Locator/ID Separation Protocol (LISP) Distinguished Name Encoding
Extracted elements (18)
AFI 17 is variable-length, unlike fixed-length AFIs (e.g., AFI 1 for IPv4 is always 4 octets). A NULL terminator (0x00) is defined to allow receivers to determine the string length without a separate explicit length field in the base EID encoding.
DNs used as EIDs for Proxy-ETR role advertisement allow the Mapping System to aggregate locators from all Proxy-ETRs into a common locator-set associated with a shared DN EID, enabling on-demand distribution of role-based locator-sets.
Practical deployments use dedicated DN registrations to drive ETR onboarding with Map-Servers as a deterministic process independent of the availability of other mappings, providing stability for reliable transport sessions through transient network events.
The Distinguished Name field in this document explicitly has no relationship to the similarly named field in PKIX/X.509 specifications (RFC 5280); the name is coincidental.
DN strings are encoded as NULL-terminated US-ASCII using the UTF-8 character set as defined in RFC 3629, which preserves the full US-ASCII range. This ensures interoperability across implementations that handle UTF-8.
LISP DN encoding has been deployed in production networks for over 10 years (as of 2025) in the open-source lispers.net implementation for NAT-traversal, self-documenting RLOC names, and EID name registrations, validating the format's practical utility.
A NULL character MUST appear only once in the Distinguished Name string and MUST be at the end of the string.
An AFI 17 Distinguished Name encoded string MUST be at least 1 octet in length; if the octet after the AFI field is the NULL octet (0x00), the string is a NULL string and MUST be accepted.
Any use cases requiring different DN uses within an Instance-ID MUST define their own Instance-ID and syntax structure for the name registered to the Mapping System.
If a NULL octet appears before the end of the octet field in an LCAF-encoded DN, the string MAY be accepted but octets after the NULL octet MUST NOT be used as part of the string.
It is RECOMMENDED that each DN use case register their DNs with a unique Instance-ID to avoid name collisions.
When DNs are encoded in LCAF encodings with an explicit length field, the length field MUST include the NULL octet (0x00), and the string MUST still be NULL-terminated.
When performing DN-EID lookups, Map-Request messages MUST carry an EID Mask-Len length equal to the length of the name string in bits, instructing the Mapping System to perform exact-match or longest-match lookup.
DN-EID lookups support longest-match: if a less specific name is registered than what is requested, the Map-Server returns the registered name with its registered EID Mask-Len length. For example, a request for 'ietf.lisp' (80 bits) may return 'ietf' (40 bits).
DNs can be used as EIDs to register resources or services in the Mapping System, or as RLOCs to label equipment type, location, or other self-documenting information alongside address-specific EIDs or RLOC parameters.
When DNs are encoded as EIDs, the EID Mask-Len in EID-Records for all LISP control messages is the length of the string in bits, including the NULL-terminating 0x00 octet.
DNs are used in mappings that are part of the LISP control plane and may be encoded using LCAF; thus, the security considerations of RFC 9301 (LISP Control Plane) and RFC 8060 (LCAF) apply to DN usage.
AFI 17 Distinguished Name is encoded as a 2-octet AFI field (value 17) followed by a variable-length NULL-terminated (0x00) US-ASCII string. The NULL terminator allows length determination for this variable-length AFI type.