Editing SCADA (section)

== Architecture development ==
[[File:SCADA C4ISR Facilities.pdf|thumb|The [[United States Army]]'s Training Manual 5-601 covers "SCADA Systems for [[C4ISTAR|C4ISR]] Facilities"]]

SCADA systems have evolved through four generations as follows:<ref>{{cite web |url=https://scadahacker.com/library/Documents/ICS_Basics/SCADA%20Basics%20-%20NCS%20TIB%2004-1.pdf |title=Supervisory Control and Data Acquisition (SCADA) Systems |date=October 2004 |publisher=NATIONAL COMMUNICATIONS SYSTEM |author=OFFICE OF THE MANAGER NATIONAL COMMUNICATIONS SYSTEM |access-date=14 July 2015 |archive-url=https://web.archive.org/web/20150714225002/https://scadahacker.com/library/Documents/ICS_Basics/SCADA%20Basics%20-%20NCS%20TIB%2004-1.pdf |archive-date=14 July 2015 |url-status=dead }}</ref><ref>{{cite web |url=http://www.engineersgarage.com/articles/scada-systems |title=SCADA Systems april 2014}}</ref><ref>{{cite web |url=http://scadahistory.com/ |title=A Brief History of SCADA/EMS (2015) |author=J. Russel |url-status=dead |archive-url=https://web.archive.org/web/20150811051350/http://scadahistory.com/ |archive-date=11 August 2015 |df=dmy-all }}</ref><ref>Abbas, H.A. (2014). Future SCADA challenges and the promising solution: the agent-based SCADA. IJCIS, 10, 307-333.</ref>

Early SCADA system computing was done by large [[minicomputers]]. Common network services did not exist at the time SCADA was developed. Thus SCADA systems were independent systems with no connectivity to other systems. The communication protocols used were strictly proprietary at that time. The first-generation SCADA system redundancy was achieved using a back-up mainframe system connected to all the [[Remote Terminal Unit]] sites and was used in the event of failure of the primary mainframe system.<ref name="Proquest-text">{{cite book|title=Security Hardened Remote Terminal Units for SCADA Networks|url=https://books.google.com/books?id=d5O5N1vjbQgC&pg=PA12|year=2008|isbn=978-0-549-54831-7|pages=12–}}</ref>  Some first generation SCADA systems were developed as "turn key" operations that ran on minicomputers such as the [[PDP-11]] series.<ref>{{Cite web|last=UJVAROSI |first=Alexandru |date=2 November 2016 |title=EVOLUTION OF SCADA SYSTEMS |url=http://webbut.unitbv.ro/BU2015/Series%20I/2016/BULETIN%20I%20PDF/Ujvarosi_Al.pdf |url-status=dead |archive-url=https://web.archive.org/web/20211028142517/https://webbut.unitbv.ro/BU2015/Series%20I/2016/BULETIN%20I%20PDF/Ujvarosi_Al.pdf |archive-date=2021-10-28}}</ref>

SCADA information and command processing were distributed across multiple stations which were connected through a LAN. Information was shared in near real time. Each station was responsible for a particular task, which reduced the cost as compared to First Generation SCADA. The network protocols used were still not standardized. Since these protocols were proprietary, very few people beyond the developers knew enough to determine how secure a SCADA installation was. Security of the SCADA installation was usually overlooked.

Similar to a distributed architecture, any complex SCADA can be reduced to the simplest components and connected through communication protocols. In the case of a networked design, the system may be spread across more than one LAN network called a [[Process control network|process control network (PCN)]] and separated geographically. Several distributed architecture SCADAs running in parallel, with a single supervisor and historian, could be considered a network architecture. This allows for a more cost-effective solution in very large scale systems.

The growth of the internet has led SCADA systems to implement web technologies allowing users to view data, exchange information and control processes from anywhere in the world through web SOCKET connection.<ref>{{citation |title=R. Fan, L. Cheded and O. Toker, "Internet-based SCADA: a new approach using Java and XML," in Computing & Control Engineering Journal, vol. 16, no. 5, pp. 22-26, Oct.-Nov. 2005 |s2cid=62150803 }}</ref><ref>{{citation |title=R. J. Robles and T. H. Kim, "Architecture for SCADA with Mobile Remote Components", Proceedings of the 12th WSEAS International Conference on Automatic Control, Modelling & Simulation |date=29 May 2010 |pages=346–350 |url=https://dl.acm.org/doi/10.5555/1844174.1844240 |via=dl.acm.org |doi= |isbn=
978-954-92600-1-4}}</ref> The early 2000s saw the proliferation of Web SCADA systems.<ref name="web SCADA">{{citation |title=Abbas, H.A. and Mohamed, A.M. (2011) 'Review on the design of web based SCADA systems based on OPC DA protocol', International Journal of Computer Networks, February, Vol. 2, No. 6, pp.266–277, Malaysia |s2cid=18743659 }}</ref><ref>{{citation |title=Qiu B, Gooi HB. Web-based scada display systems (wsds) for access via internet. Power Systems, IEEE Transactions on 2000;15(2):681–686 |doi=10.1109/59.867159 |url=https://ieeexplore.ieee.org/document/867159 |via=ieeexplore.ieee.org|url-access=subscription }}</ref><ref>{{citation |title=Li D, Serizawa Y, Kiuchi M. Concept design for a web-based supervisory control and data-acquisition (scada) system. In: Transmission and Distribution Conference and Exhibition 2002: Asia Pacific. IEEE/PES; Vol. 1; p. 32–36 |doi=10.1109/TDC.2002.1178256 |s2cid=113523881 }}</ref> Web SCADA systems use web browsers such as Google Chrome and Mozilla Firefox as the graphical user interface (GUI) for the operators HMI.<ref>{{citation |title=Kovaliuk, D. O., Huza, K. M., & Kovaliuk, O. O. (2018). Development of SCADA System based on Web Technologies. International Journal of Information Engineering and Electronic Business (IJIEEB), 10(2), 25-32 |doi=10.5815/IJIEEB.2018.02.04 |s2cid=65360293 |doi-access=free }}</ref><ref name="web SCADA"/> This simplifies the client side installation and enables users to access the system from various platforms with web browsers such as servers, personal computers, laptops, tablets and mobile phones.<ref name="web SCADA"/><ref>{{citation |title=J. M. Lynch, "An Internet Based SCADA System", BSc Project Report, University of Southern Queensland, Queensland, Oct. 2005 |s2cid=109628360 }}</ref>