MSG in RSLogix5000

Could someone explain what the Destination Link and the Source Link mean in a message instruction.

Destination Link
Link ID of Remote DH+ Link

Source Link
Link ID of Local DH+ Link

your help is greatly appriciated...

These are only relevant if you're message has to "bridge" from one DH+ network to another (e.g. via DH or DHII). If the node you're communicating with is on the same physical network as the CLX, then enter 0 (zero) in both link ID fields.