CIMD Interface Specification - Elisa

4.4.1 Positive response message
Note
CIMD Interface Specification
After processing the request message, the SME or MC sends back a positive
response message. The operation code of the response packet is fixed to be 50
more than the operation code of the request packet. The packet number is the
same as the request message.
A positive response message informs the initiator of the operation that the request
message was received correctly and the operation was performed successfully.
In some exceptional cases (for example, cancel message), the response message
assures only that the request message was received correctly and the operation
will be performed, but the result of the operation is not available.
4.4.2 Negative response message
4.4.3 Nack message
If the request contains invalid parameters or cannot be performed, a negative
response message is sent back to the initiator of the operation. Positive and
negative responses have the same operation code and packet number, but the
negative response message has an error code and optionally an error text
parameter. The usage of error texts is set in the interface profile.
A negative response message informs the initiator of the operation that the request
message was received correctly, but the operation could not be performed
successfully.
A nack message is a special case that performs either of the following actions:
1. It can be used to trigger a retransmission of the request message in case the
checksum calculated by the receiver does not match the checksum found in
the packet.
2. It can be used to indicate that the packet number used is not the expected
number. The packet number of the nack message always contains the
expected packet number.
The MC will never change the packet number because of the nack message. The
MC always assumes that the packet number confusion should be corrected by the
SME.
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