RADIUS attribute from rfc2866

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Acct-Status-Type

This attribute indicates whether this Accounting-Request marks the
      beginning of the user service (Start) or the end (Stop).

      It MAY be used by the client to mark the start of accounting (for
      example, upon booting) by specifying Accounting-On and to mark the
      end of accounting (for example, just before a scheduled reboot) by
      specifying Accounting-Off.

   A summary of the Acct-Status-Type attribute format is shown below.
   The fields are transmitted from left to right.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |             Value
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Value (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Type

      40 for Acct-Status-Type.

   Length

      6

   Value

      The Value field is four octets.

       1      Start
       2      Stop
       3      Interim-Update
       7      Accounting-On
       8      Accounting-Off
       9-14   Reserved for Tunnel Accounting
      15      Reserved for Failed

        FreeRADIUS Vendor-Specific dictionary values:

                    1 - Start 
                    2 - Stop 
                    3 - Alive 
                    3 - Interim-Update 
                    7 - Accounting-On 
                    8 - Accounting-Off 
                    15 - Failed 
                    9 - Tunnel-Start 
                    10 - Tunnel-Stop 
                    11 - Tunnel-Reject 
                    12 - Tunnel-Link-Start 
                    13 - Tunnel-Link-Stop 
                    14 - Tunnel-Link-Reject 
            

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