ATM网络中特殊的信令-元信令

本文介绍了ATM网络信令系统中的元信令,分析了元信令在ATM网络中的作用及元信令规程与N－IS－DN信令规程的对应关系,并将元信令的功能作了总结。     

ATM UNI信令协议的研究

ＡＴＭ技术是一种基于连接的网络技术。网络中任何两点在交换信息之前，都必须建立相应的虚连接。ＡＴＭ ＵＮＩ信令协议是研究ＡＴＭ网络的端节点和交换机之间建立，维护，释放，管理虚连接的协议规范。     

ATM适配层数据通信协议研究

本文讨论了ＡＴＭ网络用于数据通信的ＡＴＭ适配层协议：ＡＡＬ３／４和ＡＡＬ５，研究其协议格式，传输效率。在此基础上，提出了一种具有ＡＡＬ３／４，ＡＡＬ５协议优点的ＭＡＡＬ３协议，并对这三种协议的功能，传输效率进行了比较研究。     

ATM接入交换机信令软件的设计与实现

ATM接入交换机是实现传统局域网与ATM网络互连的一种关键设备,它所采用的信令是UNI信令。本文重点介绍了在接入交换机中采用的信令技术,给出了ATM信令模块的设计与实现,并给出了重点函数的算法流程。     

基于ATM局域网的多媒体信令系统的研究

多媒体信息的交互特性主要是由信令系统实现的。要提供完善的交互操作,就必须有一个功能强大的信令系统。本文首先论述了ＡＴＭ信令的结构,并从分析各种多媒体信息的特征入手,讨论了几种典型的多媒体系统的交互式操作的要求,然后在一个宽带局域ＡＴＭ网络的环境下给出一个交互式多媒体信令系统的研究设计。     

ATM UNI信令的软件实现

介绍了在ＱＮＸ操作系统上实现ＡＴＭ ＵＮＩ信令（用户端功能）的设计思想和程序结构。     

ATM中SAAL有保障信令的设计

首先论述了ＳＳＣＯＰ在ＡＴＭ协议体制中的地位和功能,而后论述了有保障模式的结构及实例,最后对此算法进行了分析。     

ATM交换连接控制与UNI信令协议

ＡＴＭ是一种面向连接的信息转移模式。这些连接分为永久型虚连接（ＰＶＣ）和交换型虚连接（ＳＶＣ）。提供ＰＶＣ是ＡＴＭ网络管理的功能之一，而提供ＳＶＣ则是信令系统的基本任务。完整的信令系统包括ＵＮＩ信令和ＮＮＩ信令。本文对ＵＮＩ信令系统的功能、体系结构及有关协议进行简要的描述，从而有助于信令软件的设计。     

ATM网络ABR业务的公平流量控制的研究

ATM网中ABR业务能根据网络信道情况动态地调整速率。本文讨论了针对ABR业务的几种流量控制机制,对它们各自的特点作了比较深入的分析和研究,提出了作者自己的改进方法,使网络的性能得到了改善。     

Real-time error concealing bitstream adaptation methods for SVC in IPTV systems

The current heterogeneity in networks and devices demands for a high degree of flexibility in IPTV systems for digital television. A scalable video coding scheme (in this paper we focus on H.264/AVC’s scalable video coding extension SVC) accommodates this flexibility from the coding point of view. Because the IP-based network delivery chain in IPTV systems may suffer from packet loss (having a severe impact on the visual quality) it is necessary to provide means for error concealment. In this paper we propose a novel method that performs adaptation on impaired SVC bitstreams so that the resulting adapted bitstream is compliant to the SVC specification and that the reconstruction result at the decoder is equivalent compared to the approach where the error concealment is implemented in the decoder itself. The adapted bitstreams have a significantly higher visual quality while our approach does not require any modification to existing SVC-compliant decoders. The results of several experiments show that the proposed method is extremely fast (over 900 frames/s) and that it introduces a negligible overhead in terms of bit rate (ca. 0.02%).     

The sticky buffer flow control for the ATM

Data from different applications — voice, video, file transfer, interactive — will be multiplexed in the future over broadband integrated services digital networks (BISDN). Data are segmented into 48-byte blocks prefixed by a 5-byte header and transported over the network using the asynchronous transfer mode (ATM).

An ATM connection-request is a contract between the user and the network; the user specifies a rate requirement, delay constraints, a bound on the cell-loss probability and other quality of service parameters. If the network can meet these requirements, a connection is made. Bursty traffic producing peak traffic rates in excess of the projected average rate could result in congestion and lead to performance degradation. As a result, the network might no longer be able to deliver the negotiated quality of service to existing connections. To lessen the chance of congestion, input rate control must be implemented.

This paper contains a performance analysis of the sticky buffer (SB), a moving window input rate control scheme intended to limit the rate at which input traffic may enter a network. Policing is achieved by buffering and hence delaying the entry of ATM-cells into the network. The scheme is determined by parameters (R,T) which specify that no more than R ATM-cells are permitted to enter the network in every window of size T cells. We present an exact analysis, deriving the probability generating function of the queue length distribution. A comparison with the leaky bucket is given. Our numerical examples show the required buffer size is comparable to that required by the leaky bucket.     

基于参数自适应的ATM流量控制的研究

论文在总结各种ATM网络流量控制方法的基础上提出了一种参数自适应控制方法。该方案法对系统信元传输的不确定时延和不确定源节点数实现估计,并在保证参数全局稳定收敛的基础上提出了新的控制律。仿真结果证明了该方法的有效性。     

A cell spacing device for congestion control in ATM networks

In this paper, we study a cell spacing method of congestion control in ATM networks. The idea is to smooth the input flows at the access nodes in order to prevent cells from entering the network in a manner that could affect its performance. We consider a queueing system that prevents any two successive cells from being transmitted within a time shorter than a variable value. This device does not interfere with cells that find the queue empty and arrive a sufficiently long time after the last departure but spaces apart those which arrive too closely to each other. We analyze the statistical properties of the output traffic of such a cell spacer when the input process is modeled as a Compound-MMPP.     

基于CRC算法的ATM信头校验

采用一种迭代算法实现ATM信头错误定位,对CRC进行校验并纠正32位原始数据和8位CRC码中单比特传输错误电路.实验结粜表明,相对于一般的查找表,该种电路结构简单、运行速度高.     

Routing with admission control in ATM networks

An optimal control parameter, , was developed by optimal control theory for Asynchronous Transfer Mode (ATM) networks. The parameter is related to link utilization, buffer occupancy, system throughput and cell rejection characteristics and is applied to routing and admission control in simulation of a network carrying multiclass traffic. Simulation results show that the parameter produces better performance with respect to cell rejection rate characteristics compared with the traditional control parameter for utilization, .This research has been supported by the ATI as part of the Navy Contract N00140-94-C-BC03. Some parts of the paper were presented at Globecom'94.     

Ping-pong flow control for ATM ABR traffic

In this paper, we propose an improved technique for congestion control, named as ping-pong flow control (PPFC), for asynchronous transfer mode (ATM) available bit rate (ABR) traffic. This is a rate-based flow control scheme, in which the rate regulation is achieved by directly adjusting the transmission rate in the source end station. The proposed algorithm uses a bipolar feedback strategy, which employs positive and negative feedbacks to control the transmission rate for different switch states. These states are determined using the traditional threshold-based method. We also introduce state early detection (SED), which enables the PPFC to control traffic flows more precisely and accurately at critical moments. The simulation results show that the proposed algorithm provides a higher throughput and lower cell loss ratio when compared to the well-known backward explicit congestion notification (BECN). Furthermore, these results also show that PPFC is robust against feedback losses.     

ATM congestion control using Minimal Resource Allocation Networks (MRAN)

This paper presents a congestion control scheme for ATM traffic using a minimal radial basis function neural network referred to as Minimal Resource Allocation Network (MRAN). Earlier studies have shown that MRAN is well suited for online adaptive control of nonlinear time varying systems as it can adjust its size by adding and pruning the hidden neurons based on the input data. Since ATM traffic is nonlinear and time varying performance of MRAN as a congestion controller is investigated here. These studies are carried out using OPNET to model the ATM traffic. The ATM traffic model consists of bursty, Variable Bit-Rate (VBR) and custom traffic in a multiplexed form so as to generate a heavily congested traffic situation. For this scenario, the controller has to minimize the congestion episodes and maintain the Quality of Service (QoS) requirements. This paper compares the performance of the MRAN congestion controller with that of a modified Explicit Rate Indication with Congestion Avoidance (ERICA) scheme and a Back-Propagation (BP) neural controller. Simulation results indicate that MRAN controller performs better than the modified ERICA and BP controller in reducing the congestion episodes and maintaining the desirable QoS.     

Efficient adaptive connection admission control algorithms for real-time ATM LANs

This study aims to provide adaptive communication services for real-time applications. In particular, how to admit adaptive real-time connections is addressed. Various search techniques in connection with admission control are investigated, and their tradeoffs under different performance criteria are assessed. The implementation and application of this new connection model in the NetEx system is also discussed.