6.1.1. Basic Elements

An OPT pseudo-RR (sometimes called a meta-RR) MAY be added to the additional data section of a request.

An OPT is called a pseudo-RR because it pertains to a particular transport level message and not to any actual DNS data. OPT RRs MUST NOT be cached, forwarded, or stored in or loaded from zone files. The quantity of OPT pseudo-RRs per message MUST be either 0 or 1, but not greater.

The OPT RR specifies only the maximum message size.