16.1.4 Protocol Stacks

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

The following protocols are supported on S2a:

– GTP.

– PMIPv6.

IPv4 address and IPv6 prefix allocation considerations are equally valid for GTP and PMIPv6 S2a options.

The figure below illustrates the control plane for S2a Tunnel Management and the user plane for GTP option, respectively for Transparent Single-Connection mode, Single-Connection mode and for Multi-Connection mode.

Legend:

802.11: This refers to Layer 1 and Layer 2 defined by IEEE Std 802.11-2012 [64]. Layer 2 of 802.11 is used as L2 attach and detach triggers. L2 attach trigger is mandatory with IPv6 and IPv4v6 PDN Types, and optional for IPv4 PDN Type.

L3 trigger: This refers to DHCPv4 which can be used as optional L3 attach trigger with IPv4 PDN Type.

GTP-C: The GPRS Tunnelling Protocol control plane consists of signalling messages between the Trusted WLAN Access Gateway and the PDN- GW over the S2a interface. It is defined in TS 29.274 [57].

GTP-U: The GPRS Tunnelling Protocol user plane tunnels user data between the Trusted WLAN Access Gateway and the PDN GW over the S2a interface. It is defined in TS 29.281 [63].

UDP: This is the transport layer protocol onto which both GTP-C and GTP-U are layered.

IPv4/IPv6: This refers to network layer protocols. On the TWAN this includes termination of the UE-TWAN link-local protocols (e.g. IPv6 Neighbor Discovery, ARP) and forwarding of user plane IP packets between the UE-TWAN point-to-point link and the relevant S2a tunnel.

Figure 16.1.4-1: Protocols for control and user planes of GTP-based S2a for Transparent Single-Connection mode

Legend:

802.11: This refers to Layer 1 and Layer 2 defined by IEEE Std 802.11-2012 [64]. Layer 2 of 802.11 is used as L2 attach and detach triggers.

GTP-C: The GPRS Tunnelling Protocol control plane consists of signalling messages between the Trusted WLAN Access Gateway and the PDN- GW over the S2a interface. It is defined in TS 29.274 [57].

GTP-U: The GPRS Tunnelling Protocol user plane tunnels user data between the Trusted WLAN Access Gateway and the PDN GW over the S2a interface. It is defined in TS 29.281 [63].

UDP: This is the transport layer protocol onto which both GTP-C and GTP-U are layered.

IPv4/IPv6: This refers to network layer protocols.

Figure 16.1.4-2: Protocols for control and user planes of GTP-based S2a for Single-Connection mode

Legend:

802.11: This refers to Layer 1 and Layer 2 defined by IEEE Std 802.11-2012 [64]. The TWAG MAC address is used as a multiplexing identifier between multiple PDN connections which belong to the same UE.

WLCP: WLAN Control Protocol (WLCP) is used to establish and release PDN connections. The functionality of WLCP is defined in 16.1.4A.3.1.

GTP-C: The GPRS Tunnelling Protocol control plane consists of signalling messages between the Trusted WLAN Access Gateway and the PDN- GW over the S2a interface. It is defined in TS 29.274 [57].

GTP-U: The GPRS Tunnelling Protocol user plane tunnels user data between the Trusted WLAN Access Gateway and the PDN GW over the S2a interface. It is defined in TS 29.281 [63].

DTLS: Datagram Transport Layer Security (DTLS) is used to protect WLCP signalling as described in TS 33.402 [45].

UDP: This is the transport layer protocol onto which both GTP-C and GTP-U are layered.

IPv4/IPv6: This refers to network layer protocols.

Figure 16.1.4-3: Protocols for control and user planes for GTP-based S2a for Multi-Connection mode

When PMIP based S2a is used with Trusted WLAN, the PMIPv6 protocol stacks described in clause 6.1.1 apply.