Traditionally SCADA communications have been Point-to-Multipoint serial communications over lease line or private radio systems (i.e. RS232, RS485, BEL202). With the advent of Internet Protocol (IP), IP Technology has seen increased use in SCADA applications.
Internet SCADA or Web-based SCADA makes use of IP technology in SCADA and can range from IP tunnels over satellite, frame relay, fiber, radio to link SCADA networks to central office to individually IP addressed instruments or use IP enabled devices or web-based SCADA Host MMI Software such as our NetSCADA.
IP TECHNOLOGIES FOR INTERNET SCADA
The following is a list of common IP technologies and a summary how they are apply to Internet SCADA systems.
Cellular Modems
Cellular modems enable wireless connectivity to a TCP/IP network. Cellular modems allow IP hosts to connectivity remote site SCADA & Telemetry equipment like RTU’s, PLC’s, dataloggers, flowcomputers & VFD’s.
Wireless Ethernet Radios
Increasingly, PLC’s and RTU’s are incorporating Ethernet interfaces. Wireless Ethernet Radio Links enable IP connection to these newer Ethernet-enabled devices. Wireless Ethernet can also be used to bridge remote SCADA networks together.
Tunneling over the Internet
Where secure SCADA communications are required over the public internet, VPN’s (Virtual Private Networks) can provide the level of needed security. A VPN is a private network created on top of the public internet. Clients use VPN to create a secure and private “tunnel” to the Server with the security being provided by the VPN’s user authentication and data encryption.
Serial to Ethernet Gateways / Terminal Server
Ethernet to Serial Gateways enable serial devices to communicate over TCP/IP networks or allow SCADA hosts to reach Serial devices over IP networks.
Cloud Servers
Servers can be rented from server providers such Google and Amagon allowing implementation of highly reliable servers connected by high speed internet links. Cloud services offer 24/7 service, redundancy, and uptime that is hard to achieve at comparable costs with private servers.
Web Servers
Web Server technology has enabled web browser technology to be used to access MMI screens for PLC,RTU, controllers and to view SCADA systems. Newer PLC’s and RTU’s frequently incorporate web servers that allow diagnostics and monitoring via user web browsers.
Web-enabled SCADA hosts enable users to remotely monitor, control remote sites via a web browser. Web access may augment traditional thick client access to SCADA systems. Hosted SCADA services allow users to monitor or control their remote equipment with access using a standard web browser and logging onto a secure website.
Email for Alarms or Reports
Internet SCADA systems use emails for alarming or reporting. When an alarm occurs, alarm emails are sent out to email-enabled cell phones and PCs.
FTP for File Transfer
FTP stands for File Transfer Protocol. This can in Internet SCADA to transfer files between Host and Remote sites for Data logging, Reporting or Configuration.
Telnet for Remote Configuration
Telnet is an IP-based remote access utility used in Internet SCADA to remotely configure RTU, PLC and other SCADA equipment.
TCP, UDP for Data Communication
TCP is a Internet protocol used to ensure reliable End-to-End communication. UDP is a much simpler Internet protocol which does not check for End-to-End communication reliability. Consequently, UDP is much faster but is not as reliable.
The choice of which to use is dependent on the SCADA application. TCP is typically used for applications like alarming where the information is critical and cannot be lost. UDP is used when throughput is more important than reliability.
IP Protocols
IP protocols enables data communications to be routed over the Internet. The most common protocol used is TCP/IP which results in reliable routable End-to-End messaging.
Ping
This IP utility is used to check if a remote SCADA device is accessible. Like a normal PC, the remote SCADA device must respond with a Ping reply if it sees a Ping message destined for it. If there is a timeout instead, this indicates a problem exists with the device or the network path.
SCADA ASP
Cloud based SCADA Application Server Provider provide Cloud based SCADA hosting & Remote Monitoring.
IoT – Internet of Things
source - scadalink