PDP Address Allocation | LTE AND IPV6

PDP addresses are handled differently for PDN interworking of type PPP and IP (IPv4 or IPv6).

1 Interworking with PDN Based on IP

During PDP context activation, the MS can configure an IPv4 address, or obtain an IPv6 interface identifier to be used during the IETF-based IP address allocation after PDP context establishment.

The MS can obtain an IPv4 address or an IPv6 prefix via an IETF-based IP address allocation mechanism once the PDP context is established.

The EPS specifies the following IETF-based IP address/prefix allocation methods:

1. IPv4 parameter configuration and IPv4 address allocation through the DHCPv4.
2. IPv6 parameter configuration through a stateless DHCPv6
3. /64 IPv6 prefix allocation through IPv6 stateless address autoconfiguration

The MS releases any allocated IPv4 address or IPv6 prefix locally for the corresponding PDN connection upon deactivation of a default PDP context.

2 Interworking with PDN Based on PPP

No PDP address is configured during PDP context activation. Instead, such information is negotiated and configured during the NCP phase of PPP.

3 IP Address Allocation via NAS Signalling

The MS sets the PDP type in the PDP address field using the ACTIVATE PDP CONTEXT REQUEST message. This is done when requesting default PDP context establishment.

If the MS requires using DHCPv4 for IPv4 address assignment, it indicates that to the network within the Protocol Configuration Options in the ACTIVATE PDP CONTEXT REQUEST message.

When the MS requests IPv6 address allocation, the network accommodates it in one of two parts: a /64 IPv6 prefix and an interface identifier of 64 bits length. The MSN doesn't use the IPv6 prefix part immediately by the MS; however, the network uses the same IPv6 prefix in IETF-based IP address allocation subsequent procedures. The interface identifier is only used to build a unique link-local IPv6 address.