ATM VPX生存网络的综合控制策略

ＡＴＭＶＰ交叉连接（ＶＰＸ）网络自愈得以了深入的研究，网络自愈也是一个控制问题，然而在以往的文献中，常规控制和自愈控制是分开研究的，本文首次提出了ＡＴＭＶＰＸ生存网络的综合控制策略，把两者有机地结合在起来，作为一整体来设计，以降低控制复杂度，并通过计算机模拟验证了该策略的可操作性和正确性，该控制策略能够运行在常规条件下和发生故障环境中，使得网络规划和设计达到成本有效性要求。     

Fast restoration of ATM networks

Asynchronous transfer mode (ATM) is now well recognized as the fundamental switching and multiplexing technique for future broadband ISDN. As these networks will be increasingly relied upon for providing a multitude of integrated voice, data, and video services, network reliability is a key concern. There are several intrinsic features of ATM networks that could potentially be exploited to provide improved restoration techniques, beyond those established for synchronous transfer mode (STM) networks, such as digital cross-connect restoration or self-healing rings. These features include ATM cell level error detection, inherent rate adaptation and nonhierarchical multiplexing. The authors explore the use of these features in developing fast restoration strategies for ATM networks. In particular, they address: (1) ATM error detection capabilities for enhanced failure detection, (2) network rerouting strategies, (3) spare capacity allocation, and (4) network control architecture and related implementation aspects. Their findings suggest that fast network span failure detection and bandwidth-efficient rerouting capabilities can be combined to develop restoration strategies for ATM networks with significantly greater performance-cost ratios when compared to existing STM network restoration strategies     

Multiple-availability-level ATM network architecture

Because of their high flexibility, ATM networks have the potential to achieve two objectives: switch cost reduction and multi-level network availability. For that purpose, this article proposes to use virtual circuit (VC) route self-healing schemes to achieve a multiple-availability-level ATM network. Flexible multi-QoS logical ATM network (Full-Net), a new concept for ATM networks, is now being studied at NTT Laboratories. Full-Net is a very flexible network design strategy for survivable networks that is based on a self-healing VC network. Defining several logical configurations of the VC network allows us to support multiple levels of network availability, simplifies the adaptation to future and unknown service requirements, and significantly reduces overall ATM network cost. Offering different levels of availability not only saves the network's resources, but also allows the network operator to provide its customers with services at the most appropriate cost. We introduce the advantages of VC route restoration for ATM networks, and compare virtual path (VP) level and physical level restoration strategies. We explain Full-Net's concept, propose a VC route self-healing scheme, and show the impact of the logical network configurations on network survivability and resource management     

Restoration message transfer mechanism and restorationcharacteristics of double-search self-healing ATM network

The self-healing network is particularly interesting with regard to ATM networks, because the restoration time can be shortened by using the advantages of the ATM network. This paper studies a self-healing ATM network based on virtual path (VP) protection switching. First, a novel self-healing algorithm-the double-search self-healing algorithm-is proposed. It is shown that this algorithm can restore failed bidirectional VPs faster and find alternate VPs more effectively than existing self-healing algorithms. Second, it is shown that the restoration information for self-healing control (SHC) messages must be transferred by specific cells carrying the control and OAM information (Ic&o). Message parameters and a cell format are proposed. Third, evaluation of the restoration characteristics using the proposed self-healing algorithm by computer simulation indicates that good performance against a transmission link failure is obtained even in a large-scale network model with 110 nodes. The results also indicate that the VP group (VPG) method can improve the restoration time without reducing the restoration ratio     

A New ATM Self-Healing Algorithm with Back-Routing Capacity

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Restoration strategies and spare capacity requirements inself-healing ATM networks

This paper studies the capacity and flow assignment problem arising in the design of self-healing asynchronous transfer mode (ATM) networks using the virtual path concept. The problem is formulated here as a linear programming problem which is solved using standard methods. The objective is to minimize the spare capacity cost for the given restoration requirement. The spare cost depends on the restoration strategies used in the network. We compare several restoration strategies quantitatively in terms of spare cost, notably: global versus failure-oriented reconfiguration, path versus link restoration, and state-dependent versus state-independent restoration. The advantages and disadvantages of various restoration strategies are also highlighted. Such comparisons provide useful guidance for real network design. Further, a new heuristic algorithm based on the minimum cost route concept is developed for the design of large self-healing ATM networks using path restoration. Numerical results illustrate that the heuristic algorithm is efficient and gives near-optimal solutions for the spare capacity allocation and flow assignment for tested examples     

Control protocol and its performance analysis for distributed ATMvirtual path self-healing network

A restorable network comprised of a mesh of ATM virtual paths (AVPs) is expected to be superior to distributed SONET digital cross-connect self-healing networks in terms of restoration time. The paper presents a reliable protocol and evaluation of its performance for control information transfer in distributed AVP self-healing networks. Two error-recovery technologies for the data-link level (selective retransmission and go-back-N) in AVP networks are reviewed, and a model for evaluating the delay of the go-back-N method that has been used in existing terrestrial systems is derived analytically. The proposed analytic model is combined with a self-healing simulator for AVP mesh networks to evaluate the restoration time characteristics. Case study results for the worst-case scenario show that the total restoration time, including link-by-link error control for self-healing control messages, is expected to be less than 2 s, which is the time objective for complete restoration for a metropolitan LATA network. The results also show that the estimated average delay penalty for adding the link-by-link error recovery process is 7.5 ms for complete service restoration     

ATM网中ABR业务的拥塞控制机制

描述了ＡＴＭ网络的拥塞控制机制，解释了选择这些机制的理由。特别阐述了在基于速率和基于信用的方法进行选择时应采用的选择时应采用的选择则和两种则和两种方法的争论焦点。描述了ＡＴＭ论坛最终选择的基于速率的方法的几个曾经考虑过的其他策略。     

A self-healing ATM network based on multilink principles

Self-healing is the ability of a network to reconfigure itself around failures such that calls in progress are not dropped and suffer of no or almost no degradation in quality of service. Providing self-healing capabilities in all parts of the future ATM network in a cost effective way is therefore a key challenge. A new self-healing method based on the multilink concept is presented for dedicated parts of the ATM network, such as, for instance, feeder networks. In the multilink concept that is proposed, the cells of an ATM connection carried by a multilink are distributed over several physical links. If a physical link supporting the multilink fails, the cells will be distributed among the remaining physical links thus providing a self-healing capacity. In this way the quality of service can be maintained at the expense of a higher load on the remaining physical links. The speed of restoration only relies on the detection and signaling of the failure since spare capacity is available on the very multilink. The sharing of spare capacity in addition to the statistical multiplexing gain provides a cost effective self-healing method and leads to a simplified network resource management. The proposed multilink concept is based on an extension of the multipath self-routing concept, which is currently applied by Alcatel in its ATM switching fabric     

Architectures for ATM network survivability

This article surveys the restoration architectures for asynchronous transfer mode (ATM) network survivability that have been actively studied in this decade. Network reliability is critical for recent and future networks that will advance the information era. Moreover, it is one of the biggest factors in designing and managing networks. Since the early telecom network era, many restoration systems have been developed for plesiochronous digital hierarchy (PDH), synchronous digital hierarchy (SDH), synchronous optical network (SONET), leased lines and so on; and they were surveyed in many papers and books. This article focuses on new restoration techniques for ATM networks. First, the requirement studies are introduced. This includes the scant results published on the influence of failure and the state of failure analysis. Next, restoration schemes are categorized and briefly introduced. Examples include centralized control, automatic protection switch (APS), self-healing ring (SHR), self-healing network (SHN) and failure resistant virtual path (FRVP). In order to achieve adequate restoration probability with minimum cost, a network design scheme is necessary; thus, network design issues are introduced. Finally, this article focuses on the issues, future work, and problems that remain to be solved.     

Architectures for ATM network survivability and their fielddeployment

Future networks must offer extremely high levels of reliability because information has become critical to the continued well-being of society. This article shows the approaches to the survivable ATM network. The reliability requirements of future networks are discussed first. Development results of three typical restoration architectures (automatic protection switch (APS), self-healing network (SHN), and failure-resistant virtual path (FRVP)) for ATM networks are then shown. Next, we describe current progress in standardization activities. They also discuss open issues that must be resolved in future studies     

A passive protected self-healing mesh network architecture andapplications

The self-healing mesh network architecture using digital cross-connect systems (DCSs) is a crucial part of an integrated network restoration system. The conventional DCS self-healing networks using logical channel protection may require a large amount of spare capacity for network components (such as DCSs) and may not restore services fast enough (e.g., within 2 s). The authors propose a passive protected DCS self-healing network (PPDSHN) architecture using a passive protection cross-connect network for network protection. For the PPDSHN architecture, network restoration is performed in the optical domain and is controlled by electronic working DCS systems. Some case studies have suggested that the proposed PPDSHN architecture may restore services within a two-second objective with less equipment cost than the conventional DCS self-healing network architecture in high-demand metropolitan areas for local exchange carrier networks. The proposed PPDSHN architecture may apply to not only the centralized and distributed control DCS network architectures, but also asynchronous, SONET and ATM DCS networks. Transparency of line rates and transmission formats makes the PPDSHN network even more attractive when network evolution is a key concern of network planning     

An overview of broad-band access technologies

The provision of broad-band services based on either the Internet or the asynchronous transfer mode (ATM) technique requires a new generation of access networks. In the short term, solutions such as x-digital subscriber line (DSL) and hybrid fiber coaxial (HFC), allowing the reuse of existing infrastructures look very promising. For the longer term, new infrastructures based either on radio or on optical access links seem preferable. Three x-DSL techniques aiming at high-bit-rate transmission over twisted pairs are presented: high-bit-rate DSL, asymmetrical DSL, and very-high-bit-rate DSL. An extension of existing cable television networks known as HFC is also described. Two other prospective approaches, wireless in the loop (WITL) and fiber in the loop (FITL), are then presented. Several techniques are considered for WITL: digital enhanced cordless telecommunication local multipoint distribution service, wireless ATM, and low Earth orbit satellite constellations. The various architectural alternatives for the FITL approach are discussed, a special interest being dedicated to the synchronous digital hierarchy self-healing loop and the ATM over a passive optical network. We mention the main experiments and the standardization activities inherent to the domain     

ATM基本技术及其在公用网应用的主要难点

ＡＴＭ技术已被公认为实现宽带综合业务数字网（Ｂ－ＩＳＤＮ）的关键技术。本文将介绍ＡＴＭ技术的基本原理－ＡＴＭ概念，ＡＴＭ协议的分层结构，ＡＴＭ网络和接口，ＡＴＭ传输与复用技术，ＡＴＭ的交换技术，ＡＴＭ的信令方式，ＡＴＭ网络管理和管制以及ＡＴＭ技术在公用网应用中的主要难点。     

神经网络在通信网控制中的应用

介绍神经网络解决ＡＴＭ通信网中业国质量控制的一种学习方法。以呼叫管理控制为例，评估这种网络控制中的性能，并给同了模拟结果。结果表明：使用神经网络的学习控制方法实现的控制器可自适应地控制特征不断变化的ＡＴＭ通信网。     

Optimal capacity and flow assignment for self-healing ATM networksbased on line and end-to-end restoration

This paper addresses an optimal link capacity design problem for self-healing asynchronous transfer mode (ATM) networks based on two different restoration schemes: line restoration and end-to-end restoration. Given a projected traffic demand, capacity and flow assignment is jointly optimized to find an optimal capacity placement. The problem can be formulated as a large-scale linear programming. The basis matrix can be readily factorized into an LU form by taking advantage of its special structure, which results in a substantial reduction on the computation time of the revised simplex method. A row generation and deletion mechanism is developed to cope with the explosive number of constraints for the end-to-end restoration-based networks. In self-healing networks, end-to-end restoration schemes have been considered more advantageous than line restoration schemes because of a possible reduction of the redundant capacity to construct a fully restorable network. A comparative analysis is presented to clarify the benefit of end-to-end restoration schemes quantitatively in terms of the minimum resource installation cost. Several networks with diverse topological characteristics as well as multiple projected traffic demand patterns are employed in the experiments to see the effect of various network parameters. The results indicate that the network topology has a significant impact on the required resource installation cost for each restoration scheme. Contrary to a wide belief in the economic advantage of the end-to-end restoration scheme, this study reveals that the attainable gain could be marginal for a well-connected and/or unbalanced network     

多层宽带网络生存性及其综合控制策略

介绍了宽带网络生存性的最新国内外研究动态，进而深入讨论了我层网络生存性综合控制策略，并提出了一种有效的ＳＤＨ／ＡＴＭ网络一存性控制策略，并给出一些有待研究的课题及研究方法。     

Trajectory Controlling and Collision Warning Device Based on Self-Healing and Conductive Castor Oil-Based Waterborne Polyurethane in Automated Guided Vehicles

Sustainable castor oil-based waterborne polyurethanes (WPUs) are widely applied in multiple fields, while the strategies to simultaneously realize reprocessing, self-healing, and novel applications are attractive and highly demanded. Herein, a molecular design strategy is proposed to incorporate dynamic oxime-carbamate bonds into the castor oil-based WPUs. The obtained networks exhibit excellent toughness (>44 MPa), adequate stretchability, and wonderful self-healing efficiency (>95% at 80 °C for 8 h), which stand out among the reported cases. Moreover, the WPU film retained almost 100% of the original mechanical properties after consecutive reprocessing. With the incorporation of carbon nanotubes, the films are endowed with good electric conductivity, providing a general platform for fabricating flexible electronic devices. Specifically, wonderful performance in trajectory control and collision warning is displayed, which is expected to be an alternative to minimize the utilization of expensive and complex obstacle sensors in automated guided vehicles. This study contributes to the development of sustainable and self-healing WPU-based flexible material and opens the gate for novel and identified applications.     

Dynamics of TCP traffic over ATM networks

Investigates the performance of transport control protocol (TCP) connections over ATM networks without ATM-level congestion control and compares it to the performance of TCP over packet-based networks. For simulations of congested networks, the effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as the congested link transmits cells from “corrupted” packets, i.e., packets in which at least one cell is dropped by the switch. The authors investigate two packet-discard strategies that alleviate the effects of fragmentation. Partial packet discard, in which remaining cells are discarded after one cell has been dropped from a packet, somewhat improves throughput. They introduce early packet discard, a strategy in which the switch drops whole packets prior to buffer overflow. This mechanism prevents fragmentation and restores throughput to maximal levels