2.2.1.15 Client Control PDU - Cooperate

The Client Control (Cooperate) PDU is an RDP Connection Sequence PDU sent from client to server during the Connection Finalization phase of the RDP Connection Sequence (see section 1.3.1.1 for an overview of the RDP Connection Sequence phases). It is sent after transmitting the Client Synchronize PDU (section 2.2.1.14).


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tpktHeader

x224Data

mcsSDrq (variable)

...

securityHeader (variable)

...

controlPduData (26 bytes)

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tpktHeader (4 bytes): A TPKT Header, as specified in [T123] section 8.

x224Data (3 bytes): An X.224 Class 0 Data TPDU, as specified in [X224] section 13.7.

mcsSDrq (variable): Variable-length PER-encoded MCS Domain PDU (DomainMCSPDU) which encapsulates an MCS Send Data Request structure (SDrq, choice 25 from DomainMCSPDU), as specified in [T125] section 11.32 (the ASN.1 structure definitions are given in [T125] section 7, parts 7 and 10). The userData field of the MCS Send Data Request contains a Security Header and a Control PDU Data (section 2.2.1.15.1) structure.

securityHeader (variable):  Optional security header. The presence and format of the security header depends on the Encryption Level and Encryption Method selected by the server (sections 5.3.2 and 2.2.1.4.3). If the Encryption Level selected by the server is greater than ENCRYPTION_LEVEL_NONE (0) and the Encryption Method selected by the server is greater than ENCRYPTION_METHOD_NONE (0), then this field MUST contain one of the following headers:

  • Non-FIPS Security Header (section 2.2.8.1.1.2.2) if the Encryption Method selected by the server is ENCRYPTION_METHOD_40BIT (0x00000001), ENCRYPTION_METHOD_56BIT (0x00000008), or ENCRYPTION_METHOD_128BIT (0x00000002).

  • FIPS Security Header (section 2.2.8.1.1.2.3) if the Encryption Method selected by the server is ENCRYPTION_METHOD_FIPS (0x00000010).

If the Encryption Level selected by the server is ENCRYPTION_LEVEL_NONE (0) and the Encryption Method selected by the server is ENCRYPTION_METHOD_NONE (0), then this header MUST NOT be included in the PDU.

controlPduData (26 bytes): The actual contents of the Control PDU, as specified in section 2.2.1.15.1. The grantId and controlId fields of the Control PDU Data MUST both be set to zero, while the action field MUST be set to CTRLACTION_COOPERATE (0x0004).