A Network Architecture with High Availability for Real-time Premium Traffic over the Internet

Real-time traffic will be a predominant traffic type in the next generation networks, and networks with 100% reliability and availability will be required by real-time premium traffic. It is believed that QoS guarantees could be better provided by connection oriented networks such as Multi Protocol Label Switching (MPLS). These connection oriented networks are more vulnerable to network failure. Conventional path protection methods perform re-routing to cope with this. However, re-routing always causes packet losses and results in service outage. These losses are bursty in nature and highly degrade the QoS of the real-time premium traffic. Thus, 100% availability cannot be achieved by conventional methods. The novel path protection proposed in this paper recovers the bursty packet losses due to re-routing by using forward error correction (FEC) path. Therefore, it can provide network architecture with no service outage for such traffic. The numerical results show that the proposed method can achieve a very high availability for real-time premium traffic in future IP/MPLS networks.

VB程序设计考核自动评阅系统中若干问题的研究

在大规模的计算机应用能力考核中,必须要实现自动阅卷,对于Visual Basic基础程序设计考核,提出了一种自动评阅的方法,详细描述了该软件的设计思想、设计目的,并对阅卷过程中影响系统健壮性的因素作了深入分析。     

移动分组无线网中可靠传输技术的研究*

数据传输可靠性是移动分组无线网（MPRN）的关键问题,但由于MPRN受到节点移动和带宽的限制,已有的传输技术可靠性不高。在仿真实验平台上进行了传输技术的模拟和性能分析,研究了分组递交率和端到端时延的变化情况。实验结果显示该技术可以有效提高数据传输的可靠性。     

Casting traceability with direct part marking using reconfigurable pin-type tooling based on paraffin–graphite actuators

Green sand moulding machines for cast iron foundries are presently unable to uniquely identify individual castings. An insert tool concept is developed and tested via incremental mock-up development. The tool is part of the pattern plate and changes shape between each moulding, thus giving each mould a unique ID by embossing a Data Matrix symbol into the sand. In the process of producing the mould, each casting can be given a unique (DPM), enabling part tracking throughout the casting's life cycle. Sand embossing is achieved with paraffin-actuated reconfigurable pin-type tooling under simulated processing conditions. The marker geometry limitations have been tested using static symbol patterns, both for sand embossing and actual casting marking. The marked castings have successfully been identified with decoding software. The study shows that the function of each element of this technology can be successfully applied within the foundry industry.     

PS业务变速率功能在包调度算法中的应用

本文介绍了包调度算法中各种业务的状态转换，即PS(Packet Schedule)业务速率变化的状态以及在测试中触发这些状态转换的条件。     

局域网协议测试仪的设计与实现

为了有效地管理网络，通常需要使用协议测试仪这样的工具。文章介绍了网络协议测试软件LPT-2000的体系结构和实现细节。通过对比测试表明，LPT-2000具有较高的包捕获能力和产生负载能力。     

基于IP的MPLS网分组丢失模型研究

分组丢失率是在基于IP的MPLS网中把分组映射到哪条LSP的重要参考指标。文章对基于IP的MPLS网的分组丢失率进行一般性建模,在定义了一些运算的基础上,给出了MPLS网的分组丢失率的精确的迭代公式。它比马尔可夫模型更加广泛。     

基于TCAM的快速更新算法

目前用于实现绕道数据包处理的硬件设备主要是TCAM。对于如何保持TCAM列表的排序这个问题，通常的解决方案提高了平均性能，但是浪费了TCAM空间。论述了一种改进的算法来管理TCAM使得其在最差情况下递增式更新时间保持较小，通过分析使其也能够用于解决数据包分类问题。     

并行数据包采集代理系统中的故障检测与恢复

在基于网络的IDS中，并行多采集代理技术可以有效地降低系统丢包率，但这种并行结构也造成了系统的可靠性下降。为了提高系组统可靠性．给出了并行采集代理的故障模型，针对并行采集代理中包选择算法的特点和并行采集所应用的环境，提出了基于检测代理和基于故障状态广播的两种故障检测与恢复模型，并分析了两者各自的优势和适用范围。最后定量给出了系统性能和可靠性之间的关系     

Routing on Meshes with Buses

We consider the problem of routing packets on an MIMD mesh-connected array of processors augmented with row and column buses. We give lower bounds and randomized algorithms for the problem of routing k-permutations (where each processor is the source and destination of exactly k packets) on a d-dimensional mesh with buses, which we call the (k,d)-routing problem. We give a general class of ``hard' permutations which we use to prove lower bounds for the (k,d)-routing problem, for all k,d≥ 1. For the (1,1)- and (1,2)-routing problems the worst-case permutations from this class are identical to ones published by other authors, as are the resulting lower bounds. However, we further show that the (1,d)-routing problem requires 0.72 ... n steps for d=3, 0.76 ... n steps for d=4, and slightly more than steps for all d≥ 5. We also obtain new lower bounds for the (k,d)-routing problem for k,d > 1, which improve on the bisection lower bound in some cases. These lower bounds hold for off-line routing as well. We develop efficient algorithms for the (k,1)-routing problem and for the problem of routing k-randomizations (where each processor has k packets initially and each packet is routed to a random destination) on the one-dimensional mesh and use them in a general (k,d)-routing algorithm which improves considerably on previous results. In particular, the routing time for the (1,d)-routing problem is bounded by steps with high probability (whp), whenever for some constant ε > 0, and the routing time for the (k,d)-routing problem is steps whp whenever for some constant ε > 0 and k≥ 3.6 ... d, matching the bisection lower bound. We then present a simple algorithm for the (2,2)-routing problem running in 1.39 ... n+o(n) steps whp. Finally, for the important special case of routing permutations on two-dimensional meshes with buses, the (1,2)-routing problem, we give a more sophisticated algorithm that runs in 0.78 ... n+o(n) steps whp. Received May 18, 1994; revised June 23, 1995.