Nevion Multicon MRP - Manual (Page 8)

Modular Routing Protocol - MRP Rev. L
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Lock command/state Partial Protect Lock Decimal
Unlock/unprotect 0 0 0 0
Lock 0 0 1 1
Protect 0 1 0 2
N/A 0 1 1 3
N/A 1 0 0 4
Partial lock 1 0 1 5
Partial protect 1 1 0 6
Partial lock + protect 1 1 1 7
Table 1. Lock command/state definitions
<user ID> is a two-byte number specifying the user id of the user that locked the item.
User privileges are defined at configuration time. The optional user id is ignored in
commands, but legal for backwards compatibility. Refer to chapter 3.2.
When setting a lock, only LOCK, PROTECT and UNLOCK are valid commands. In status
messages, the state values are considered bitmask values, enabling a combined status
value ranging from 0-7 (Table 1).
2.6 Check Sum (Cyclic Redundancy Checksum, CRC)
If the message is terminated by a * followed by 4 hexadecimal numbers, and then two
<LF>, the message contains a check sum. The receiver of the message should verify that
the check sum is correct, before executing the command.
The checksum is not needed for operation of the server. The checksum is a 16-bit word.
The polynomial used for CRC calculation is defined in CCITT X.25 and UIT V.41. [*CRC]
denotes proper placement of the checksum in commands and responses.
Example:
x l3 52 27 *53A2
2.7 Protocol error handling
Unknown or misspelled commands and syntactic errors return the same error message.
Example command response:
? "portocol"
ERROR: Unknown command
2.8 Future expansion
New commands and status messages may be added in the future, and messages may
have parameters added. A client or host implementation must be able to ignore these extra
parameters and messages without system failure. New parameters will always be added at
the end of the command or status line.