Token ring network management: Change management

This article, which is the fifth in the series on Token Ring Network Management, will discuss selected aspects of Change Management that are relevant in today's Token Ring networking environment.     

Token ring network management: Problem management

Following the tutorial ‘Token Ring Network Management’ article in the previous issue of the International Journal of Network Management, this article takes us through some more detailed Problem Management scenarios.     

Token ring network management: Performance management

In this sixth (and final) article in the series on Token Ring Network Management we will discuss Performance Management, which is relevant for many parts of the distributed Token Ring environment     

Token ring network management: Problem determination

In this article we will look at Problem Determination as the phase to initiate and go through when the normal Problem Management reporting mechanisms and procedures are not adequate.     

Configuration management and security

Proper configuration management is vital for host and network security. We outline the problems, especially for large-scale environments, and discuss the security aspects of a number of different configuration scenarios, including security appliances (e.g., firewalls), desktop and server computers, and PDAs. We conclude by discussing research challenges.     

An atmospheric optical ring network

An experimental 10-Mb/s token-ring local area network (LAN) that uses atmospheric optical communication links is described. Objective and subjective performance results are reported for operation over a 170-m-long outdoor path. The data support the following hypotheses. Atmospheric optical communications may find LAN applications as bridges between buildings containing cable subnetworks or as temporary quick connects for new outlying hosts for which cable runs are initially unavailable. LAN protocols for networks incorporating atmospheric optical communications should be modified to best insulate users from the occasional error bursts and bad-weather outages suffered by such links     

WDM环形网络的保护

详细讨论了WDM环形网络中保护我条件的检测和撤消,保护倒换的协调以及故障条件的恢复检测问题,并得出了一些重要的结论,最后我们建议使用自动保护倒换（APS）协议来实现网络的有效保护。     

有线电视环网传输技术研究

随着有线电视数字化的发展,广播电视的音视频基带信号已进行了数字化处理,电视前端的信号处理系统已实现了数字化改造?但目前有线数字电视的传输系统仍然采用射频调制的传输方式,而由于有线电视数字节目的扩容,高清节目,互动电视的开播以及有线数字电视信号传输的安全稳定性越来越重要等因素,这种传统的射频传输方式已不适应有线电视数字化的进一步深入发展? 结合目前的数字电视平台和数字通信领域的传输技术,阐述了数字电视信号在同步数字体系(synchronous digital hierarchy, SDH)传送的基本原理,分析了基于SDH网络的数字电视平台基本架构,并对基于ASI信号和基于IP信号的数字电视传输网 的组网方式进行了对比,经过比较得出有线电视的环网传输更适宜采用基于IP网络的传输架构?     

High-capacity packet-switched optical ring network

We propose a novel architecture with MAC and admission control protocols for a high-capacity packet-switched optical ring network. In this network the link capacity significantly exceeds the node bit rate. Nodes transmit and receive packets on multiple wavelengths in parallel by using novel optical techniques. Network control is simple since the load is balanced over wavelengths at the physical layer. The MAC protocol is based on credits, and the derived admission control protocol has similar complexity as in a single channel network. Consequently, the network can follow fast traffic changes which are typical in data networks     

Multicast capacity of optical ring network with hotspot traffic: The bi-directional WDM packet ring

Packet-switching WDM ring networks with a hotspot transporting unicast, multicast, and broadcast traffic are important components of high-speed metropolitan area networks. For an arbitrary multicast fanout traffic model with uniform, hotspot destination, and hotspot source packet traffic, we analyze the maximum achievable long-run average packet throughput, which we refer to as multicast capacity, of bi-directional shortest path routed WDM rings. We identify three segments that can experience the maximum utilization, and thus, limit the multicast capacity. We characterize the segment utilization probabilities through bounds and approximations, which we verify through simulations. We discover that shortest path routing can lead to utilization probabilities above one half for moderate to large portions of hotspot source multi- and broadcast traffic, and consequently multicast capacities of less than two simultaneous packet transmissions. We outline a one-copy routing strategy that guarantees a multicast capacity of at least two simultaneous packet transmissions for arbitrary hotspot source traffic.     

An integrated services token-controlled ring network

A ring protocol is proposed that allows voice and data traffic to coexist within the ring. This ring has the following distinct features: (1) it allows synchronous traffic such as voice and video to have a definite access to the channel within each packetization period (or frame); (2) it allows data messages to have a higher channel access priority provided that the synchronous traffic is not delayed by more than one frame; (3) it supports variable rate data circuits. Simulation results show that the data-message delay is much smaller than for other integrated services schemes. Urgent messages can be transmitted with a higher priority over voice. Since the voice packet delay is bounded within one packetization period, no time-stamping is needed and the voice loss can be completely avoided by reserving a sufficient number of slots. Continual speech reception is possible by synchronizing the speech regeneration process to the end of each frame. Since the ring is synchronized, gateway switching to external circuit-switched and packet-switched networks is very simple     

Reliability polynomial for a ring network

A mathematical model is developed for the reliability of a system made up of m unreliable nodes arranged in a ring. The model can be used to calculate the reliability of single-ring networks in which the network recovery mechanism depends on bypassing failed stations, but link signal power margins are inadequate to overcome losses due to more than n bypass switches in series. Computational complexity is 0(n²m+nm²/2) in time, and 0(m²/2) in memory requirements     

HORNET: a packet-over-WDM multiple access metropolitan area ring network

Current metropolitan area networks (MANs) based on the SONET transport are not developing at the rate required to support the phenomenal increase in data traffic. To address the needs of future MANs, the Optical Communications Research Laboratory at Stanford University and Sprint Advanced Technology Laboratories are building HORNET (Hybrid Optoelectronic Ring NETwork). HORNET has a multiple access architecture, in which nodes access any WDM channel using a novel media access control protocol and fast tunable laser transmitters. HORNET transports data packets directly over the WDM ring, eliminating the SONET transport. This paper presents the HORNET architecture, the node design consisting of novel packet-over-WDM components, and the experimental testbed with results.     

Configuration selection for two-layer memory network pattern classifiers

Appropriate allocation of decision-making tasks between processing levels in a hierarchical memory network pattern classifier can enhance efficient utilisation of resources and reduce implementation complexity. The letter describes and compares two strategies for such resource allocation, with specific reference to decision refinement between processing levels.     

令牌网络中非对称性问题研究

本文采用嵌入马尔可夫链理论和概率母函数的方法，根据循环查询时间变量的二阶特性，在离散时间状态下对非对称性令牌网络进行了分析，给出了一种报文分组平均等待时间的近似解析式，同时也给出了计算机模拟实验结果。     

下一代网络的基本原则、功能结构和实现

详细讲解下一代网络的结构，主要讨论下一代网络的基本原则、功能结构和典型的实现方法．以及IP多媒体子系统的结构和功能实体等。