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Showing papers on "Node (networking) published in 1976"


Journal ArticleDOI
01 Mar 1976
TL;DR: Numerical results for a variety of network configurations indicate that the heuristic algorithm, while not theoretically convergent, yields practicable low cost solutions with substantial savings in computer processing time and storage requirements.
Abstract: The problems of file allocation and capacity assignment in a fixed topology distributed computer network are examined. These two aspects of the design are tightly coupled by means of an average message delay constraint. The objective is to allocate copies of information files to network nodes and capacities to network links so that a minimum cost is achieved subject to network delay and file availability constraints. A model for solving the problem is formulated and the resulting optimization problem is shown to fall into a class of nonlinear integer programming problems. Deterministic techniques for solving this class of problems are computationally cumbersome, even for small size problems. A new heuristic algorithm is developed, which is based on a decomposition technique that greatly reduces the computational complexity of the problem. Numerical results for a variety of network configurations indicate that the heuristic algorithm, while not theoretically convergent, yields practicable low cost solutions with substantial savings in computer processing time and storage requirements. Moreover, it is shown that this algorithm is capable of solving realistic network problems whose solutions using deterministic techniques are computationally intractable.

203 citations


Journal ArticleDOI
01 Jan 1976-Networks
TL;DR: On the basis of both theoretical and computational evidence, one of the three methods is seen to offer an extremely effective procedure for finding the k shortest paths from a given node in a network.
Abstract: This paper presents and develops an algebraic structure for determining the k shortest paths from a given node to all other nodes of a network. Three new methods for calculating such k shortest path information are examined and compared. These methods are based on a fairly strong analogy which exists between the solution of such network problems and traditional techniques for solving linear equations. On the basis of both theoretical and computational evidence, one of the three methods is seen to offer an extremely effective procedure for finding the k shortest paths from a given node in a network.

104 citations


Journal ArticleDOI
Simon S. Lam1
TL;DR: A model for a packet switching network in which each node has a finite pool of S/F buffers is presented and a heuristic algorithm for determining a balanced assignment of nodal S/f buffer capacities is proposed.
Abstract: Previous analytic models for packet switching networks have always assumed infinite storage capacity in store-store-and-forward (S/F) nodes. In this paper, we relax this assumption and present a model for a packet switching network in which each node has a finite pool of S/F buffers. A packet arriving at a node in which all S/F buffers are temporarily filled is discarded. The channel transmission control mechanisms of positive acknowledgment and time-out of packets are included in this model. Individual S/F nodes are analyzed separately as queueing networks with different classes of packets. The single node results are interfaced by imposing a continuity of flow constraint. A heuristic algorithm for determining a balanced assignment of nodal S/F buffer capacities is proposed. Numerical results for the performance of a 19 node network are illustrated.

70 citations


Journal ArticleDOI
TL;DR: The gradient projection algorithm is a gradient-type search procedure designed to handle constrained optimization problems, into which category the routing problem falls, and Calculations of the computational complexity of this algorithm indicate that it is particularly well-suited to networks with a limited number of commodities or source-destination pairs.
Abstract: Various algorithms have been proposed for determining the routing paths designed to minimize the average overall message time delay in message-switched networks. In this paper we describe the application of the gradient projection algorithm to this problem. This algorithm is a gradient-type search procedure designed to handle constrained optimization problems, into which category the routing problem falls. Calculations of the computational complexity of this algorithm indicate that it is particularly well-suited to networks with a limited number of commodities or source-destination pairs. The algorithm is applied to a representative group of distributed-type networks, of varying complexity. Execution times for this algorithm are compared with those obtained using the flow deviation routing algorithm. These agree roughly with the results of the computational requirement calculations; i.e., this algorithm generally requires less execution time for networks with a relatively small number of commodities than does the flow deviation method. (The actual running time depends significantly on the choice of the initial flows or routing paths, however.) For those networks in which all network nodes may be expected to communicate with all other nodes, however, the flow deviation method would be expected to be superior.

53 citations



Journal ArticleDOI
TL;DR: Two analytic models of a store-and-forward communications network are constructed, one to find the optimal message routing and the other to illustrate the equilibrium (stationary state) maintained by an adaptive routing algorithm.
Abstract: Two analytic models of a store-and-forward communications network are constructed, one to find the optimal message routing and the other to illustrate the equilibrium (stationary state) maintained by an adaptive routing algorithm. These models show that adaptive routing does not satisfy the necessary conditions for an optimal routing. Adaptive routing tends to overuse the direct path and underuse alternate routes because it does not consider the impact of its current routing decision on the future state of the network. The form of the optimality conditions suggests that a modification of the adaptive algorithm will result in optimality. The modification requires the substitution of a quadratic bias term instead of a linear one in the routing table maintained at each network node. Simulation results are presented which confirm the theoretical analysis for a simple network.

29 citations



Patent
Lewis Frank Long1
17 Dec 1976
TL;DR: In this article, a method and apparatus for testing a network, such as a printed circuit board, to check whether it conforms to its design as to having a plurality of network nodes and a predetermined node-connection pattern defining a division of the network nodes into plurality of groups.
Abstract: The present invention provides method and apparatus for testing a network, such as a printed circuit board, to check whether it conforms to its design as to having a plurality of network nodes and a predetermined node-connection pattern defining a division of the network nodes into a plurality of groups. In a conforming network, each network node is connected in common to all other network nodes in its group, and is isolated from the network nodes in each other group. In accordance with the invention, one of the network nodes is selected to serve initially as a present FROM node. There is thereafter selected repeatedly, from the network nodes that have not previously served as a present FROM node, a network node to serve temporarily as a present FROM node. Each time a network node is selected to serve as a present FROM node, there is selected a network node, from the group containing the present FROM node, to serve temporarily as a present TO node such that, as to each group, network nodes thereof are sequentially selected to serve as TO nodes in the same order that they are sequentially selected to serve as FROM nodes. Each time two different nodes are selected as present FROM and TO nodes, continuity therebetween is verified.

24 citations


Book ChapterDOI
01 Jan 1976
TL;DR: A detailed comparison of the output from these two models is presented for a 76 arc, 24 node sketch planning network used to model the city of Sioux Falls, South Dakota, indicating that the difference between the two sets of flows is small enough to justify the simplifying assumption that total user cost is minimized.
Abstract: This paper compares modeling of traffic flow on networks in such a manner that total user cost is minimized with the modeling of flow so that an equilibrium is achieved. A detailed comparison of the output from these two models is presented for a 76 arc, 24 node sketch planning network used to model the city of Sioux Falls, South Dakota. The results indicate that the difference between the two sets of flows is small enough to justify the simplifying assumption that total user cost is minimized. Such an assumption is often made in network design or link addition models to achieve computational ease, particularly in the context of multiple objectives.

17 citations


Patent
31 Aug 1976
TL;DR: In this article, a method for limiting the number of build-up packets during the process of building-up a routing address for the subsequent transmission of address-coded packets, the addresses of these packets being this said routing address, from a first to a second subscriber of a digital telecommunication network was proposed.
Abstract: The invention relates to a method for limiting the number of build-up packets during the process of building-up a routing address for the subsequent transmission of address-coded packets, the addresses of these packets being this said routing address, from a first to a second subscriber of a digital telecommunication network. This network comprises a plurality of switching nodes, a plurality of subscribers, a plurality of bearer channels connecting each switching node with at least one other switching node and with no subscriber, or with one or more of said subscribers, a plurality of routing words individually assigned to the bearer channels and a plurality of call numbers individually assigned to the subscribers. During the process of building-up a routing address the first subscriber despatches a build-up packet containing the call number of the called second subscriber, said build-up packet received by a first switching node is retransmitted through all bearer channels connected to this switching node, such retransmission being continued at each switching node upon reception of each build-up packet, thus the number of build-up packets increasing rapidly within the network. The method for limiting this number of build-up packets comprises at each switching node the storing of the call number of the second subscriber upon reception of a first build-up packet during a predetermined time interval starting with the reception of this first build-up packet, comparing during said time interval the call numbers contained in the subsequently received build-up packets with the call number stored, counting all of said subsequently received build-up packets with a call number corresponding with the call number stored, comparing respective count with a predetermined limiting value, and eliminating each of said subsequently received build-up packet, if said respective count is higher than said predetermined limiting value.

14 citations


Proceedings ArticleDOI
29 Mar 1976
TL;DR: The results obtained show that when neglecting the interferences between paths the response time is independent of the order of the stations, and prove the necessity to have a limited memorisation capacity at each node of a packet-switching network.
Abstract: We consider packet-switching network as a queueing system with constant service times: that means that the lengths of the packets are equal. We study such a network by isolating a particular path, that we consider as a tandem system of queueing. Two aspects of the question will be examined:1 - The study of the response time of such a system2 - The study of the throughput of such a system when introducing the notion of time-out for each packet.The results we obtained show that when neglecting the interferences between paths the response time is independent of the order of the stations. The control policy we examined prove the necessity to have a limited memorisation capacity at each node of a packet-switching network. These results confirm the intuitive options taken in a network like CYCLADES.

Journal ArticleDOI
TL;DR: A network model for the analysis of waste management systems that resembles the maximal multi-commodity flow model with positive gains single transformation along the arcs, but in addition it admits multi-transformations, interrelations among arc flows, and flow-dependent budget restrictions.
Abstract: This paper presents a network model for the analysis of waste management systems. In the “waste management network” that we develop waste-generating activities correspond to sources, each node corresponds to a specific flow waste form, and each arc to a flow transformation; a chain from a source to a destination represents in turn waste generation, treatment, and disposal, while a feasible flow pattern constitutes a possible waste management system. The model resembles the maximal multi-commodity flow model with positive gains single transformation along the arcs, but in addition it admits multi-transformations, interrelations among arc flows, and flow-dependent budget restrictions. The problem is formulated as a linear program where each column in the constraint matrix corresponds to a chain in the network. The solution procedure uses a column-generation scheme based on a shortest route algorithm adapted for multi-transformed flows. Recycling, discharge and effluent standards, charges, damage costs and various budgeting schemes can be handled. An illustrative hypothetical example is given.

Journal ArticleDOI
TL;DR: In a functionally distributed computer system, the system function is partitioned into less complex functions which reside at decreasing functional hierarchy levels, and all software and hardware required to implement an identified function are confined to a node of the system.
Abstract: In a functionally distributed computer system, the system function is partitioned into less complex functions which reside at decreasing functional hierarchy levels. At some point in the partitioning process, all software and hardware required to implement an identified function are confined to a node of the system. The type of hardware elements and the form of the software required at the node are determined by the node function. This principle is illustrated in the case of a task scheduler for the common node of a distributed function laboratory computer system having a star-like configuration.

Journal ArticleDOI
TL;DR: Basic node-to-node protocol of a packet-switched network based on the multiplexing of the link into N logical channels is first described and some questions are raised in connection with adaptive-routing algorithms.
Abstract: Basic node-to-node protocol of a packet-switched network based on the multiplexing of the link into N logical channels is first described The node structure is then described based on a set of queues, an input routine, a main-task routine, and an output routine Three protocols which are based on different implementations of the transmission of the acknowledgment (ACK) block are then introduced The first one is the 1972 version of the Advanced Research Projects Agency Network (ARPANET), the second places the ACK block in regular packets, and the third uses only control packets The simulation program developed to compare these protocols is then described It studies the behavior of a link between two nodes, which consists of a full-duplex line and of two sets of queues The rest of the packet-switched network is simulated by a packet generator which feeds the two sides of the link First, comparison of protocols is done using symmetrical and asymmetrical loading conditions In this last case, interesting results are obtained in relation to momentary saturation of the N logical channels The influence of the limitation of buffers allocated to an output line is also discussed Sensitivity of protocols to reverse traffic characteristics is then studied and, based on the results, choice of a protocol is discussed Based on the dynamic behavior of the queue, some questions are raised in connection with adaptive-routing algorithms

Journal ArticleDOI
TL;DR: The procedures and data structures used to manage both logical and physical resources required during processing of a transaction by the common node are discussed.
Abstract: A computer network architecture consisting of a common node processor for managing peripherals and files and a number of private node processors for laboratory experiment control has been given elsewhere. The mode of comnmunication between the nodes is that of the transaction. The procedures and data structures used to manage both logical and physical resources required during processing of a transaction by the common node are discussed.

01 Mar 1976
TL;DR: The synthesis of optimal reliable (invulnerable) topological structures for message-switching communication networks is considered, and complete networks are shown to be optimal if the resulting lines have a high average line utilization value.
Abstract: The synthesis of optimal reliable (invulnerable) topological structures for message-switching communication networks is considered. The connectivity of the underlying graphs is used as a measure of the network invulnerability. The maximal average message delay value is utilized as the network delay measure. Simultaneously with choosing the topological structure, optimal line capacities are assigned. Therefore, the performance measure of a given network structure is chosen to be given by its delay-capacity product function, incorporating the product of the prescribed network maximal delay value and the associated minimal overall line capacity value. The latter involves a distance-independent link cost function incorporating the line capacity. A general routing discipline is used to account for dynamic updating of fixed routing procedures, needed to accomodate terminal traffic flow fluctuations. n -node k -connected graphs yielding networks with minimal delaycapacity product functions are characterized and realized. Complete networks (utilizing direct dedicated lines) are shown to be optimal if the resulting lines have a high average line utilization value. Otherwise (under appropriate symmetry conditions on the network traffic matrix), the optimal message-switching reliable network structures are characterized by a family of graphs of diameter two. The latter thus allow between any pair of nodes a route which is either a direct line or contains a single intermediate node. Also noted is a family of k -connected networks, for which the delay-capacity product function is not increased by more than twice upon the failure of (k-1) or less nodes or lines.

Journal ArticleDOI
TL;DR: To study the performance of a full-duplex messageswitched computer network, called TIDAS-T, during various conditions a simulation model has been built in order to simulate the procedure.
Abstract: To study the performance of a full-duplex messageswitched computer network, called TIDAS-T, during various conditions a simulation model has been built in order to simulate the procedure. The model describes the communication and the line procedure in the TIDAS network very closely. The only simplification made is that the processing time in the node computers is disregarded as being insignificant in comparison with the transmission and queueing times. The model, programmed in SIMSCRIPT 1.5, is very flexible because all important parameters are given by input data. The outputs from a simulation differ from run to run due to the object defined by input data parameters. The statistical results are mostly presented as complete statistical distributions. It has turned out that the model has been a splendid tool in order to study and view the consequences of different design approaches. Some of the problems in building such a complex model axe elucidated and some simulation runs are given as illustrations. As the model is very flexible it may be used to study computer networks other than TIDAS.

Journal ArticleDOI
TL;DR: The results obtained show that when the interference between paths is neglected the response time is independent of the order of the stations, which proves the necessity to have a limitated memory capacity at each node of a packet-switching network.
Abstract: We consider a packet-switching network as a queueing system with constant service times: that means that the lengths of the packets are equal. We study such a network by isolating a particular path which we treat as tandem queueing system. Two aspects will be examined: the study of the response time of such a system, and the throughput of such a system when time-outs are used to destroy packets. The results we obtain show that when the interference between paths is neglected the response time is independent of the order of the stations. The control policy we examine proves the necessity to have a limitated memory capacity at each node of a packet-switching network. These results confirm the intuitive options taken in a network like CYCLADES.

Proceedings ArticleDOI
07 Jun 1976
TL;DR: The advent of the microprocessor has opened up new avenues for the system designer to provide more powerful, more reliable and more user oriented computer systems to the user community for the same or lower costs.
Abstract: The advent of the microprocessor has opened up new avenues for the system designer to provide more powerful, more reliable and more user oriented computer systems to the user community for the same or lower costs. The problem confronting the designer is: How to achieve these goals? This paper describes one such method called Distributed Function Multiple Processor (DFMP).The system described uses several micro processors each with its own memory to form a cluster. These processors are differentiated by the functions they perform such as file managing, intelligent terminal, etc. and communicate via a Restricted Cross Bar Switch (RCBS). Further, several clusters or nodes can be linked to form a local network. Interprocessor and internode communications are controlled by a special processor called the Interprocessor Controller (PC) located in each node. The IPC's use an adaptive technique to determine traffic flows.


Patent
28 May 1976
TL;DR: In this article, a method and apparatus are described synchronizing oscillators at the network junctions in a pulse code modulation (PCM), time division multiplex (TDM) telecommunication network.
Abstract: A method and apparatus are described synchronizing oscillators at the network junctions in a pulse code modulation (PCM), time division multiplex (TDM) telecommunication network. In each network node pulse trains of clock pulses are received via incoming lines, and corresponding clock pulse trains are produced in the network node in accordance with the node's clock frequency division factor. The received and locally produced pulse trains are phase-compared, and a control signal resulting from the comparison is used to control the frequency of the clock oscillator in the network node. In each network node of a first network which has a direct line connection to a network node in a second network a phase comparison takes place between the two networks, and the result of the latter comparison is compared with the result of an intra-network comparison. The result of the latter comparison is used to adjust the line clock frequency of a given network.


Journal ArticleDOI
TL;DR: It is shown that there is a set of conditions, one for each node, which is sufficient to establish network synchronism, and that the master—slave scheme of synchronization is obtained as the special case of discrete-control correction.
Abstract: Discrete-control correction is a method of synchronizing the clocks of a digital communication network by means of periodic corrections to their frequencies, the correction to each clock being derived from the change in the buffer level at that node. This paper presents a comprehensive treatment of this method and extends the results of earlier papers to more general situations. It is shown that there is a set of conditions, one for each node, which is sufficient to establish network synchronism. Explicit formulae are derived for the frequency of synchronism and the steady-state buffer levels. It is shown also that the master—slave scheme of synchronization, in which the clocks of the network are synchronized to a designated master clock, is obtained as the special case of discrete-control correction in which corrections are made to all the clocks except the master clock. It is pointed out that in the event of disruption of a part of the network, the surviving part or parts of the network are assured of r...

Proceedings ArticleDOI
07 Jun 1976
TL;DR: A novel way of monitoring a network node using a separate processor is developed and applied to the London node of ARPANET and some of the results obtained are presented.
Abstract: At University College London, we have developed a novel way of monitoring a network node using a separate processor and have applied this technique to the London node of ARPANET. A monitoring program on a PDP-9 records usage of the London-TIP via the dial-up ports and these data are sent to the Rutherford Laboratory IBM 360/195 for detailed analysis. In this paper, we describe the method we have developed and present some of the results we have so far obtained.

Journal ArticleDOI
TL;DR: The software design aspects of a distributed medical data base, to be implemented on a homogeneous minicomputer loop network of PDP-11/45s, using the UNIX operating system is described.

Journal ArticleDOI
TL;DR: The first step in attacking the nature of the human/computer interaction remains the critical problem is the development of a depository health-science network that provides an easy user interface in both information management and in effective inter-user communication.
Abstract: Many recent experiences with medical computer systems have clearly shown that the nature of the human/computer interaction remains the critical problem. We suggest that the first step in attacking this problem is the development of a depository health-science network that provides an easy user interface in both information management and in effective inter-user communication.Such a depository network would consist of two types of node: the depository node and the local node. The depository node would be an information centre through which the local nodes would deposit, retrieve and transfer information. The local node would provide computational power and would support the man/machine interface to users. When a local node was approximately self-sufficient, its communication to the outside world would be reduced to a minimum. To achieve a desirable cost/benefit ratio from a local node, a group of users must share one system. However, this system should be small enough for local control, both administrative...