Following the fiber distributed data interface

The fiber distributed data interface (FDDI) follow-on local area network (FFOL) work was initiated in February 1990 by Task Group X3T9.5 of Accredited Standards Committee (ASC) X3 to establish requirements and formal projects for a next-generation LAN. The background for startup of the FFOL project, including its requirements and current status, are presented. It is shown that the higher performance of FFOL and its ability to handle all FDDI data formats will allow its use as a backbone to existing FDDI installations. FFOL will also be used as a replacement for FDDI and other LANs when its higher performance is required     

Bandwidth-efficient digital transmission over unshieldedtwisted-pair wiring

Describes techniques for achieving data rates up to 155 Mb/s over unshielded twisted-pair (UTP) wiring for local area network (LAN) applications in premises distribution systems. Duplex operation at these high data rates is achieved over two pairs of UTP wiring and with a bandwidth utilization that is less than 30 MHz, thus avoiding potential problems with radiation limits. The transmission scheme used for these LAN applications is carrierless AM/PM (CAP), which is a bandwidth-efficient two-dimensional passband encoding scheme. The paper also discusses in some detail a technique called NEXT equalization, which allows several users to share the same cable     

A quaternary partial-response class-IV transceiver for 125 Mbit/sdata transmission over unshielded twisted-pair cables: principles ofoperation and VLSI realization

The paper describes an experimental transceiver for full-duplex transmission at a rate of 125 Mbit/s over unshielded twisted-pair cables of ordinary voice-grade quality, intended for use in a fiber distributed data interface (FDDI) network. Quaternary partial-response class-IV (QPRIV) overall-channel signaling with near-end crosstalk (NEXT) cancellation and maximum-likelihood sequence detection is employed. The spectral shape of the QPRIV signals facilitates equalization and achieving compliance with EMC regulations. Since in an FDDI system each transmitter can be clocked independently, the receiver must cope with phase drift between NEXT signals to be cancelled and signals received from the remote transmitter. With the chosen transceiver architecture, digital-to-analog conversion of transmit signals, analog-to-digital conversion of receive signals, and adaptive NEXT cancellation are performed synchronously with the transmitter clock. The rate change from transmit timing to controlled receive timing is accomplished by an adaptive equalizer in conjunction with an elastic buffer and occasional coefficient shifts. The equalizer is adjusted rapidly enough to allow for a maximal phase drift of ±100 ppm. The implementation of all digital signal-processing functions in a single 0.5 μm CMOS VLSI prototype chip is discussed. The employed standard-cell design resulted in a power consumption of 6 W. Significantly lower power consumption can be achieved by custom design of highly repetitive processing elements     

Trends in network media and wiring strategies: LAN life cycle cost implications

The main objective of this paper is to present this author's assessment of the impact that alternative network media and wiring strategies have on the life-cycle cost of a local area network (LAN). In terms of trends and issues related to media such as twisted-pair, optical fiber and coaxial cable and wiring strategies, the author sees the following: 1) a general feeling of confusion among many potential LAN customers, 2) for those organizations which did choose a particular media and wiring strategy such as broadband or baseband coaxial cable, an increased move toward multiple media networks which can support various communication architectures, and 3) increasing management concern for LAN life-cycle costs. These subjects are addressed further as part of this paper.     

Approximating dependability measures of computer networks: an FDDIcase study

An approximation technique is presented to evaluate the dependability of FDDI networks. This technique, based on the most likely paths to failure concept, is simple and practical. It may be applied easily to evaluate and compare the dependability of different FDDI network configurations. The effects of various network parameters on the network availability are examined. We conclude that, in order to guarantee high availability, an FDDI network backbone should be interconnected using dual-attachment concentrators. Furthermore, dual-homing configurations are required for high-availability paths between end stations and the backbone. For less stringent availability requirements, single-attachment concentrator trees with single attachment stations may suffice. We also discuss how the technique may be extended easily to more general heterogeneous networks including Token Ring and Ethernet     

基于CX28975芯片组带多种接口的G.SHDSL传输设备的设计与实现

通过对美国敏讯(Mindspeed)公司开发的CX28975芯片组的结构和特性进行介绍,分析了该芯片组的工作原理,并提出了一种利用该芯片组设计的带以太网、UART接口的G.SHDSL多速率传输设备的软硬件实现方案和程序流程,最终根据该方案实现了在一对双绞线上传输对称的、全双工的信号。     

Analysis of tuning of FDDI media access control protocol

The fiber distributed data interface (FDDI) provides a 100 Mb/s communication system to interconnect computer and peripheral equipment using fiber optics as the transmission medium in a ring configuration. The performance of the FDDI media-access control (MAC) protocol, a timed-token protocol, is analyzed. The FDDI MAC priority mechanism supports two classes of traffic: synchronous and asynchronous. The focus is on the relationship between the FDDI MAC parameter settings, the ring configuration, and the performance of the asynchronous priority levels. A procedure to calculate estimates for the throughput of each asynchronous priority level over a range of frame-arrival rates is developed. Performance results are presented to demonstrate characteristics of the FDDI priority mechanism. A procedure is described that can be used to tune the FDDI parameters so that given performance objectives for the various priority levels are achieved     

Evaluation of a data communication model for switched fibre channel

The ANSI standard fibre channel is emerging as the networking protocol of choice for high bandwidth applications. Fibre channel is an enabling technology because of the tremendous advantages in speed and latency it provides over existing networking technologies. Applications that weren't feasible before are now possible, and more applications that demand similar performance will follow. Fibre channel is the high performance alternative to existing networking technologies such as FDDI, Fast Ethernet, and ATM. Fibre channel (FC) provides for two different data communication models: connection (class 1 service) and connectionless (class 2 or 3 service). Although interoperable, some of these implementations may not result in optimal performance. There is some disagreement in the FC community as to which is more appropriate. Both have their advantages and disadvantages, and so it's necessary to look at each application individually. The article addresses some of these issues by simulating these two communication models over different switch architectures     

Performance analysis of the timed token protocol of FDDI andFDDI-II

The performance behavior of an FDDI (fiber distributed data interface) system with synchronous traffic as well as an extended FDDI (FDDI-II) system with isochronous and asynchronous traffic is evaluated. Multiple asynchronous priorities are considered, one priority level at each station. an iterative algorithm to calculate the first two moments of the cycle (i.e. token rotation) time is presented, and the major system characteristics are derived from the analysis in terms of queue-length distributions and mean waiting times of the packets. Since the model considers queues with limited buffer size, loss probabilities of data packets can also be calculated. Some results obtained by the approximate analysis are discussed using example configuration, and the accuracy is validated by detailed computer simulations. The complexity and convergence behavior of the algorithm is studied, and it is shown that the algorithm converges very quickly     

Forging FDDI

The development of the fiber distributed data interface (FDDI), a 100-Mb/s token ring that uses optical fiber that has become the premier high-speed local area network (LAN) standard, is examined. The important decisions that shaped FDDI are described. It is shown that technical innovation came from a variety of contributors and that adopting their ideas converted contributors into supporters. Adopting new ideas also improved the FDDI standards; by the time FDDI matured, it had become a family of standards with much broader appeal than was imagined initially     

51.84 Mb/s 16-CAP ATM LAN standard

The paper describes the characteristics and performance of the 16-CAP transmission scheme that has been chosen by the Technical Committee of the ATM Forum as the ATM LAN physical layer interface standard at 51.84 Mb/s for category 3 unshielded-twisted-pair (UTP) wiring. The two most attractive features of the 16-CAP transceiver are its capability of operating in the presence of multiple users in a voice-grade UTP cable and the straightforward way in which it can provide scalability to lower speeds. It is also shown in the paper how the carrierless AM/PM (CAP) modulation scheme used for the ATM LAN standard can be utilized to provide substantially higher data rates than 51 Mb/s when there is only one user in a cable. Under this condition, data rates up to 155 Mb/s can be achieved over category 3 wiring and significantly higher rates can be achieved over high-performance category 5 wiring     

100BASE-T2: a new standard for 100 Mb/s Ethernet transmission overvoice-grade cables

100BASE-T2 is a new physical-layer specification for IEEE 802.3 LANs operating at 100 Mb/s (“Fast Ethernet”). It enables users of the prevailing 10BASE-T Ethernet LAN technology to upgrade their networks from 10 to 100 Mb/s performance while retaining an existing voice-grade cabling infrastructure. 100BASE-T2 transceivers will operate over two pairs in unshielded twisted-pair cables corresponding to EIA/TIA category 3 (UTP-3), as minimally required for 10BASE-T. In a four-pair UTP-3 cable, simultaneous operation of two 100BASE-T2 links, or one 100BASE-T2 and one 10BASE-T link, is permitted. Since voice-grade cables exhibit more signal attenuation and significantly higher crosstalk coupling between adjacent pairs than data-grade cables, sophisticated digital signal processing techniques are needed to achieve reliable duplex 100 Mb/s transmission over two pairs. The 100BASE-T2 standard defines dual-duplex baseband transmission at a modulation rate of 25 Mbaud. During each modulation interval, a four-bit data nibble or Ethernet-specific control information is encoded into a pair of quinary signals. These signals are transmitted simultaneously on the two wire pairs in both signaling directions. In the receivers, adaptive digital filters are required for echo and NEXT cancellation, equalization, and interference suppression     

The IEEE 802.17 media access protocol for high-speed metropolitan-area resilient packet rings

The resilient packet ring (RPR) IEEE 802.17 standards is under development as a new high-speed technology for metropolitan backbone networks. A key performance objective of PRP is to simultaneously achieve high utilization, spatial reuse, and fairness, an objective not achieved by current technologies such as SONET and Gigabit Ethernet or legacy ring technologies, such as FDDI. The core technical challenge for RPR is the design of a fairness algorithm that dynamically throttles traffic to achieve these properties. The difficulty is in the distributed nature of the problem, that upstream ring nodes must inject traffic at a rate according to congestion and fairness criteria downstream. This article provides an overview of the RPR protocol with a focus on medium access and fairness.     

Cable measurements supporting xDSL technologies

The ongoing developments in the field of high-speed data transmission over twisted-pair cables (DSL-Digital Subscriber Line) leads to methods that can exploit the transmission media with increased efficiency. MIMO (Multiple-Input Multiple-Output) transmission, i.e., the coordinated use of many pairs within a bundle, is such an emering DSL technology. A further goal is to maintain a certain transmission quality in the presence of non-DSL noise. For example, cancellation techniques to combat narrowband radio interference, which is generated by radio amateur transmitters and may be picked up by the wire close to the subscriber or by the in-hourse wiring, become important. The efficiency of these techniques strongly depends on cable properties that have not been the focus of cable measurements so far. This paper gives an overview of special cable measurements and shows their importance for future DSL technologies.     

Hardware invariant protocol disruptive interference for 100BaseTX Ethernet communications

In this paper, we introduce a new concept that we refer to as hardware invariant protocol disruptive interference (HIPDI). Such interference would pose a severe threat as intentional EMI to the corresponding protocol for which it was designed. In this paper, we consider only the 100BaseTX Ethernet protocol over UTP CAT-5 cable which is used extensively in local-area networks. We show that low power, narrowband, differential-mode voltage levels on a 100BaseTX Ethernet twisted-pair can seriously degrade network throughput independent of the physical features of the network or the protocol interpreter hardware. Moreover, we show that the required parameters of disruptive interference can be derived from the protocol itself using a concept we call hardware aperture. The experimental results reported herein indicate that creating such interference is practically feasible and therefore, is a possible threat to existing communication networks.     

千兆比以太网技术

千兆比以太网是一种新型高速局域网，它一方面兼容传统以太网的主要标准结构，保护了用户先前的投资和系统配置，并使系统升级方便，以较实际的价格赢得了支持的发展。另一方面，它又采纳了光纤通道的低层协议以及其他一些在行兆比速率下应作的改进，使它获得了高速宽带性能。本文还列举了从快速以太网和ＦＤＤＩ向千兆比以太网迁移的网络配置策略。     

A method-of-moments solution to the twisted-pair transmission line

A method of moments (MoM) approach to modeling the unshielded, twisted-pair transmission line is developed and validated. The approach described has proven capable of predicting the operational performance characteristics of the twisted-pair transmission line, and can be implemented to analyze attenuation and crosstalk under fault conditions. The model is validated for an unfaulted transmission line by comparison with measured data as well as the classical, distributed-parameter model     

FEXT cancellation for twisted-pair transmission

This paper discusses a far-end crosstalk (FEXT) canceller for twisted-pair transmission. Many twisted-pair systems such as fiber-to-the-curb, very high-speed digital subscriber line, and high-speed LAN systems, use frequency-division duplexing (FDD) for duplex transmission. It is shown that the maximum reach of FDD twisted-pair system is limited by the performance of its upstream channel, which is assumed to be located at higher frequencies than the downstream channel. In order to improve the performance of such an FDD transceiver, FEXT cancellation is introduced for the channel at higher frequencies. A system arrangement and its blind startup procedure are studied when the FEXT canceller and equalizer are jointly adapted to combat channel intersymbol interference, FEXT, and other additive noise. We investigate the initial convergence and the steady-state behavior of the proposed twisted-pair system without requiring transmission of an ideal training sequence. Measured characteristics as well as analytical model of the FEXT channel are used to estimate the time span needed for the FEXT canceller. It is also shown that the memory span for the FEXT canceller is almost independent of the channel, thus making our results useful for the twisted-pair system over all different channels     

倍福Beckhoff在步进电机控制中的应用

PLC控制近一千个步进电机时控制规模大、成本高、网络通信复杂,而德国倍福CX1000设备系列适用于中等规模的控制任务,采用该系列设备控制近千个步进电机具有成本低、控制可靠、接线简单、占用空间小、结构紧凑等优点。倍福运动控制器本身集成双Ethernet接口,一个向上连接工业以太网,另一个通过实时的超高速以太网EtherCAT与步进电机驱动器连接构成运动控制网络系统,实现了分控系统与主控系统的通信,且通信可靠,实时性好。     

High-performance optical local and metropolitan area networks:enhancement of FDDI and IEEE 802.6 DQDB

The fiber distributed data interface (FDDI) and the IEEE 802.6 distributed queueing dual bus (DQDB) are emerging standards for high-speed (45-150-Mb/s) local and metropolitan area networks. The authors describe several ways to build on these emerging standards to significantly increase the achievable throughput and lower th e end-to-end delay. Without increasing the number of transceivers or their rate, substantial throughput increases are obtained by a highly concurrent logical interconnection pattern of user modes, and the end-to-end delay is decreased by the use of more efficient media-access techniques. The most promising architecture is a multiconnected ring having only two transmitters and two receivers per node, where each node needs to handle or process only a small fraction of the network traffic. In one example, the authors describe a 24-node, distributed, packet-switched network, with only two 100-Mb/s transmitters and two 100-Mb/s receivers per node; it has a maximum throughput of 1.5 Gb/s-15 times the 100/Mb/s throughput of FDDI. Such a system has the potential to be a follow-on standard to FDDI (or IEEE 802.6) or to provide a high-performance LAN/MAN that can interwork with standard systems