This indicates an attempt to use the DHCPv6 protocol.
DHCPv6 is the Dynamic Host Configuration Protocol for IPv6. Although IPv6's stateless address autoconfiguration removes the primary motivation for DHCP in IPv6, DHCPv6 can still be used to assign addresses statefully if the network administrator desires more control over addressing. It can also be used to distribute other configuration information as is the practice in IPv4. A notable case is Domain Name System servers used on a network, albeit other mechanisms exist for this in the Neighbour Discovery Protocol.