The modernized version has added a general ship layer, including the administrative layer as one of its components, and an off-ship layer. Each network on this layer would typically cover a limited number of devices, dependent on physical area and function. Several isolated instrument networks may be used to implement redundant process segments, e. An instrument network may or may not support redundancy in itself.
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The modernized version has added a general ship layer, including the administrative layer as one of its components, and an off-ship layer. Each network on this layer would typically cover a limited number of devices, dependent on physical area and function. Several isolated instrument networks may be used to implement redundant process segments, e.
An instrument network may or may not support redundancy in itself. The next layer is the process layer which is used to integrate all functionality in one process segment, e.
Again, redundancy may be required and this could be done by implementing two independent process network, by supplying redundancy in the network itself or both. This is used to interconnect different process segments as required and also to bridge over to administrative functions where this is needed. As the ISC layer potentially connects to all process segments, one single error on the ISC layer may propagate down into several systems if no safeguard is put in place.
It contains only three network layers: The instrument layer integrates sensors and actuators for each process segment, the control layers corresponds to the ISC layer in the new model and the administrative layer is now part of the general ship layer. The higher complexity of the current model is a good indicator of the significant developments that have been made in integrated ship control since This is currently in draft form, but will probably be published as final standard mid The ship network architecture is similar to the one presented above and the standard deals mostly with high level design and operational issues.
Thus, it is on a higher level than many of the other standards presented here and of a more general nature. It is intended for use mainly in the navigation system on the process layer, although it can also support instrument layer integration and also on ISC layer, if desired.
The latter components are a set of constructs to group and further characterize the sentences. Messages consist of a number of sentences with additional data such as sentence number, grouping information, sender and receiver identities and put into an UDP datagram.
The maximum size of the datagram is about bytes. The UDP datagram is sent as a multicast to one of 16 predefined addresses.
Eight of these are default addresses based on the type of sentences in the datagram. The default selection can be overridden by configuration. There are a number of restrictions on network equipment defined in the standard that are intended to ensure easy integration and safety of operation.
This includes bridging to other networks and what types of routers to use in the system. The nominal data rate is kbps at bus lengths up to m. This translates to about kbps for user payload.
An overview of the standard can be found in Luft L. It requires a two-bus redundant system with backup of all vital components such as power supplies. This is supported by NMEA , but is optional in that specification. As a bus type network represents a single point of failure in itself, it was decided to require redundancy also on network level.
This is not a requirement in IEC One of the news articles can be found on Digital Ship. It has since been continuously updated and was at time of writing at edition 2.
NMEA is a serial line standard allowing up to 10 receivers to connect to one sender. Data is sent as text messages with a distinct format, well known to those working with integration of bridge equipment.
An example is shown below. The limitation is in the receivers ability to process data as well as in the physical interfaces used. Later versions of NMEA contains sentences for many ship applications as well as for AIS shore data network operation and management. Below is a brief example that shows explicit grouping of the last two messages shown above. It only allows 4. Only lists of allowed sentence formatters will be included as well as other relevant specifications for IEC.
IEC includes all provisions of IEC , but allows an alternate transmission speed of This is mainly to support very fast transmitting devices such as gyros.
Full Description IEC specifies interface requirements and methods of test for high speed communication between shipboard navigation and radiocommunication equipment as well as between such systems and other ship systems that need to communicate with navigation and radio-communication equipment. This document is based on the application of an appropriate suite of existing international standards to provide a framework for implementing data transfer between devices on a shipboard Ethernet network. This document specifies an Ethernet based bus type network where any listener can receive messages from any sender with the following properties. By specifying protocols for transmission of IEC sentences, IEC PGN messages and general binary file data, these requirements will guarantee interoperability between equipment implementing this document as well as a certain level of safe behaviour of the equipment itself. This document does not contain any system requirements other than the ones that can be inferred from the sum of individual equipment requirements.
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Most recent IEC Ed. This part of IEC is intended to support one-way serial data transmission from a single talker to one or more listeners. These data are in printable ASCII form and may include information such as position, speed, depth, frequency allocation, etc. Typical messages may be from about 11 to a maximum of 79 characters in length and generally require transmission no more rapidly than one message per second.
This document provides requirements and test methods for equipment to be used in an IEC compliant network as well as requirements for the network itself and requirements for interconnection from the network to other networks. This document also contains requirements for a redundant IEC compliant network. This document does not introduce new application level protocol requirements to those that are defined in IEC This second edition of IEC cancels and replaces the first edition published in This edition constitutes a technical revision.
IEC contains the requirements for data communication between maritime electronic instruments, navigation and radiocommunication equipment when interconnected via an appropriate system. This part of IEC is intended to support one-way serial data transmission from a single talker to one or more listeners. These data are in printable ASCII form and may include information such as position, speed, depth, frequency allocation, etc. Typical messages may be from about 11 to a maximum of 79 characters in length and generally require transmission no more rapidly than one message per second. The electrical definitions in this standard are not intended to accommodate high-bandwidth applications such as radar or video imagery, or intensive database or file transfer applications. Since there is no provision for guaranteed delivery of messages and only limited error checking capability, this standard should be used with caution in all safety applications.