Methods among nodes of a computer network for establishing a connection between the server and the client. A client node sends a session-invitation message to a server node. The session-invitation message is in a first protocol that establishes a channel between the client and the server according to parameters of the session-invitation message that specify characteristics of session in a second protocol. The server receives the session-invitation message, sends a provisional response back to the client, and holds in abeyance a success or failure response to the session-invitation, without establishing a channel at the level of the first protocol if no such channel is previously established, and without disrupting a channel at the level of the first protocol if such channel has been previously established.