毕业论文外文翻译-工业以太网与智能建筑

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工业以太网与智能建筑

1 工业以太网产生的背景

(1) 统一现场总线标准成为泡影，诱惑依然

1984年美国着手制定现场总线国际标准，若干年以来，世界各大公司为了商业的利益，现场总线标准始终不能统一。通过多次投票、协商，2000年1月宣布的现场总线国际标准IEC61158将八种总线（Profibus，Interbus，P-NET，Worldfip等）同时列为国际标准（目前已达10种），形成一个妥协的结果。

同时，国外各大公司又推出了自己的标准，如LONWORKS、CAN、日本三菱、法国Schneider等，目前多种总线的标准同时存在的局面依然存在，人们所说的开放性和互操作性只能在同一种总线标准下实现，不同标准总线之间仍然受到限制。不同总线之间的互联性得不到保证，因此人们在努力寻求一种统一标准的现场总线，有人提出了采用TCP/IP协议的以太网。

(2) 系统集成的需求

①工业自动化的管控一体化企业信息化是我国的国策，以制造自动化及信息化为例：在需要改变业务流程度的同时，将管理信息系统与电子商务、分散的网络化制造加以集成，把现有的企业资源ERP改造成为基于WEB的应用系统。目前工业自动化已从单机自动化、工厂自动化，向系统自动化发展，底层的信息要集成到上层的信息网上以实现管控一体化。

现代化生产系统为一个多层的工业控制系统，一般分为三层：

? 设备层联接检测设备和执行机构；

? 控制层从现场设备取得数据，完成各种控制，监测运行参数，报警和历史趋势分析等；

? 信息层将控制系统的各种数据加工后传至上级管理网络（TCP/IP以太网），以便实现管控一体化。

②智能建筑的系统集成城市信息化、数字化的发展、智能建筑（包括智能化住宅小区），已成为数字化城市的信息站点，要实现信息共享，必须实现控制网与信息网的纵向集成，即控制网与TCP/IP的以太网集成。各子系统（空调、给排水、供电……）由控制网互联再经网关接入TCP/IP以太网，或者各子系统经网关直接接入TCP/IP以太网。

由于各子系统及各现场设备通讯协议是多样化的，这两种集成模式都要开发网关，以实现协议的转换和统一，这样加大了系统集成技术的复杂性，提高了成本。有人大胆提出能否用TCP/IP协议作为一个统一的协议，各子系统及各现场设备直接接到以太网上以简化系统集成的技术难度，降低成本，使控制信号直接由以太网传输，工业以太网的概念因此被提出。

2 以太网与CSMA/CD

(1) 以太网

以太网（Ethernet）1975年由美国XEROX公司研制成功，由于采用无源介质（如双绞线、同轴电缆等）来传播信息，所以以历史上把传播电磁波称为“以太”（Ether）来命名。

1980年由DEC、INTEL、XEROX三家联合推出了EthernetV2，是世界上第一个局域网规范。1983年IEEEE802委员会以DIX EthernetV2为基础推出了IEEE803，采用了CSMA/CD介质访问控制技术。

802.3是指采用CSMA/CD的网络，而以太网的标准由DIX EthernetV2定义，在不严格的情况下，可以称之为802.3局域网，也就是以太网。

。以现代制造业为例，其现代制造自动化模型如图

工业以太网就是将商用以太网应用到工业控制系统，两种网络并没有本质的区别，两者是兼容的。

(2) CSMA/CD（Carrier Sense Multiple Access with Collision Detection，载波监听多路访问/冲突检测）

CSMA/CD最早是由CSMA改进而来。

①CSMA（载波监听多路访问）：一个站要发送信号，首先要监听总线，以决定

介质是否存在其它站发来的信号。

? 如果介质是空闲的，则可以发送；

? 如果介质正处于工作状态，则等待一段间隔后重试，当听到介质处于忙状态，CSMA有几种不同的方法处理，可得到的侦听信号：非坚持CSMA、1—坚持CSMA、P—坚持CSMA。

②CSMA/CD不但先听后发，而且还边听边发，总线上发生了冲突，而且一旦冲突被检测到，便停止发送该帧，放弃自已的帧。为了使其它站也能知道产生了冲突，监听到冲突的站还向总线上传播一个干扰阻塞信号，通知总线各站冲突已发生，这样通道的容量不致因传送已损坏的帧而浪费。随着网络负载的加大，碰撞的机会会增加，网络效率明显下降。

3 工业以太网的特点

(1) 技术成熟，使用方便以太网是美国XEROX公司于1975年推出的，至今已有30年历史，得到全世界众多厂家的支持，在军事、工业、民用领域得到了广泛应用。

(2) 具有统一的标准，开放性好采用统一的IEEE802.3以太网标准CSMA/CD，是IEEE802.3采用的介质访问控制技术，可以实现不同厂家之间的产品互联，是一种开放式标准网络。

(3) 通信速率高，传播速度快以太网的通信速率目前已经由10M提高到100M、1 000M，甚至10G。

(4) 可分段地实现远程访问、诊断和维护。

(5) 支持冗余连接配置，数据可达性强数据有多条通路，可达目的地。

(6) 系统容量大，不会因为系统扩大出现不可预料的故障，有成熟可靠的系统安全体系。

(7) 投资成本低，包括初期投资、培训费用及维护费用。

(8) 线路采用变压器双端隔离或光纤，抗干扰性强。

4 工业以太网目前存在的问题

现场总线是用于工业控制并为复杂而又恶劣环境的工业现场而设计的，因此对系统的实时性和响应时间有严格要求，对供电方式使用环境有特殊要求。由于以太网是为信息通信而设计的，用于工业控制存在以下问题：

(1) 以太网采用CSMA/CD访问协议，这是一种非确定性的网络，对于实时性要求高的控制系统，这种不确定性将造成信息不能按要求传递。同一网段上受到CSMA/CD 媒体访问控制方式的制约。所谓网段是指连在同一共享式网络总线上，可以侦听到对方发出的信息，处于同一冲突碰撞区域（指会发生冲突碰撞的区域）的工作站和服务器连成的网络区。例如在一个冲突碰撞区域中有一个工作群组（由一台服务器和多台工作站组成），当多台工作站访问一个服务器时，由于受CSMA/CD的约束，同一时刻只允许一个工作站与服务器通信，其它工作站只能等待。各工作站争抢通信信道，从而使工作站的通信产生延时，而且这种延时时间是不确定的，工作站愈多争抢通信等待时间愈长，这种情况被称为负荷愈重等待时间愈长。

若在一个碰撞域中，假设有两个工作群组，处于一个碰撞域中，第一个工作群组工作站访问服务器时，要竞争网络宽带（例如100M），另一个工作群组中所有工作站及服务器都处于等待状态而无法运行。两个工作群组要分割原有网络宽带（100M），一个工作群组工作时，另一个群组必须等待，这样不仅具有延时，而且这种延时是不确定的。由于CSMA/CD有无法预见的延时，特别在重负载下，实时数据传送更得不到保证。控制系统要有实时性保证，必须在任何时间都要及时响应，不允许有任何不确定性。因此以太网用于控制系统必须解决实时性和不确定性问题。

(2) 以太网在可靠性方面不如现场总线，现场总线是为工业控制设计的，能适应易燃、易爆（如化工、制药）、干扰强烈场合及其它环境恶劣的场合。现场总线有屏蔽，接地与防爆等措施，而以太网需要解决这些问题。

(3) 现场总线规范要求网段上配有电源，为所有非自供电的设备提供电源，而以太网不提供电源，必须增加额外的供电电缆。

5 工业以太网的应用可行性

工业以太网用于工业控制，对于上述问题，随着以太网技术的发展和相应措施的实施，其实时性及可确定性取得很大改善：

(1) 不断提高以太网速率：近来年以太网的速率由10Mbps、100Mbps增加到1 000Mbps并已广泛应用。目前10Gbps的以太网已经商业化，数据传输时间大大缩短，响应时间得到提高，系统的实时性及不可确定性得到了改善。

(2) 采用交换机以太网技术：由于共享式以太网工作站点争抢信道而产生冲突碰撞影响了系统的实时性和不确定性，采用交换机以太网技术可使其得到改善。交换型的以太网中采用以太网交换机，交换机各端口之间同时可以形成多个数据通道，每个端口可连一个网段，端口之间帧的输入和输出不再受CSMA/CD介质访问控制协议的约束。当系统包括多个工作群组，一般让每个组群单独组成一个网段，每个网段占用交换器（机）一个端口（如图4所示交换机有A、B、C、D四个网段），各网段的工作大部分时间是独立的，当任意两个网段需要信息交换时，交换机能在2个独立网段之间建立信息通道一旦信息交换结束，通道即断开。

由此看出，交换式以太网可以克服共享式以太网存在的问题：

? 交换机每个端口上，可连接一个网段，每个网段可独享带宽；

? 交换机每个端口上，所接网段之间是独立的、被隔离的，如需要网段间进行信息通信的话，可以暂建立信息信道，经过交换机的隔离，可大大减小冲突发生的概率，改善实时性和不确定性；

? 交换机VLAN技术的普遍采用，使交换系统能够分配给控制信息点专有的通道和带宽，从而保证在网络繁忙的时候，控制系统仍有足够宽裕的带宽，使以太网信息传输的实时性和不确定性基本上保持在理论的水平上。

(3) 在某些应用场合允许的情况下，尽量将控制网与信息网分割开来使用，以避免实时数据与非实时数据的碰撞，使工业控制站点之间的以太网为独立网段，从而改善实时性和不确定性。除此之外，还可以采用全双工技术降低网络负载，以及在

Ethernet+TCP/IP协议的基础上制订统一并适用于工业现场控制的应用层技术规范等措施。采取以上措施可以使工业以太网在某些军事、工业、民用的领域的现场测控中得到初步应用。例如，国外不少国家核加速器最新测控方案选择了以太网，除此之外汽车装

配线、薄钢生产线等均采用工业以太网的方案，从测控领域的发展方向上看，工业以太网将是未来测控领域中的一个重要发展方向，也是企业管控一体化和智能建筑系统集成的一种最佳方案。

(4) 以太网的供电问题，多年来一直是一个缺陷，特别是随着IP电话、IP摄像机、无线AP、ENC（Ethernet Control System）等系统的应用，人们更提出以太网在传输数据的同时，传送部分能量，以满足小型网络设备用电的需求，解决小型网络设备供电的无序状态和居高不下的电源布线成本。因此IEEE 802.3af标准呼之即出，已形成一个以太网供电的国际标准，目前3COM、华为、DLINK等公司都有符合802.3af标准的交换机产品。IEEE 802.3af 标准的核心是在满足802.3 标准的同时，由交换机向网络终端设备提供48V或24V电源，至此工业以太网的供电问题得到很好的解决，其原理如图1所示。

图1以太网自供电原理图

(5) 以太网是一种网络形式，TCP/IP协议是一种开放通信协议。安全问题不属于网络形式和TCP/IP协议。网络的安全性最终关心的是在网络上传输的应用层信息的安全，使它不被非法的修改、使用。保障信息及传输的安全不外乎两种方式：专有独立通道和信息加密。前一种方式目的是让不该得到的得不到，后一种方式让不该得到的得到了也不知道。以太网的虚拟专用网交换技术现已成为一种最基本的网络专用通道技术，已经非常成熟并广泛使用。以太网可以很方便的将需要的通道隔离出来。Internet的信息加密是TCP/IP之上的基本与之无关的应用信息处理方法。信息在发出之前要进行加密处理，信息在使用之后要进行解密处理。现在基本上都采用公开的加密算法，秘密不靠加密方法保证，而是靠密码（key）。信息安全的最后和最关键的因素是持有重要密码的人，他保管使用密码的过程、方式是通信系统的安全的核心。

6 工业以太网在智能建筑中的应用实例

(1) ENC-2001IP工业以太网测控系统简介

北京楼宇自动化工程中心（简称为北京楼宇自控中心）采用ENC-2001IP工业以太网测控系统对某小区15栋高层住宅的充配电、换热、采暖、通风、供水、消防、三表查收及楼宇对讲六个子系统远程监控，取得较好效果。

ENC工业以太网控制系统结构框如图6所示。

这些ENC参量控制模块可以把智能建筑各子系统集成到以太网、电梯系统、火灾报警等传统设备上，带有RS232或RS485接口，分别可接到ENCTRS200及ENCTRS400网关转换模块集成到以太网上，而IP电话及IP摄像机可以直接集成到以太网上。除此之外还提供CDMA/GRPS无线网关接口，例如系统报警信息即可通过该网关接口直接发送到手机上，并可通过手机对系统进行控制。

AI：模拟量输入模块（ENC AI）DI：数字量输入模块（ENC DI）

AO：模拟量输出模块（ENC AO）DO：数字量输出模块（ENC DO）

FI：脉冲输入模块（ENC FI）FO：脉冲输出模块（ENC FO）

网络实现数据管理系统：对底层设备的实时数据进行管理。

WEB服务：完成对整个系统的操作控制。

本地监控管理站：实际上是本地监控浏览器（Broswer）通过浏览器，可对系统监视。

远程工作站：实际上是远程监控浏览器（Broswer）在网上通过浏览器对系统进行监视

(2) ENC参量集成模块

ENC参量集成模块由北京楼宇自控中心开发。

①功能

? 内嵌WEB SEVER，可以通过浏览器直接对其进行监控，配置校准；

? 客户认证功能；

? 内嵌防火墙功能；

? 支持SOCKET的通信规程；

? 完善的TCP/IP协议；

? 10/100baset符合IEEE 802.3af 标准的以太网接口。

②硬件结构：由中央处理器MCU、以太网网卡、传感器、执行器、I/O接口以及存储器（电子硬盘），电源组成。

③系统结构：内嵌WEB SEVER，可与客户端（Broswer）进行通信，如图8所示。

(3) ENC系统特点

①实现信息网络与控制网络统一

取消控制网与信息网的界限，控制信息化。所有设备通过ENC参量集成模块或接口直接集成到以太网上，ENC参量控制模块都是一个网络服务器，内嵌WEB服务器。

②采用网络控制服务管理方式

中央控制中心是一套主服务器，控制各参量集成模块，可集中或分布处理各种数据，通过参量集成模块完成各种类型控制要求。

③系统结构简单，组网方便灵活，扩展维护方便

该系统通过以太网进行集成，智能建筑中局域网是不可缺少的，利用局域网这些模块可以就近插接，不用重新布线，所需器件均为标准化的，组网方便灵活，扩展维护方便。

④将控制系统升级为服务系统

该系统始终贯穿一种服务的理念，将设备的控制升级为设备对外提供的信息服务。这种服务的对象可以为人，也可以为机器。建筑中有了众多设备提供的优秀服务，智能建筑就成了一套智能服务系统集合，这正是人们所期待的。

7 结语

20世纪90年代以来，工业以太网取代控制网络进行了尝试，有不少成功的案例。以工业以太网为核心的测控技术是测控领域中的一个重要发展方向，但其实时性、可靠性、安全性、互操作性等尚需进一步研究完善。

原文

Industrial Ethernet and Intelligent Building

1 Industrial Ethernet the background

(1) Unified field bus standards dashed, the temptation remains

In 1984 the United States proceed to develop international standards field bus, a few years, the major companies for commercial interests, Field bus standards can not always uniform. Through multiple voting, consultation, in January 2000 announced that the field bus international standards IEC61158 will be eight bus (Prefabs, Interfuse, P-NET, World, etc.) at the same time as international standards (currently has 10 kinds), formed The outcome of a compromise.

At the same time, major foreign companies have also launched its own standards, such as LONWORKS, CAN, Japan's Mitsubishi, France Schneider, the current number of bus standards at the same time the situation still exists, they say the openness and interoperability only At the same can be achieved under a bus standard, different standards between the bus is still limited. The interconnection between different bus and can not be guaranteed, so people in their efforts to seek a unified standard field bus, some people have proposed the use of TCP / IP protocol Ethernet.

(2) The demand for system integration

① industrial automation control integrated enterprise information is China's national policy to create automation and information technology as an example: In the need to change the business processes of the same time, management information systems and e-commerce, decentralized network of manufacturers to be integrated, the existing enterprise resource ERP transformed into WEB-based applications. The current single from the automation of industrial automation, factory automation, to the development of automation systems, the underlying message should be integrated into the upper information online in order to achieve the integration of control as shown in an integrated system.

Modern production system for a multi-storey industrial control systems, generally fall into three tiers:

? Equipment-testing equipment and connectivity implementing agencies;

? Control of the data obtained from the scene equipment, complete the various control, monitoring operating parameters, alarm and historical trend analysis;

? Information layer will control the data processing system after spread to the higher level management network (TCP / IP Ethernet), in order to achieve integrated management of its network structure 。

② Intelligent Building of the urban information system integration, the development of digital, intelligent building (including intelligent residential district), has become a digital city's information site, in order to achieve information sharing, the need to achieve control network and information network of vertical integration, that is, Control network and TCP / IP Ethernet integration.

As various subsystems and communications equipment at the scene agreement is diversified and integrated these two models must be developed gateways, in order to achieve the conversion agreement and unity, this has increased the complexity of system integration technology and increase costs. It was boldly put forward can use TCP / IP protocol as a unified agreement, the scene of the subsystems and equipment directly from Ethernet to simplify the system integration of technical difficulty, lower costs, so that control signals directly from the Ethernet transmission, So the concept of industrial Ethernet has been raised.

2 Ethernet and CSMA / CD

(1) Ethernet

Ethernet (Ethernet) 1975 by the United States XEROX company successfully developed, as a passive medium (such as twisted pair, coaxial cable, etc.) to disseminate information, to the history of the spread of electromagnetic waves known as the "Ethernet" (Ether ) To name. 1980 by the DEC, INTEL, XEROX jointly launched a three EthernetV2, is the world's first LAN standard. 1983 IEEEE802 Committee DIX EthernetV2 based introduced IEEE803, using the CSMA / CD MAC technology.

802.3 refer to a CSMA / CD networks, and Ethernet DIX EthernetV2 from the standard definition, not strictly in the circumstances, can be called 802.3 LAN, which is Ethernet.

To the modern manufacturing industry as an example, its modern manufacturing automation model in Figure

Industrial Ethernet is the commercial application of Ethernet to industrial control systems, the two networks is not essentially different from, the two are compatible.

(2) CSMA / CD (Carrier Sense Multiple Access with Collision Detection

Multi-carrier monitoring visit / conflict detection)

CSMA / CD are the first improvement comes from CSMA.

① CSMA (Carrier monitor multiple access): stop trying to send a signal, first of all to monitor bus, to determine whether there is other media, to stop the signal.

? If the media is free, you can send;

? If the media are in working condition, then wait so me try again after the interval, when heard in a busy state media, CSMA There are several different ways to deal with, the availability of interception of signal: adhere to non-CSMA, 1 - adhere to CSMA, P -- Consistently CSMA.

② CSMA / CD to hear not only the first, but also Baiting Bain hair, a bus in the conflict, but once the conflict was detected; they stopped sending the frame, to give up their own frame. In order to know that other stations can also have a conflict, listening to the conflict to the bus station on the spread of a blocking signal interference, informed the bus station in the conflict have taken place, the capacity of this channel will not be sent because the frame was damaged

and waste. With the increased network load, the collision would increase the opportunities, network efficiency decreased significantly.

3 Industrial Ethernet features

(1) technology is mature, easy to use Ethernet XEROX company in the United States launched in 1975, has been in 30 history, many manufacturers around the world have the support of the military, industrial, civilian areas have been widely used.

(2) With uniform standards, open good adopt a unified standard IEEE802.3 Ethernet CSMA / CD, is IEEE802.3 used MAC technology, can be achieved between different manufacturers of products Internet, is an open - Standard network.

(3) High-speed communications, high speed Ethernet transmission rate of communication has increased from 10 M to 100 M, 1 000M, or even 10 G.

(4) To achieve sub-remote access, diagnosis and maintenance.

(5) To support redundant connection configuration, data up to a number of strong data access, up to destination.

(6) System capacity, not because there can not be expected to expand the system failure,

a mature and reliable system security system.

(7) Low investment costs, including the initial investment, training costs and maintenance costs.

(8) Lines using double-isolation transformers or optical fiber, and strong

anti-interference.

4 Industrial Ethernet the existing problems

Field Bus is used for industrial control and complex and harsh environment of industrial design at the scene, the system of real-time and response time have strict demands on electricity use of the environment, there are special requirements. Since Ethernet is designed for information and communications, industrial control for the existence of the following questions:

(1)using Ethernet CSMA / CD Access Protocol, which is a non-deterministic network

The high demand for real-time control systems, this uncertainty will result in the requested information can not convey. The so-called network segment is even shared the same bus network, you can listen to the message sent by the other side, at the same collision regional conflict (a conflict that will impact the region) of workstations and servers to connect the network area. For example, in a collision conflict in the region have a working group (from a server and workstation components multiple), when more than one visit a server workstation, due to the CSMA / CD bound by the same time allowing only a workstation and server Communications, can only wait for the other workstations. Competition for the workstation communication channel so that the communication workstations have delayed, and this extension

When the time is uncertain, workstations more competition for communications for the longer this situation known as the load was more severe the longer the waiting time.

If in a collision domain, assume that two working groups, in a collision domain, the first work group servers, workstations access to competitive broadband networks (such as 100 M), another working group of all workstations and servers Are in a wait state and can not run. The two working groups to split the original broadband network (100 M), a working group work, must wait for another group, this has not only delayed, and this delay is uncertain. As CSMA / CD have unforeseen delay, particularly in the heavy load, the more real-time data transmission can not be guaranteed. Therefore Ethernet control system must be solved for real-time and uncertainty.

(2) Ethernet in reliability than Bus at the scene

Field Bus is designed for industrial control, able to adapt flammable, explosive (such as chemicals, pharmaceuticals), strong interference and other occasions poor environment occasions. Field bus have shielding, grounding and explosion-proof measures, such as Ethernet and the need to address these issues.

(3) Field bus specifications on the network segment with a power supply

For all non-self-powered equipment to power and Ethernet does not provide power, the need for additional electricity supply lines.

5 feasibility of the application of Industrial Ethernet

Industrial Ethernet for industrial control, the above-mentioned problems, with the Ethernet technology development and the implementation of corresponding measures, in fact, and the uncertainty can be made great improvements:

(1) Continuously improve Ethernet rate:

The rate in recent years Ethernet from 10 Mbps, 100Mbps to 1 000Mbps and has been widely applied. At present 10 Gaps Ethernet has been commercialized, greatly shortening the data transmission time, improve response time, the system's real-time and non uncertainties have improved.

(2)using Ethernet switch technology

As the work site shared Ethernet channel competition arising from the conflict affected the collision of real-time system and uncertainty, Ethernet switch technology can be used to be improved. Ethernet-based exchange used in Ethernet switch, switch between the port at the same time can create a number of data channels, each connected to a network port, the port frame between the input and output no longer subject to CSMA / CD MAC bound by the agreement. When the system includes a number of working groups, in general so that each group formed a separate network segment, each of the occupation of the exchange network (of) a port (shown in Figure 4 switches are A, B, C, D 4 net), net of most of the time the work is independent, when any two of the need for information exchange network, the switch in two independent network of information between the channel .Once the end of the exchange of information, access is disconnected.

This shows that switched Ethernet shared Ethernet can be overcome existing problems: ? Switches on each port can connect a network segment; each of the network bandwidth can be exclusive;

? switches on each port, the network of access between the independent an d isolated, such as the need for inter-network of information and communication, it can temporarily establish an information channel, after the switch isolation, can greatly reduce the probability of conflict To improve the real-time and uncertainty;

? sw itch VLAN technology commonly used to exchange control system can be allocated to the proprietary information, access and bandwidth, thus ensuring the network's busiest time, the control system is still comfortable enough bandwidth to enable Ethernet transmission of real-time information And uncertainty remained largely theoretical level.

(3) In some applications to allow the circumstances,

Try to control network and information networks to use separate, in order to avoid

real-time data and non-real-time data of the collision, between the industrial site for independent Ethernet network segment, Thereby improving the real-time and uncertainty. In addition, full-duplex technology can be used to reduce network load, and Ethernet + TCP / IP protocol on the basis of a uniform and apply to the industrial field of application-level control measures such as technical specifications. The above measures can be taken so that in some industrial Ethernet military, industrial, civilian areas of the site has been initially applied in the measurement and control. For example, many countries abroad nuclear accelerator as the Ethernet monitoring and control options, in addition automobile assembly line, thin steel production lines and so on a programmed of industrial Ethernet, monitoring and control from the direction of development of the area, the industrial Ethernet will be Monitoring is the future in the field of an important direction of development, but also the corporate-controlled integration and intelligent building systems integration as a best option.

(4)Ethernet power supply problem,

Over the years has been a defect, especially as IP phones, IP cameras, wireless AP, ENC (Ethernet Control System) system and other applications, more people put in Ethernet transmission Data at the same time, send some energy, small network equipment to meet the demand for electricity, power supply network equipment to solve the small state of disorder and the high cost of power supply wiring. So the IEEE 802.3af standard that is called out, has formed an Ethernet-powered international standards, 3 COM, Hawaii, DLINK, and other companies have with 802.3 aft-standard switching products. IEEE 802.3af standard is the core to meet the standards of 802.3 at the same time, by switching to the network terminal equipment to provide 48 V or 24 V power, the power supply to this industrial Ethernet issues have been very good solution, the principle shown in Figure 1.

Figure 1 principle of self-powered Ethernet

(5) Network of Ethernet

TCP / IP protocol is an open communication protocol. Security issues do not belong to form networks and TCP / IP protocol. Network security is the ultimate concern of the transmission network in the application layer of information security; it is not illegal changes to use. Protect the security of information transmission and either two ways: exclusive and independent access encrypted information. Before a way to let the lack should not be, the latter should not be the way to get the do not know. Ethernet virtual private network switching technology has become a basic network dedicated channel technology, already very mature and widely used. Ethernet can easily access will require isolation from. Internet information is encrypted TCP / IP on the basic nothing to do with the application of information processing methods. Prior to the issue of information is encrypted with information to carry out the use of declassified after treatment. Now basically an open encryption algorithms, do not rely on secret encryption guarantees, but by password (key). Information security key to the final and most important factor is the holder of the password; he kept using the password of course, and means the security communication system is the core.