2.2.1 SMB2 Packet Header
The SMB2 Packet Header (also called the SMB2 header) is the header of all SMB 2 Protocol requests and responses.
There are two variants of this header:
If the SMB2_FLAGS_ASYNC_COMMAND bit is set in Flags, the header takes the form SMB2 Packet Header – ASYNC (section 188.8.131.52). This header format is used for responses to requests processed asynchronously by the server, as specified in sections 184.108.40.206, 220.127.116.11, 18.104.22.168, and 22.214.171.124.5. This header format MAY be used for any request, and the SMB2 CANCEL Request MUST use this format for canceling requests that have received an interim response, as specified in sections 126.96.36.199 and 188.8.131.52.