The idea is that the channel is created on demand by the server after receiving a specific
request issued by the initiator. As soon as the second peer joins the channel, conversation
can start. Message exchanging always happens through the server, which basically acts
as a transparent relay node. When one of the peers decides to quit an ongoing conversation, it issues an ad hoc message (called Bye in the figure) towards the server, before disconnecting. This message is dispatched by the server to the remote party, which alsodisconnects, after having sent an acknowledgment back to the server. The receipt of the
acknowledgment eventually triggers the channel reset procedure on the server’s side,
thus bringing the overall scenario back to its original configuration.