RFC 3093:Firewall Enhancement Protocol (FEP)
RFC-Ref

service


Click on the red underlined text to get to the source

... TCP_DODO. IP4_Type_of_Service (this name is case sensitive) - This is an obsolete name for a field in the IPv4 header ...
... IP_$$ - The 6-bit Differentiated Services field, encapsulated as an UTF-8 string ...
... IP_$$ - the 6-bit Differentiated Services field - see above IP ...



Google
Web
RFC-Ref