Showing papers on "Node (networking) published in 1993"

Congestion control for cell networks

Abstract: A feedback control system for congestion prevention in a cell (packet) switching communication network is described. Congestion control is accomplished by controlling the transmission rate of bursty traffic in the presence of high priority, voice, low speed statistical, high speed deterministic and multicast data. Because bursty traffic is relatively insensitive to delay, adequate buffercapacity can be provided at the network nodes in order to minimize bursty data cell loss. By monitoring the buffer queue lengths at the nodes, a control signal can be generated at each intermediate node indicating the state of congestion. Excess queue length indicates incipient congestion while short queue lengths indicate excess capacity. Queue status is forwarded to the destination node where it is interpreted and sent back to the source node as a feedback rate control signal using a 2-bit code. The source node regulates the rate of bursty data transmission over the cell network in accordance with the feedback control signal thus minimizing congestion and concomitant data loss while efficiently utilizing available network bandwidth.

Method and apparatus for making a cluster of computers appear as a single host on a network

Abstract: The present invention provides a method and apparatus for enabling a cluster of computers to appear as a single computer to host computers outside the cluster. A host computer communicates only with a gateway to access destination nodes and processes within the cluster. The gateway has at least one message switch which processes incoming and outgoing port type messages crossing the cluster boundary. This processing comprises examining certain information on the message headers and then changing some of this header information either to route an incoming message to the proper computer node, port and process or to make an outgoing message appear as if originated at the gateway node. The message switch uses a table to match incoming messages to a particular routing function which can be run to perform the changes necessary to correctly route different kinds of messages.

Method and apparatus for providing attribute nodes in a graphical data flow environment

Abstract: A system and method for providing attribute nodes in a data flow diagram which allow a user to programmatically access various parameters of a control or indicator. In this manner, a user can programmatically make changes that affect the output or appearance of controls and indicators. A user can also access these parameters interactively during execution of a block diagram. A user can creates an attribute node containing one or more attributes corresponding to controls that affect a parameter of the control, such as the color used for the respective display, the visibility of the control, the scales or cursor position for respective graphs or charts, etc. The purpose of an attribute node is to affect the visual output of a control provided on the front panel depending on events which occur during execution of a VI or on user input during execution of a VI. An attribute node thus allows the execution subsystem to monitor user interaction by reading attribute data that previously was not available to the program. An attribute node allows two types of operations, these being reading an attribute node or writing to an attribute node. These operations of reading and writing an attribute node can be performed either by a block diagram during execution, wherein the user has programmed the block diagram to perform this function, or interactively by the user during execution. The process of writing to an attribute node refers to the execution subsystem updating an attribute of a control in the front panel display to reflect an attribute that has been set programmatically in a block diagram. The user can also "write" to an attribute node by providing input to a control in the front panel during execution of a block diagram. Reading an attribute node refers to the execution subsystem reading the value of an attribute for a certain control during block diagram execution that may have been changed by the user, or may have been changed during execution of a VI by the execution subsystem. Reading an attribute also refers to the user viewing changes to the attribute during execution.

Feedback control of congestion in packet switching networks: the case of a single congested node

Abstract: Addresses a rate-based feedback approach to congestion control in packet switching networks where sources adjust their transmission rate in response to feedback information from the network nodes. Specifically, a controller structure and system architecture are introduced and the analysis of the resulting closed loop system is presented. Conditions for asymptotic stability are derived. A design technique for the controller gains is developed and an illustrative example is considered. The results show that, under appropriately selected control gains, a stable (nonoscillatory) operation of store-and-forward packet switching networks with feedback congestion control is possible. >

Flexible scheme for admission control of multimedia streams on integrated networks

Abstract: An admission control scheme for real-time traffic requests in communication networks is disclosed. The scheme monitors tile performance of each link and predicts the traffic guarantees that can be offered when certain dummy traffic (pseudo traffic) mimicking the behavior of real-time streams is added to the existing traffic. When an application requests connection to the network, it specifies a Quality of Service (QoS) bound that it desires. A routing subsystem of tile network makes use of the predicted values while attempting to find a path over which tile application's QoS bound requirement will be satisfied. After the route is chosen, connection setup will involve verifying at each node along the route whether sufficient resources exist to support tile new connection. This explicit verification is likely to be necessary because the routing subsystem does not normally have up-to-date global state information. After admitting tile application, the network provides a soft guarantee that the QoS bound provided to it will be adhered to for most of the time. On the other hand, if no path through the network satisfies the QoS hound, tile application is denied connection to the network.

Loop-free routing using diffusing computations

Abstract: A family of distributed algorithms for the dynamic computation of the shortest paths in a computer network or internet is presented, validated, and analyzed. According to these algorithms, each node maintains a vector with its distance to every other node. Update messages from a node are sent only to its neighbors; each such message contains a distance vector of one or more entries, and each entry specifies the length of the selected path to a network destination, as well as an indication of whether the entry constitutes an update, a query, or a reply to a previous query. The new algorithms treat the problem of distributed shortest-path routing as one of diffusing computations, which was first proposed by Dijkstra and Scholten (1980). They improve on a number of algorithms introduced previously. The new algorithms are shown to converge in finite time after an arbitrary sequence of link cost or topological changes, to be loop-free at every instant, and to outperform all other loop-free routing algorithms previously proposed from the standpoint of the combined temporal, message, and storage complexities. >

Time dependent, shortest-path algorithm for real-time intelligent vehicle highway system applications

Abstract: An algorithm is introduced that calculates the time-dependent shortest paths from all nodes in a network to a given destination node for every time step over a given time horizon in a network with time-dependent arc costs. Unlike other time-dependent algorithms, this approach can handle networks where the travel cost is not necessarily the travel time itself. The algorithm is based on the general Bellman's principle of optimality. It descretizes the horizon of interest into small time intervals. Starting from the destination node, it calculates the paths operating backwards. A proof of the correctness of the proposed algorithm is presented. The algorithm is efficiently implemented and coded on a CRAY Y/MP-8 supercomputer and tested on a large actual street network as well as several random networks. The motivation for this study was the need to compute time-dependent shortest paths in a real-time environment in connection with intelligent vehicle highway systems. The suitability of the proposed algorithm for such applications is demonstrated.

The J-machine multicomputer: an architectural evaluation

Abstract: The MIT J-Machine multicomputer has been constructed to study the role of a set of primitive mechanisms in providing efficient support for parallel computing. Each J-Machine node consists of an integrated multicomputer component, the Message-Driven Processor (MDP), and 1 MByte of DRAM. The MDP provides mechanisms to support efficient communication, synchronization, and naming. A 512 node J-Machine is operational and is due to be expanded to 1024 nodes in March 1993. In this paper we discuss the design of the J-Machine and evaluate the effectiveness of the mechanisms incorporated into the MDP. We measure the performance of the communication and synchronization mechanisms directly and investigate the behavior of four complete applications.

Interactive home information system with signal assignment

Abstract: An interactive home information system having a node in television communication and data communication with a group of home interface controllers. At each home interface controller, there is a signal input for receiving television signals from the node over a cable television distribution network and a data transceiver for conducting data communications with the node. The node determines whether a home interface controller is requesting interactive service. For each interface controller requesting interactive service, the node assigns a television information signal to the requesting home interface controller. Thus, signal assignment is accomplished on a demand basis for those interface controllers determined to be placed in an interactive mode. Signal assignment may involve selection of a given carrier frequency. Alternatively, signal assignment may involve selection of a time slice.

Object-oriented networking system with dynamically configurable communication links

Abstract: Novel object-oriented client-server facility (CSF) and networking service facility (NSF) interfaces implement communication between application programs residing in client and server nodes of a distributed services network. The CSF interface includes remote procedure call (RPC) objects for invoking and responding to service requests at the nodes, and application programming interface (API) objects for transporting those requests between the nodes. However, the API objects only provide communication transports within a node. Accordingly, the API and RPC objects interact with dynamically-configurable protocol stacks within the NSF interfaces to complete the transport mechanism needed by an application program on the client node when accessing services on a remote server node. A preferred embodiment provides an efficient way to perform object operations in a broadcast fashion over a communication network and ensures the receipt and execution of the operation by each target of the broadcast.

Transmission of check images by way of a public switched telephone network

Abstract: Checks used to effectuate commercial and private transactions may be cleared through the banking system by transporting images of those checks between sending institutions and receiving institutions in forward and reverse flow paths between banks of first deposit and payor banks. The check images are transported through a public switched telephone network which contains a special check imaging node which provides a network based check clearing service for customers of telephone network. The check imaging node receives images of checks from institutions which subscribe to this service and routes those images through the telephone network to intended subscriber and non-subscriber recipients. Transmission of check images through a public switched telephone network may completely replace existing check clearance procedures or may be used in conjunction with existing procedures.

Portable point of sale terminal

Abstract: A point of sale terminal (11) is disclosed that provides all of the usual point of sale terminal functions, but that is entirely field portable. Data pertinent to each purchase can be input to the terminal via a keyboard assembly (17), a touch-screen display (19) or a signature-capture screen assembly (25), or via an antenna (39) and radio link from an associated bar code scanner. Data may be communicated at any time to a remote host computer, also via a separate antenna and radio link. The communication links with the host computer and the bar code scanner operate independently and simultaneously, using mutually compatible modulation schemes such as a spread spectrum scheme for the host computer link and a narrowband or spread spectrum scheme for the bar code scanner link. The terminal thereby functions as a portable repeater or node in a data communications network.

Locating resources in computer networks having cache server nodes

Abstract: A computer network in which resources are dynamically located through the use of LOCATE requests includes multiple cache server nodes, network nodes which have an additional obligation to build and maintain large caches of directory entries. Cache server nodes play a key role in the LOCATE process and can prevent redundant network-wide broadcasts of LOCATE requests. Where an origin cache server node receives a request from a served node, the cache server node searches its local directories first, then forwards the request to alternate cache server nodes if necessary. If the necessary information isn't found locally or in alternate cache server nodes, the LOCATE request is then broadcast to all network nodes in the network. If the broadcast results are negative, the request is forwarded to selected gateway nodes to permit the search to continue in adjacent networks.

Client server system and method of operation including a dynamically configurable protocol stack

Abstract: Novel object-oriented client-server facility (CSF) and networking service facility (NSF) interfaces implement communication between application programs residing in client and server nodes of a distributed services network. The CSF interface includes remote procedure call (RPC) objects for invoking and responding to service requests at the nodes, and application programming interface (API) objects for transporting those requests between the nodes. However, the API objects only provide communication transports within a node. Accordingly, the API and RPC objects interact with dynamically-configurable protocol stacks within the NSF interfaces to complete the transport mechanism needed by an application program on the client node when accessing services on a remote server node.

A method for congestion management in a frame relay network and a node in a frame relay network

Abstract: The invention relates to a method for congestion management in a frame relay network. In the method, a virtual channel associated with a frame (39) to be transferred is determined. In order to provide a congestion management method which is reliable and capable of rapid responding and which allows event virtual connections to be prioritized with respect to the throughput probability, (a) at least some of the virtual channels are assigned a respective service level; (b) a congestion level having values in a predetermined relationship to the values of the service levels is determined for a network resource (15) liable to congestion; (c) the value representing the service level of the virtual channel of the FR frame (39) is compared with the value representing the congestion level of said resource; and (d) when the result of the comparison falls outside a predetermined value range, the frame (39) is discarded.

Topological optimization of a communication network subject to a reliability constraint

Abstract: Network topological optimization with a reliability constraint is considered. The objective is to find the topological layout of links, at a minimal cost, under the constraint that the network reliability is not less than a given level of system reliability. A decomposition method, based on branch and bound, is used for solving the problem. In order to speed up the procedure, an upper bound on system reliability, in terms of node degrees, is applied. A numerical example illustrates the effectiveness of the method. >

Network architecture suitable for multicasting and resource locking

Abstract: A data communications network in which multiple host processors are linked in a ring network by respective network interface processors or nodes includes circuitry in each of the nodes which aids in the implementation of a distributed resource locking scheme and a reliable multicasting system. The circuitry includes a packet generator which automatically generates specialized packets that are used to procure resource locks and to implement the multicast system. In addition, the node includes circuitry which may be used to modify the contents of a received packet and circuitry which automatically retransmits the packet onto the network. The node is controlled by a set of state machines which implement the resource locking and multicasting protocols. In addition, the nodes include circuitry which detects congestion in the node and in the network and acts automatically to relieve the congestion. This circuitry notifies other nodes when a receive queue in the node is almost full so that the other nodes can suspend communications with the node. Other circuitry detects when the node is unable to transmit a message to cause the node to allocate an owned packet which may be used only by the node to transmit data.

Many birds with one stone: multi-objective approximation algorithms

Abstract: We study network-design problems with multiple design objectives. In particular, we look at two cost measures to be minimized simultaneously: the total cost of the network and the maximum degree of any node in the network. Our main result can be roughly stated as follows: given an integer $b$, we present approximation algorithms for a variety of network-design problems on an $n$-node graph in which the degree of the output network is $O(b \log (\frac{n}{b}))$ and the cost of this network is $O(\log n)$ times that of the minimum-cost degree-$b$-bounded network. These algorithms can handle costs on nodes as well as edges. Moreover, we can construct such networks so as to satisfy a variety of connectivity specifications including spanning trees, Steiner trees and generalized Steiner forests. The performance guarantee on the cost of the output network is nearly best-possible unless $NP = \tilde{P}$. We also address the special case in which the costs obey the triangle inequality. In this case, we obtain a polynomial-time approximation algorithm with a stronger performance guarantee. Given a bound $b$ on the degree, the algorithm finds a degree-$b$-bounded network of cost at most a constant time optimum. There is no algorithm that does as well in the absence of triangle inequality unless $P = NP$. We also show that in the case of spanning networks, we can simultaneously approximate within a constant factor yet another objective: the maximum cost of any edge in the network, also called the bottleneck cost of the network. We extend our algorithms to find TSP tours and $k$-connected spanning networks for any fixed $k$ that simultaneously approximate all these three cost measures.

Communications protocol for digital telemetry system

Abstract: The present invention relates to a communications protocol for a digital telemetry system which enables more efficient digital data transmission between a plurality of digital communications nodes The protocol is implemented using uplink and downlink packets and superpackets Each node forms an uplink packet which contains node data and protocols Those packets are packaged into uplink superpackets and transmitted to a control node Downlink superpackets containing information signifying which of the uplink superpackets were received correctly are formed and transmitted to the individual nodes In response, any uplink superpacket received incorrectly is retransmitted Additionally, the communications protocol also time stamps messages received from the nodes to provide for digital communications time correlation

High speed data transfer over twisted pair cabling

Abstract: A method provides for a first network node in a plurality of network nodes to transmit a data packet to a hub. The hub and the network nodes are interconnected within a local network system. Control signals are exchanged between the first network node and the hub. The exchange of control signals is done in a first signal frequency range. A data packet is sent from the first network node to the hub. The data packet is sent using data signals within a second signal frequency range. The first signal frequency range and the second signal frequency range do not overlap.

Robust packet routing over a distributed network containing malicious failures

Abstract: A method and system for routing information packets among nodes interconnected by links to form a network, each information packet traversing a path of links and nodes from a source node to a destination node. Information indicating the relationships of nodes and links in the network is assembled in the source node. The entire route from the source node to the destination node is computed prior to sending each information packet and the information packet is routed through the network in accordance with the computed route. Information is assembled about the local topology of the network including the identities of the neighboring nodes which are connected via links to the local node. The local topology information of each local node is distributed to every other node in the network. Each node is assigned a unique identifier, a unique public key and an associated private key. The source node's assigned identifier, public key and private key are assembled in the source node along with the assigned identifier, public key and associated private key of each of a plurality of other nodes. The computed route is enclosed in a packet. The packet containing the routes is signed and transmitted to each node on the route.

Signaling network having common signaling node for protocol conversion

Abstract: A common channel signaling network comprises a first and a second subnetwork each being composed of interconnected signaling nodes having a service entity. The first and second subnetworks employ different versions of protocol for message transmission. A common signaling node is provided for protocol conversion. As the common signaling node receives a message from a service entity of each subnetwork, it converts the message format to the protocol of the other subnetwork, and transmits it to a service entity of the other subnetwork.

Expert system having a plurality of security inspectors for detecting security flaws in a computer system

Abstract: A new security system including a plurality of inspectors each of which performs a security check operation in connection with a particular class of possible security violation conditions. One inspector detects security violation conditions reflecting selection of passwords using easily-guessable formatives. Another inspector detects security violation conditions reflecting ability of a network node to improperly use another node over a network. A third inspector determines whether the operating system files have satisfactory protection. Finally, a fourth inspector determines whether security violation conditions arise in connection with applications programs. If, during a security check operation, an inspector determines that a security violation condition exists, it records the condition in a common working memory for further reporting or analysis.

Forecasting using a neural network and a statistical forecast

Abstract: A system and method for forecasting that combines a neural network with a statistical forecast is presented. A neural network having an input layer, a hidden layer, and an output layer with each layer having one or more nodes is presented. Each node in the input layer is connected to each node in the hidden layer and each node in the hidden layer is connected to each node in the output layer. Each connection between nodes has an associated weight. One node in the input layer is connected to a statistical forecast that is produced by a statistical model. All other nodes in the input layer are connected to a different historical datum from the set of historical data. The neural network being operative by outputting a forecast, the output of the output layer nodes, when presented with input data. The weights associated with the connections of the neural network are first adjusted by a training device. The training device applies a plurality of training sets to the neural network, each training set consisting of historical data, an associated statistical output and a desired forecast, with each set of training data the training device determines a difference between the forecast produced by the neural network given the training data and the desired forecast, the training device then adjusts the weights of the neural network based on the difference.

Method simulating data traffic on network in accordance with a client/server paradigm

Abstract: A method for modeling traffic on a network according to a Client/Server paradigm is disclosed. The method includes the steps of exctracting the model parameters from known or measured interactions between a client node running a particular application and a server node with no other activity on the network. The method is repeated for each nodal configuration and for each application until the traffic for each node-application combination has, been modeled with no other load on the network. Scripts are created from the Paradigm parameters and are used in conjunction with a traffic generator to create discreet events mimicking the traffic which would be generated from each node. The model will insure that the traffic generated by each traffic source will be adjusted as a function of the response of the network under the load created by all of the traffic loading the network.

Acknowledgment protocol for serial data network with out-of-order delivery

Abstract: A system and method for controlling the transmission of frames or packets of data in a serial network which allows out-of-order delivery. The data frames transmitted by the initiator node to the recipient node include frame serial number or sequence count information. Acknowledgment frames, transmitted by the recipient node to indicate delivery of the data frame or packet, include matching serial number or sequence count information. According to one form of the present invention, the initiator node and recipient node include resources which relate the serial number or sequence count information, resources which include control information in the acknowledgment frame, and resources which determine the transmit status of all acknowledgment frames prior to that specified by serial number or sequence count in the acknowledgment frame. The status information is used at the initiator node to update the status of any data frames whose acknowledgment has not been received as a consequence of an out-of-order delivery to the recipient, a delay in processing by the recipient, a delay of the acknowledgment frame in the transmission back to the initiator node, or a complete loss of the acknowledgment frame.

Dynamic shortest paths in acyclic networks with Markovian arc costs

Abstract: We examine shortest path problems in acyclic networks in which arc costs are known functions of certain environment variables at network nodes. Each of these variables evolves according to an independent Markov process. The vehicle can wait at a node (at a cost) in anticipation of more favorable arc costs. We first develop two recursive procedures for the individual arc case, one based on successive approximations, and the other on policy iteration. We also solve the same problem via parametric linear programming. We show that the optimal policy essentially classifies the state of the environment variable at a node into two categories: green states for which the optimal action is to immediately traverse the arc, and red states for which the optimal action is to wait. We then extend these concepts for the entire network by developing a dynamic programming procedure that solves the corresponding problem. The complexity of this method is shown to be O(n2K + nK3), where n is the number of network nodes and K ...

Apparatus and method for incorporating a large number of destinations over circuit-switched wide area network connections

Abstract: In a wide-area computer network system providing bandwidth based on network demand, throughput, and delay requirements, distribution of network load over multiple, parallel connections from the originating node to a distinction node, an apparatus and method of enabling efficient exchange of packet data routing information for information protocol and information protocol exchange routers by providing different routing table information maintenance modes which a user can select, such as a default mode, a forced mode, and a periodic mode. In addition, the system provides, a virtual interface as a logical network interface for providing circuit switched connectivity, such as a connection between a host/application and a remote network where a particular path between a host and a remote network is dynamically assigned based on the network traffic demand at that time.

Object-oriented network protocol configuration system utilizing a dynamically configurable protocol stack

Abstract: Novel object-oriented client-server facility (CSF) and networking service facility (NSF) interfaces implement communication between application programs residing in client and server nodes of a distributed services network. The CSF interface includes remote procedure call (RPC) objects for invoking and responding to service requests at the nodes, and application programming interface (API) objects for transporting those requests between the nodes. However, the API objects only provide communication transports within a node. Accordingly, the API and RPC objects interact with dynamically-configurable protocol stacks within the NSF interfaces to complete the transport mechanism needed by an application program on the client node when accessing services on a remote server node.

Joint source/channel coding of statistically multiplexed real-time services on packet networks

Abstract: The interaction of congestion control with the partitioning of source information into components of varying importance for variable-bit-rate packet voice and packet video is investigated. High-priority transport for the more important signal components results in substantially increased objective service quality. Using a Markov chain voice source model with simple PCM speech encoding and a priority queue, simulation results show a signal-to-noise ratio improvement of 45 dB with two priorities over an unprioritized system. Performance is sensitive to the fraction of traffic placed in each priority, and the optimal partition depends on network loss conditions. When this partition is optimized dynamically, quality degrades gracefully over a wide range of load values. Results with DCT encoded speech and video samples show similar behavior. Variations are investigated such as further partition of low-priority information into multiple priorities. A simulation with delay added to represent other network nodes shows general insensitivity to delay of network feedback information. A comparison is made between dropping packets on buffer overflow and timeout based on service requirements. >