The forward payment is a fixed fee of 1 msat that is paid unconditionally when offering an HTLC to help protect the network against spam attacks. The backward payment, called hold_fees, is paid when receiving an HTLC but is refunded if the HTLC is settled before the hold_grace_period ends. The participants also discuss the values for the forward and backward fees. They agree that 1 msat for the forward fee is probably not enough and suggest using a value that would allow routing nodes to earn up to 5% per year on their committed capital. To calculate the appropriate fees, they consider a scenario where the Lightning Network consists only of 1 BTC and 483 slot channels. They aim to determine the fees that would enable even an attacked routing node to still earn 5% through hold fees in both the controlled and uncontrolled spam scenarios.