Configure maximum fragment size about dnp3 HOT 2 CLOSED

Some relevant extracts from IEEE 1815-2012, section 4.3:

Rule 1: DNP3 devices that are able to set their maximum transmit fragment size larger than 2048 octets shall provide the ability to limit the size (via configuration) to a maximum of 2048 octets.

Rule 3: Outstations shall be prepared to receive fragment sizes of at least 249 octets, and masters shall be prepared to receive fragment sizes of at least 2048 octets.

Rule 4: Master devices shall only send requests that fit within a single fragment. Any master that is capable of sending fragments larger than 249 octets shall be configurable to restrict the maximum fragment size of all requests to 249 octets.

^ We should at least check for command requests to split them if too big.

from dnp3.

I don't think automatic splitting is a desirable behavior. We can just fail the task with a write error to indicating to the user that the request is too big. I'd rather do that than get some undesirable result having sent the controls in multiple requests.

from dnp3.