DNS Scoped Data Through Attribute Leaves
Historically, any DNS RR may occur for any name. Recent additions have defined DNS leaf nodes that contain a reserved node name, beginning with an underscore. With the underscore construct, the choice of valid RRs is limited to a defined set. The underscore construct is a basic paradigm modification to the DNS, because it defines a scope-constrained attribute space for the containing domain name. This note defines the nature of this DNS usage and defines the procedures for registering new "underscore names" with IANA.