Maintain privacy while providing low-latency information
Another important issue is to protect the endpoint privacy of all participants. To help multiple indirect transfers, participants need to have a hot wallet. In this setting, you'd better not expose your endpoint publicly. Therefore, a passive communication protocol such as Whisper is needed, but at the same time it needs to be able to scale to millions of users.
Light client
We assume that 99% of participants will use Raidenlight clients instead of full nodes to access the system. Similar to the current user using Metamask to access Dapps. Then there needs to be a protocol that can support weak connections and nodes with weaker accessibility in the network.