Showing papers on "Fast packet switching published in 1980"

Packet Switching in Radio Channels: New Conflict-Free Multiple Access Schemes

Abstract: We study new access schemes for a population of geographically distributed data users who communicate with each other and/or with a central station over a multiple-access broadcast ground radio packet-switching channel. We introduce and analyze alternating priorities (AP), round robin (RR), and random order (RO) as new conflict-free methods for multiplexing buffered users without control from a central station. These methods are effective when the number of users is not too large; as the number grows, a large overhead leads to a performance degradation. To reduce this degradation, we consider a natural extension of AP, called minislotted alternating priorities (MSAP) which reduces the overhead and is superior to fixed assignment, polling, and known random access schemes under heavy traffic conditions. At light input loads, only random access schemes outperform MSAP when we have a large population of users. In addition, and of major importance, is the fact that MSAP does not require control from a central station.

Isolation Method in a Network of Queues

Abstract: In this paper a new method for analyzing complex queueing networks is proposed: the isolation method. As an example, we study packet switching networks with finite buffer size at each node.

Analysis and Optimal Design of a Packet-Voice Receiver

Abstract: The analysis problems arising from a digital packet switched speech network are outlined in a wide statistical environment. The statistical models assumed are discussed with respect to practical applications. Particular attention is devoted to a formal description of the influence of the packet voice receiver on the system behavior in terms of the delay pdf. The optimization of the system performance, in order to obtain the best voice quality, is stated as an optimal control problem, and the analysis results play a central role in the construction of the objective functions. The problem is solved in a particular analytical environment. The outlined analytical results are supported by critical comments on their comparison with practical implementations, allowing the designer a better capability in handling any problems.

A new class of protocols for multiple access in satellite networks

Abstract: In this paper, a class of multiple access schemes is introduced, especially suited for use in packet switched satellite networks. These schemes, called the Interleaved Frame Flush-Out (IFFO) protocols, are characterized by the mixing of free contention and regulated access for the use of the satellite channel. Such hybrid schemes possess desirable features of both extreme strategies and have a built-in capability to adapt to the traffic load profile. A Markov chain model is introduced for their description and analysis, and an optimization problem is formulated for choosing the "best" among the members of this class of protocols. The performance of the protocols is evaluated by computation and simulation, and comparison to other protocols. It is shown to be stable and superior to that of the other protocols over a wide range of throughput values.

A Tradeoff Study of Switching Systems in Computer Communication Networks

Abstract: This paper is concerned with a comparison study of three switching techniques used in computer-based communication networks: circuit switching, message (packet) switching, and cut-through switching. Our comparison is based on the delay performance as obtained through analytic models of these techniques. For circuit switching, the model reflects the phenomenon of channel reservation through which it can be shown that when circuit switching is used, data communication networks saturate rapidly. Through numerical examples, it is shown that the boundary between the areas of relative effectiveness of these switching techniques depends very much on the network topology (more precisely the path length of communication), the message length, and the useful utilization.

Deadlock- and livelock-free packet switching networks

Abstract: A controller for a packet switching network is an algorithm to control the flow of packets through the network. A local controller is a controller executed independently by each node in the network, using only local information available to these nodes. A controller is deadlock- and livelock-free if it guarantees that every packet in the network reaches its destination within a finite amount of time. We present a local controller which is proved to be deadlock- and livelock-free.

Computer-communications concentrator for transmission and switching of packetized data

Abstract: A computer-communications concentrator for establishing connections between a plurality of asynchronous computer-communications terminals and a two-way computer-communications channel for transmission and switching of packetized data. The concentrator is comprised of one processing unit which is operated asynchronously and is connected to the computer-communications terminals. One X25 interface normalizing function processing unit is connected to the two-way computer-communication channel, with, between the two processing units, a communication system comprised of one memory unit having a first part in which each packet transmitted in one or the other direction is stored, and a second part comprised of forward and return cell pairs. Each cell is provided to store a packet header during a transfer into the communication system, each local header containing the address of the packet stored in the first part of the memory unit, its length, and some data relevant to the type of packet, the interpretation of which is used to determine in the processing unit which reads it, the appropriate processing to be done for the packet at hand. Each link between a terminal and the two-way channel makes use of a couple of selected pairs of cells, each packet being stored in a location available from the first part of the processing unit which introduces this packet into the memory inserting a local header in the corresponding outgoing cell from the associated cell pair, then transferring this local header into the return cell of the other pair from the set associated with the unit which will output the packet from the memory unit when this cell is available as indicated by a particular value of the packet type information.

Analysis of a Two-Hop Centralized Packet Radio Network--Part II: Carrier Sense Multiple Access

Abstract: We continue in this paper our study of two-hop centralized packet radio networks in view of understanding the behavior of these systems. Traffic originates at terminals, is destined to a central station, and requires for its transport the relaying of packets by store-and-forward repeaters. We consider here that all devices employ the nonpersistent carrier sense multiple-access mode. System capacity and through-put-delay tradeoffs are derived and compared to those obtained for slotted ALOHA in Part I [l].

Voice/Data Integration Using Circuit Switched Networks

Abstract: This paper assesses the impact of integrating voice and data over circuit switched networks. Three main types of circuit switching are considered: 1) traditional circuit switching, 2)fast circuit switchingemploying advanced switching speeds, and 3) enhanced circuit switchingemploying time assigned speech interpolation (TASI) and adaptive data multiplexing (ADM) techniques. The circuit switching networks are evaluated in terms of two main network performance parameters: transmission efficiency and delay. In addition, an evaluation is made of such things as protocol and error control, precedence and preemption, routing and flow control, synchronization, voice continuity, probability of error or loss, and classmarking flexibility. One of the main conclusions of this paper is that circuit switching technologies have several deficiencies associated with providing integrated voice/data service and that the future lies in the effective use of packet and hybrid (circuit/packet) switching technologies.

Delta Modulators in Packet Voice Networks

Abstract: In this paper, the performances of the Song Voice Adaptive Delta Modulator (SVADM) and the Continuously Variable Slope Delta Modulator (CVSD) in terms of dynamic range, sampling rate and the channel errors are compared. The use of the SVADM and the CVSD in a packet voice system, the algorithms for digital detection of silent periods and the performance of a packet voice system using the SVADM and the CVSD as source encoders are presented. The parameters employed for subjective evaluation of the packet voice system are packet size, silence detection algorithm, bit rate and packet loss rate.

Comparison of two packet-retransmission techniques (Corresp.)

Abstract: Two methods of dealing with the overflow problem in packet switches are compared: switch-retransmission and host-retransmission. The comparison is based on approximate analytic models of tandem queueing networks and is verified by simulation.

Integrated Voice/Data Packet Switching Techniques for Future Military Networks

Abstract: Virtual circuit and pure packet (datagram) based switching techniques are studied for future application to the integrated voice/data telecommunications. The coexistence of voice with both interactive and bulk data in an integrated network suggests the desirability of a mixed switching technique to allow the efficient sharing of both the switching and communications resources. Such a mixed packet switching scheme is also evaluated. It uses virtual circuit for regular traffic (voice and bulk data), and uses pure packet (datagram) for bursty traffic (interactive and query/response). It also adapts to changes in voice/ data input traffic mixture.

Design and use of Comflex - a hardware-controlled packet switch

Abstract: The paper describes Comflex, a packet switching node intended to provide local computer-to-computer and computer-to-peripheral communication. It has been developed as part of the Flex distributed computer system being produced at RSRE. Comflex is capable of transmitting data at magnetic-disc speed; hence, it makes feasible the use of remote file-stores (and other peripherals) in a local network. High performance is achieved by implementing the most important control algorithm in hardware (unlike conventional packet switches, which are controlled by software). The paper describes the design of Comflex and the major influences it has on the overall system design and operation.

Message Waiting Time in a Packet Switching System

Abstract: The behavior of a buffer having an arbitrary number of common output channels in a packet switchmg system with an arbitrary number of priority classes of messages as studied Because of the random lengths of the messages and the fixed packet size, some messages must be split into several packets. Packets of the same message may not be sent immediately m sequence because of the packets of higher priority messages Therefore, the message wamng tame is defined as the wamng tame of the last packet carrying a part of the given message The hmmng probability dastnbution of thas delay is calculated for the case of mdependent packet amval processes wRh stataonary independent increments Some numerical results are also presented The results obtamed can be used m the analysis of message path delay in certain store-and-forward commumcatton systems, particularly loop communication systems.

A Simple Model for Computation of Packet Radio Network Communication Performance

Abstract: A model is presented that allows the computation of the approximate level of communication performance for an arbitrary packet radio network using one of a variety of protocols. The communication performance is specified in terms of the end-to-end message delays incurred for a given level of end-to-end traffic rates. The network is specified in terms of its link capacities. While the model makes a variety of assumptions to allow simple computation of the performance level, agreement within a factor of two is obtained with results from simulation. As the number of nodes in the network and its connectivity is increased, the model is expected to give better accuracy. Thus, the model should prove to be a useful tool in the design and analysis of large packet radio networks where detailed analysis and simulation would prove too cumbersome.

Control system for transmission of confirmation packet on loop transmission line

Abstract: PURPOSE:To improve the use efficiency of a loop transmission line, by controlling the transmission time of a confirmation packet CONSTITUTION:When a CPU3 designates a destination and requests a communication control device 4 to transmit a confirmation packet, a destination discriminating processing part 6 of the device 4 inspects the type of a subsystem to which the confirmation packet should be transmitted, and the inspection result is sent to a confirmation packet transmission time calculating part 7 The calculating part 7 calculates a time from the data packet transmission to the confirmation packet transmission on a basis of destination discrimination information, and after the calculated time from the time of the data packet transmission, the calculating part 7 requests a confirmation packet output part 8 to transmit the confirmation packet The confirmation packet from the output part 8 is transmitted onto a loop transmission line 2 through a highway control part 9

Microprocessor Utilization in Satellite-Born Packet Switching

Abstract: This correspondence deals with the application of a bit slice microprocessor to a satellite born packet switch. A system architecture for accomplishing this task is proposed, and the performance of the packet switch is evaluated by obtaining an upper bound on the system throughput.

Congestion Control Techniques for Packet Networks

Abstract: Congestion control mechanisms are needed for store-and-forward packet networks to maintain a high level of throughput. The basic requirements of network congestion control and some specific control techniques are examined. The use of input buffer (IB) limits for network congestion control is introduced. The rationale for the effectiveness of IB limits is discussed. Strategies for the design of IB limits have been investigated using both queueing analysis and simulation experiments. Some of our preliminary findings are presented.

Fundamental consideration on heterogeneous packet switching involving message communications application

Abstract: Recently, the packet switching network which deals with relatively short data packets has been developed for the conversation-type communication between the periphery and computer. However, in the message communication in which files and picture information are exchanged, the packet switching network must deal with long packets. The packet switching network which deals with long and short packets is called the heterogeneous packet switching network. In this paper, the optimum packet size for the message communication is discussed from the viewpoint of communication cost. Further, the segregated-type and integrated-type heterogeneous packet switching systems, the buffer memory and packet transfer delay time, are evaluated and compared.

Microprocessor Utilization in Satellite-Born Packet Switching

Abstract: This correspondence deals with the application of a bit slice microprocessor to a satellite born packet switch. A system architecture for accomplishing this task is proposed, and the performance of the packet switch is evaluated by obtaining an upper bound on the system throughput.