fast access to the routing tables, and are very efficient in terms of the size of the resulting routing space. The context of the present work is a high-speed network in which the local label swapping on data messages is performed in hardware by the switching subsystem, while the connection setup is done in software by the switch control subsystem. The correctness of the protocol is formally proved. The protocol ensures the integrity of the tree, and, when failures occur, the tree is gracefully degraded into a smaller tree. >

An analysis of deflection routing in multi-dimensional regular mesh networks

Abstract: A Markov Chain based analysis for deflection routing in n-dimensional regular mesh networks is presented. Detailed analyses are given for the 2D mesh, and a generalization to higher dimensions is outlined. Analytic results are shown to agree very closely with simulations. A basic routing scheme in which all packets have equal priority and a priority scheme in which packets with fewer alternative routes are given priority are proposed and analyzed. Results show that the priority scheme gives higher maximum throughput and lower average packet delay than the basic scheme by reducing average deflections under heavy loads. With the priority scheme, the network performance is almost identical to that of the optimal diagonal routing scheme. By doubling the number of links the throughput is always more than doubled. The authors conclude that in the 2D case, bidirectional links are more cost-effective than unidirectional ones assuming the cost is the number of optical transceivers. >

The chaos router: a practical application of randomization in network routing

Abstract: We present the chaos router, an asynchronous adaptive router, which under certain circumstances can send messages farther from their destinations. The chaos router greatly simplifies the routing logic by removing the livelock protection of previous schemes. Through an effective use of randomness, whose sources include that due to the adaptively processed load, the natural timing differences of selftimed circuitry and explicitly injected randomization, the chaos router avoids long message routes with high probability. In this paper the router is described, it is argued that the chaos router is deadlock free and probabilistically live-lock and starvation free, and simulation results are presented showing that the chaos router performs well.

Adaptive routing in generalized hypercube architectures

Abstract: The authors study generalized hypercube (GHC) interconnection networks. This network provides a rich interconnection topology, is symmetric, and potentially forms the basis of a very reliable architecture. They propose a general taxonomy for adaptive routing protocols, and identify three classes of protocols for generalized hypercubes in particular. These protocols are fully distributed, resilient to link failures or bottlenecks, and require comparatively little additional routing overhead over current fixed path routing protocols. The performance of the three protocols is evaluated for a 64 node circuit switched GHC. The authors propose metrics in addition to the commonly used metrics of latency and path length, to capture the unique behavior of such adaptive protocols. >

Method and circuit arrangement for the acceptance and forwarding of message cells transmitted according to an asynchronous transfer mode by an asynchronous transfer mode switching equipment

Abstract: For receiving and forwarding message cells transmitted according to an asynchronous transfer mode (ATM) by an ATM switching equipment which comprises a multi-stage reversing switching matrix network, each of the message cells has a routing information block having a plurality of routing information corresponding in number of the plurality of switching matrix stages to be traversed located in front thereof within the ATM switching equipment and the routing information just evaluated for the forwarding of a message cell through one of the switching matrix stages is subsequently displaced to the end of the respective routing information block. It is thereby provided that each of the routing information of the routing information block has a separate security information attached thereto and the security information is falsified, together with the displacement of a routing information to the end of the respective routing information block. A message cell is thereby only forwarded via a switching matrix stage when the routing information to be evaluated for that purpose has been recognized as being free of error on the basis of the attached security information.

Deterministic and chaotic adaptive routing in multicomputers

Abstract: Multicomputers such as the Caltech Cosmic Cube and its commercial descendants, employing distributed memory and message passing, manage to avoid the scalability problems of shared-memory multiprocessors, thus becoming a promising approach to massive parallelism. The efficient routing of messages is one of the fundamental issues in multicomputers. State-of-the-art systems implement oblivious routing, where the path of each message is unique and completely determined by its source and destination addresses. Oblivious routers, although simple to implement, exhibit poor performance under traffic known to create hot-spots and they are fault-intolerant. Adaptive routers, an alternative to obliviousness, select message paths based on the local load characteristics. As a result they are better at diffusing congestion and they are more fault-tolerant. In this thesis, two novel adaptive routing schemes are introduced, a minimal and nonminimal one. In the minimal router, the Zenith router, messages are always routed closer to their destination and message delivery can be deterministically guaranteed. In the nonminimal router, the Chaos router, messages can be occasionally sent further from their destination. The hardware requirements and control complexity of the Chaos router are superior to that of any minimal router. This reduction in hardware stems from the fact that the Chaos router does not need to use priority routing, like other nonminimal routers in order to guarantee message delivery. Rather, randomization in the message derouting process is used to guarantee message delivery with high probability. The performance of the suggested routers is evaluated through simulations and their hardware requirements are considered.

A minimum interference routing algorithm for a linear lightwave network

Abstract: A routing algorithm for setting up point to point connection is proposed for a linear lightwave network (LLN). The overall problem of routing is decomposed into the subproblems of physical path allocation, checking for violations of some of the special constraints (MISC (mutually independent sources combining) and color clash) of the LLN on the allocated physical path and the allocation of an appropriate channel. It is shown that the problem of finding a physical path that does not violate the MISC constraint of the LLN is NP-complete. >

Flexible, fault-tolerant routing criteria for circuit-switched hypercubes

Abstract: A set of routing criteria is proposed for circuit-switched hypercubes that exploit the flexibility provided by the hypercube. The routing criteria are provably deadlock-free and route messages along shortest paths. The number of shortest paths allowed by the routing criteria is more than one for most source-destination pairs. It is shown that the flexibility provided by the routing criteria can be used to limit the negative effects due to component-failures. The exact number of disrupted source-destination pairs are derived in the presence of a single faulty link or a single faulty node. It is shown that these numbers can be minimized using the relabeling techniques proposed. It is shown that the criteria, if used effectively, lead to a significant improvement in performance over the e-cube routing strategy for non-uniform traffic. >

Routing in a network of bridge-connected LAN Segments

Abstract: For routing of frames through a system of bridge-connected network segments, a routing table is stored in each bridge, and each frame includes fields for a source segment identifier and a destination segment identifier. The routing tables reflect predetermined paths to each network segment as destination. For routing of a normal transmission frame, only the destination segment identifier included in the frame and a table look-up in each bridge are required. For deriving unknown routing information, a discovery frame is sent from source to destination terminal, initially including empty source and destination segment fields. Using the stored routing tables, bridges insert segment identifiers and forward discovery frames in such a way that only one arrives at the destination, carrying the correct source segment identifier and destination segment identifier which are then returned to the source terminal.

Functions and operations of CEBus routers

Abstract: A router is the device in the CEBus network which connects different media. A router intelligently forwards packets onto adjacent media and maintains the tree-structure topology. These functions are provided though the interaction of four elements the communications element, the forwarding element, the directory routing table element, and the network topology protocol element. These elements, combined with the services of the other layers of the router, relieve the nodes of the costly task of network maintenance. >

A routing strategy for MAN interconnection

Abstract: The authors propose a combined routing strategy to overcome the problems connected with applying routing schemes usually adopted in bridged LANs to a LAN-MAN (metropolitan area network) internet. The strategy uses a spanning tree for multicasting within user groups, and shortest paths for point-to-point forwarding. The authors show that the algorithms can scale up efficiently to large network sizes. They also present various enhancements of the basic algorithms, which can substantially improve performance in specific environments. >

Connectivity database overhead for inter-domain policy routing

Abstract: Policy routing protocols incorporate policy related constraints into the route computation and packet forwarding functions for inter-administrative domain (AD) communication. However, this functionally exacerbates the already critical problem of routing information distribution and storage overhead in very large internets (e.g., 100000 ADs). The authors investigate the scalability of the inter-domain policy routing (IDPR) architecture. In particular, they present an informal analysis of connectivity database and update overhead. A model of the IDPR architecture is defined and tested by varying several parameters. The results obtained illustrate the scaling properties of the IDPR architecture and their dependencies upon internet configuration, connectivity among ADs, and number of policies. It is found that, under certain reasonable assumptions, global information for an internet of 5000 transit ADs (and 50000 stub ADs) will occupy on the order of 2.5 MB of storage in the route server. >