N4 Session Establishment and Modification Procedure for IPv4v6 Call Flow

The following call flow provides a high-level description of the N4 session establishment and modification procedure for IPv4v6.

The IPv4v6 session establishment and modification procedure are similar to the IPv6 session establishment and modification procedure, except for the following procedures:

StepDescription
1In the session establishment request, a PDR IE is created to include both IPv4 and IPv6 UE addresses. The SDF filter also includes the IPv4 and IPv6 filters for selecting the PDRs.
2When the IPv6 address is assigned to the UE, an extra procedure – Router Solicitation and Router Advertisement – is required. The UE sends the Router Solicitation message to the network to receive the link layer address, once the session is established. The UPF forwards this message to the SMF and the SMF sends the Router Advertisement Message with the required parameters for configuring the IPv6 address of the UE.
3The RS/RA between UPF and SMF is GTP-u encapsulated. In addition, the SMF sends an extra pair of PDRs during session establishment and modification procedure, in which the GTP-u tunnel IDs are exchanged for GTP-u tunneling.
4

The additional pair of PDRs that are sent from the SMF are as follows:

  • For forwarding IPv6 Router Solicitation from UE to SMF, one PDR’s source interface is set to access, and its destination interface is set to CP-Function. The SDF filter is present in such a way that the UPF selects this specific PDR for the IPv6 Router Solicitation from the UE.

  • For instance, permit in 58 from any to ff01::2 any.

5The UE sends the IPv6 traffic to PDN once the RS/RA procedure is complete.
6No additional procedures are required for the IPv4 traffic for this PFCP session.