(DUID) Data Unit Identifier

A Data Unit Identifier (DUID) is a unique identifier that is assigned to a data unit, such as a file, record, or packet, to distinguish it from other data units. DUIDs can be used for various purposes, such as data organization, tracking, and retrieval, and ensuring data integrity and authenticity. The format and length of a DUID can vary depending on the specific application and the requirements of the system. Some common types of DUIDs include file names, serial numbers, MAC addresses, and globally unique identifiers (GUIDs).

https://en.wikipedia.org/wiki/DHCPv6