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Section 2
DNP3 overview
2.1.3
2.1.4
8
•
Controlling all aspects of the physical layer.
•
In unsolicited reporting mode, performing collision avoidance/detection
procedures to ensure reliable transfer of data across the physical link.
•
Responding to all valid frames received from the physical layer.
Data link responsibilities:
•
Exchange of SDUs between peer DNP3 data links
•
Error notification to data link user
•
Sequencing of SDUs
•
SDU delivery quality.
Link-layer confirm usage is deprecated.
See the DNP technical bulletin TB1998-0402, section 3 for details
at www.dnp.org.
Transport pseudo-layer
To support advanced RTU functions and messages exceeding the maximum data
link frame length, a transport pseudo-layer which implements message assembly
and disassembly services was adopted. This pseudo-layer is actually a super-data
link transport protocol, which is normally included in some OSI protocol data links.
Transport functions:
•
Fragmenting user data into one or more data link frames and transmitting the
data to the data link layer
•
Assembling the data link frames received from the data link layer into user data
•
Controlling all aspects of the data link excluding data link configuration
Transport responsibilities:
•
Exchange of SDUs between peer DNP3 transport pseudo layers
•
Error notification to transport users
•
Sequencing of SDUs
Application layer
The application layer is responsible for performing operations on data objects
defined by the device or on the device itself. These operations can include
returning actual values (read function), assigning new values (write function) if the
object represents control points, arming and energizing the output point (select,
operate or direct operate functions) and if counters are used, storing actual values
(freeze functions) and clearing the counters.
1MRS757820 B
Recloser Protection and Control RER615
Communication Protocol Manual
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