RADIUS attribute from rfc2869

---

ARAP-Security

This attribute identifies the ARAP Security Module to be used in
      an Access-Challenge packet.

   A summary of the ARAP-Security 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

      73 for ARAP-Security.

   Length

      6Value

      The Value field is four octets, containing an integer specifying
      the security module signature, which is a Macintosh OSType.
      (Macintosh OSTypes are 4 ascii characters cast as a 32-bit
      integer)

---