White Paper
The Top 6 Reasons to Upgrade to DNP3 Communications
Philip Aubin, PEng Control Microsystems
The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
Summary The DNP3 communications protocol provides many advantages over conventional protocols. This white paper highlights the key reasons to consider applying DNP3 for communications with remote devices. The versatility of DNP3 has caused its application to expand into a variety of industries that require remote connection. These include: •
Upstream Oil & Gas operations
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Water & Wastewater Management
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Transportation
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Electric Power
This paper shows some of the major reasons to upgrade your communications to DNP3.
Introduction: What is DNP3? Overview DNP3, or “Distributed Network Protocol”, is a protocol that was developed to allow for flexible, secure communications between devices. DNP3 excels in telemetry applications, where requirements call for reliable communication with remote devices. These devices might include: •
RTUs - Remote Terminal Units
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SCADA Systems – Supervisory Control And Data Acquisition Systems
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IEDs – Intelligent Electronic Devices
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HMIs – Human-Machine Interfaces
A Layered Protocol DNP3 is a layered protocol. Starting with the low-level physical communications, each layer adds functionality. This sort of layered model allows DNP3 to be flexible, reliable, and standardized. Standard requirements for each layer ensure that various vendors will implement DNP3 protocols that can communicate with each other. The functions and features of the DNP3 layers lead directly to the benefits explained in this white paper.
Earlier Protocols MODBUS was created by Modicon as a proprietary standard in the 1970’s. It was originally used over serial links, and later adapted to Ethernet. It allows serial communications, using a master/slave polling approach. Only the simplest The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
of data types are allowed, such as Booleans and 16-bit counters. Because of these limitations, vendors created non-standard, non-compatible extensions. Unfortunately, these greatly limit interoperability. PROFIBUS, developed in the 1980’s, allowed communication between instrumentation and later, slow data transmission between smart devices. Its major strength is in explosion-hazardous areas.
Origins of DNP3 DNP3 was developed in the 1990’s, originally to support electrical distribution equipment. The needs of that business drove many features and functions of DNP3, such as: •
Object-oriented data, including support for meta-data
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Communication over long distances
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Ability to use complex data
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Higher levels of security
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Interoperability with a variety of devices
DNP3 was quickly adopted as a standard, and a User Group was formed in 1993. The protocol proved useful in other industries, as well, and has been adopted by the Water industry, Oil & Gas, Mining, Irrigation, and Transportation. DNP3 was also designed as an extensible protocol. This means that the protocol continues to grow, allowing for new features to be created, without impacting the underlying security and reliable communications capability.
The Top 6 Reasons to Upgrade to DNP3 #1 - Standardization & Interoperability DNP3 is an open, standards-based protocol. Various types of equipment, from a variety of vendors, can communicate with each other via DNP3. All DNP3 devices handle and present data in the same way. They use the same data types, and a very organized data structure. Furthermore, DNP3 is incorporated into industry-wide standards, such as the IEEE Standard 1379 for electrical substation communications. Today, you can find DNP3-compatible devices ranging from the simplest of field devices to powerful controllers and SCADA systems. This standardization means that you can work with existing installations, and plan for future expansions, without needing to worry about compatibility issues. This vendor
The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
independence gives you great flexibility in designing current and future architectures.
#2 – Flexibility - Many Forms of Communication DNP3 allows devices to communicate in many different ways. Far beyond oldstyle polling or token-passing methods, DNP3 allows the designer to choose the communications method that best suits the need of the application. Examples of these communications methods are shown in this section.
Change-Based Event Reporting DNP3 supports change-based event reporting. This feature allows communications load to be kept at a minimum, except when it is really needed. For example, abnormal situation reports can be triggered based on live data at the RTU. When an issue occurs, then a detailed report can be sent. Minimizing the communications load is particularly important in situations where slower communications links are in place. Change-based reporting may allow users to add features, while extending the life of older networks. Figure 1 illustrates how an event, such as a pressure spike, can trigger automatic reports for problem-solving. By capturing these bursts of high-speed data on demand, problem-solving capabilities are greatly increased, without major impacts to communications load.
Figure 1: Event-Based Reporting
The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
Time-Stamping & Meta-Data Using DNP3, data can be time-stamped. With time-stamped data, the user can determine sequence of events, and start/stop times. System real-time clocks can be synchronized using DNP3, or externally using GPS time for greater timestamp accuracy. Time-stamped events ensure that interesting process changes are captured and that there is no lost data if device communications fail. This timestamped data can be extremely useful in troubleshooting abnormal events, such as loss of power or loss of supply pressure. Meta-data, sometimes called “data attributes”, carries meaningful information about the data. For example, DNP3 can be used to report not only a value, but also the quality of the data. Meta-data can include data format description, time stamps, alarm conditions, or data quality.
Unsolicited Reporting When a remote event requires immediate action, an “unsolicited report” can be triggered immediately, from the remote device. The data is transferred immediately, allowing for fast automated response from upstream or downstream operations. This capability can be used, for example, to isolate upset conditions and prevent them from spreading.
Your Choice of Media DNP3 supports many types of physical media, including data radio, leased line, dial-up, Ethernet, and fiber optics. This means that you may be able to upgrade communications without replacing the physical media. This is a great cost and time-saving advantage.
Historic Recording Centralized data historians have become a de-facto standard. Historians can provide great insight into the process being monitored or controller. With systems using DNP3, each device can feed its data to the data historian quickly and efficiently, without custom programming or scripting. This simple configuration with DNP3 greatly reduces the setup and configuration time needed for data historians.
#3 - Security DNP3 offers greatly improved security over earlier protocols. Two mechanisms are available for securing DNP3 communications. These are encryption and authentication.
Security via Encryption To protect data during transmission, a security key is used. The raw data and the security key are combined to make an The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
encrypted message. The encrypted (unreadable) message can only be read by a device with the security key. Encryption may be desired when there is valuable data being transmitted. For example, usage information or metering information may be protected in this way, to make the data unreadable and to prevent tampering with the data along the way.
Security via Authentication Authentication is used to prevent unauthorized users from making changes. Using this technique, critical messages may be challenged by an RTU or a master. The Request-Challenge-Response sequence must be successfully completed, or the message will not be accepted. Because public utilities are a target for terrorist activities, it is important to consider the use of authentication in their design. With older protocols, security can be easily bypassed simply by connecting a new master to the network. DNP3 helps to keep your data and, more importantly, your process safe from unauthorized access.
#4 - Strong Support Organization The DNP3 Users Group is an active community of vendors and users of the DNP3 protocol. The group maintains an active website at http://www.dnp3.org There are hundreds of members, from both the vendor and user community. This healthy mix of users and vendors increases the level of communication, and allows for more rapid development and acceptance of new extensions to the DNP3 protocol. It also ensures that developers are working toward enhancements that are meaningful to the end-users. For example, the Users Group recently adjusted plans to work toward the emerging IEC 61850 standard, which allows DNP3 to communicate device profile meta-data. This can improve the reporting of device status, and simplify maintenance planning for field devices. The DNP Users group hosts an annual meeting in the first quarter of each year. This is an open volunteer group, welcoming participation by all. The major objectives of the User Group are: •
•
to maintain control of the protocol and determine the direction in which the protocol will migrate to review and add new features, functions and enhancements to the protocol
The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
• • • •
to encourage vendors and utilities to adopt the DNP3 protocol as a "standard" to define recommended protocol subsets to develop test procedures and verification programs to support implementor interaction and information exchange
With such a broad base of non-proprietary supporters, DNP3 is assured of maintenance and continued growth.
#5 - Room to Grow Flexibility to Add New Functions The DNP3 protocol is flexible and extensible. Because of its structured support for complex data, DNP3 can be adapted to some sophisticated applications. This goes far beyond the basic data-passing of MODBUS. With DNP3, you can communicate: •
Files
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Reports
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Program Changes
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High Integrity Controls
DNP3 enables a great deal of flexibility, within a secure and reliable framework.
Industry-Specific Layers DNP3 is not a static, unchanging protocol. Rather, DNP3 allows for extensions to the protocol. Users can define complete data structures, to pass industryspecific information, in complete context. This simplifies development of reapplicable displays, controls, applications, and reporting. A notable example of the industryspecific layers is the creation of the U.K. Water Industry Telemetry Standards, or WITS. This extension of DNP3 standardizes water industry data for: •
Asset Management
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Incremental Configuration
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Device Status
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Logging
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Alarming
Case Study: DNP3 Integrates Large Water System In a large West-coast city, DNP3 improved communications between wells and water distribution. Over 500 controllers, RTUs and devices now coordinate their activities directly. The utility engineer on the job says “The DNP3 standard gives us assurance that the process data is accurate, and we can now bill our customers with certainty.”
For more information on this effort, visit the WITS initiative web site at http://www.ukwits.org The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
#6 DNP3 Saves Time and Money The biggest reason to upgrade to DNP3 is that it saves time and money. With DNP3 you can perform not only data communications, but also diagnosis, fault finding, and configuration changes, remotely. This means fewer costly, time-consuming trips to the field.
Re-Use Existing Physical Media As mentioned above, DNP3 supports many types of physical media. In many cases, you can upgrade to DNP3 without replacing the physical media. On a remote communications project, routing of physical wiring can be one of the greatest costs. So re-using existing media can keep project costs down.
Remote Configuration Changes DNP3 supports remote configuration changes. This can save a huge amount of time and money. Instead of climbing in the truck for a day of service visits to all the RTUs, a DNP3 technician or engineer can sit at a desk in the home office, and upgrade configurations all over the network.
This saves valuable time, and allows a single worker to accomplish major changes in a single day, rather than phasing in changes over weeks. There are direct savings in fuel and labor. And there are indirect savings, from the ability to roll out improvements faster than ever before.
The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
Conclusions The DNP3 protocol offers major advantages over previous protocols. include:
These
1. Standardization and Interoperability 2. Flexible Communications with Many Options 3. Security 4. Strong Support Organization 5. Room to Grow 6. Saves Time and Money
Recommendations 1. To achieve the benefits listed in this paper, upgrade communications to the DNP3 protocol. 2. Lay out a specific plan for migration. Start small or start with wholesale replacement. In either case, you should lay out a full plan for migration. 3. Don’t simply replace the old communications devices with new ones. Consider the value that can be achieved by taking advantage of DNP3’s features. Be sure to consider: a. Remote configuration b. Standardized data structures c. Improved reporting d. Unsolicited event data e. Adding security features 4. Join the DNP3 Users Group, to network with other users and to meet experienced suppliers.
The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
About Control Microsystems Control Microsystems is a wholly owned subsidiary of the SCADA Group, one of the world's largest private SCADA products and services companies. Focused on remote monitoring and control applications within utility sectors, Control Microsystems and the SCADA Group bring over 25 years of experience to the market. As the products arm, Control Microsystems is a leading supplier of Supervisory Control and Data Acquisition (SCADA) hardware and software products with operations in the US, Canada, the Netherlands and Asia. At Control Microsystems, products are developed with the sole purpose of being tools for customers to create practical solutions to challenging problems. Every product that makes it through Control Microsystems’ rigid productization process is guaranteed to be an effective part of any SCADA installation, providing ease of use with performance and reliability. Whether it is our renowned SCADAPackTM Remote Terminal Units (RTUs), a SCADASenseTM Electronic Flow Measurement (EFM) product, or the state-of-the-art ClearSCADATM SCADA Host platform, Control Microsystems’ product line enables users to evolve their own creative ideas faster and more effectively than any other SCADA products provider in the market. For more information, visit http://www.controlmicrosystems.com
About Philip Aubin Philip Aubin has 23 years engineering experience with process control and wide area SCADA systems. Philip started SCADA engineering in the water sector in Australia with automation systems on water and wastewater telemetry and control systems, moving in to development of Wide Area SCADA RTU hardware and VAX / VMS master station software. He has been working in the private sector for over 12 years being responsible for outstation development based on open system protocols. Philip has been involved with Standards groups developing open protocols and joined the DNP User Group Technical Committee in 1998, where he is still active. He is currently the Director of Technology, manages the embedded firmware development teams for Control Microsystems in Canada, and is involved in SCADA RTU product architecture design with SCADAgroup companies across North America, Australia and the United Kingdom..
The Top 6 Reasons to Upgrade to DNP3 Communications November 2008
References 1. IEEE Web Site. Find a standard at http://www.ieee.org/web/standards/home/find.html 2. DNP3 Users Group Web Site at http://www.dnp3.org 3. The WITS initiative, http://www.ukwits.org
Glossary Item
Definition
DNP3
Distributed Network Protocol, version 3
HMI
Human-Machine Interface
IED
Intelligent Electronic Device
IEEE
Institute of Electrical and Electronics Engineers
Ms
milli-seconds
MODBUS MODBUS is a communications protocol. RTU
Remote Terminal Unit
SCADA
Supervisory Control And Data Acquisition
WITS
U.K. Water Industry Telemetry Standards
The Top 6 Reasons to Upgrade to DNP3 Communications November 2008