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3.1.5.1.3 SYN+ACK Datagrams

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A SYN+ACK datagram consists of a SYN packet, generated as specified in section 3.1.5.1.1, with these additional fields set as follows:

  • The snSourceAck field in the RDPUDP_FEC_HEADER structure (section 2.2.2.1) MUST be set to the snInitialSequenceNumber value received in the SYN packet (section 3.1.5.1.1).

  • The RDPUDP_FLAG_ACK flag MUST be set in the RDPUDP_FEC_HEADER structure (section 2.2.2.1).

  • The uUpStreamMtu and uDownStreamMtu in the RDPUDP_SYNDATA_PAYLOAD structure (section 2.2.2.5) MUST be set as specified in the algorithm described in section 3.1.1.3. The values of these fields MUST be in the range of 1132 to 1232 bytes.

  • The RDPUDP_SYNDATAEX_PAYLOAD structure (section 2.2.2.9) SHOULD only be present if it is also present in the received SYN packet. The uUdpVer field MUST be set to the highest RDP-UDP protocol version supported by both endpoints. The highest version supported by both endpoints, which is RDPUDP_PROTOCOL_VERSION_1 if either this packet or the SYN packet does not specify a version, is the version that MUST be used by both endpoints.