Dual Bus Metropolitan Area Networks Research Articles

Analysis of Dual-Bus Metropolitan Area Networks Using Distributed Quantitative Stochastic Simulation

The Distributed Queue Dual Bus protocol (DQDB) has been adopted by IEEE and by the International Standard Organisation as a metropolitan area net work standard. DQDB is also a European Telecom munication Standard. Using distributed simulation, this paper analyzes the performance of standard DQDB networks, DQDB networks with slot band width reuse, as well as DQDB networks with slot preuse and reuse. The results suggest that although slot preuse is a conceptual mirror image of slot reuse, the maximum improvement in throughput of the networks, the causes of unfairness, and the stations which are unfairly favoured differ depending on the choice of bandwidth single-use, reuse, preuse, or pre-and-reuse. All quantitative performance measures were estimated to a specific precision using automated distributed stochastic simulation. The design of the DQDB simulators and practical implications of the results are also discussed.

A stochastic reward net model for performance analysis of prioritized DQDB MAN

The performance of prioritized distributed queue dual bus (DQDB) metropolitan area network (MAN) under bursty traffic environment is studied in this article. The tagged node model is adopted to simplify the analysis. The processes of the packet arrivals to the tagged node, the empty-slot pattern from the upstream, and the request pattern from the downstream are assumed to be Markov Modulated Poisson Processes, a more general and appropriate model to capture the bursty characteristics existing in the traffic flows in high-speed networks. A stochastic reward nets model for the prioritized DQDB MAN is presented. With the help of the stochastic petri net package developed in Duke University, the steady state and as well as the transient behavior of packet loss ratio of tagged node are investigated. The influence of the burstiness of the empty-slot pattern, packet arrival and request pattern on the tagged node’s performance are examined.

Reservation arbitrated access for statistical multiplexing voice traffic over dual-bus metropolitan area networks

Metropolitan area networks (MANs) are well suited to serve as broadband multiplexers for asynchronous transfer mode (ATM) networks, to facilitate enterprise networking and to support future wireless personal communication systems. We propose and analyze a novel reservation arbitrated (RA) access method which provides isochronous voice transport over dual-bus MANs while enabling statistical multiplexing among voice calls. In combination with a new cyclic capturing (CC) mechanism, RA access allows stations to capture and reserve isochronous voice channels in a fair and distributive manner. This paper presents the RA access protocol, derives an analytical model for general waste-free voice reservation protocols, and analyzes the performance of RA access by computer simulations validated by analytical calculations. To assess the actual voice quality, simulation results based on a real voice signal are also presented. Results indicate that RA access offers significant improvements in channel utilization, as compared to prearbitrated (PA) access, while providing an acceptable quality of service. Therefore, RA access offers an efficient voice transport mechanism for existing switched multimegabit data service (SMDS) networks employing the IEEE 802.6 protocol, as well as emerging ATM/MAN-based broadband networks.

Reservation arbitrated access for efficient service integration over dual-bus metropolitan area networks

Dual-bus metropolitan area networks (MANs) are well suited to provide broad-band network access and network interconnection over a city area by functioning as distributed broadband multiplexers between existing corporate/public networks, multi-media terminals, and broadband integrated services' digital networks employing an asynchronous transfer mode. The authors address the important problem of integrating time-sensitive and non-time-sensitive traffic over MANs. In the proposed integration scheme, time-sensitive variable bit-rate isochronous (VBRI) traffic, such as voice and video, is statistically multiplexed over the MAN by a novel, reservation-arbitrated (RA) access protocol, while non-time-sensitive asynchronous traffic, such as data, is transported over the residual bandwidth by queue-arbitrated access. RA access allows a VBRI traffic source to capture and reserve some isochronous channels on a bandwidth-on-demand basis. Compared to previously proposed reservation protocols, RA access is fair, provides a better isochronous transport service, and is compatible to the slot format of the existing IEEE 802.6 MAN standard. The system performance is analysed by an approximate theoretical model and computer simulations. Results indicate that the proposed integration scheme can be engineered to meet the stringent quality of service requirements of the time-sensitive VBRI traffic, while providing a satisfactory service to the non-time-sensitive data traffic and ensuring efficient bandwidth utilisation.

Evaluation of reservation-arbitrated access schemes for statistical multiplexing of variable-bit-rate video traffic over dual-bus metropolitan area networks

To address the problem of video communications over 802.6 MANs, a reservation-arbitrated (RA) access protocol is proposed which allows a variable-bit-rate video source to reserve isochronous channels on a bandwidth-on-demand basis. The paper explains the general method of RA access, compares four different schemes of acquiring incremental bandwidth in response to a reservation request, and evaluates the performance of RA access by simulations using two video-source models. Results indicate that RA access provides fair service under a cyclic capturing mechanism, permits statistical multiplexing while providing nearly isochronous transport service, allows a video source to adapt to its reserved bandwidth during network congestion, and facilitates the implementation of layered video coding techniques.

A study of isochronous channel reuse in DQDB metropolitan area networks

This paper investigates the isochronous channel reuse problem (ICRP) on the IEEE 802.6 distributed-queue dual-bus (DQDB) metropolitan area network (MAN). Given a set of established isochronous connections and a set of isochronous connections requests, using a minimal number of isochronous bandwidth to service all of the connections is attempted. On the other hand, given a limited isochronous bandwidth, establishing a maximal number of isochronous connections is of primary concern. Our previous study demonstrates that the ICRP is NP-complete by showing that the simplified ICRP (SICRP), in which all of the established isochronous connections and the isochronous requests are of the same bandwidth, is NP-complete. We recommend using a tight lower bound on the number of required isochronous channels for the SICRP. An efficient isochronous channel scheduling algorithm (ICSA), capable of providing a solution close to the lower bound, is also proposed. Simulation results indicate that for a limited isochronous bandwidth, the number of isochronous connections successfully established by the ICSA is significantly more than that of the isochronous channels allocation scheme in the DQDB standard.

Reservation arbitrated access — a bandwidth on demand protocol for multiplexing variable bit rate isochronous traffic over dual bus metropolitan area networks

With the advent of multimedia communication services, transport of real-time traffic over metropolitan area networks (MANs) is becoming an important problem. We present a novel reservation arbitrated (RA) access protocol for multiplexing variable bit rate isochronous (VBRI) traffic such as packet voice and video over dual bus MANs in general and IEEE 802.6 MANs in particular. In combination with a cyclic release mechanism, RA access allows variable bit rate traffic sources (VBRSs) to capture and reserve some isochronous channels on a bandwidth on demand basis in a round robin fashion. For a reasonable bus length suitable for metropolitan coverage, it is possible to select operation parameters which enable contention free access in the reservation process. Bandwidth utilization can be further improved by employing a movable boundary option to efficiently integrate VBRI traffic with other traffic. System performances including packet loss ratio, packet delay, delay jitter, probability distribution of consecutive packet loss and channel utilization are analyzed by both theoretical computations and computer simulations for voice, video conference and motion video traffic. Results indicate that the protocol is fair and provides a nearly isochronous transport service while ensuring efficient bandwidth utilization, yielding substantial capacity improvements over pre-arbitrated (PA) access. Compared to queue-arbitrated (QA) access, RA access not only provides variable bit rate isochronous channels but also allows VBRSs to adapt to the reserved bandwidth during network congestion so that performance degradation can be minimized. RA access complements existing PA and QA access methods in 802.6 MANs to provide a complete traffic transport solution for all types of BISDN services.

Adaptive bandwidth balancing mechanisms for DQDB networks

To improve fairness in distributed queue dual bus (DQDB) metropolitan area networks a mechanism known as bandwidth balancing (BWB) has been introduced in the final version of the IEEE 802.6 standard document. Since then several changes to the basic mechanism, attempting to adhere to different interpretations of the fairness concept and to match the needs of different categories of users, have been proposed. In this paper attention is focused on the adaptive class of fairness control mechanisms and two solutions are analysed and compared. In order to do this, analytical models suited to the study of DQDB networks under overload conditions are introduced. The models are also amenable to the evaluation of the transient behaviour of DQDB networks, thus enabling a thorough investigation of the performance that can be obtained by adopting different fairness control mechanisms. The analytical models have been validated through the use of a software simulator. Numerical indices measuring the performance of the balancing mechanisms mentioned above are also given.

Sojourn time analysis of DQDB MAN for LANs interconnection

The Distributed Queue Dual Bus(DQDB) Metropolitan Area Network (MAN) is a promising solution for the evolution from current networks to B-ISDN. The performance of the DQDB MAN for Local Area Networks(LANs) interconnection is analyzed. The effects of message length, traffic load of upstream and downstream nodes and the parameters of bandwidth balancing mechanism and network counters on the sojourn time of message in the buffer are investigated, which present a valuable reference for the implementation of the DQDB MAN.

A performance analysis of the IEEE 802.6 DQDB metropolitan area network protocol

AbstractThis paper describes a performance analysis of the IEEE 802.6 distributed queue dual bus (DQDB) metropolitan area network (MAN) protocol based on computer simulation. The MAN is a new broadband communications network that is designed to support both constant and variable bit rate applications. An overview of the important fast packet technologies and the position of the DQDB MAN is explained before the performance evaluation is carried out. The network is intended to offer high data rates and throughputs for users. The main use will be to interconnect remote LANs within a city and provide LAN‐like performance with respect to delays. The analysis given here begins with a description of the MAN and the operation of the DQDB protocol. A state description is derived and expanded upon. The use of the simulation package OPNET is described and its use in modelling DQDB is explained. The method of modelling using OPNET via an extended state description is given. A model giving the full simplified functional operation of a DQDB node is arrived at and the basic model is used to analyse a fifty‐node network under varying traffic conditions; underload, overload, varied traffic mix, etc. The unfairness characteristic of the protocol is demonstrated and the conclusions drawn are that the DQDB MAN provides a fast data transport network up to very high loadings.

A study on a performance improvement algorithm in DQDB MAN

Abstract In this paper, a performance improvement algorithm in DQDB MAN (Distributed Queue Dual Bus Metropolitan Area Networks) being standardized by the IEEE 802 Committee is proposed. In DQDB MAN, it should be noted that transmission slots are never erased halfway the bus and are terminated at end of the bus. This paper proposes an algorithm for improving this point. At first, a special node called “erasure node” is introduced in a DQDB network for slot reutilization in the downstream side and the operation of the erasure node is described. In the latter half of the paper, the performance of this algorithm is estimated using a queueing model, where the M/G/1 queueing model is applied to the network model. Average and variance of queueing delay and transmission delay are calculated by this method. The results show the effectiveness of the proposed algorithm for improvement of the performance.

Distributed Queue Dual Bus Metropolitan Area Network: A Review of Performance Analysis of the Medium Access Control Protocol

Standardization, prototyping and application of unidirectional bus networks are introduced followed by a detailed description of Distributed Queue Dual Bus Medium Access Control (DQDB MAC) protocol. A review or throughput analysis and delay performance of the MAC protocol along with a survey of related literature is presented (42 refs.)

An effective scheme for pre-emptive priorities in dual bus Metropolitan Area Networks

The IEEE 802.6 standard for Metropolitan Area Networks does not provide multiple priority traffic for connectionless data services. A priority mechanism that was considered for the standard showed to be not effective. As of now, there exists no protocol for multiple access dual bus networks that is able to implement pre-emptive priorites and, at the same time, can satisfy minimal fairness requirements for transmissions at the highest priority level. In this study, a protocol with strictly pre-emptive priorities, i.e., a protocol that does not admit low priority traffic if the load from high priority traffic exceeds the capacity of the transmission channel, is presented. The protocol is derived from a unique bandwidth allocation scheme with a full utilization of the bus capacity, with a fair distribution of bandwidth respective to traffic from a particular priority level and with pre-emptive priorities. The performance of the presented protocol is compared to a priority mechanism that is based on the bandwidth balancing mechanism. It is shown that adopting the new protocol results in shorter access delays for high priority transmissions.

DQDB simulation and MAC protocol analysis

The distributed queue dual bus (DQDB) metropolitan area network (MAN) is currently being standardised by IEEE 802.6. This letter reports on a characteristic of the DQDB MAC protocol, found using simulation, which causes the end stations to experience higher delays than the middle stations under certain conditions. One mechanism is described to explain the phenomenon along with a modification to improve the protocol's behaviour.