Showing papers on "Node (networking) published in 1991"

Round-robin scheduling for max-min fairness in data networks

Abstract: The author studies a simple strategy, proposed independently by E.L. Hahne and R.G. Gallager (1986) and M.G.H. Katevenis (1987), for fairly allocating link capacity in a point-to-point packet network with virtual circuit routing. Each link offers its packet transmission slots to its user sessions by polling them in round-robin order. In addition, window flow control is used to prevent excessive packet queues at the network nodes. As the window size increases, the session throughput rates are shown to approach limits that are perfectly fair in the max-min sense. If each session has periodic input (perhaps with jitter) or has such heavy demand that packets are always waiting to enter the network, then a finite window size suffices to produce perfectly fair throughput rates. The results suggest that the transmission capacity not used by the small window session will be approximately fairly divided among the large window sessions. The focus is on the worst-case performance of round-robin scheduling with windows. >

Communication network integrating voice data and video with distributed call processing

Abstract: A token ring local area network integrates voice, data and image information over a single cable with voice packets having a higher priority than non-voice packets, and with all the voice packets having the same length and the maximum non-voice packet length being related to the voice packet length and to the maximum number of terminals in the network so as to ensure real-time voice reception Call processing functions are fully distributed among the voice terminals without the use of a centralized processing unit or a centralized data base Conference calls are effected by each party transmitting conference packets to a single destination party, with conference packets having a unique packet format wherein a single packet incorporates voice information from plural terminals so as to minimize the number of packets traversing the ring The token ring includes a plurality of interconnected stations or node coupling units, each of which is, in turn, connected to a plurality of nodes or terminals in a star-wired configuration, with each terminal having connected thereto one or more application devices, such as a digital feature telephone, a video camera, or a PC One or more of the node coupling units may be connected to a bridge for providing connection to another token ring, or to a gateway for providing connection to external networks, such as a PBX, a telephone central office, or a host computer

Networked satellite and terrestrial cellular radiotelephone systems

Abstract: There is provided a mechanism for networking satellite and terrestrial networks. It comprises: maintaining subscriber-received power levels of terrestrial network transmissions about one order of magnitude above co-channel satellite transmissions to overcome interference and maintaining subscriber transmissions to terrestrial networks at power levels about one order of magnitude of the below co-channel transmissions to satellite networks to avoid causing interference at the satellite. Such power level maintenance is provided by the network in communication with such subscriber. Moreover, a non-orbiting ("grounded") satellite cooperates as a switching node of both the satellite network and a terrestrial network to relay information between a terrestrial subscriber and the satellite radiotelephone network over a terrestrial network. The terrestrial network and the satellite network may communicate via either the inter-satellite spectrum or the terrestrial-to-satellite spectrum.

Fully decentralised algorithm for multisensor Kalman filtering

Abstract: An algorithm that achieves complete decentralisation of the Kalman filter algorithm amongst the sensing nodes of a multisensor system is preserved. This algorithm does not require any form of central processing facility or centralised communications medium. Each sensing node implements its own local Kalman filter to arrive at a partial decision which it then broadcasts to every other node. Each node then assimilates this received information to arrive at its own local estimate of the system state. The algorithm guarantees that each local estimate thus obtained is identical to the estimate that would be obtained if a conventional, completely centralised, Kalman filter were used. Because there is no single central processing node the algorithm is highly resilient to loss of one or more sensing nodes. The fully decentralised nature ensures that it is ideal for implementation on a parallel processing array, such as a transputer network. The algorithm has been tested using a simulated multiperson pursuitevasion game to check the viability. The algorithm has also been implemented on a transputer based array of cameras to perform tracking of an object moving around a room.

The wave expansion approach to broadcasting in multihop radio networks

Abstract: An algorithm for efficient communication between neighbours in multihop radio networks is proposed. The algorithm guarantees a bound on the transmission efficiency in a radio channel for arbitrary topology. The algorithm can be embedded in protocols for solving basic network problems such as broadcast, multicast, leader election, or finding shortest paths. The problem of bounded-time broadcasting utilizing the proposed algorithm is addressed. A polynomial solution in which the process of spreading information over the network is viewed as the expansion of a wave caused by a point of disturbance is presented. The broadcast originates at a source node and is accomplished in repeated transmission periods, emulating a wave progressing away from the source. The algorithm is used to select a subset of potential transmitters in each period, so that a tightly bound proportion of potential receivers receive the transmission without collisions, guaranteeing a high level of spatial reuse in the broadcast process. >

Packet-switched network having alternate virtual paths

Abstract: In a broadband ISDN system where each switching node is connected to each adjacent node by a transmission line having communication links and a service link, the switching node comprises a self-routing network for routing a cell from an input to an output of the network according to a virtual path identifier it contains. Static connections are established between communication links and the routing network by a digital cross-connect system. A virtual path memory stores data indicating link-to-link connections associated with normal virtual paths and link-to-link connections associated with alternate virtual paths. A fault detector is coupled to the communication links to detect a link failure. If a link failure occurs, a fault message is transmitted to adjacent switching nodes through service links, and data corresponding to the faulty link is retrieved from the memory in response to a fault message that is received from the fault detector or from an adjacent node. The cross-connect system is controlled in accordance with the retrieved data so that the route of the cells is switched from a normal virtual path to an alternate virtual path.

Congestion avoidance in high-speed network carrying bursty traffic

Abstract: A data communication network subject to bursty traffic employs a bandwidth allocation scheme to avoid congestion When a source node has a burst of traffic to send, it first sends a bandwidth request message through the network from source to destination At each intermediate node, this bandwidth request is examined and the node determines how much of the requested traffic level it will be able to support at a time in the future of one round-trip interval hence, and this node either grants the request or marks down the request to a level that it can support, then passes it on When the request reaches the destination, it is returned along the same path to the source, and the source then employs the marked-down allocation to select the rate used to send the burst of data The allocation for this source node remains in effect for a limited time, depending upon the amount of data to be sent in the burst, then returns to a "residual" level

Direct solution of distribution systems

Abstract: The paper reports on a direct power flow solution technique for radial distribution networks. The special topology of distribution networks has been fully exploited to make direct solution possible. A unique branch and node numbering scheme has been proposed to achieve storage and computational economy. Composite load characteristics can be easily modelled. The method developed has been extended for meshed and unbalanced distribution networks. In both cases, modifications required are few and the advantages obtained in balanced radial networks in respect of storage and computational requirements have been preserved. The proposed method has been successfully applied to the solution of a number of practical distribution networks.

Asynchronous replication of data changes by distributed update requests

Abstract: A method of replicating changes made to databases distributed throughout a computer network is described. A first program (TP1) in the Collector node instructs a second program (TP2) in the Collectee node to send all updates to a database since the last conversation. TP2 processes queries to retrieve any changes made since the last conversation between the Collector and Collectee nodes and send the data to TP1, which updates the copy of the database on its own system.

Circuitry and method for fair queuing and servicing cell traffic using hopcounts and traffic classes

Abstract: A method of fair queuing and servicing cell traffic in a telecommunication node which interfaces with a telecommunication system including a multiplicity of nodes is described. The steps include placing cells of traffic are placed in a queue according to a hopcount associated with each cell of bursty traffic, the hopcount being representative of the number of nodes traversed by the associated cell. Cells of traffic within the queue are serviced according to their associated hopcount. The hopcount associated with each cell of traffic is incremented as each cell of traffic is serviced. Circuitry providing fair queuing and servicing of cell traffic in a telecommunication node which interfaces with a telecommunication system including a multiplicity of nodes is also described.

MENTOR: an algorithm for mesh network topological optimization and routing

Abstract: The problem of obtaining a minimum cost topology for a mesh network given matrices specifying the cost of links between all pairs of nodes and the internode requirements is considered. A heuristic algorithm which works in terms of general network design principles and uses utilization as a figure of merit is presented. The procedure is applicable to a wide variety of networks, especially to the problem of obtaining starting topologies for other network design procedures. The algorithm's computational complexity is shown to be of order N/sup 2/, a significant improvement over currently used algorithms and fast enough to be embedded in the inner loop of other more general design procedures, e.g., node selection procedures. Computational experience is presented which shows that the procedure is fast and simple and yields solutions of a quality competitive with other much slower procedures. >

Using distributed topology update and preplanned configurations to achieve trunk network survivability

Abstract: The authors present a new approach for trunk network survivability. This modular approach is intended for a telephone trunk network consisting of high-bandwidth fiber-optic links connected through reconfigurable digital cross-connect nodes. It works for both node and link failures. This approach comprises a distributed protocol with two parts. First, the surviving digital cross-connect nodes are caused to converge to an agreement on the topology (i.e., what is up and what is down). Second, based on the agreed topology and on a precomputed plan for that topology, the digital cross-connect nodes are reconfigured to restore as much call-carrying capacity as possible. The modularity of this approach comes from separating the problem of devising a distributed fault-tolerant protocol to determine what the failure is from the problem of designing a network reconfiguration for that failure. >

Multihop lightwave networks: a comparison of store-and-forward and hot-potato routing

Abstract: A straightforward approach is found for computing the total aggregate capacity of a multihop network with hot-potato routing, and for finding the probability distribution of the number of hops taken by a representative test packet. The rows and columns of the state transition matrix used by this approach each contain, at most, two nonzero elements. The approach is valid for any symmetric network connection diagram under conditions of uniform loading. Results obtained for recirculating perfect shuffle connection diagrams show that the achievable aggregate capacity degrades relative to the capacity maximizing store-and-forward routing as the number of network nodes increases, but even for networks containing several thousand nodes, it is no worse than 25% of that for store-and-forward. Increasing the link data speed by more than a factor of four will produce, overall, a higher aggregate capacity. >

Distributed protocol for improving the survivability of telecommunications trunk networks

Abstract: A method for reconfiguring a telecommunications network (10) comprising a plurality of reconfigurable cross-connect nodes (A, B, C, D) interconnected by links (1 = 1, 2, 3, 4, 5) when a failure event occurs is disclosed. The method comprises storing at each node a precomputed configuration table corresponding to each of a plurality of possible network topologies which can result from a plurality of possible failure events. After a specific failure event occurs, the network is flooded with messages so that each of the nodes is informed as to the specific existing topology of the network resulting from the specific failure event. The nodes are then reconfigured in accordance with the precomputer configuration tables which correspond to the specific existing network topology.

Method and apparatus for establishing spread spectrum communications

Abstract: A method for establishing communications between a master unit (50) and a plurality of node units (51-55). Of the plurality of node units, K node units are assumed to have established communications with a master unit. A first (K+ 1) node unit of the plurality of node units desires to establish communications with the master unit. The method includes transmitting from the master unit a base-station spread spectrum signal (CSn1) having a common-signalling chip code, transmitting from the first node unit a second spread spectrum signal (CSm) with a first identification code using the common-signalling chip code, transmitting from the master unit a third spread spectrum signal (CSn2) with a master unit identification code, using the common-signalling chip code. The method further includes generating at the first node unit using the master unit identification signal (CSn2) a master unit chip code for transmitting spread spectrum signals (CNMK+1) to the master unit. Additionally, the method includes generating at the master unit using the first identification code, a first node unit chip code for transmitting spread spectrum signals (CMNk+1) to the first node unit.

Data transmission routing system

Abstract: A data transmission routing system which allows a terminal user to access an initial host within a computer network, the initial host determines a preferred target host to respond to the user's requests, the initial host communicates with a terminal or gateway node the target host's address, and the terminal or gateway node makes a connection wth the target host. Once the terminal or gateway node is in communication with the target host, the initial host forwards through the terminal or gateway node user profile information to the target host. The initial host is then disconnected and communication then proceeds with the user in contact with the target host through the terminal or gateway node. The entire process may take less than a second or two and the user may never know that a call deflection to a new host has occurred.

Multi-nodal communication network with coordinated responsibility for global functions by the nodes

Abstract: An electronic network of communication and processing nodes particularly suitable for control of environmental systems has pluralities of the nodes which are sources for certain types of status messages each of which comprise communication of a particular kind of information on the network. To resolve the question of which of the nodes shall furnish each type of status message, one node is designated the coordinator node, and it stores a status message source list which associates the node assigned for each type of status message with the status message type itself and transmits all or a part of the list on the network to allow each of the status message source nodes to determine therefrom their responsibility with respect to each status message type. These status message source nodes can also transmit request messages on the network by which they request responsibility for furnishing a particular type of status message. Upon acceptance of the request in a request message, the coordinator node enters the node transmitting the request message into the status message source list in asociation with the status message type. In one embodiment, the coordinator node monitors the transmission of status messages on the network and if an instance arises where a status message is supplied by other than the one specified in the status message source list, takes remedial action. In another embodiment each node is given a priority for a particular type of status message, allowing the coordinator node to replace a node assigned to a particular type of status message with another node.

Improved hypercube topology for multiprocessor computer systems

Abstract: A hypercube system which has been modified by adding additional communication links between the most distant nodes of a classic hypercube topology is described herein. This improvement in a hypercube topology is termed as a Modified Hypercube topology. Such a topology contains extra links which connects a node to another node in the topology which requires the greatest number of nodal hops over the shortest path. Also stated another way, that node having the greatest number of singly traversed or hopped nodes along the shortest path from an originating node to that node makes that node the most distant processor node. If hamming were to be implemented in the system, there is added an extra link between two nodes having the greatest hamming distance. Such a system makes a technological trade off to reduce the diameter of a classic hypercube at the cost of incrementally increasing the number of I/O ports at each node. This trade off has been recognized in the industry as advantageous since a great gain in performance is achieved n exchange for an incremental impact to the hardware. Clearly the performance advantages of the present invention grows as the number of nodes in the hypercube grows and the maximum distance between nodes increases.

Optical communication network with passive monitoring

Abstract: An optical communication network includes at least one single-mode fiber, referred to as a "primary fiber," for transmission between a central office and a distribution node, and at least one multiplicity of single-mode fibers, referred to as "distribution fibers," for transmission between the distribution node and a multiplicity of optical network units (ONUs). Transmissions are exchanged between the primary and distribution fibers via at least one optical coupler located at the distribution node. The network is passive in the sense that all monitoring of the transmission media and the ONUs can be performed at the central office, without active intervention at remote locations. The network includes a monitor and a multiplicity of bypass lines by means of which at least a portion of inbound signals from the distribution fibers are transmitted to the monitor without passing through the optical coupler at the distribution node.

Realistic Simulation of Water Distribution System

Abstract: Due to financial constraints in developing countries, water supply to various consumers is quite less than actual demand. A technique for simulation of water distribution network duly considering this low supply situation is presented. This is accomplished by satisfying an additional constraint of head-flow relationship at each node. The conventional methods just give the resulting pressures at various nodes in the prescribed demand condition. This is meaningless in a low-supply situation. The proposed method gives actual supply quantity from each node based on inherent characteristics of the system. The practical advantages are also discussed.

Telecommunications network restoration architecture

Abstract: A restoration system is provided for enhancing the reliability of a telecommunications network such that particular traffic which is disrupted by, for example, a faulty link, may be quickly rerouted via an alternate route established "on the fly". In particular, each node and link forming the network is monitored, and in the event that such monitoring detects a faulty link or node then a central controller is notified. The controller is arranged to locate spare capacity and establish an alternate route, in which the continuity of the alternate route is confirmed before the disrupted traffic is transferred thereto.

WDM passive star-protocols and performance analysis

Abstract: A wavelength division multiplexing (WDM) transmissive star network is investigated, in which each node has one tunable transmitter with limited tuning capability and multiple fixed receivers. Two synchronous channel access protocols requiring no pretransmission penalty are considered: random access and fixed transmission scheduling. An efficient approximate analysis with drastically reduced computational complexity is presented. In spite of the reduced complexity, the presented approach produces very accurate results and can serve in producing the most cost-effective system design for given performance requirements. >

Border node having routing and functional capability in a first network and only local address capability in a second network

Abstract: A method and apparatus for interconnecting multiple data processing networks, each data processing network including: multiple network nodes having routing and functional capability within a data processing network; and, multiple endpoint nodes, each including only local address capability. Each network node may be connected to multiple endpoint nodes and other network nodes; however, connection is only permitted to network nodes within the same data processing network. A border node is established for interconnection between two data processing networks. The border node includes a network node interface having routing and functional capability within a first data processing network and an endpoint node interface having local address capability. When interconnected between the first data processing network and a network node within a second data processing network, the border node emulates a network node within the first data processing network while appearing as an endpoint node within the second data processing network, permitting full connectivity between the two networks. The border node then maintains routing information for communication between the two data processing networks in two segments. A first segment details the route between the first data processing network and the border node while a second segment details the route between the border node and a node within the second data processing network.

A study of slot reuse in dual bus multiple access networks

Abstract: In dual unidirectional bus networks, packets usually occupy fixed-length slots form the sending station to the end of the network. An erasure node is a specialized station which recognizes packets which have passed their destination stations and releases the slots for subsequent use. The authors derive the optimal locations for erasure nodes and show analytically, for uniform traffic, that only several erasure nodes are needed to achieve throughput close to twice the nominal network bandwidth. The results are tested by simulation of the DQDB (distributed queue dual bus) protocol, which demonstrates a realistic improvement of 40% with only three erasure nodes. Fair access among the stations is improved as well. The authors generalize the analytic results by providing an algorithm for determining the optimal erasure node locations and the throughput improvement, given any arbitrary traffic pattern. The application of this methodology to the related problem of bridged subnetworks is briefly discussed. >

Method and apparatus for multistage document format transformation in a data processing system

Abstract: A method and apparatus for determining an optimal multistage transformation from a first document format to a second document format via multiple format type transformation applications. Each document format type within a data processing system is identified and associated with a node within a format type network. An expenditure cost associated with each format type transformation application, such as time cost or information loss cost, is identified and associated with a link between two associated nodes in the format type network. An optimal path from a first node within the format type network to a second node is then calculated by means of links having minimal expenditure cost associated therewith. In one depicted embodiment of the present invention an optimal path from a selected node to all other nodes within the format type network is calculated and utilized for all future desired transformations.

Frequency agile tdma communications system

Abstract: An intelligent communications node (20) is capable of dynamically selecting frequency and time slot assignments for com-munications with remote communication devices (22, 24, 26) having different communication protocols including different avail-able frequencies and time slots in a TDMA system. A frequency agile transmitter (62) and receiver (32) combined with an adapt-able time slot selector (38, 60) enables communications with remote devices utilizing different protocols. The time and frequency management capabilities of the node (20) makes greater spectral efficiencies possible.