2.1 Transport
The Remote Desktop Protocol: Multitransport Extension operates over the RDP-UDP protocol, as defined in [MS-RDPEUDP], sections 1, 2 and 3.
Multitransport connections are bootstrapped using the Initiate Multitransport Request PDU ([MS-RDPBCGR] section 2.2.15.1), which is sent from server to client over the main RDP connection.