Message Transmission Time Research Articles

Fixed point model for adaptive token passing bus protocol

The performance of an adaptive token passing bus protocol is analysed by modelling the behaviour of each node as an M/GI/1 queue and deriving a set of fixed point equations. The technique is shown to be applicable to the analysis of a number of variants of the token passing bus protocol which arise in communication networks and computer integrated manufacturing systems. The validity of the independence assumption underlying this approach is investigated by first examining the autocorrelation function of the simulated time series of token passing cycles. This indicates that cycles are not highly correlated except at high traffic loads. Mean message transmission times predicted by the models are compared with the corresponding results of simulation experiments and the performance of the adaptive protocol is compared quantitatively with that of the standard protocol.

Approximate analysis of asymmetric single-service prioritized token passing systems

A LAN or MAN (local or metropolitan area network) using token passing to allow stations to access the transmission medium is studied. Ibe and Cheng (1989) recently presented an approximate derivation of message delays for an asymmetric single-service token passing with only one type of message. In the present work, this analysis is extended to an operation with nonpreemptive priority queuing. The number of message priority levels and the walktime vary from one station to another. Moreover, the assumed Poisson message arrival process and the message transmission time vary, not only from one station to another, but also from one class to another. The performance, as measured by the mean delay for any message class at any station, is derived. The simulation results show excellent agreement with the analytical results, even under heavy loading. The results confirm earlier findings that the performance at a station is influenced by its position relative to heavily loaded stations. >

Performance simulation of a token ring

Most of performance studies for local area networks (LANs) have been based upon the average transmission time of a packet (or frame) as a performance criterion. Those models have been developed for the performance measure of the low-level physical and data link layers of LANs. They predict the relative efficiency of different network topologies, transmission media, and access protocols. However, they often fail to measure an end-user's message transmission time. A realistic performance measure for end-users should attempt to measure the average transmission time of the entire user message. The authors concentrate on the performance of a token ring LAN system for a users' view. A simulator has been developed to quantitatively measure the elapsed time of an end-user's message. Simulation results show that the performance of the network with the exhaustive service (ES) strategy is much better than that of the network which works with the non-exhaustive service (NES) strategy. Also, the measure based on user messages is compared with the conventional performance measure based on packets and shows differences in performance measurement. >

Approximate analysis of asymmetric single-service token-passing systems

Consideration is given to token-passing or polling systems in which the message arrival process, the message transmission time distribution, and the walk time vary from one station to another. An approximate analysis of these systems is obtained. The results obtained from the approximate analysis are compared against both simulation results and those obtained from two approximate methods that have been proposed earlier. For the special case of a symmetric system, it is shown that the approximate analysis is exact when the walk time is constant. Even when the walk time is exponentially distributed, it is shown that the approximate analysis gives an approximation error of less than 0.3% in the range of offered load that is generally of interest.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The helical window token ring

An access rule for token ring local-area networks called the helical-window token-ring protocol is introduced. It features the use of a window that limits the allowable messages a token-holding station can send. With the window, the operation of the protocol approaches that of a central single-server queuing system in the sense that messages are delivered in near first-come-first-served order on a network-wide basis. The introduction of the window also makes analysis of the networks tractable. Exact analytical formulas for the capacity and for the mean, variance, and moment-generating function of the message waiting time are derived. Numerical simulation is used to verify the results. Comparisons with continuous polling systems show that the imposition of the windowed access rule can lead to significant reductions in the delay variance (at the cost of increasing the mean system time) when the traffic is heavy and/or the message transmission time is large with respect to the walk time of the ring.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Channel allocation protocols in frequency-time controlled high speed networks

In conventional high-speed systems, the high ratio between the end-to-end propagation delay and the message transmission time severely restricts the system performance. Thus, the increase in channel bandwidth may be accompanied by only a marginal increase in actual system capacity. A combined frequency-time division-based control of the high-speed channel that significantly reduces this problem is proposed. The design of protocols subject to the unique channel control penalties of the resulting multichannel system is considered. The allocation of channels on a demand assignment basis is hindered in the multichannel configuration by the time penalty involved in locating an idle channel and by practical limitations on the transmit/receive multichannels mode interface. A new class of fixed allocation protocols is introduced in which the channel access is obtained without the aforementioned penalties. The protocols build on the allocation of source and destination oriented transmission rights, taking into account the implementation aspects of multichannel networks. It is shown that this class of protocols covers the whole range of random-access to fixed-channel-access control policies. An analytic approach for a uniform analytic treatment is introduced, showing the potential for a significant improvement in the system capacity and the average message delay. >

A verified sliding window protocol with variable flow control

We present a verified sliding window protocol which uses modulo- N sequence numbers to achieve reliable flow-controlled data transfer between a source and a destination. Communication channels are assumed to lose, duplicate and reorder messages in transit. The destination's data needs are represented by a receive window whose size can vary with time. The destination entity uses acknowledgement messages to inform the source entity of the current receive window size and the sequence number of the data word next expected. The source entity responds by sending segments of data words that lie within the allowed window. Each data segment is accompanied by an identifying sequence number and the size of the data segment. The destination entity also uses selective acknowledgement and selective reject messages to inform the source entity of the reception or lack of reception, respectively, of out-of-sequence data segments. Thus, this protocol is a proper extension of the Arpanet's TCP. We have obtained the minimum value of N that ensures correct data transfer and flow control, in terms of the minimum message transmission time, the maximum message lifetime, and the maximum receive window size. The protocol imposes no constraints on the retransmissions of messages or on the data segment sizes; thus, any retransmission policy that optimizes the protocol's performance can be used.

Frequency-time controlled (FTC) networks for high speed communication

The development of “very high speed” networks is being motivated by emerging applications and is therefore attracting increasing attention. As demonstrated in the past, in conventional high speed systems the high ratio between the end-to-end propagation delay and the message transmission time severely restricts the system performance. Thus the increase in channel bandwidth may be accompanied by only a marginal increase in actual system capacity. In this paper we propose a network architecture which eliminates this problem by introducing a combined Frequency - Time Division based control of the high speed channel. We consider the implementation characteristics of the resulting multichannel system and show that the design of protocols in these systems is subject to unique channel control penalties. Specifically, we show that in addition to the relatively high cost of channel sensing, the allocation of channel on a demand assignment basis is hindered in the multichannel configuration by the time penalty involved in locating an idle channel and by practical limitations of multichannel node interface design. We therefore introduce a new class of “allocation” protocols in which the channel access is obtained without the aforementioned penalties. The allocation protocols build on message source and destination oriented transmission rights allocation, taking into account the implementation aspects of multichannel networks. We show that the class of “multichannel allocation” protocols covers the whole range of random access to fixed channel access control policies and introduce an analytic approach for a uniform analytic treatment. The analysis demonstrates the potential for a significant improvement in the system capacity and the average message delay, when compared to a conventional single (undivided) channel system.

Optimal precision in the presence of uncertainty

We consider the problem of achieving coordinated actions in a real-time distributed system. In particular, we consider how closely (in terms of real time) processors can be guaranteed to perform a particular action, in a system where message transmission is guaranteed, but there is some uncertainty in message transmission time. We present an algorithm to achieve optimal precision in arbitrary networks. In networks where clocks run at the rate of real time, the optimal precision achievable in a network is exactly how tightly clocks can be guaranteed to be synchronized.

An Analysis of the Effect of Network Parameters on the Performance of Distributed Database Systems

Performance analysis studies of distributed database systems in the past have assumed that the message transmission time between any two nodes of a network is constant. They disregard the effect of communication network parameters such as network traffic, network topology, and capacity of transmission channels. In this paper, an analytical model is used to estimate the delays in transmission channels of the long haul network supporting the distributed database system. The analysis shows that the constant transmission time assumption cannot be justified in many cases, and that the response time is sensitive to the parameters mentioned above. Extensions and performance analysis in the context of interconnection networks are also discussed.

The design of distributed control computer systems

The top-down approach in the design of Distributed Control Computer Systems, DCCS, is presented. The starting point of the study is three statements: (i) the design approach should be production process control oriented; (ii) for real time process control applications, computer networks require an efficient communication subsystem, the most important features of which are high reliability and short message transmission times and (iii) recent research has shown that the tools and methodologies used in both computing and control should be complementary to each other in order to solve some of the distributed control computer system/distributed computer control system design problems. The paper contains the design problems of distributed control computer systems, the presentation of the methods and tools for the study and design of the DCCS, the top-down approach in the design of the DCCS, and examples of two design stages.

Join and Semijoin Algorithms for a Multiprocessor Database Machine

This paper presents and analyzes algorithms for computing joins and semijoins of relations in a multiprocessor database machine. First, a model of the multiprocessor architecture is described, incorporating parameters defining I/O, CPU, and message transmission times that permit calculation of the execution times of these algorithms. Then, three join algorithms are presented and compared. It is shown that, for a given configuration, each algorithm has an application domain defined by the characteristics of the operand and result relations. Since a semijoin operator is useful for decreasing I/O and transmission times in a multiprocessor system, we present and compare two equi-semijoin algorithms and one non-equi-semijoin algorithm. The execution times of these algorithms are generally linearly proportional to the size of the operand and result relations, and inversely proportional to the number of processors. We then compare a method which consists of joining two relations to a method whereby one joins their semijoins. Finally, it is shown that the latter method, using semijoins, is generally better. The various algorithms presented are implemented in the SABRE database system; an evaluation model selects the best algorithm for performing a join according to the results presented here. A first version of the SABRE system is currently operational at INRIA.

A Unified Approach to Scan Time Analysis of Token Rings and Polling Networks.

Token rings and multipoint polled lines are two widely used network interconnection techniques. The general concept of cyclic allocation processes is defined and used to characterize token passing and polling in these networks. Scan time, the time to poll all nodes at least once, is an important quantity in the response time analysis of such networks. We derive expressions for the mean and variance of scan times using a direct, operational approach. Resulting expressions are general and are applicable to both exhaustive and non-exhaustive service. The effect of higher level protocols is easily incorporated in the analysis via calculations of constituent quantities. The expression for mean scan time is exact and depends only on the means of message transmission times and arrival rates. The approximate analysis of variance takes into account the correlation between message transmissions at different nodes. Expected level of accuracy is indicated by an example.

Implementation and Performance Evaluation of a Distributed Splitted-Bus Multiple Computer System

A simple scheme of implementation of one-dimensional splitted-bus structure is proposed. Insertion of routing switches into the bus enables a distributed multiple-computer system to transmit variable-length messages simultaneously between several distinct processor-node pairs so long as the data links used for them do not conflict with one another. The interconnection topology and the mode of control for such an experimental system are described. Its characteristic performance values, such as data-line utilization, mean total message transmission time, etc. are given as results of simulation. These values are compared with similar results for other well-known loop networks found in the literature.

Modeling a new technique for accessing shared buses

Consider a queueing system in which customers (or jobs) arrive to one of Q separate queues to await service from one of S identical servers (Figure 1). Once a job enters a queue it does not leave that queue until it has been selected for service. Any server can serve any job from any queue. A job selected for service cannot be preempted. In this paper we consider jobs to be in a single class; for the multiple class result see [AFSH81a]. We assume once a queue has been selected, job scheduling from that queue is fair. In particular, our results hold for first come first serve as well as random selection [SPIR79] and, for that matter, any fair nonpreemptive scheduling policy within a queue. We assume that arrivals to each queue follow a Poisson process with the mean arrival rate to queue q being λ q . The S identical exponential servers are each processing work at a mean rate of μ. This system is general enough to be adaptable for modeling many different applications. By choosing the policy employed for queue selection by the servers, we can model multiplexers, channels, remote job entry stations, certain types of communication processors embedded in communication networks, and sets of shared buses. In this paper we will use the latter application to discuss a realistic situation. The elements (“jobs”) in the queues are messages to be sent from modules connected to the shared bus of the system. The servers are the buses; their service times are equal to the message transmission times. The queues are in the interface modules connected to and sharing the buses.

Confidence Estimates for Acquisition Times and Hold-In Times for PN-SSMA Synchronizer Employing Envelope Correlation

Pseudonoise-modulated spread spectrum communication transceivers enable utilzation of broadcast communications facilities including satellite links, radio networks, and coaxial cable networks for point-to-point communications. In this paper, a bound on the acquisition time probability distribution is obtained by calculating the variance of the acquisition time and using Chebyshev's inequality. Recursive computer calculations are used to show that the hold-in time distribution is approximately exponential. The means and variances of the acquisition and hold-in times, together with the distribution estimate and bound, are determined in terms of the number of users and power-to(Gaussian) noise density ratio of the channel. These calculations pertain to a receiver used by Hopkins, which combines acquisition and tracking in a way which facilitates implementation. The utility of the distribution estimates in comparing and relating synchronization times, failure to achieve synchronization, message transmission times, and message error rates is illustrated for two data transmission protocols. The dependence of these quantities on the number of users, information bit rate, data block format, and power-to-noise ratio of the (Gaussian) transmission channel is also illustrated.

Investigation of Signalling Flow Transfer Processes based on SCTP Protocol

To establish reliable signalling information transmission over IP network is used SIGTRAN protocol containing a protocol with the transport flows. This protocol, uses signalling messages over IP network, to determine maximum time and number of repetitions. Reports contain the signalling messages transmission over IP network algorithm, which simulated a notification request over IP network, taking into account differences in SCTP message transmission time. A provisional value of transmission characteristics over IP network is determined. Ill. 8, bibl. 7, tabl. 1 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.108.2.140