RFC-2139 (RADIUS Accounting) has the translations for what's in RFC-2138
(RADIUS)
   Type
      49 for Acct-Terminate-Cause
   Length
      6
   Value
      The Value field is four octets, containing an integer specifying
      the cause of session termination, as follows:
      1       User Request
      2       Lost Carrier
      3       Lost Service
      4       Idle Timeout
      5       Session Timeout
      6       Admin Reset
      7       Admin Reboot
      8       Port Error
      9       NAS Error
      10      NAS Request
      11      NAS Reboot
      12      Port Unneeded
      13      Port Preempted
      14      Port Suspended
      15      Service Unavailable
      16      Callback
      17      User Error
      18      Host Request
      The termination causes are as follows:
      User Request         User requested termination of service, for
                           example with LCP Terminate or by logging out.
      Lost Carrier         DCD was dropped on the port.
      Lost Service         Service can no longer be provided; for
                           example, user's connection to a host was
                           interrupted.
      Idle Timeout         Idle timer expired.
      Session Timeout      Maximum session length timer expired.
      Admin Reset          Administrator reset the port or session.
      Admin Reboot         Administrator is ending service on the NAS,
                           for example prior to rebooting the NAS.
      Port Error           NAS detected an error on the port which
                           required ending the session.
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