共查询到19条相似文献,搜索用时 156 毫秒
1.
2.
3.
ABR流量控制-一种神经网络方法 总被引:4,自引:0,他引:4
本文提出ATM网络中ABR业务流量控制的一种基于神经网络方法。利用神经网络对缓冲队列的长度及其变化和相应可能的信元丢失率进行预测,通过自适应地调整业务源端的发送速率,从而更准确地确定RM信元中相应域的显式速率值。同传统静态反馈方法相比,本方法不仅提高了网络资源利用率,而且改善了信元丢失率。另外,对在具有CBR背景业务情况下本方法的性能也进行了讨论,仿真结果证明了神经网络方法的有效性。 相似文献
4.
该文提出了一种基于有限容量缓冲区下CBR业务信元丢失率和最小速率替换的线性近似连接允许控制机制,与原有的CAC机制相比,该文的CAC机制存在两个方面的改进:一方面,使用更合理、精确的CLR表达式,从而能够作出更为准确的连接允许判断:另一方面,能够提供服务质量服务。 相似文献
5.
信元在 ATM 网内传输时,由于网内缓存的存在,造成了信元延时变化。信元延时变化对基于锁相环(PLL)的恒定比特率业务时钟的恢复有很大影响,即时钟的抖动和漂移比较明显。从而使这种基于 PLL 的CBR 业务时钟恢复方案在某些场合不能应用。本文提出了一种基于 PLL 的时钟恢复新方案,该方案可以明显地降低由于信元延时变化而造成的 CBR 业务时钟的抖动和漂移,同时不增加缓存的容量。 相似文献
6.
信元在ATM网内传输时,由于网内缓存的存在,造成了信元延时抖动。信元延时抖动对基于PLL的恒定比特率业务时钟的自适应恢复有很大影响,即时钟的抖动/漂移比较明显。这使得这种基于PLL的CBR业务时钟恢复方案在某些场合不能应用。本文提出了一种基于差分技术的时钟自适应恢复新方案,该方案可以明显地降低由于信元延时抖动而造成的CBR业务时钟的抖动和漂移,同时不增加缓存的容量。 相似文献
7.
含丢失优先级机制的ATM Mux中的信元丢失率分析是ATM网络流量控制研究中的一个重要问题.本文用两状态的MMDP近似实际输入过程,并采用流体流技术对不同优先级信元在ATM Mux中的丢失率进行了分析,得到了各类信元的丢失率与缓冲容量之间关系的解析式.模拟文验表明该方法足够精确,完全可以满足实际应用的需要. 相似文献
8.
主要讨论突发业务情况下的ATM缓存的排队性能.首先采用状态转移概率进行模型分析,然后再给出信元丢失率和信元延时的分布. 相似文献
9.
10.
11.
A new method for in-service cell loss ratio (CLR) QoS estimation for asynchronous transfer mode (ATM) networks has been developed. For a typical CLR, a large number of cells must be observed before statistically meaningful results can be achieved. These results may be obsolete resulting in ineffective network management reactions. For a variety of arrival processes, many analyses have shown there exists a relationship between the logarithm of the cell loss probability and buffer size. For models that do not possess long-range dependence, this relationship is often linear. On the other hand, for the fractional Brownian motion model that captures long-range dependent traffic behavior, this relationship has a polynomial form. The proposed method uses these relationships and observations of cell loss for several small pseudo-buffers to characterize the behavior of the actual system. Specifically, a real-time technique to dynamically detect the failure of meeting a cell loss quality of service (QoS) objective has been developed. The method requires a short observation period and is suitable for in-service monitoring of CLR QoS. Simulation studies show the effectiveness of this method for both modeled traffic and measured network trace data 相似文献
12.
Bensaou B. Lam S.T.C. Hon-Wai Chu Tsang D.H.K. 《Networking, IEEE/ACM Transactions on》1997,5(4):572-584
An important parameter in asynchronous transfer model (ATM)-based network design and management is the cell loss ratio (CLR) in ATM multiplexers. It is a key parameter to many vital functions in the network such as call admission control (CAC), bandwidth allocation, etc. However, the CLR depends usually on many unknown and unpredictable traffic parameters such as input traffic correlations. In this paper, we propose a simple and robust fuzzy-based algorithm to predict the CLR in large-sized systems based on both a small amount of information from small-sized systems, and the asymptotic behavior for very large systems. Unlike the model-based approaches, our approximation avoids the problem of assuming any traffic parameters or arrival process. This algorithm is used with real-time traffic measurement to propose an effective measurement-based call admission control framework for ATM networks 相似文献
13.
14.
A hot topic in the research community is the interworking of integrated IP services, defined by the IETF, with ATM, a technology designed for the transport of multimedia traffic. In particular, the IETF recommends the ATM CBR, nrt-VBR, and ABR service classes for the transport of controlled-load service (CLS) over ATM. In this work the first two alternatives are examined and compared, in order to determine which is the most convenient for CLS. The comparison is carried out in terms of QoS and amount of buffering required at the IP/ATM routers. These performance parameters strongly depend on the parameters of the CLS token bucket shaper, that is, the token bucket depth and token bucket input buffer capacity. A nrt-VBR connection is able to offer a given performance level over a range of values of the token bucket parameters wider than that permitted by a CBR connection. Moreover, in all the examined cases the nrt-VBR connection needs a relatively small ATM buffer at the IP/ATM routers. Since, in order to guarantee acceptable performance, some CLS requests must be rejected, the utilization of the ATM link can be relatively low; this drawback can be overcome by serving the rejected CLS requests as classic best-effort traffic 相似文献
15.
DAVID W. PETR VICTOR S. FROST TIMOTHY G. KELLEY CAMERON BRAUN ANN DEMIRTJIS 《International Journal of Communication Systems》1996,9(2):97-104
This paper explores and evaluates several aspects of quality of service (QOS) in an integrated traffic ATM network. Specifically, we consider the relationships between service class definitions, usage parameter control (UPC) or policing of customer traffic, network resource allocation mechanisms, and specific network conditions under which realistic QOS limits on cell loss ratio (CLR) can be met. Traffic consists of a mixture of voice, video, image and data divided into two service classes for UPC and network resource allocation. The block oriented network simulator (BONeS) tool is used for performance evaluations. Limitations associated with evaluating very low CLR values (e.g. 10−8 and 10−6) via simulation are overcome by a hybrid simulation and extrapolation technique. It is found that these stringent QOS limits on CLR can be met for most traffic with the techniques used here, reasonable backbone trunk loads (75 per cent) and reasonable buffer sizes (200–250 cell buffers per queue). However, meeting similar limits for extremely bursty traffic (such as our image traffic model) would require extra care in network design and operation, including judicious segregation of traffic. 相似文献
16.
17.
Asha Dinesh W. Melody Moh Kia Makki 《International Journal of Communication Systems》1999,12(4):249-279
Asychronous transfer mode (ATM) networks are high‐speed networks with guaranteed quality of service. The main cause of congestion in ATM networks is over utilization of physical bandwidth. Unlike constant bit‐rate (CBR) traffic, the bandwidth reserved by variable bit‐rate (VBR) traffic is not fully utilized at all instances. Hence, this unused bandwidth is allocated to available bit‐rate (ABR) traffic. As the bandwidth used by VBR traffic changes, available bandwidth for ABR traffic varies; i.e., available bandwidth for ABR traffic is inversely proportional to the bandwidth used by the VBR traffic. Based on this fact, a rate‐based congestion control algorithm, Explicit Allowed Rate Algorithm (EARA), is presented in this paper. EARA is compared with Proportional Rate Control Algorithm (PRCA) and Explicit Rate Indication Congestion Avoidance Algorithm (ERICA), in both LAN and WAN environments. Simulations of all three algorithms are conducted under both congestion and fairness configurations with simultaneous generation of CBR, rt‐VBR, nrt‐VBR and ABR traffic. The results show that, with very small over‐head on the switch, EARA significantly decreases the required buffer space and improves the network throughput. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
18.
Liao Jianxin Li Lemin Sun Hairong 《电子科学学刊(英文版)》1997,14(2):133-139
Traditional packet switching networks have typically employed window-based congestion control schemes in order to regulate traffic flow. In ATM networks, the high speed of the communication links and the varied nature of the carried traffic make such schemes inappropriate. Therefore, simpler and more efficient schemes have to be proposed to improve the congestion control for ATM switching. This paper presents an exact performance analysis of ATM switching whose inputs consist of Continuous-Bit-Rate(CBR) and bursty traffic. The CBR traffic and bursty traffic are described by Bernoulli process and the Interrupted Bernoulli Process(IBP), respectively. Bursty traffic smoothing mechanism is analyzed. With the use of a recursive algorithm, the cell loss probability and the average delay for ATM switching of mixed CBR and bursty traffic are exactly calculated. Traffic smoothing could be implemented at a slower peak rate keeping the average rate constant or decreasing the average bursty length. Both numerical a 相似文献