IPFIX:
In June 2014 IANA assigned pmacct PEN #43874. Field types 1-32767 are reserved
to official pmacct project fields definition. Users are welcome to define own
field types (ie. due to customizations to the pmacct software) and can use for
the purpose field types from 32768 onwards. 

Official pmacct project fields definition:

ElementID	Name	Data Type	Semantics	Description
1		tag	unsigned64	identifier	tag primitive value
2		tag2	unsigned64	identifier	tag2 primitive value
 
