工業(yè)網(wǎng)絡(luò)通信

　　工業(yè)應(yīng)用中的聯(lián)網(wǎng)問題有著悠久而相當(dāng)混亂的歷史。每一個(gè)行業(yè)都面臨著在單個(gè)設(shè)備上部署電子控制的任務(wù)，將這些控制連接到自動(dòng)化的孤島上，最后將這些島嶼拉進(jìn)一個(gè)工廠范圍內(nèi)的網(wǎng)絡(luò)。它們現(xiàn)在與企業(yè)網(wǎng)絡(luò)相連，并與銷售預(yù)測、庫存控制和管理信息系統(tǒng)等相關(guān)聯(lián)。然而，這超出了這一塊的范圍。這種方法的問題是，不同的行業(yè)開發(fā)了不同的實(shí)現(xiàn)網(wǎng)絡(luò)的方法。在20世紀(jì)80年代，有一種運(yùn)動(dòng)，用ISO來創(chuàng)建一個(gè)描述OSI（開放系統(tǒng)互連）模型的網(wǎng)絡(luò)的通用方法，并使用這種模型來發(fā)現(xiàn)不同網(wǎng)絡(luò)技術(shù)的交互方式。本文將通信視為七層模型。第1級是物理層，它定義了電線、連接器和信號穿越導(dǎo)線（或光纖）的方式。這些層變得越來越抽象，直到第7層，應(yīng)用層，它是網(wǎng)絡(luò)和通信軟件之間的接口。

　　At the time there was a huge investment in OSI activities， with an important legacy consisting of the ability to describe current networking technologies in terms of the relevant OSI layers， even if they were not designed with that approach.

　　Today there are several networking technologies being deployed. Industrial Ethernet is making steady progress， particularly as it is seen as compatible with standard Ethernet. While it has significant plus points， it does have some disadvantages， particularly for hard real-time applications. Despite this， many earlier networking technologies， such as Modbus and Profibus， have been adapted as overlays on Ethernet.