ATM交换机时延抖动仿真中的队列模型

时延抖动参数是网络QoS的一个重要指标。首先概要介绍时延抖动的概念,简单介绍实际的ATM交换机中继队列,在此基础上归纳出ATM交换机中继队列仿真模型的设计原则,并通过分析,设计出简洁、可行的仿真方案。给出仿真模型的状态转移图以及各状态处理过程,并给出了实际测试结果与仿真结果的比较,验证了仿真模型的准确性。     

Jitter control in QoS networks

We study jitter control in networks with guaranteed quality of service (QoS) from the competitive analysis point of view: we propose on-line algorithms that control jitter and compare their performance to the best possible (by an off-line algorithm) for any given arrival sequence. For delay jitter, where the goal is to minimize the difference between delay times of different packets, we show that a simple on-line algorithm using a buffer of B slots guarantees the same delay jitter as the best off-line algorithm using buffer space B/2. We prove that the guarantees made by our on-line algorithm hold, even for simple distributed implementations, where the total buffer space is distributed along the path of the connection, provided that the input stream satisfies a certain simple property. For rate jitter, where the goal is to minimize the difference between inter-arrival times, we develop an on-line algorithm using a buffer of size 2B+h for any h⩾1, and compare its jitter to the jitter of an optimal off-line algorithm using buffer size B. We prove that our algorithm guarantees that the difference is bounded by a term proportional to B/h     

Priority management in ATM switching nodes

Various space priority mechanisms and their detailed performance evaluation are described. A comparative performance study is given, indicating the excellent performance characteristics of a simple buffer management scheme called partial buffer sharing. The introduction of a second bearer capability provides a 10^-6 cell loss rate instead of 10^-10     

Jitter performance in ethernet passive optical networks

Ethernet passive optical networks (EPONs) have emerged as one of the most promising access network technologies. Propelled by rapid price declines in fiber optics and Ethernet components, these architectures combine the latest in optical and electronic advances and are poised to become the dominant means of delivering gigabit broadband connectivity to homes over a unified single platform. As this technology matures, related quality of service (QoS) issues are becoming a key concern. This paper proposes a novel dynamic scheduling algorithm, termed hybrid granting protocol (HGP), to support different QoS in EPON. Specifically, the proposed dynamic scheduling algorithm minimizes packet delay and jitter for delay and delay-variation sensitive traffic (e.g., voice transmissions) by allocating bandwidth in a grant-before-report (GBR) fashion. This considerably improves their performance without degrading QoS guarantees for other service types. Detailed simulation experiments are presented to validate the effectiveness of the proposed algorithm.     

Satellite ATM networks: a survey

Satellite ATM networks have significant advantages over terrestrial ATM networks. Satellites provide unique advantages such as remote coverage with rapid deployment, distance insensitivity, bandwidth on demand, immunity to terrestrial disasters, and offering broadband links. Satellite ATM networks will play an important role in the rapidly evolving information infrastructure. However, there are several obstacles which need to be overcome so that satellite ATM networks can operate in full service. The objective of this survey is to present the state of the art in satellite ATM networks and to point out open research problems. We explain the satellite ATM network architecture and cover the requirements and technical barriers for seamless integration of ATM and satellite networks. We describe the feasibility of the existing ATM cell transport methods, and deal with conventional and new satellite link access methods, and some error control schemes for the satellite environment. We then describe the problems of the proposed traffic and congestion control schemes, followed by the error performance of the Transmission Control Protocol (TCP) and Service-Specific Connection-Oriented Protocol (SSCOP) for the satellite ATM network. We present basic requirements and a possible architecture for local area-metropolitan area network (LAN-MAN) interconnection using satellite ATM and then discuss the requirements for multimedia services in satellite ATM networks     

Neuro-fuzzy control in ATM networks

The aynchronous transfer mode (ATM) has been deemed the transfer technique of choice in an integrated environment supporting multimedia services. The authors present an extensive review of fuzzy-logic-based and artificial-neural-network-based traffic control mechanisms that have been proposed in the field of asynchronous transfer mode networking. Following a qualitative review of the models used, system architectures suggested and results obtained, future trends and directions are briefly discussed     

Feedback control of congestion in packet switching networks: the case of multiple congested nodes

In this paper, an analytical method for the design of a congestion control scheme in packet switching networks is presented. This scheme is particularly suitable for implementation in ATM switches, for the support of the available bit rate (ABR) service in ATM networks. The control architecture is rate-based with a local feedback controller associated with each switching node. The controller itself is a generalization of the standard proportional-plus-derivative controller, with the difference that extra higher-order derivative terms are involved to accommodate the delay present in high-speed networks. It is shown that, under the specific service discipline introduced here, there exists a set of control gains that result in asymptotic stability of the linearized network model. A method for calculating these gains is given. In addition, it is shown that the resulting steady state rate allocation possesses the so-called max-min fairness property. The theoretical results are illustrated by a simulation example, where it is shown that the controller designed, using the methods developed here, works well for both the service discipline introduced in this paper and for the standard FCFS scheme. © 1997 John Wiley & Sons, Ltd.     

Traffic profiles in ATM networks

A lot of studies have been made to characterize and model sources of ATM traffic (voice, data, video) and to evaluate the performance of a multiplexer whose input is a superposition of these sources, using different methods and techniques (fluid flow, matrix-analytic, etc.). However, in order to better understand the end-to-end performance of ATM connections, characterizations and models of ATM traffic inside the network (i.e. after passage through one or more network elements) are needed. In this paper we intend to study the following problems: (i) Traffic profile of an ATM connection after being policed, in particular worst case traffic, and evaluation of the performance of the related statistical multiplexer. (ii) Traffic profile of the output of a multiplexer (characterized by means of the interdeparture time distribution and the index of dispersion for counts and the index of dispersion for interarrival times). (iii) Traffic profile of a single connection after passing a multiplexer. The aim is to obtain useful characterizations and models of ATM traffic in order to evaluate the performance and the efficiency of ATM network elements and of traffic control functions.This work was supported in part by the Commission of the European Communities, under project RACE R2024 (Research and Development on Advanced Communications in Europe) on Broadband Access Facilities.     

Cell multiplexing in ATM networks

Formulates, analyzes, and compares several connection multiplexing algorithms for a multiplexer residing in the equivalent terminal of the asynchronous transfer mode (ATM) layer at the user premise. The primary goal is to find an algorithm that efficiently combats the cell delay variation (CDV) introduced by the multiplexer. Several performance criteria are examined, one of which is unique to ATM networks. This one is the proportion of arriving cells that do not conform to the traffic contract of the connection. The conformance is being tracked by a generic cell rate algorithm (GCRA) recommended (but not mandatory) by CCITT. Other criteria are the classical buffer requirements and the cell delay. Service fairness among connections is also evaluated with respect to each performance criterion. The impact of the following five multiplexing policies on the performance criteria are evaluated for constant bit rate (CBR) traffic sources. The policies are first in, first out (FIFO), round robin (RR), least time to reach bound (LTRB), most behind expected arrival (MBEA), and golden ratio (GR). Extensive numerical examples reveal that there is no single policy that is best across all criteria. With respect to cell conformance, most behind expected arrival (MBEA) emerges as the preferred one. FIFO is best with respect to cell delay, except for high utilizations where RR dominates. The LTRB is marginally better than all other policies with respect to buffer requirements     

Data communication in ATM networks

An increasing number of customers require LAN access with high bandwidth and low delay over long distances. To satisfy these needs, several high-speed network techniques have been developed. Asynchronous transfer mode (ATM) is superior compared to other networking technologies, as it offers high bandwidth and is scalable in the sense that the bandwidth capacity of an ATM system is not fundamentally limited to the technology itself. Initial ATM installations will operate as subnetworks of existing networks and MAC layer protocols. One of the main challenges in ATM is the transparent support of existing connectionless LAN services. Several activities have been launched within international standard bodies and forums to specify ways of providing data communication services over ATM. Most notable examples are Switched Multimegabit Data Service (SMDS) and the similar Connectionless Broadband Data Service (CBDS) supported mostly by public network service providers. But also other approaches such as IP over ATM, and LAN emulation that show more adherence to the existing local and campus area networking paradigms. The article presents the requirements and architecture of the LAN emulation service. It describes the alternative methods for carrying IP packets over ATM, a public broadband service architecture and CBDS. The traffic management aspects of the data communication services are also discussed     

周期性业务流通过ATM复用器的时延抖动分析

ＡＴＭ通信网中需要传送多种业务，其中有一类是具有连续比特流的业务，这种业务的发送信元到达时间是周期性的，本文分析了一种周期性信元流通过ＡＴＭ复用器的排队模型，得出信元流排队时延的概率分布，时延抖动的自相关函数的功率谱。     

ATM local area networks

LAN emulation offers a best-effort, connectionless, packet transfer service at the MAC sublayer, implemented on top of a connection-oriented ATM network LAN emulation using switched virtual connections requires address resolution to locate the destination end station followed by connection establishment to the resulting ATM address. Address resolution may be implemented by a broadcast technique or by an address server. The broadcast method is the simplest for small networks but a combination of both is probably better. The use of the MAC address to identify an end station, with dynamic binding to its current physical location in the ATM network, allows the ATM LAN segment to be viewed as a virtual LAN. The virtual LAN model permits end stations to move and change physical location while maintaining connection to the same ATM LAN segment. This greatly simplifies the management of large data networks     

Optimal bandwidth and buffer allocation method for heterogeneoustraffic with multiple QoS in ATM networks

An optimal bandwidth and buffer allocation scheme is proposed which maximises network utilisation and satisfies both cell loss rate (CLR) and delay requirements for heterogeneous traffic with multiple quality of service. Simulation results show that the proposed scheme satisfies CLR and delay requirements and also utilises network resources efficiently     

Dynamic resource allocation in ATM networks

This article investigates resource allocation in ATM networks and emphasizes bandwidth allocation. Resource allocation methods are categorized, and static and dynamic allocation strategies are compared. Dynamic allocation uses actual traffic behavior, while static allocation uses only the reference traffic condition given a priori. Examples of dynamic allocation strategies are available bit rate flow control, dynamic connection admission control, and dynamic VP bandwidth control. Dynamic resource allocation is shown to be promising for situations where the a priori reference model is unclear     

Mobile location management in ATM networks

This paper presents two mobile location management algorithms for ATM (asynchronous transfer mode) networks based on the PNNI (private network-to-network interface) standard. The first solution is called the mobile PNNI scheme because it builds on the PNNI routing protocol. It uses limited-scope (characterized by a parameter S) reachability updates, forwarding pointers, and a route optimization procedure. The second solution is called the LR (location registers) scheme because it introduces location registers (such as the cellular home and visitor location registers) into the PNNI standards-based hierarchical networks. This scheme uses a hierarchical arrangement of location registers with the hierarchy limited to a certain level S. Analytical models are set up to compare the average move, search, and total costs per move of these two schemes for different values of the CMR (call-to-mobility ratio), and to provide guidelines for selecting parameters of the algorithms. Results show that at low CMRs (CMR<0.025), the LR scheme performs better than the mobile PNNI scheme. We also observe that the two schemes show a contrasting behavior in terms of the value to be used for the parameter S to achieve the least average total cost. At low CMRs, the parameter S should be high for the mobile PNNI scheme, but low for the LR scheme, and vice versa for high CMRs     

Technology interoperation in ATM networks: the REFORM system

This article addresses the applicability and interoperation of standards and emerging technologies for the operation and management of ATM networks. The issue is tackled from a practical perspective based on experiences gained through the design, realization, and experimentation of a system developed by the ACTS AC208 REFORM project. Assuming an ATM-based network infrastructure offering a range of services with distinct QoS guarantees, the REFORM system encompasses the required functions for ensuring cost-effective network survivability and availability; fast-responding reliable fault detection and self-healing mechanisms, distributed dynamic routing functions with inherent load balancing capabilities, efficient VP layer design, and dynamic network reconfiguration functions. A number of standards and emerging technologies were used for designing and realizing the wide spectrum of functionality incorporated within the REFORM system, including ITU-T OAM 1.610 and Q.2931, ATM Forum UNI 3.0 and PNNI v. 1, OMG CORBA and Component Model, TINA NRA and ISO/OSI, and ITU-T TMN. Based on the experience gained, the article discusses and draws conclusions on the applicability, coexistence, and interoperation of the adopted technologies. It is shown that these technologies can coexist, through careful design, to the benefit of network design and operation     

An efficient demand-assignment multiple access protocol for wireless packet (ATM) networks

In a wireless packet (ATM) network that supports an integrated mix of multimedia traffic, the channel access protocol needs to be designed such that mobiles share the limited communications bandwidth in an efficient manner: maximizing the utilization of the frequency spectrum and minimizing the delay experienced by mobiles. In this paper, we propose and study an efficient demand-assignment channel access protocol, which we call Distributed-Queueing Request Update Multiple Access (DQRUMA). The protocol can be used for a wide range of applications and geographic distances. Mobiles need to send requests to the base station only for packets that arrive to an empty buffer. For packets that arrive to a non-empty buffer, transmission requests are placed collision-free by piggybacking the requests with packet transmissions. The simulation results show that even with the worst possible traffic characteristics, the delay-throughput performance of DQRUMA is close to the best possible with any access protocol. In addition, explicit slot-by-slot announcement of the transmit permissions gives the base station complete control over the order in which mobiles transmit their packets. This important feature helps the base station satisfy diverse Quality-of-Service (QoS) requirements in a wireless ATM network.     

Applications of ATM in global networks

This article describes the market drivers, objectives, and consequences of introducing ATM into public and private networks. To serve the diverse needs of environments and applications, ATM presents a broad choice of characteristics to users and providers. To harness this diversity and bring structure to the choices, this article discusses ATM transfer capabilities (ATCs) and quality of service (QoS) classes as specified in ITU-T Study Group 13. Industry aims to achieve consistency between the ITU-T and ATM Forum specifications. This article includes consideration of AALs and interworking in developing network strategies. Providers will offer a selection of the possible services defined for ATM. Also, each provider will communicate their strategy for preferred network utilization and efficient traffic through incentives to users     

ARCMA—adaptive request channel multiple access protocol for wireless ATM networks

We propose a new multiple access protocol based on demand assignment. This protocol is designed to reduce contention in the request phase while minimizing transmission delay under various network (ATM) environments. Our protocol uses an adaptive scheme that changes under heavy traffic conditions, and also provides priority to certain delay‐sensitive traffic. Copyright © 2001 John Wiley & Sons, Ltd.     

Route optimization in mobile ATM networks

This paper presents an algorithm for optimizing the route of a connection that becomes suboptimal due to operations such as handoffs and location-based reroutes, and applies this algorithm to the handoff management problem in mobile ATM (Asynchronous Transfer Mode) networks based on the PNNI (Private Network-to-Network Interface) standard. The route optimization algorithm uses hierarchical route information of the connection and summarized topology and loading information of the network to determine a “crossover node” such that adjusting the connection from that crossover node results in an optimally routed connection. Handoff management schemes that perform local rerouting of connections have been proposed in order to support fast handoffs. These methods result in suboptimally routed connections. In this paper, we demonstrate how this route optimization algorithm can be used to optimize the route of a connection after such a handoff is executed, as the second phase of a two-phase handoff scheme. This route optimization procedure can also be executed as part of the handoff procedure resulting in a one-phase handoff scheme. Applying this route optimization algorithm, we propose two one-phase schemes, the one-phase optimal scheme and the one-phase minimal scheme. A comparative performance analysis of one- and two-phase handoff schemes is presented. Measures of comparison are handoff latency and the amount of network resources used by a connection. Handoff latency in the one-phase optimal scheme is greater than that in the two-phase schemes, and handoff latency in the one-phase minimal scheme is smaller than that in the two-phase schemes. The one-phase methods show a significant increase in efficiency of the connection compared to the two-phase methods. This revised version was published online in June 2006 with corrections to the Cover Date.