7.1 Control and User Plane Protocol Stacks

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

7.1.1 Protocol Options for S2b

The following protocol may be supported on S2b:

– PMIPv6;

– GTP.

Figures 7.1.1-1 and 7.1.1-2 illustrate the control plane for Mobility Management (MM) and the user plane on S2b for the PMIPv6 and GTP variants of S2b respectively.

Legend:

– According to terms defined in PMIPv6 specification, RFC 5213 [8], the functional entities terminating both the control and user planes are denoted MAG in the non-3GPP IP access and LMA in the Gateway. LMA includes also the function of a Home Agent.

– The MM control plane stack is PMIPv6 (RFC 5213 [8]) over IPv6/IPv4.

– The user plane carries remote IPv4/v6 packets over either an IPv4 or an IPv6 transport network. Between the UE and the ePDG, packets are encapsulated using IPSEC RFC 3948 [48].

– The tunnelling layer implements GRE encapsulation applicable for PMIPv6.

– IPv4/IPv6: This refers to network layer protocols. On the ePDG MAG user plane this includes termination of the UE-MAG IP messages that may be handled by the ePDG (e.g. DHCP) and forwarding of user plane IP packets between the UE-MAG point-to-point logical link and the S2b tunnel for the UE.

Figure 7.1.1-1: Protocols for MM control and user planes of S2b for the PMIPv6 option

Legend:

– GPRS Tunnelling Protocol for the control plane (GTP-C): This protocol tunnels signalling messages between the ePDG and the P-GW (S2b).

– GPRS Tunnelling Protocol for the user plane (GTP-U): This protocol tunnels user data between the ePDG and the P‑GW in the backbone network. GTP shall encapsulate all end user IP packets.

– UDP/IP: These are the backbone network protocols used for routing user data and control signalling.

Figure 7.1.1-2: Protocols for MM control and user planes of S2b for the GTP option

7.1.2 Protocol Options for S2c over Un-trusted Non-3GPP IP Accesses

The following protocols shall be supported for S2c over un-trusted non-3GPP IP accesses:

– DSMIPv6, with IPsec and IKEv2 used to secure mobility signalling, as specified in RFC 4877 [22].

The figure below illustrates the control plane for Mobility Management (MM) and the user plane.

Legend:

– According to terms defined in DSMIPv6, RFC 5555 [10], the functional entities terminating both the control and user planes are denoted MN (Mobile Node) in the UE, and HA (Home Agent) in the Gateway.

– The MM control plane stack is DSMIPv6, RFC 5555 [10] over IPv6/IPv4.

– The user plane carries remote IPv4/v6 packets over either an IPv4 or an IPv6 transport network. Between the UE and the ePDG, packets are encapsulated using IPSEC RFC 3948 [48].

– The tunnelling layer implements IP encapsulation applicable for MIPv6 as defined in DSMIPv6 [10]. In some cases the tunnelling layer may be transparent.

Figure 6.1.2-1: Protocols for MM control and user planes of S2c for the DSMIPv6 option