The LonTalk/IP Protocol is an IP protocol that provides comprehensive control services over standard IP. The upper layers of the LonTalk/IP Protocol are called the LonTalk/IP control services, and the lower layers are called the LonTalk/IP transport services. The LonTalk/IP control services are defined by Layers 4 through 7 of the ISO/IEC 14908-1 Control Network Protocol (CNP). The transport services are channel-type dependent. For native IP channels such as Ethernet or Wi-Fi, the transport services are defined by the RFC-791/793 TCP/IP protocol. For ISO/IEC 14908-1 native LON channels such as FT, the Layer 2 through 3 transport services are defined by the ISO/IEC 14908-1 protocol standard.
The LonTalk/IP Protocol provides services required for control applications spanning a range of industries and requirements. The LonTalk/IP Protocol provides a robust communications solution that meets the needs of a broad range of control applications today, and will continue to meet the needs of evolving control applications in the future.
The following list summarizes the key features of the LonTalk/IP Protocol:
IP addressing to every device. Every device in a LonTalk/IP network has an IP address, including classic LON devices behind an IzoT Router. The IzoT Router automatically translates IP addresses on the LAN channel to compressed IP address on the LON channel, so that all devices in a LonTalk/IP network, including classic LON devices, can be reached with an IP addressed message. The mapping of LAN to LON IP addresses is described in LonTalk/IP Network Addresses.
Efficient delivery of small messages. A typical control message may consist of 1 to 8 bytes of data, though larger and smaller messages are supported. A LonTalk/IP device can transmit a message with as few as 9 bytes of protocol overhead. Messages may be delivered to a single device or to any group of devices.
Reliable delivery of messages. Even though an individual message may consist of a few bytes, the reliable delivery of every message may be critical to the application. The LonTalk/IP Protocol includes reliable message delivery services that retry a message transmission when a communication failure occurs and informs the sending application if an unrecoverable failure occurs. Resynchronization is immediate if a previously unreachable destination becomes reachable within the retry interval.
Duplicate message detection. Some types of control messages must not be delivered multiple times. For example, if a monitoring application that is counting events were to receive duplicate messages, the event count would become incorrect. The LonTalk/IP Protocol prevents duplicate messages from being passed to the receiving application.
Wired, wireless, and power line communications media. Many control systems require multiple communications media to minimize total system cost. Twisted-pair or Cat 5e cable provides the best performance and is a good solution where it is practical to install the cable. Communications over 802.15.4 RF, Wi-Fi, or existing power lines provides the lowest installation cost. The LonTalk/IP Protocol is media independent so that all these media, and more, are supported. In addition, the LonTalk/IP Protocol also supports multi-media routers so that devices on different channels with different channel types can interoperate. A hierarchical addressing scheme is used to support low-cost, easy-to-install, and easy-to-maintain routers.
Low device cost. A control device may be as simple as a sensor for a single point such as a limit switch or a temperature sensor. With the capability to put control in every point, it is important that the protocol not be too demanding in terms of memory and computing resources at each device. The LonTalk/IP Protocol minimizes the code size of protocol firmware and also minimizes RAM requirements for buffer storage. For example, the complete implementation of the LonTalk/IP Protocol running on a Neuron core requires less than 10 Kbytes of code and less than 1 Kbyte of RAM.
Low installation and maintenance cost. Low device cost does not lead to low system cost unless devices are easily installed in networks, networks are easily modified, and repairing networks after a failure is simple. The LonTalk/IP Protocol includes complete support for installation and maintenance so that simple devices in simple networks can manage their own network installation, low-cost installation tools can be used to install and maintain more complex networks, and low-cost diagnostic tools can be used to diagnose failures in any type of network.
Efficient use of channel bandwidth. To keep system costs down, many devices must be able to efficiently share a single communications channel. The LonTalk/IP Protocol uses innovative media access technologies to provide the most efficient use of the communications channels, even under conditions of high loading.
Interoperable systems. Multiple systems may need to interoperate to provide additional benefits to the end users. For example, a fire alarm system may interoperate with an elevator control system to keep elevators away from burning floors and may interoperate with an emergency exit lighting system to illuminate exit signs. In addition to supporting interoperability between devices, the LonTalk/IP Protocol also allows devices from different vendors to be installed using a common set of installation strategies and tools.
Separation of systems. Multiple systems that should not interoperate may share a common communication medium, especially in the case of open media such as power line. The LonTalk/IP Protocol allows these systems to operate independently without mutual interference by isolating devices that communicate with each other into domains. A domain is a logical collection of devices that communicate with each other. Devices in different domains cannot communicate directly with each other—they must communicate through a common gateway.
Prevent tampering. Because control systems do more than just move data, it should not be possible for an unauthorized user to inject commands into the network. The LonTalk/IP Protocol includes an authentication protocol that prevents tampering by unauthorized users.