The TS_UD_CS_MULTITRANSPORT packet is used to indicate support for the RDP Multitransport Layer ([MS-RDPEMT] section 1.3) and to specify multitransport characteristics. This packet is an Extended Client Data Block and MUST NOT be sent to a server which does not advertise support for Extended Client Data Blocks by using the EXTENDED_CLIENT_DATA_SUPPORTED flag (0x00000001) as described in section 2.2.1.2.1.