5.14 Support IPv6 Prefix Delegation

29.2443GPPInterface between the Control Plane and the User Plane nodesRelease 17TS

Clause 5.3.1.2.6 of 3GPP TS 23.401 [14] and clause 4.6.2.3 of 3GPP TS 23.316 [57] specify requirements for IPv6 Prefix Delegation via DHCPv6, that allow assigning a single network prefix shorter than the default /64 prefix to a PDN connection or a PDU session.

The CP function shall assign, or request the UP function to assign (if the UP function indicates support of the UEIP feature, see clause 8.2.25), the network prefix shorter than the default /64 prefix by provisioning the UE IP Address IE in the UP function with:

– the IPv6D flag set to "1" and the IPv6 Prefix Delegation Bits field indicating the length of IPv6 Prefix for delegation (see clause 8.2.62); or

– the IP6PL flag set to "1" and the IPv6 Prefix Length field indicating the length of IPv6 Prefix for delegation (see clause 8.2.62), if the UP function supports the IP6PL feature (see clauses 5.21.1 and 8.2.25).

When UP function is requested to perform UE IP address allocation and IPv6 prefix delegation is used, the IPv6 prefix length may be determined by the CP function or the UP function:

– if it is determined by the CP function, the IPv6 Prefix Delegation Bits or IPv6 Prefix Length fields shall be set according to the desired IPv6 prefix length by the CP function;

– or if the IPv6 prefix length is determined by the UP function, the CP function shall set the IPv6 Prefix Delegation Bits or IPv6 Prefix Length fields to "0".

NOTE: The IPv6 prefix shorter than the default /64 prefix for IPv6 Prefix Delegation can include the /64 default prefix used for IPv6 stateless autoconfiguration (in EPS and 5GS) or not (5GS). In the latter case, the total IPv6 address space available for the PDU Session cannot be aggregated into one single IPv6 prefix; support of this latter case requires support of the IP6PL feature (see clauses 5.21.1 and 8.2.25).

When assigning additional IPv6 prefixes (i.e. prefixes in addition to the default prefix) to a UE, the CP function shall provision/update the UE IP Address IE in the PDI which may be as part of a Create PDR IE or a Update PDR IE, or in the Create Traffic EndPoint IE or Update Traffic EndPoint IE to the UP function as described above.