2.2.1.1 RDP-UDP2 Packet Header

The Header field is mandatory, and it specifies the presence of the various optional payloads that follow.

0	1	2	3	4	5	6	7	8	9	1 0	1	2	3	4	5	6	7	8	9	2 0	1	2	3	4	5	6	7	8	9	3 0	1
Flags												A

Flags (12 bits): A 12-bit unsigned integer that specifies a bitmap of flags indicating the presence of optional payloads that follow the header. In a packet, one or more of the flags MUST be specified in the Header field.

Flags	Meaning
ACK 0x001	ACK payload (section 2.2.1.2.1) is present. This flag MUST NOT be set if the ACKVEC flag is set.
DATA 0x004	DataHeader payload (section 2.2.1.2.5) and DataBody payload (section 2.2.1.2.7) are present.
ACKVEC 0x008	ACK Vector payload (section 2.2.1.2.6) is present. This flag MUST NOT be set if the ACK flag is set.
AOA 0x010	AckOfAcks payload (section 2.2.1.2.4) is present.
OVERHEADSIZE 0x040	OverheadSize payload (section 2.2.1.2.2) is present.
DELAYACKINFO 0x100	DelayAckInfo payload (section 2.2.1.2.3) is present.

A - LogWindowSize (4 bits): A 4-bit unsigned integer that specifies the logarithm base 2 of the maximum buffer size in multiples of the MTU. This variable is imposed on the Receiver of the Sender endpoint when receiving packets from the Sender of the receiver endpoint. The maximum buffer size is equal to (1<< LogWindowSize)*MTU, in bytes.