RADIUS attribute from rfc2869

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Prompt

This attribute is used only in Access-Challenge packets, and
      indicates to the NAS whether it should echo the user's response as
      it is entered, or not echo it.


   A summary of the Prompt 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

      76 for Prompt.Length

      6

   Value

      The Value field is four octets.

       0      No Echo
       1      Echo

        FreeRADIUS Vendor-Specific dictionary values:

                    0 - No-Echo 
                    1 - Echo 
            

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