The RFC “Remote Authentication Dial In User Service (RADIUS)” [RFC2865] defines a Packet Type Code and an Attribute Type Code. The IANA registry of these codes and subordinate assigned values is listed here according to [RFC3575].
Radius Attribute Types
Specifications which would allocate more than 20 percent of the remaining standard space attributes should have all allocations made from the extended space. Otherwise,
specifications allocating fewer than 10 attributes should have allocations made in the standard space. Specifications which allocate a data type TLV should receive an allocation from the extended space. Specifications requesting allocation of an attribute which can transport 253 or more octets of data should have that attribute allocated from within the long extended space. See section 10.3.4 of [RFC6929].
RADIUS Protocol RFC Documents