RFC 3123 (rfc3123) - Page 2 of 8
A DNS RR Type for Lists of Address Prefixes (APL RR)
Alternative Format: Original Text Document
RFC 3123 DNS APL RR June 2001 3. APL RR Type An APL record has the DNS type of "APL" and a numeric value of 42 [IANA]. The APL RR is defined in the IN class only. APL RRs cause no additional section processing. 4. APL RDATA format The RDATA section consists of zero or more items () of the form +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | ADDRESSFAMILY | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | PREFIX | N | AFDLENGTH | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ / AFDPART / | | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ ADDRESSFAMILY 16 bit unsigned value as assigned by IANA (see IANA Considerations) PREFIX 8 bit unsigned binary coded prefix length. Upper and lower bounds and interpretation of this value are address family specific. N negation flag, indicates the presence of the "!" character in the textual format. It has the value "1" if the "!" was given, "0" else. AFDLENGTH length in octets of the following address family dependent part (7 bit unsigned). AFDPART address family dependent part. See below. This document defines the AFDPARTs for address families 1 (IPv4) and 2 (IPv6). Future revisions may deal with additional address families. 4.1. AFDPART for IPv4 The encoding of an IPv4 address (address family 1) follows the encoding specified for the A RR by [RFC 1035], section 3.4.1. PREFIX specifies the number of bits of the IPv4 address starting at the most significant bit. Legal values range from 0 to 32. Trailing zero octets do not bear any information (e.g., there is no semantic difference between 10.0.0.0/16 and 10/16) in an address prefix, so the shortest possible AFDLENGTH can be used to encode it. However, for DNSSEC [RFC 2535] a single wire encoding must be used by Koch Experimental
