IEC TR 62056-51:1998 pdf download – Electricity metering – Data exchange formeter reading, tariff and load control – Part 51: Application layer protocols

IEC TR 62056-51:1998 pdf download – Electricity metering – Data exchange formeter reading, tariff and load control – Part 51: Application layer protocols.
This technical report describes an architectured application layer used for communication with metering equipments in general, whatever the associated physical medium and lower layer protocols In a collapsed three-layer model are.
This technical report specifies the protocols to be applied for the application layer except the DLMS (Distribution Line Message Specification) model, which is already covered by
IEC 61334-4-41
1.2 NormatIve references
The following normative documents contain provisions which, through reference In this text, Constitute provisions of this technical repori At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this technical report are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards
IEC 61334-4-41:1996, Distnbution automation using distribution line carrier systems — Part 4:
Data communication protocols — Section 41: Application protocols — Distribution line message
specification (DLMS)
ISOIEC 8824:1990, Information technology — Open Systems Interconnection — Specilication of Abstract Syntax Notation One (ASN. I)
2 General description
2.1 BasIc vocabulary
All communications involve two sets of equipment represented by the terms Caller system and Called system. The Caller is the system that decides to initiate a communication with a remote system known as the Called party these denominations remain valid throughout the duration of the communication.
A communication is broken down into a certain number of transactions. Each transaction is represented by a transmission from the Transmitter to the Receiver During the sequence of transactions, the Caller and Called systems take turns to act as Transmitter and Receiver.
The most important properties of the Transport sub-layer are end-to-end transport (mentioned above), transparency (any binary configuration must be accepted by the transport protocol and delivered without modification, whatever its format or size) and selection of a quality of service. The notion of quality of service Is mentioned here for information only, as the Transport. protocol is oriented without connection.
The Transport sub-layer accepts the messages from the Application sub-layer As the size of these messages is dictated by the application, the Transport sub-layer must segment them into packets (called TPDUs: transport protocol data units) and transmit them to the correspondent Transport sub-layer. Reciprocally, it must receive the packets from the correspondent Transport sub-layer and assemble them into coherent messages for the Application sub-layer,
The Transport. protocol must be able to transmit data in parallel in both directions, Caller- Called and CalledCaller. Moreover, the multiplexing of transport connections on the same virtual circuit means that several application associations can coexist in a given communication,
Whatever their origin, the TPDUs are transmitted using the services of the Data Link layer, Of course, this sub-layer is not aware of the multiplexing implemented at the higher level.
33 Transport protocol classes
The ISO proposes different types of network services depending on the residual errors in the transmissions at the lower levels, Two sorts of error are Identified: the reported errors (for example forced disconnection with error indication) and the unreported errors (undetected and uncorrected transmission errors). On this basis, there are three types of network, summarized in table 2.
3.6 Transport parameters
In the absence of an explicit connection stage, the number of transport connections and the size of the buffers are not negotiated. The following rules are observed:
— a maximum of 4 096 transport connections each identified by a (STSAP, DTSAP) pair;
— a memory space requirement f or all the transmission and reception buffers of all the active transport connections that does not exceed the capacity of the remote equipment.
The actual size of the overall memory space depends on each equipment but shall not be less than 512 octets. A DLMS management variable, Buff erPoolSize, contains the corresponding value. This variable Is accessible through the communication protocols management DIMS Server
The value of the Packet field size, MaxPktSeze, shall be adjusted to the frame capacity of the Data Link layer.
3.7 State transitions
The state machine of the Caller is strictly identical to that of the Called system. The two systems are in turn Transmitter and Receiver of TSDU5. At any time, there Is only one occurrence of this controller in each set of equipment.