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2.2.7.21 SESSIONSTATE

  • Article

Token Stream Name: 

 SESSIONSTATE

Token Stream Function:

Used to send session state data to the client. The data format defined here can also be used to send session state data for session recovery during login and login response.

Token Stream Comments:

  • The token value is 0xE4.

  • This token stream MUST NOT be sent if the SESSIONRECOVERY feature is not negotiated on the connection.

  • When this token stream is sent, the next token MUST be DONE (section 2.2.7.6) or DONEPROC (section 2.2.7.8) with DONE_FINAL.

  • If the SESSIONRECOVERY feature is negotiated on the connection, the server SHOULD send this token to the client to inform any session state update.

Token Stream-Specific Rules: 

 fRecoverable            =   BIT
            
 TokenType               =   BYTE
 Length                  =   DWORD
 SeqNo                   =   DWORD
 Status                  =   fRecoverable 7FRESERVEDBIT
            
 StateId                 =   BYTE
 StateLen                =   BYTE          ; 0-%xFE
                             /
                            (%xFF DWORD)   ; %xFF - %xFFFF
            
            
 SessionStateData        =   StateId
                             StateLen
                             StateValue
            
 SessionStateDataSet     =   1*SessionStateData

Token Stream Definition: 

 SESSIONSTATE            =   TokenType
                             Length
                             SeqNo
                             Status
                             SessionStateDataSet

Token Stream Parameter Details

Parameter

Description

TokenType

SESSIONSTATE_TOKEN

Length

The length, in bytes, of the token stream (excluding TokenType and Length).

SeqNo

The sequence number of the SESSIONSTATE token in the connection. This number, which starts at 0 and increases by one each time, can be used to track the order of SESSIONSTATE tokens sent during the course of a connection. The SeqNo applies to all StateIds in the token. If the SeqNo for any StateId reaches %xFFFFFFFF, both client and server MUST consider that the SESSIONRECOVERY feature is permanently disabled on the connection. The server SHOULD send a token with fRecoverable set to FALSE to disable SESSIONRECOVERY for this session. The client SHOULD NOT set either ResetConn bit (RESETCONNECTION or RESETCONNECTIONSKIPTRAN) on the connection once it receives any SeqNo of %xFFFFFFFF because ResetConn could reset a connection back to an initial recoverable state and SESSIONRECOVERY needs to be permanently disabled on the connection in this case. If the server does receive ResetConn after SeqNo reaches %xFFFFFFFF, it SHOULD reuse this same SeqNo to disable SESSIONRECOVERY.

The client SHOULD track SeqNo for each StateId and keep the latest data for session recovery.

Status

Status of the session StateId in this token.

fRecoverable: TRUE means all session StateIds in this token are recoverable.

The client SHOULD track Status for each StateId and keep the latest data for session recovery. A client MUST NOT try to recover a dead connection unless fRecoverable is TRUE for all session StateIds received from server.

StateId

The identification number of the session state. %xFF is reserved.

StateLen

The length, in bytes, of the corresponding StateValue. If the length is 254 bytes or smaller, one BYTE is used to represent the field. If the length is 255 bytes or larger, %xFF followed by a DWORD is used to represent the field. If this field is 0, client SHOULD skip sending SessionStateData for the StateId during session recovery.

StateValue

The value of the session state. This can be any arbitrary data as long as the server understands it.