The forward fee is meant to fight uncontrolled spam while the backward fee is meant to fight controlled spam. It was suggested that implementing the easier uncontrolled spam protection via the forward payment could be a good first step. However, potential weaknesses such as griefing attacks should also be considered. One concern raised was whether the amounts required to thwart attacks would be too high for honest users or certain uses. The forward payment can be small since uncontrolled spam can only be in-flight for a short time. Calculations were done to determine the annual return needed for a 1 BTC/483 slot channel, which was found to require a forward payment of approximately 1 sat/hour. The total "damage" caused by uncontrolled spam was also calculated and found to require a forward payment of 150 msat to cover it. However, if the attacker is on the other end of the uncontrolled spam payment, collecting the forward payments but not holding the payment, this raises another issue. For the backward payment, the maximum expiry of the htlc is 2000 blocks, about 160 hours on average along the route. Ideally, the attacker at the far end of the route should pay 3200 sat, but this cost may not be liked by everyone.