3.2.5.3.1 Sending X.224 Connection Request PDU

The structure and fields of the X.224 Connection Request PDU are specified in section 2.2.1.1.

The tpktHeader field is initialized as specified in [T123] section 8, while the x224Crq field is initialized as specified in [X224] section 13.3 (the Destination reference and Source reference fields are both set to zero, and the Class and options fields are both set to zero). Parameter fields MUST NOT be specified in the variable part of the Connection Request PDU. This implies that the default maximum size of an X.224 Data PDU payload (65528 bytes) is used because the maximum TPDU size and preferred maximum TPDU size are not present.

The routingToken field is optional. If the client is in possession of a routing token, it MUST populate the routingToken field. The primary source of a routing token is the LoadBalanceInfo field of the Server Redirection PDU (section 2.2.13.1). However other methods, such as scriptable APIs or file input, can be used to provide a client with a routing token before a connection to an RDP server is initiated. For more information about load balancing of Remote Desktop sessions and the routing token format, see [MSFT-SDLBTS] sections "Load-Balanced Configurations", "Revectoring Clients", and "Routing Token Format".

The cookie field is optional and MUST NOT be present if the routingToken field is present.<43>

The optional rdpNegData field contains an RDP Negotiation Request structure, as specified in section 2.2.1.1.1. The requestedProtocols field is initialized with flags describing the security protocols which the client supports (see section 5.4 for more details on Enhanced RDP Security).

Upon successfully transmitting the X.224 Connection Request PDU, the client MUST update the Connection Start Time store (section 3.2.1.16).