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General Internet Engineering Task Force ipv6 link-local amateur radio packet radio This document presents a process by which IPv6 addresses can be uniquely and automatically assigned to amateur packet radio nodes without the need for central coordination.

Introduction When coordinating a global-scale packet radio network, it may not be practical or desireable to require all participating stations to request and/or register their local IP addresses with a central authority. The addressing technique presented in this document aims to provide a standard method by which radio nodes can self-assign addresses by utilizing the existing guarantee that all station callsigns are unique.

Node Addressing Packet radio stations (also referred to as "nodes") are generally identified via their station callsign followed by an informational number or letter, this suffix is used to describe the type or an arbitrary ID of the station. Unlike other common network protocols used by packet radio nodes, IPv6 does not offer a mechanism for addressing another node by its callsign and ID. This means that an alternate addressing scheme, such as the one defined in this document, is needed to allow nodes to communicate with each other using IPv6.

A Note on Prefix Length While the addressing method defined in the following section may be applied to nearly any network prefix length, usage of a 64 bit long network portion is strongly encouraged to ensure all implementations are interoperable.

Determining the Address for a Station Given an IPv6 prefix with a 64 bit long network portion, the host address for station is calculated via the following steps:

1. Compute the SHA-256 hash of the station's UPPERCASE callsign.
2. Use the first 60 bits of the hash as the first 60 bits of the host portion of the IP address.
3. Use the final 4 bits of the address' host portion to store the station's ID.

Using this method to compute the address for a station with the callsign "VA3ZZA" and the ID "10" as a host in the prefix "2001:db8::/64" would result in the station address: "2001:db8::9846:807d:5b56:3a7a".

Benefits of this method This method of IP address assignment has several benefits:

• Callsigns are uniquely assigned to stations by existing governing bodies. Using them as the basis of address creation will ensure a unique base hash for each station.
• Hashing callsigns instead of trying to plainly hex encode them allows support for excessively long callsigns.
• Encoding the station ID in the final nibble of the address allows for up to 16 nodes under the same callsign to be assigned addresses within the same /124. This allows address-based access control logic to operate on a whole callsign (first 60 bits of the host portion) at once, an ability not possible if the ID was also hashed.

Drawbacks of this method While it is possible for one node to correlate another's IP address to its station callsign via a lookup table, ideally the raw callsign could be encoded directly into the IPv6 address. Doing so would both allow for a node to easily determine the callsign of a sending station without additional metadata embedded in the received packet, and allow the source address on outgoing packets to be used to satisfy legal station identification requirements. Unfortunately, this is not feasible due to many governments assigning temporary "special event callsigns" to stations. These special callsigns often do not follow the general length restrictions on permanent callsigns, raising the possibility that a station will be assigned a callsign longer than is possible to encode directly in an IPv6 address, thus being un-addressable.

IANA Considerations This memo includes no request to IANA.

Security Considerations This document should not affect the security of the Internet.

References Normative References Informative References