RADIUS attribute from rfc2869

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ARAP-Password

This attribute is only present in an Access-Request packet
      containing a Framed-Protocol of ARAP.

      Only one of User-Password, CHAP-Password, or ARAP-Password needs
      to be present in an Access-Request, or one or more EAP-Messages.

   A summary of the ARAP-Password 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     |             Value1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |             Value2
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |             Value3
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |             Value4
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Type

      70 for ARAP-Password.

   Length

      18

   Value

      This attribute contains a 16 octet string, used to carry the
      dial-in user's response to the NAS challenge and the client's own
      challenge to the NAS.  The high-order octets (Value1 and Value2)
      contain the dial-in user's challenge to the NAS (2 32-bit numbers,
      8 octets) and the low-order octets (Value3 and Value4) contain the
      dial-in user's response to the NAS challenge (2 32-bit numbers, 8
      octets).

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