Showing papers on "Routing table published in 1996"

Quality-of-service routing for supporting multimedia applications

Abstract: Several new architectures have been developed for supporting multimedia applications such as digital video and audio. However, quality-of-service (QoS) routing is an important element that is still missing from these architectures. In this paper, we consider a number of issues in QoS routing. We first examine the basic problem of QoS routing, namely, finding a path that satisfies multiple constraints, and its implications on routing metric selection, and then present three path computation algorithms for source routing and for hop-by-hop routing.

Design of logical topologies for wavelength-routed optical networks

Abstract: The problem of designing a logical topology over a wavelength-routed all-optical network (AON) physical topology is studied. The physical topology consists of the nodes and fiber links in the network. On an AON physical topology, we can set up lightpaths between pairs of nodes, where a lightpath represents a direct optical connection without any intermediate electronics. The set of lightpaths along with the nodes constitutes the logical topology. For a given network physical topology and traffic pattern, our objective is to design the logical topology and the routing algorithm so as to minimize the network congestion while constraining the average delay seen by a source-destination pair and the amount of processing required at the nodes (degree of the logical topology). Ignoring the delay constraints can result in fairly convoluted logical topologies with very long delays. On the other hand, in all our examples, imposing it results in a minimal increase in congestion. While the number of wavelengths required to imbed the resulting logical topology on the physical all optical topology is also a constraint in general, we find that in many cases of interest this number can be quite small. We formulate the combined logical topology design and routing problem described above as a mixed integer linear programming problem which we then solve for a number of cases of a six-node network. This programming problem is split into two subproblems: logical topology design, and routing. We then compare the performance of several heuristic topology design algorithms against that of randomly generated topologies, as well as lower bounds.

End-to-end routing behavior in the internet

Abstract: The large-scale behavior of routing in the Internet has gone virtually without any formal study, the exception being Chinoy's analysis of the dynamics of Internet routing information [Ch93]. We report on an analysis of 40,000 end-to-end route measurements conducted using repeated "traceroutes" between 37 Internet sites. We analyze the routing behavior for pathological conditions, routing stability, and routing symmetry. For pathologies, we characterize the prevalence of routing loops, erroneous routing, infrastructure failures, and temporary outages. We find that the likelihood of encountering a major routing pathology more than doubled between the end of 1994 and the end of 1995, rising from 1.5% to 3.4%. For routing stability, we define two separate types of stability, "prevalence" meaning the overall likelihood that a particular route is encountered, and "persistence," the likelihood that a route remains unchanged over a long period of time. We find that Internet paths are heavily dominated by a single prevalent route, but that the time periods over which routes persist show wide variation, ranging from seconds up to days. About 2/3's of the Internet paths had routes persisting for either days or weeks. For routing symmetry, we look at the likelihood that a path through the Internet visits at least one different city in the two directions. At the end of 1995, this was the case half the time, and at least one different autonomous system was visited 30% of the time.

FPGA architecture with repeatable tiles including routing matrices and logic matrices

Abstract: An FPGA architecture offers logic elements with direct connection to neighboring logic elements and indirect connection through a routing matrix. A logic element and a portion of the routing matrix are formed as part of a tile, and tiles are joined to form arrays of selectable size. The routing matrix includes routing lines which connect just from one tile to the next and routing lines which extend longer distances through several tiles or through the entire chip. This combination is achieved by the formation of individual tiles, all of which are identical.

Routing on longest-matching prefixes

Abstract: This article describes the dynamic prefix tries, a novel data structure with algorithms for insertion, deletion, and retrieval to build and maintain a dynamic database of binary keys of arbitrary length. These tries extend the concepts of compact digital (Patricia) tries to support the storage of prefixes and to guarantee retrieval times at most linear in the length of the input key irrespective of the trie size, even when searching for longest-matching prefixes. The new design permits very efficient, simple and nonrecursive implementations of small code size and minimal storage requirements. Insert and delete operations have strictly local effects, and their particular sequence is irrelevant for the structure of the resulting trie, thus maintaining at all times the desired storage and computational efficiency. The algorithms have bees successfully employed in experimental communication systems and products for a variety of networking functions such as address resolution, maintenance and verification of access control lists, and high-performance routing tables in operating system kernels.

Arrangement for rendering forwarding decisions for packets transferred among network switches

Abstract: An arrangement facilitates rendering of a forwarding decision for a packet transferred between high-speed switches of a network using a path identifier (PTID) encapsulated within the packet. The PTID is a tag associated with a destination address of the packet and comprises a value that uniquely identifies a corresponding entry of a forwarding table of the switch. Rather than requiring a full compare of the destination address with the contents of the forwarding table, the PTID is used as a direct index address into the table that identifies the corresponding entry in a fast and efficient manner.

Routing high-bandwidth traffic in max-min fair share networks

Abstract: We study how to improve the throughput of high-bandwidth traffic such as large file transfers in a network where resources are fairly shared among connections. While it is possible to devise priority or reservation-based schemes that give high-bandwidth traffic preferential treatment at the expense of other connections, we focus on the use of routing algorithms that improve resource allocation while maintaining max-min fair share semantics. In our approach, routing is closely coupled with congestion control in the sense that congestion information, such as the rates allocated to existing connections, is used by the routing algorithm. To reduce the amount of routing information that must be distributed, an abstraction of the congestion information is introduced. Using an extensive set of simulation, we identify a link-cost or cost metric for "shortest-path" routing that performs uniformly better than the minimal-hop routing and shortest-widest path routing algorithms. To further improve throughput without reducing the fair share of single-path connections, we propose a novel prioritized multi-path routing algorithm in which low priority paths share the bandwidth left unused by higher priority paths. This leads to a conservative extension of max-min fairness called prioritized multi-level max-min fairness. Simulation results confirm the advantages of our multi-path routing algorithm.

A necessary and sufficient condition for deadlock-free routing in cut-through and store-and-forward networks

Abstract: This paper develops the theoretical background for the design of deadlock-free adaptive routing algorithms for virtual cut-through and store-and-forward switching. This theory is valid for networks using either central buffers or edge buffers. Some basic definitions and three theorems are proposed, developing conditions to verify that an adaptive algorithm is deadlock-free, even when there are cyclic dependencies between routing resources. Moreover, we propose a necessary and sufficient condition for deadlock-free routing. Also, a design methodology is proposed. It supplies fully adaptive, minimal and non-minimal routing algorithms, guaranteeing that they are deadlock-free. The theory proposed in this paper extends the necessary and sufficient condition for wormhole switching previously proposed by us. The resulting routing algorithms are more flexible than the ones for wormhole switching. Also, the design methodology is much easier to apply because it automatically supplies deadlock-free routing algorithms.

Call distribution control method and call distribution control system

Abstract: In a call distribution control method for terminating an incoming call from a trunk or another extension at a pilot extension in a private branch exchange and routing the incoming call from the pilot extension to an idle agent in an agent group, a routing table corresponding to the pilot extension is provided for designating one or plural agent groups to which the incoming call is to be routed. Priorities are assigned to agents constituting the agent groups, and an agent group to which the incoming call is to be routed is decided, based upon the routing table when the incoming call is terminated at the pilot extension. The incoming call is routed to an idle agent, in the order of priority thereof, in the agent group to which the incoming call has been routed. Further, a prescribed agent is allocated to a plurality of agent groups upon assigning a priority to this agent.

Digital network including early packet discard mechanism with adjustable threshold

Abstract: A computer network includes a plurality of routing nodes, each routing node being connected to selected ones of the other routing nodes and at least some of the routing nodes being connected to one of a plurality of packet sources or one of a plurality of packet destinations. Each routing node routes packets that are generated by the packet sources to respective ones of the packet destinations, each packet including a plurality of serially-transmitted cells. At least some of the routing nodes, in response to detection of a selected degree of congestion, enable an "early packet discard control arrangement," in which they discards cells which they receive which are related to packets for which they did not receive a cell prior to enabling the early packet discard control arrangement. The routing nodes periodically adjust the degree of congestion at which they will activate the early packet discard mechanism in relation to information corresponding to rates of reception and transmission of cells over a selected period of time prior thereto.

Fault-tolerant routing in hypercube multicomputers using local safety information

Abstract: Previous methods of making wormhole-routed meshes fault tolerant have been based on adding virtual channels to the networks. This paper proposes an alternative method, one based on the turn model for designing wormhole routing algorithms. The turn model produces routing algorithms that are deadlock free, very adaptive, minimal or nonminimal, and livelock free for direct networks--whether or not they contain virtual channels. This paper illustrates how to modify the routing algorithms produced by the turn model to handle dynamic faults. This paper first describes how to modify the negative-first routing algorithm, which the turn model produces for n-dimensional meshes without virtual channels, to make it one-fault tolerant. Simulations of the one-fault-tolerant routing algorithm and other minimal and nonminimal routing algorithms in a two-dimensional mesh indicate that misrouting increases communication latencies significantly at high throughputs. The conclusion is that misrouting should be used only for increasing the degree of fault tolerance, never for just increasing adaptiveness. Finally , the paper describes how to modify the negative-first routing algorithm to make it (n - 1)-fault tolerant for n-dimensional meshes without virtual channels.

Automatic layout standard cell routing

Abstract: A method of interconnecting transistors and other devices in order to optimize area of a layout of a cell while honoring performance constraints (1502) and enhancing yield starts with a prerouting step (152) that routes adjacent transistors using diffusion wiring (1506), routes power and ground nets (1508), routes aligned gates (1510), routes all remaining aligned source/drain nets as well as any special nets (1512). Next, all of the remaining nets are routed using an area based router (1408). Nets are order based on time criticality or net topology (1602). A routing grid is assigned for all the layers to be used in routing (1604). An initial coarse routing is performed (1606). Wire groups are assigned to routing layers (1608). Routing is improved and vias are minimized (1610). A determination is then made whether the routing solution is acceptable (1612). If the routintg solution is not acceptable, the routing space is expanded and routing costs and via costs are modifyied to improve the routing solution. Finally, the best routing solution is picked (1414).

Routing method and system using an internet protocol

Abstract: Routing methods, using an Internet protocol, which allows free alteration of the connection of a terminal between subnetworks such as local area networks (LANs) without necessitating modification of IP (Internet Protocol) addresses. The subnetworks are unified to constitute a network by a plurality of routers and each router is provided with a table which stores information according to every router indicating terminal addresses and times of connection to the network for every terminal included within the network. When a terminal is connected to any one of the subnetworks, the router corresponding to that subnetwork both updates the content of the table incorporated in that router and communicates to other routers the address and connection time of the connected terminal by means of a subscriber signal. A router which receives the subscriber signal updates the table incorporated in that router based on the results of comparing the connection time within the subscriber signal with the connection time within its own table.

Method of automatic updating and use of routing information by programmable and manual routing information configuration based on least lost routing

Abstract: In an electronic messaging system which has multiple sites, and in which each site is defined by a unique address space and has connectivity to at least one other site, messages are sent by receiving at a first site message routing information from a second site. The message routing information defines routes from the second site to one or more of the plurality of sites. The received message routing information is assimilated into previously known routing information to generate an updated accumulation of routing information. The updated accumulation of routing information is used to route messages to one or more of the plurality of sites. The updated accumulation of routing information may be replicated to still other sites in the messaging system, which in turn assimilate the information into their respective collections of known routing information. This process of receiving, assimilating and replicating may be repeated until each of the sites has substantially the same updated accumulation of routing information.

High performance fault tolerant switching system for multimedia satellite and terrestrial communications networks

Abstract: A switch that has a plurality of inputs in which cells are received at these inputs. Each cell received at the inputs of the switch contain routing information. A routing means is employed to route the cells received at the inputs of the switch to outputs using routing information in which a number of the cells are misrouted by the routing means during the process of routing the cells to the outputs. Bus means is employed to route a cell to the destination in which the bus means is connected to the routing means. The bus means routes misrouted cells that are misrouted from the destination by some selected amount.

Adaptive routing in irregular networks using cut-through switches

Abstract: Many cut-through switches, which can greatly reduce network latency, are commercially available for the construction of high-speed local area networks. The interconnection of cut-through switches provides an excellent network platform for high-performance workstation clusters. A novel deadlock-free adaptive routing algorithm is proposed to allow irregular interconnection of cut-through switches. The adaptive routing algorithm is based on two unidirectional adaptive trails constructed from two opposite unidirectional Eulerian trails. Some heuristics are suggested in terms of the selection of Eulerian trails, the avoidance of long routing paths, and the degree of adaptivity. Extensive simulation experiments based on a more realistic finite input source model are conducted to evaluate the network performance under different network parameters and traffic conditions. Both bimodal and bursty messages are considered. Such switch-based irregular networks are truly incrementally scalable and have potential to be reconfigured to adapt to the dynamics of network traffic conditions.

System for generating explicit routing advertisements to specify a selected path through a connectionless network to a destination by a specific router

Abstract: A system for providing explicit routing functions in a connectionless network. A specific router selects a path through the connectionless network to a destination. Explicit routing advertisements are generated by the specific router and contain information regarding the selected path. Routing state is installed according to information contained in the explicit routing advertisements. The explicit routing advertisements are forwarded to each next hop router. Each next hop router installs routing state, generates the explicit routing advertisement, and forwards the explicit routing advertisement to further propagate the routing information.

Method for deadlock-free message passing in MIMD systems using routers and buffers

Abstract: A message passing system for an MIMD parallel processing computer system utilizing a CSP programming model is relatively simple and inexpensive, yet allows for deadlock-free message passing, as well as the ability to support irregular connection topologies among nodes in the computer system. Messages are passed from node to node utilizing buffers at intermediate nodes to temporarily store the messages. In accordance with the CSP programming model, the user code is divided into multiple concurrent user processes which communicate with each other via channels. Each user process executing at a node is also provided with a corresponding, but separate, router process which uses a set of N-1 virtual channels to communicate with all other processes in the system, where N is the number of processes. The router process is preferably provided with a routing table that implements an acyclic sub-graph solution for interconnecting nodes in any arbitrary network topology, including irregular network topologies. The router process also allows for standard I/O functions to be emulated at every node in the system, not just those nodes which are directly connected to an I/O device. Preferably, the router process implements a buffer pool management structure which is organized first by channels and then by hops.

A fault-tolerant routing strategy in hypercube multicomputers

Abstract: We investigate fault-tolerant routing which aims at finding feasible minimum paths in a faulty hypercube. The concept of unsafe node and its extension are used in our scheme. A set of stringent criteria is proposed to identify the possibly bad candidates for forwarding a message. As a result, the number of such undesirable nodes is reduced without sacrificing the functionality of the mechanism. Furthermore, the notion of degree of unsafeness for classifying the unsafe nodes is introduced to facilitate the design of efficient routing algorithms which rely on having each node keep the states of its nearest neighbors. We show that a feasible path of length no more than the Hamming distance between the source and the destination plus four can always be established by the routing algorithm as long as the hypercube is not fully unsafe. The issue of deadlock freeness is also addressed in this research. More importantly, another fault-tolerant routing algorithm, which requires only a constant of five virtual networks in wormhole routing to ensure the property of deadlock freeness for a hypercube of any size, is presented in this paper.

SVC routing in network with static routing tables

Abstract: A method is disclosed for establishing a switched virtual circuit in a digital network having network nodes with static routing tables. The static routing tables contain at least primary and alternate routing data. When a node is unable to forward a call over its outgoing primary route due to congestion or physical failure and its alternate route is the same as the route on which a call setup request arrived, it clears the call at that node and sends a crankback message to the preceding node, which responds to the crankback message to attempt to dynamically re-route the call over the alternate route stored in the routing table of the preceding node. If the attempt is unsuccessful, it sends the message back to the next preceding node and so on.

Proxy terminal for network controlling of power managed user terminals in suspend mode

Abstract: A network system comprises a plurality of network segments. Each of the network segments connects a plurality of user terminals that can be set in a suspend mode. When a network segment is connected to the network system via a router, it is possible that the network address of a user terminal is deleted from the routing table in the router during an aging process. In this situation, the user terminal is not accessible in the suspend mode via the router. To solve this problem, a proxy terminal is connected to a network segment to receive requests from the router for the user terminals connected to that network segment. In response to a request from the router to a destined user terminal located in that network segment, the proxy terminal wakes up the destined user terminal, thus restoring the access to the destined user terminal.

Method and apparatus for restoration of an ATM network

Abstract: The present invention is a restoration scheme for an ad-hoc ATM LAN wherein ATM cells are transported over a wireless point-to-point link. A method for restoring communications in the ATM network includes the steps of: generating a failure message indicative of a failure of a network element, the failure message including an identification of said network element and a predetermined VPI/VCI reserved for failure reporting; communicating the failure message to all said switching nodes in said network; and referencing updated routing tables at said switching nodes, wherein said network element indicated in said failure message is eliminated from routes in said network. Each of the switching nodes is included in a network tree spanning all said switching nodes in the network, wherein each of the switching nodes is included as a root in a specific network tree, each said network tree having a tree identification, the failure message further including a tree identification field containing the tree identification. The method also includes the step of routing the failure message in the switching nodes of the network based on the tree identification. The failure message includes a time stamp indicative of the time said failure message was generated, and the referencing of the updated routing tables is delayed a predetermined time period from the time of said time stamp before referencing said updated routing tables.

Interchangeable pin routing with application to package layout

Abstract: Many practical routing problems such as BGA, PGA, pin redistribution and test fixture routing involve routing with interchangeable pins. These routing problems, especially package layout, are becoming more difficult to do manually due to increasing speed and I/O. Currently, no commercial or university router is available for this task. In this paper, we unify these different problems as instances of the interchangeable pin routing (IPR) problem, which is NP-complete. By representing the solution space with flows in a triangulated routing network instead of grids, we developed a min-cost max-flow heuristic considering only the most important cuts in the design. The heuristic handles multiple layers, prerouted nets, and all-angle, octilinear or rectilinear wiring styles. Experiments show that the heuristic is very effective on most practical examples. It had been used to route industry designs with thousands of interchangeable pins.

Method and arrangement for establishing call connections in a telecommunications network using a virtual transport server

Abstract: A telecommunications network comprises a virtual transport server (VTS) for making network routing decisions and establishing call connections. Each VTS is interconnected to each signal transfer point in a common channel signaling (CCS) system associated with the network. Each VTS is also interconnected to at least one switch in a transmission network, such as an asynchronous transfer mode (ATM) switch. The VTS maintains routing tables identifying trunk groups associated with each central office switch in the network. During operation, an initial address message received from a signal transfer point in the VTS is processed and subsequently extended to an ATM switch so that a call connection can be established. Upon completion of the established call, the VTS releases resources associated with the ATM switch.

Aim switching system and path changing method

Abstract: An ATM switching system at each node of a network performs route changing or rerouting promptly when a failure occurs. In each of ATM switching systems at nodes N1 to N6: a route table 21 of a line interface 102 is set with conversion header information of a normal route, and an alternate routing table 25 is set with header information of one or more alternate routes. Subsequently, each line interface tests, when a packet arrives, whether or not a failure has occurred in an output line involved in the normal route, by referring to a bitmap 264 storing failure lines and a VP failures. The line interface executes header conversion by applying the normal header information stored in the routing table 21 in the case of no failure set for the normal route and by applying the header information stored in the alternate routing table 25 in case a failure has occurred on the normal route, and then outputs the packet to an ATM switch 101. Since the alternate route is promptly selected at the time of a failure of a net line and not in response to decoding a header of a received packet, the number of packets discarded due to the failure is reduced, and the rerouting operation is promptly executed even in the case of multiple failures.

Automatic provisioning of trunking and routing parameters in a telecommunications network

Abstract: A telecommunication network may be arranged in accord with the invention so that a change in provisioning data occurring at one element of the network is automatically supplied to the other elements of the network, thereby eliminating the need of having a network administration facility to communicate manually the change to the other network elements. For example, if a local central office switch is rehomed from a first toll switch to a second toll switch, then the first and second toll switches form messages respectively characterizing the rehome and then send the messages to each of the other network toll switches so that the other toll switches may update their respective routing and trunking data relating to the rehomed switch. The network is also arranged to implement a rule-based, end-to-end routing scheme which automatically selects a routing path from multiple candidates based on (a) class-of-service parameters and (b) availability of network capacity. The automatic selection of a routing path thus replaces the provisioning of routing data in the toll switches, which data was priorly needed to select the appropriate routing path.

Snapshot routing with route aging

Abstract: A method and system for maintaining and updating routing information in a packet switching network for a set of quasidynamic routes, in which intermittent routing updates are permitted, so that routes are no longer "always static" or "always dynamic", but may change over time between static and dynamic, and are treated accordingly. The invention is particularly applicable to dial-on-demand serial communication links, but is also useful in any situation where it is desired to reduce the overhead from routing updates over a communication link, or where transmission over a communication link is not reliable. A protocol manager for a dynamic routing protocol is modified to determine, for each route, (1) whether to send updated routing information for that route (at the time it would otherwise send an up-date for a particular route), and (2) whether to age that route in its routing tables (at the time it would otherwise age that route). The modified protocol manager thus prevents automatic aging of routes, while avoiding the use of manually configured static routing tables. Routing information is thus learned automatically and dynamically at appropriate times, and refreshed periodically so that it eventually reflects actual changes to the network topology.

Stochastic circuit identification in a multi-protocol network switch

Abstract: A flow based network switch function is based on a route cache and flow detect logic which generates hash codes for use in accessing the route cache. Flow detect logic is implemented with read-write register functions. A network switch which comprises a port for access to a communication medium to receive incoming frames. A route table memory has a set of accessible locations for storing routing information. The set of accessible locations is addressable in response to N bits, and locations in the set store a tag comprising M bits for identifying a network flow. Routing information is also stored in each of the accessible locations for the identified network flow. Flow detect logic is coupled with a port and monitors frames received by the port generate and N bit address, and an identifying tag comprising M bits for use in accessing the route table memory in response to an incoming frame on the port. Match logic is coupled with the route table memory and the flow detect logic, which accesses a particular location in the set of accessible locations in the route table memory in response to the N bit address, compares the identifying tag with the tag stored in the particular location to determine whether the incoming frame matches the network flow identified by the stored tag, and supplies the routing information for level 3 or higher stored in the particular location if a match occurs. If a match does not occur, a route table miss is indicated, and the frame is forwarded to multi-protocol routing algorithms for the purpose of generating the routing information for the incoming frame.