I think it depends on the isolation of each part. If the incoming data is fine, then you have the problem narrowed down already. If it isn't, then you have to

I think it depends on the isolation of each part. If the incoming data is fine, then you have the problem narrowed down already. If it isn't, then you have to figure out why it was sent in the first place, probably by detecting something wrong in the sender at run time so you can see what led to the bad message.