Editing SCADA (section)

== Communication infrastructure and methods ==

SCADA systems have traditionally used combinations of radio and direct wired connections, although [[Synchronous optical networking|SONET/SDH]] is also frequently used for large systems such as railways and power stations. The remote management or monitoring function of a SCADA system is often referred to as [[telemetry]]. Some users want SCADA data to travel over their pre-established corporate networks or to share the network with other applications. The legacy of the early low-bandwidth protocols remains, though.

SCADA protocols are designed to be very compact. Many are designed to send information only when the master station polls the RTU. Typical legacy SCADA protocols include [[Modbus]] RTU, [[RP-570]], [[Profibus]] and Conitel. These communication protocols, with the exception of Modbus (Modbus has been made open by Schneider Electric), are all SCADA-vendor specific but are widely adopted and used. Standard protocols are [[IEC 60870-5|IEC 60870-5-101 or 104]], [[IEC 61850]] and [[DNP3]]. These communication protocols are standardized and recognized by all major SCADA vendors. Many of these protocols now contain extensions to operate over [[TCP/IP]]. Although the use of conventional networking specifications, such as [[TCP/IP]], blurs the line between traditional and industrial networking, they each fulfill fundamentally differing requirements.<ref name=GallowayIntro>{{cite journal|title=Introduction to Industrial Control Networks|journal=IEEE Communications Surveys and Tutorials|year=2012|url=http://www.rfidblog.org.uk/Preprint-GallowayHancke-IndustrialControlSurvey.pdf}}</ref> [[Network simulation]] can be used in conjunction with SCADA simulators to perform various 'what-if' analyses.

With increasing security demands (such as [[North American Electric Reliability Corporation]] (NERC) and [[critical infrastructure protection]] (CIP) in the US), there is increasing use of satellite-based communication. This has the key advantages that the infrastructure can be self-contained (not using circuits from the public telephone system), can have built-in encryption, and can be engineered to the availability and reliability required by the SCADA system operator.  Earlier experiences using consumer-grade [[Very-small-aperture terminal|VSAT]] were poor. Modern carrier-class systems provide the quality of service required for SCADA.<ref name=berganELP>{{cite journal|last=Bergan|first=Christian|title=Demystifying Satellite for the Smart Grid: Four Common Misconceptions|journal=Electric Light & Power|date=August 2011|volume=16|series=Utility Automation & Engineering T&D|issue=8|url=http://www.elp.com/index/display/article-display/5666163079/articles/utility-automation-engineering-td/volume-16/issue-8/features/demystifying-satellite-for-the-smart-grid-four-common-misconceptions.html|access-date=2 May 2012|at=Four|publisher=PennWell|location=Tulsa, OK|quote=satellite is a cost-effective and secure solution that can provide backup communications and easily support core smart grid applications like SCADA, telemetry, AMI backhaul and distribution automation|archive-url=https://web.archive.org/web/20120331210553/http://www.elp.com/index/display/article-display/5666163079/articles/utility-automation-engineering-td/volume-16/issue-8/features/demystifying-satellite-for-the-smart-grid-four-common-misconceptions.html|archive-date=31 March 2012|url-status=dead}}</ref>

RTUs and other automatic controller devices were developed before the advent of industry wide standards for interoperability. The result is that developers and their management created a multitude of control protocols. Among the larger vendors, there was also the incentive to create their own protocol to "lock in" their customer base. A [[list of automation protocols]] is compiled here.

An example of efforts by vendor groups to standardize automation protocols is the OPC-UA (formerly "OLE for process control" now [[OPC Unified Architecture|Open Platform Communications Unified Architecture]]).