2.2.14 Call Disconnect Message (SSTP_MSG_CALL_DISCONNECT)
This message is sent by an SSTP peer to the SSTP far end in order to initiate the normal disconnection of the SSTP connection, such as when a user initiates a manual disconnect.
The following diagram specifies the format that MUST be used for this message. This message follows the format of an SSTP control packet as specified in section 2.2.2. This message SHOULD have one Status Info attribute.<4> This message MUST NOT have any other attributes.
The fields of the structure MUST be transmitted in network byte order from left to right.
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Version |
Reserved |
C |
LengthPacket |
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Message Type |
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Reserved1 |
AttributeID |
LengthPacket1 |
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Reserved2 |
AttribID |
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Status |
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Version (1 byte): An 8-bit (1-byte) field that is used to communicate and negotiate the version of SSTP that is being used. The upper 4 bits are MAJOR version, which MUST be 0x1, and the lower 4 bits are MINOR version, which MUST be set to 0x0. Therefore, the 8-bit value of the Version field MUST be 0x10 and corresponds to Version 1.0.
Reserved (7 bits): This 7-bit field is reserved for future use. MUST be set to zero when sent and MUST be ignored on receipt.
C (1 bit): A 1-bit field that is used to indicate whether the packet is an SSTP control packet or an SSTP data packet. The value MUST be 1 when this message is a control packet.
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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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 this entire message.
Message Type (2 bytes): A 16-bit field in network byte order that specifies the type of message. It MUST be 0x0006 (that is, SSTP_MSG_CALL_DISCONNECT).
Num Attributes (2 bytes): A 16-bit field in network byte order that specifies the number of attributes in the message. This value MUST be set to 1 if a Status Info attribute is being sent along with this message. If no Status Info attribute is present in this message, this value MUST be set to 0.
Reserved1 (1 byte): This 8-bit (1-byte) field is reserved for future use. MUST be set to zero when sent and MUST be ignored on receipt.
AttributeID (1 byte): An 8-bit (1-byte) field that is used to specify the type of attribute; its value MUST be 0x02 for the Status Info attribute.
LengthPacket1 (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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R1
Length1
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R1 (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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Length1 (12 bits): A 12-bit unsigned integer in network byte order that contains the value 12 plus the length of the AttribValue field.
Reserved2 (3 bytes): This 24-bit field is reserved for future use. MUST be set to zero when sent and MUST be ignored on receipt.
AttribID (1 byte): A 1-byte field that specifies the attribute ID whose status is given by the Status Info attribute. Its value MUST be set to SSTP_ATTRIB_NO_ERROR (0x0).
Status (4 bytes): A 4-byte field that specifies the reason for the disconnect. Its value MUST be set to ATTRIB_STATUS_NO_ERROR (0x0).