LON

What is LON (LonWorks)?

LON (Local Operating Network), better known by its platform name LonWorks, is a distributed communication protocol that lets sensors, actuators and controllers in building automation, infrastructure and industry work together directly, without a central master. The protocol, originally called LonTalk, was developed by the American company Echelon Corporation and is defined in the international standard ISO/IEC 14908. In the 1990s and 2000s LON was one of the dominant networks for HVAC, lighting and sun shading, and it still runs in countless offices, hospitals and public buildings. For anyone managing a building management system today, LON is therefore mainly a question of maintenance, security and migration.

🧠 How did LON originate and who maintains it now?

Echelon was founded in Palo Alto in February 1988 by Mike Markkula, one of Apple’s first investors, and launched the LonWorks platform in 1990. The idea was to give every device its own small computer, the Neuron chip, containing both the protocol stack and the application. By around 2010 an estimated 90 million LonWorks devices had been installed. Echelon also supplied the network technology behind Italy’s smart meter programme, with more than 27 million connected electricity meters.

Ownership changed several times after that:

For installation owners this means that the suppliers of tools, gateways and chips have shifted. If you keep a LON installation running, make the availability of parts and software an explicit part of your lifecycle management.

🔧 How does the LON protocol work technically?

LonTalk covers all seven layers of the OSI model. Its core consists of a few concepts:

• Distributed intelligence - every node contains its own logic and memory; a thermostat drives a valve actuator itself, without involving a central controller.
• Network variables - devices exchange data through network variables. During commissioning an output (for example a temperature) is linked (bound) to an input on another device. From then on the sender automatically transmits an update on every change, peer-to-peer.
• SNVTs and functional profiles - LonMark International maintains the list of Standard Network Variable Types. SNVT_temp, for instance, is a 2-byte value with a resolution of 0.1 °C. These standard types allow devices from different manufacturers to understand each other.
• Hierarchical addressing - a logical address consists of domain, subnet and node. A domain holds up to 255 subnets of 127 nodes, so 32,385 devices. Devices in different domains do not communicate directly.
• Reliable delivery - the protocol supports acknowledged messages with retries and detects duplicate messages.

Which physical media does LON use?

The free topology of FT-10 was a major selling point: installers can lay out star, ring and mixed forms with a single terminator. In a bus layout terminated at both ends, stubs may be at most 3 metres long. Exact lengths depend on the cable type, so always check the transceiver specification.

🏢 Where is LON used?

In buildings LON often works alongside other standards. BACnet even lists LonTalk as one of its data link layers, and energy meters are regularly read out via M-Bus or Modbus while room control runs on LON. In process plants the role of LON is smaller; there process automation relies mostly on fieldbuses such as Profibus.

🔄 How does LON compare with BACnet, KNX and Modbus?

Many organisations migrate from LON to BACnet/IP, often step by step using gateways so that field devices can stay in place until they are due for replacement.

🔐 How do you secure a LON network?

From a security perspective, classic LonTalk offers authentication but no encryption. A sender can have messages authenticated through a challenge-response based on a shared 48-bit key, so a receiver only executes commands from known devices. Message content, however, travels in clear text, and many installations do not use authentication at all. An attacker with access to the bus or the LON/IP segment can therefore read network variables and often overwrite them or carry out a replay attack.

Practical measures following the defence in depth principle:

1. Inventory all LON devices, routers and IP gateways in an asset inventory, including firmware and the management software in use.
2. Segment LON/IP traffic into its own VLAN and zone, separated from office IT, in line with the zones and conduits model from IEC 62443.
3. Filter traffic on UDP 1628/1629 and the management ports of servers with a firewall; allow only known configuration servers and SCADA or BMS servers.
4. Restrict remote access to a secured VPN route with multi-factor authentication, never to a gateway that is directly reachable from the internet.
5. Monitor the network passively for new devices and unusual write actions.

For organisations within the scope of NIS2 and the Dutch Cybersecurity Act, such as hospitals and drinking water companies, building automation belongs in the risk assessment. A failed climate control system in an operating theatre or data centre is as much a continuity risk as a failure in process control.

🏭 How do you approach LON management and migration in practice?

A phased approach avoids replacing a working installation unnecessarily:

• Step 1: restore documentation - many LON networks were originally set up with an LNS database in LonMaker or its successor, the IzoT Commissioning Tool. Without that database, binding and replacing devices is difficult. Safeguard the database and the licences.
• Step 2: assess remaining life - determine the age, availability and criticality of each device. Treat the installation as a legacy system with an explicit replacement plan.
• Step 3: expose data through gateways - connect LON data via a gateway to BACnet/IP, OPC UA or MQTT, so that new analytics applications do not need direct access to the bus.
• Step 4: replace at natural moments - replace controllers floor by floor or per installation section during renovations.

The European Energy Performance of Buildings Directive (EPBD) requires building automation and control systems in larger non-residential buildings with an effective rated output above 290 kW for heating or air conditioning. In the Netherlands this obligation has applied since 1 January 2026, and the recast EPBD lowers the threshold to 70 kW, which the Netherlands applies from 2030. That increases the pressure to open up old networks such as LON for energy monitoring.

❓ Frequently asked questions

Is LON still used?

Yes, LON is still widely used in existing commercial buildings and infrastructure, although new construction usually opts for BACnet or KNX. The chips and tools remain available through Renesas and EnOcean, but the market is shrinking.

What is the difference between LON, LonWorks and LonTalk?

LON (Local Operating Network) is the general name of the network, LonWorks is Echelon’s platform name and LonTalk is the actual communication protocol. In the standard, LonTalk is called the Control Network Protocol and is defined in ISO/IEC 14908-1.

Is LON secure?

In its classic form LON offers only authentication with a shared 48-bit key and no encryption. A LON network is therefore only secure when it is physically and logically shielded with segmentation, firewalls and controlled remote access.

How many devices fit on a LON segment?

An FT-10 segment with standard transceivers supports up to 64 devices, and 128 with link-power transceivers. With routers a LON domain can grow to 32,385 devices, divided over 255 subnets of 127 nodes each.

Can LON communicate over IP?

Yes, LON messages can be tunnelled over IP according to ISO/IEC 14908-4 (ANSI/CEA-852), using UDP ports 1628 and 1629. This lets separate LON segments and a building management system connect over an ordinary Ethernet network.

Should I replace my LON installation with BACnet?

A working LON installation does not need to be replaced immediately. It is wise, however, to draw up a migration plan, expose the LON data through a gateway and replace devices with BACnet or KNX equipment during renovations or at end of life.

📌 In summary

LON (LonWorks) is a distributed, peer-to-peer communication protocol based on ISO/IEC 14908 that lets devices in buildings and infrastructure work together without a central master.

LON shaped building automation for decades, with the Neuron chip, network variables and free topology as its hallmarks. Today it runs mainly in existing installations alongside BACnet, KNX and M-Bus. Because the classic protocol has no encryption, LON calls for network segmentation, careful management of gateways and a well-considered migration plan.