Payment in both µRaiden and Raiden Network are design for mainly off-chain process. This means it run outside the blockchain to speed things up and will use on-chain process when necessary. Utilizing the Digital signature and its Protocol that allow payment through routing the already existing channel between peers. The channels are usually open and close all the time so in order to keep the channel open for lifetime, There’ll be a need to lock some token in as a security in smart contract to prevent the Double spending problem.
Each peer in the channel will keep the latest copy of the Certified checks and The Balance proof that is a final sum of all Raiden transfer up to a certain point which digitally signed by sender. Each time they’d rebalance, The balance proof will be sent back and forth to proof they’re right and gain access to the fund received.
Note: The Channels can be either a straight line : A <-> B or a loop : A <-> B <-> C <-> A