The RADIUS attribute "class" has the data type called "octets" which means a byte array. In DualShield, you must use the hexadecimal value of the data or use the "bytes" function:

1.  If the value is a fixed value, then use the hexadecimal form of the value. For example, if the value is "123", then use "313233".
2.  If the value is a dynamic value, then use the function "bytes" to get the value. For example, "domain.name.bytes", "groups.name.byte", etc

There are several other RADIUS attributes that are defined as "octets" Please refer to:

http://opensource.apple.com/source/freeradius/freeradius-11/freeradius/share/dictionary.rfc2865