DCP Hello is sent on transition to link down

If configured to send DCP Hello frames, the protocol stack currently sends DCP Hello frames if the following conditions are fullfilled

• no AR exists (thus no cyclic communication active)
• Link change occurs on one of IO Device ports

However, this includes the scenario that a link changes from up to down. However, it is unexpected (and useless) that DCP Hello is send if a transition from LinkUp to LinkDown.