摘要:

AbstractThe occurrence of congestion severely degrades the performance, especially in high‐speed networks with long propagation delay relative to packet transmission time. This is because it is very likely that a large number of transit packets are flying over such networks at a time and many of them will get lost if they arrive at some congested node. Among ways of controlling traffic to avoid congestion, this paper deals with a class of rate‐based congestion controls (RBCC) which regulate input traffic based on feedback information about network congestion status. Although such mechanisms have been studied recently, the mechanism to be considered, referred to asproportionalRBCC, differs from them in that the amount of input traffic allowed to enter in the network isproportionalto the network resources available, keeping a closer track of the network resources than the previous ones, where the network status is described by two states, congested or not. The mechanism seeks an optimal network operating point, adapting to dynamic changes of carried traffic. We carry out the stability analysis and the transient analysis of some performance measures related to the proportional RBCC, and also address fairness aspects in providing control to various source‐destination connections, while K. W. Fendicket al.have analysed the stability of a general class of RBCC. Furthermore, by making a comparison between the control mechanism analysed here and the ones based on binary feedback information, we show the effectiveness of the f

ISSN:1074-5351    

DOI:10.1002/dac.4500080202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractDeterministic rule based traffic descriptors in general, and leaky bucket based (LBB) traffic descriptors in particular, offer many advantages over statistical descriptors for specifying and monitoring traffic in the ATM based broadband ISDN (BISDN). However, these traffic descriptors do not specify the traffic pattern uniquely. Thus, acceptance of a connection request with specific traffic descriptor parameter values implies that the network has agreed to guaranteeing the quality of service (QOS) for the worst case traffic compliant with the traffic descriptor (and hence allowed by the monitor). This poses challenges which have not been addressed adequately. Two of the important ones are: (i) definition of the worst case behaviour and characterization of the worst case traffic compliant with the traffic descriptor; (ii) connection acceptance controls (CAC) for the worst case traffic sources compliant with the traffic descriptors. In this paper we address these questions for leaky bucket based (LBB) traffic descriptors. The focus is on the first problem. The implications on the second problem are discussed briefly. The performance measure and QOS requirements are in terms of the cell loss ratios.We first define the worst case behaviour for homogeneous and heterogeneous environments in terms of collective cell loss ratio (CLR)) from the multiplexer. We consider both the unbuffered and buffered cases. However, most of the results here are for the unbuffered case. FOTthe case of an unbuffered multiplexer and homogeneous source environment, we show that a simple on‐off source represents the worst case behaviour of an LBB source. In a heterogeneous source traffic environment, the on‐off behaviour is the worst only in a limited sense and the use of a collective measure results in anomalous relationships between the source behaviour and the CLR. A more appropriate measure should be based on individual cell loss ratios or on the maximum of the individual CLRs. We analyse LBB sources with respect to these measures and unbuffered resources, and obtain further characterization of the worst case behaviour. However, we also uncover some counter‐intuitive relationships. In particular, a seemingly ‘smooth’ source may be worse for the other sources than a seemingly ‘bursty’ source.For a buffered multiplexer, we show, via an example, that a three‐state source may be worse than an on‐off source even in a homogeneous source traffic environment. A complete characterization of the worst case behaviour for a buffered multiplexer remains an open challenge. Moreover, the LBB sources exhibit deterministic behaviour and their equivalent bandwidth need not be sub‐additive in sources. That is, adding the equivalent bandwidths of individual sources to obtain an ‘estimate’ of the equivalent bandwidth for a collection of such sources could be too optimistic in some situations. A fresh look at the connection acceptance control for such sources

ISSN:1074-5351    

DOI:10.1002/dac.4500080203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper describes the architecture and performance analysis of a system using narrowband broadcasting channels for real‐time information delivery. Broadcast delivery is attractive because a single transmission of a piece of information will satisfy all users waiting for that information. Therefore, the system may support an unlimited number of users with no effect on system response time. The main drawback of these types of systems compared with interactive systems is that a user must wait until the required information arrives. In order to reduce this waiting time, high data rate networks must be used if real‐time information is to be broadcast. In this paper, a new method is proposed to enable inexpensive narrowband networks to be u

ISSN:1074-5351    

DOI:10.1002/dac.4500080204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractSince computer networks play an important role in distributed computing environments, an application's performance depends heavily on the quality of service provided by the communication networks. To ensure a high performance, the characteristics of wide area networks, WANs, must be well understood. This paper presents methodologies to characterize WAN traffic based on real measurements from Bellcore's backbone network that connects remote sites using dedicated T1 links. This paper also suggests some workload models that can be used for wide area network sizing and performance evaluation studies. It is found that the inter‐site traffic pattern depends on the time of the day and the day of the week. Furthermore, the traffic between two sites is found to be reasonably symmetric, except for those sites designated as back‐up sites. The coefficient of variation is used as a measure for the traffic burstiness and it is found to be 1·5 degree during working hours. The methods presented here are easy to use and cost‐eff

ISSN:1074-5351    

DOI:10.1002/dac.4500080205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper is concerned with the analysis and design of an improved differential heterodyne optical receiver for differentially‐encoded binary PSK (briefly, DPSK) signals in a coherent lightwave communication system. In the first part of the paper, we discuss the relevant design criteria to be employed when dealing with asynchronous heterodyne receivers for ASK, FSK or DPSK optical signals. In particular, we introduce a convenient definition of the signal‐to‐noise ratio at the data detector input to be assumed as the system performance measure when the non‐negligible linewidth of the transmit/receive laser sources are to be taken into account. Following this design approach, we show that by properly modifying the traditional delay‐and‐multiply DPSK receiver, i. e. by allowing the delay to be a fraction of the symbol interval, we can considerably reduce the performance degradation caused by laser phase noise. We show thus that the superior power‐efficiency of DPSK can be traded in favour of a decreased sensitivity to phase noise through a proper choice of the differential detector delay. In this respect, our results reveal that DPSK may still be competitive with other modulation formats even with non‐negligible linewidth sources. In the last part of the paper, the behaviour of the optimized DPSK, ASK and large‐deviation FSK data demodulators in the presence of a quasistationary frequency detuning of the local laser is also discussed under the same set of conditions as in the previous analysis. The results can be employed to derive accurate design requirements for the AFC loo

ISSN:1074-5351    

DOI:10.1002/dac.4500080206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPeriodical performance evaluation and adaptive resource assignment, already proposed as performance‐oriented management, seems to be the most suitable strategy for network planning under demand uncertainty. In this paper, we exploit the inherent capability of ATM networks to rearrange dynamically the already installed resources, and propose performance‐oriented management combined with virtual path bandwidth (VPB) control for the planning of the extensions of bandwidth capacities of virtual paths (VPs) and transmission links of the network. We define a large network optimization problem and solve it by a rigorous, analytical procedure. The optimization model comprises specific requirements of the network‐planning problem and a bandwidth distribution scheme ensuring network reliability. We reveal the efficiency of the proposed scheme by applying it on a model network, considering two realistic case‐studies of network‐traffic evolution. We show that in the presence of VPB control: (a) the initial distribution of the total bandwidth to VPs is of no importance, since it can be adaptively rearranged according to the offered traffic, (b) the network is well used and bandwidth investment could be saved, and (c) whenever additional bandwidth must be installed in VPs which have an unanticipated bad grade‐of‐service, time savings result. We present the network performance in detail, in figures, and compare this with the performance of the network in the absence o

ISSN:1074-5351    

DOI:10.1002/dac.4500080207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1074-5351    

DOI:10.1002/dac.4500080208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1074-5351    

DOI:10.1002/dac.4500080201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY