I've been educating myself on how the Lightning Network protocol works, and I have some questions.
Let's say that a user sends a small payment to someone and it makes multiple hops through the network before reaching the recipient. The payment then propagates backward through the chain until it reaches the payer, and everything settles out.
It's possible that a node in the middle either either intentionally or unintentionally does not pay the next node down the line. The recourse is for the node that did not get paid to broadcast the transaction to the blockchain (and close the channel?).
Who pays the fees for for that transaction? What happens if the fee is significantly larger than the amount of money the node would gain by broadcasting the transactions?
This seems like it could potentially be a large attack vector. Is there something I am misunderstanding?