2.2.4 SSTP Attributes
The following diagram specifies the format that MUST be used for all SSTP attributes.
The fields of the structure MUST be transmitted as bytes from left to right.
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Reserved |
Attribute ID |
LengthPacket |
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Value (variable) |
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Reserved (1 byte): This 8-bit field is reserved for future use. MUST be set to zero when sent and MUST be ignored on receipt.
Attribute ID (1 byte): An 8-bit (1-byte) field that is used to specify the type of attribute; its value MUST be one of the following.
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Name
Value
SSTP_ATTRIB_ENCAPSULATED_PROTOCOL_ID
0x01
SSTP_ATTRIB_STATUS_INFO
0x02
SSTP_ATTRIB_CRYPTO_BINDING
0x03
SSTP_ATTRIB_CRYPTO_BINDING_REQ
0x04
LengthPacket (2 bytes): A 16-bit unsigned integer in network byte order that packs data for two fields, configured in the following format.
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0
1
2
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9
1
0
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4
5
R
Length
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R (4 bits): This 4-bit field is reserved for future use. MUST be set to zero when sent and MUST be ignored on receipt.
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Length (12 bits): A 12-bit unsigned integer in network byte order that MUST specify the length, in bytes, of the entire SSTP attribute, including the 4-byte attribute header (that is, 1-byte Reserved field, 1-byte Attribute ID, 4-bit R field, and 12-bit Length field).
Value (variable): A variable-length field with length equal to field Length minus 4 that contains the attribute-specific data. The different attribute-specific data are described in sections 2.2.5 to 2.2.8. The fields "Reserved", "Attribute ID", and "LengthPacket" have been repeated in those sections for complete illustration.