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I-D Internet-Draft Internet Protocol, version 6 (IPv6) defines a Unique Local IPv6 Unicast Address (ULA) format based on the IANA-assigned prefix fc00::/7. The structure for sub-prefix fd00::/8 is well defined, but the remaining sub-prefix fc00::/8 is reserved for future use. This document proposes a use for sub-prefix fc00::/8 in conjunction with the Universally Unique Interface IDentifier (UUID).

When two or more IPv6 nodes come together within a common local operating region (e.g., during the formation of a Mobile Ad-hoc Network (MANET)), they must be able to assign unique local-use addresses and exchange IPv6 packets even if there is no operator infrastructure present. The key feature of these local-use IPv6 addresses is that they must be assured unique so that there is no chance of conflicting with an address assigned by another node. There is no requirement that the addresses have topologically-oriented prefixes, since the (newly-formed) local network may not (yet) connect to any other Internetworking topologies. The local-use IPv6 addresses could then be used for continuous local communications and/or to bootstrap the assignment of topologically-oriented addresses under the IPv6 multi-addressing architecture . IPv6 defines a Unique Local IPv6 Unicast address (ULA) format based on the IANA-assigned prefix fc00::/7. The sub-prefix fd00::/8 is well defined, but the remaining sub-prefix fc00::/8 is reserved for future use. This document proposes a use for sub-prefix fc00::/8 in conjunction with the Universally Unique Interface IDentifier (UUID) .

The IPv6 addressing architecture specified in and defines the supported IPv6 address forms for unicast, multicast and anycast. Unicast addresses are typically assigned through Stateless Address AutoConfiguration (SLAAC) and/or the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) , but these services require the presence of IPv6 network infrastructure which may not be immediately available in spontaneously-formed MANETs or other isolated local networks. A new IPv6 address type known as the DRIP Entity Tag (DET) (or, Hierarchical Host Identity Tag (HHIT)) provides a well-structured address format with exceptional uniqueness properties. A portion of the address includes the node's self-generated Overlay Routable Cryptographic Hash IDentifier (ORCHID) while the remainder of the address includes a well-formed IPv6 prefix corresponding to an attestation service that supports address proof-of-ownership. Verification of the attestation aspect of the address requires access to network infrastructure, but this may not always be available. This document therefore proposes a new fully-self-generated IPv6 unicast address format that can be used either instead of or in addition to a DET/HHIT and/or other IPv6 unicast address types (noting again that a single interface may have multiple IPv6 addresses ). The address uses the 8-bit ULA prefix fc00::/8 along with a 120-bit interface identifier that includes the 120 least-significant bits of a Universally Unique IDentifier (UUID). With reference to Figure 8 of which depicts the UUIDv4 format, this "IPv6 ULA-UUID address" format is shown in :

To form an IPv6 ULA-UUID, the node creates a 128-bit UUIDv4 per then simply replaces the most significant 8 bits with the constant string '11111100' (0xfc); the resulting 128-bit ULA-UUID then has the format of an IPv6 address with an 8-bit subnet prefix and 120-bit interface identifier as permitted by the IPv6 addressing architecture. For example: fc84:6c29:de12:4b74:884e:9d2a:73fc:2d94::/8 After a node creates a ULA-UUID, it can use the address within the context of spontaneously-organized local networks in which two or more nodes come together in the absence of supporting infrastructure and can still exchange IPv6 packets with little or no chance of address collisions. The use could be limited to bootstrapping the assignment of topologically correct IPv6 addresses through other means mentioned earlier, or it could extend to longer term usage patterns such as sustained communications with single-hop neighbors on a local link or even between multi-hop peers within a MANET. Note: while the ULA-UUID format specified above is relative to UUIDv4, the same format can be applied also to all other UUID versions specified in , i.e. by replacing the most significant 8 bits of the UUID with the constant string '11111100' (0xfc).

IPv6 ULA-UUID addresses based on the prefix "fc00::/8" have no topological orientation and can therefore be assigned to any of a node's IPv6 interfaces. The addresses may serve as a basis for multihop forwarding over a MANET interface and/or for local neighborhood discovery over other IPv6 interface types. Due to their uniqueness properties, IPv6 ULA-UUID addresses can be assigned to interfaces without invoking Duplicate Address Detection (DAD).

In progress.

This document has no requirements for IANA.

TBD.

This work was inspired by continued investigations into 5G MANET operations in cooperation with the Virginia Tech National Security Institute (VTNSI). Emerging discussions on the IPv6 maintenance (6man) mailing list are expected to shape future versions of this document. The author acknowledges all those whose useful comments have helped further the understanding of this proposal. Kyzer Davis (RFC9562 author) is acknowledged for his review and comments that helped shape the document. Honoring life, liberty and the pursuit of happiness.

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