In a recent article, we looked at just how valuable Ethernet connectivity has become to the marine electronics world. In this article, we delve a layer deeper, exploring the real power behind Ethernet using IEC 61162-450 and 460, for sending data between multiple talkers and listeners over Ethernet; how tag blocks work, and the ability to mitigate cybersecurity threats with the 460 standard.
Our development team at Actisense are already working to embed these into our PRO Range buffers and multiplexers – with delivery expected around Q2 in 2026.
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What is IEC 61162-450?
IEC 61162-450 is an international standard developed by the International Electrotechnical Commission (IEC) which governs maritime navigation and radiocommunication equipment. It defines the interface requirements and testing methods for high-speed digital communication between shipboard systems using Ethernet networks.
This standard is part of the broader IEC 61162 series, which addresses digital interfaces for maritime electronics. IEC 61162-450 specifically focuses on multiple talkers and multiple listeners in an Ethernet environment, enabling efficient and interoperable data exchange.
Its objectives include supporting the distribution of data formatted according to IEC 61162-1, 2 and 3, ensuring interoperability among equipment from different manufacturers, and enabling high-speed, reliable data transmission throughout maritime networks.
Core Features and Specifications
Ethernet-Based Network
IEC 61162-450 defines a network where any listener can receive messages from any sender. This setup supports:
- Communication for position fixes, measurements, vessel info, etc…
- Transmission of safety and voyage-critical data, such as radar data, to Voyage Data Recorders (VDRs)
Protocol Support
The standard supports:
- IEC 61162-1 sentences (NMEA 0183)
- IEC 61162-2 sentences (NMEA 0183 HS)
- IEC 61162-3 PGN messages (NMEA 2000)
OSI (Open System Interconnection) Layer Restrictions
The network is limited to OSI Layer 1 and Layer 2 devices, meaning it includes only physical and data link layer components (e.g., switches, cables). Higher-layer protocols are not specified, ensuring simplicity and reliability.
IEC 61162-450 defines equipment interface requirements to ensure reliable and safe operation within maritime Ethernet networks. It utilises network traffic filtering to prevent overload and allows compatibility with other protocols if they meet the standard’s criteria.
Additionally, by standardising the transmission of IEC 61162-1, 2 and 3 messages, it ensures interoperability between compliant devices and guarantees safe equipment performance.
Applications in the Marine Industry
IEC 61162-450 is widely used in:
- Integrated Bridge Systems (IBS)
- Electronic Chart Display and Information Systems (ECDIS)
- Voyage Data Recorders (VDR)
- Autonomous and remote-controlled vessels
Its Ethernet-based approach allows for scalable, high-bandwidth communication, essential for modern digital ships.
Tag Blocks in IEC 61162-450
In marine communication systems, particularly those adhering to standards like IEC 61162-450 and NMEA 0183, tag blocks are metadata elements appended to messages or data packets transmitted over Ethernet networks.
These blocks serve multiple critical functions: they include authentication tags (e.g., ”a:”) that help verify the origin and integrity of data, enhancing cybersecurity by ensuring only trusted sources are active on the network.
They also support data identification, which is essential in environments with multiple talkers and listeners—such as radar, GPS, and ECDIS systems—by clearly labelling the type and source of each message. Additionally, tag blocks enable traffic filtering, allowing devices to process only relevant messages, thereby optimising performance and reducing unnecessary load on equipment.
Tag Blocks
IEC 61162-450 enables NMEA data to be transmitted via IP Networks. In the context of IEC 61162-450, the term ”tag blocks” refers to a specific mechanism used for data authentication and cybersecurity management within Ethernet-based maritime communication networks.
What Are Tag Blocks in NMEA?
Tag blocks are prefixes to NMEA sentences, enclosed between backslashes (\) and typically formatted as comma-separated key-value pairs, followed by a checksum. For example:
\s:01234567,c:1234567890*0B\!AIVDM,1,1,,A,16:=;0P00,SstvFnFbeGH6L088h,0*44
Common Tag Block Elements:
- s: — Source identifier (e.g., sensor ID)
- c: — Unix timestamp of when the message was generated
- g: — Grouping information for multipart messages
- a: — Authentication tag (used in IEC 61162-450 for cybersecurity)
- *XX — Checksum for the tag block itself
In NMEA 2000, the concept of tag blocks as used in NMEA 0183 is not used. NMEA 2000 is a binary, CAN-based protocol that uses a structured message format rather than ASCII sentences with metadata prefixes.
- No textual tag blocks: Unlike NMEA 0183, which uses tag blocks like \s:12345,c:1671620143*5F\ to add metadata, NMEA 2000 embeds metadata directly into its binary message structure.
- Parameter Group Numbers (PGNs): In NMEA 2000, each message is identified by a PGN, which defines the type of data being transmitted (e.g., engine parameters, GPS position, wind speed).
- Fast Packet Protocol: For messages larger than 8 bytes, NMEA 2000 uses a Fast Packet system to fragment and reassemble data across multiple CAN frames.
While NMEA 2000 does not utilise tag blocks, it achieves similar functionality through its structured binary communication framework. This includes PGN-based identification, which defines the type and source of each message, device instance numbers that distinguish between multiple similar devices on the same network (such as two GPS units), and transport protocols that ensure message integrity and proper sequencing.
These mechanisms collectively provide the metadata and organisational benefits of tag blocks, enabling reliable, secure, and efficient data exchange across complex marine networks.
So, while tag blocks as a textual metadata prefix are not part of NMEA 2000, the protocol includes built-in mechanisms for identifying, authenticating, and managing data flow between devices.
IEC 61162-460: Enhancing Safety and Security in Maritime Ethernet Networks
Overview
IEC 61162-460 is an international standard developed by the International Electrotechnical Commission (IEC), which focuses on maritime navigation and radiocommunication equipment. The standard is an add-on to IEC 61162-450, designed to address heightened safety and cybersecurity requirements in Ethernet-based shipboard networks.
Purpose and Scope
IEC 61162-460 is intended for use in environments where:
- Systems are exposed to external threats
- There is a need to improve network integrity
- Redundant and secure communication is critical
It applies to networks with multiple talkers and multiple listeners, using Ethernet interconnection for digital interfaces in maritime systems.
Key Features and Requirements
IEC 61162-460 does not introduce new application-level protocols beyond those defined in IEC 61162-450. Instead, it strengthens the network-level requirements to ensure robust performance and security. Key features include:
Enhanced Network Monitoring
- IGMP snooping for switches and forwarders to reduce unnecessary traffic and improve efficiency
IGMP snooping (Internet Group Management Protocol snooping) is a network switch feature that optimises multicast traffic handling. In Ethernet networks, multicast allows one device to send data to multiple recipients simultaneously. Without IGMP snooping, switches treat multicast like broadcast, sending data to all ports, which can lead to unnecessary traffic and network congestion.
With IGMP snooping enabled, the switch listens to IGMP messages exchanged between devices and builds a map of which ports have requested specific multicast groups. This allows the switch to forward multicast traffic only to the relevant ports, improving efficiency and reducing load—especially important in marine networks where bandwidth and reliability are critical for systems like radar, navigation, and video surveillance.
- SFI collision detection for faster troubleshooting and fault isolation
SFI (System Function Identifier) collision detection is a network monitoring feature introduced in the IEC 61162-460 standard to enhance fault diagnosis and operational reliability in maritime Ethernet networks. Collision detection identifies when multiple devices attempt to transmit data simultaneously in a way that causes interference or data loss. By monitoring SFI collisions, the system can quickly pinpoint conflicting data sources or misconfigured devices, enabling faster troubleshooting and maintaining the integrity of critical shipboard communications.
Improved Isolation
Secure and non-secure network zones must be separated using a 460-Forwarder, which acts as a firewall-like device to prevent unauthorised access and data leakage.
A 460-Forwarder is a specialised network device defined in the IEC 61162-460 standard, used to isolate secure and non-secure zones within a shipboard Ethernet network. Its primary function is to act as a controlled gateway, ensuring that data traffic between different security domains is properly filtered and monitored.
This isolation helps prevent unauthorised access and data leakage, enhancing the overall cybersecurity posture of maritime systems. Additionally, 460-Forwarders are required to support IGMP snooping and SFI collision detection.
Cybersecurity Significance
As maritime vessels evolve into sophisticated floating data hubs, the risk of cyberattacks has grown significantly due to increased connectivity and reliance on networked systems.
IEC 61162-460 plays a vital role in addressing these challenges by providing a framework for mitigating cyber threats, protecting sensitive navigation and control systems, and ensuring compliance with international cybersecurity regulations.
This standard enhances the resilience of shipboard Ethernet networks by introducing secure communication practices, redundancy, and authentication mechanisms, making it a cornerstone of modern maritime cybersecurity strategy.
Industry reports suggest that the financial impact of maritime cyber incidents has surged by nearly 200% since 2022, with average ransom demands reaching $3.2 million. IEC 61162-460 helps ship operators and equipment manufacturers build networks resilient to such threats.
Final thoughts
IEC 61162-450 and 460 together establish the backbone of modern maritime Ethernet networking.
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450 delivers fast, interoperable data exchange between devices.
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460 adds the critical layers of safety, monitoring, and cybersecurity needed for autonomous and connected vessels.
As the marine industry continues its digital transformation, these standards will define how navigation and control systems communicate — safely, reliably, and at scale.
NMEA 0183 data streaming over Ethernet: Benefits and how it works 
How onboard device data is used in the commercial marine sector 
Ethernet in the Marine Industry: Transforming Ship Connectivity and Automation