UMTS - Proxy Mobile IPv6 Protocol

It is a mobility management protocol standardized by Internet Engineering Task Force (IETF) which works on developing internet protocol standards.

Dual Stack Capability

Dual stack capability for PMIPv6 has two targets −

To support IPv4 home addresses
To allow IPv4 only transport across the access network; in this case the MAG may use also an IPv4 private address, and a NAT may be deployed along the path towards the LMA.

These two features can be used independently. To solve these requirements, the following extensions made −

In the Binding Cache of LMA −

IPv4 address assigned to the mobile node and now registered with the mobile access gateway (including corresponding subnet mask). It comes either from static configuration/profile or is dynamically allocated by LMA.
IPv4 default-router address assigned to the mobile node.

In the Binding Update list of MAG −

IPv4 home address assigned to the mobile attached interface.
IPv4 default router of the mobile node. The LMA and MAG should implement IPv6, and they also need an IPv4 address. MAG is the IPv4 Default Router for the UE on its access link.

PMIPv6 Signaling

Table below provides an overview of PMIPv6 signaling messages (basic PMIPv6 and specified improvements in IETF for connecting dismissal and way of management). Signaling PMIPv6 base is made with "Binding Update" (BU) MAG to LMA, and a corresponding "Update acknowledgment Binding" (BUA) messages back to MAG is used for registering, refreshing and binding deletion. IP address information (IPv4 or IPv6 address prefix) is usually requested by the LMA and MAG assigned by the initial enrollment.

PMIPv6 Signaling Message		Direction	Description
Binding Update	PBU	MAG → LMA	Requests creations, extension and deletion of a mobility binding. It is also used to request a new IPv4 address.
Binding Update Acknowledgement	PBA	LMA → MAG	Acknowledges the requests for creation, extension and deletion of a mobility binding. It is also used to allocate and IPv4 address.
Binding Revocation Indication	BRI	LAM → MAG	Notification that a binding is revoked and thus will be deleted by LAM, allows also bulk revocations.
Binding Revocation Acknowledgement	BRA	MAG → LMA	Acknowledges a binding revocation.
Heartbeat	HB	MAG → LMA LMA → MAG	Periodic signaling message, used for detecting failure.

3GPP Specific Information Elements Added to PMIPv6

PMIPv6 is designed for a very general use; 3GPP has some special requirements arising from the need to make it compatible as possible with capacities of GTP.

Vendor Specific Information	Direction	Explanation
Protocol Configuration Options	MAG → LMA LMA → MAG	Mirrored from GTP, used to transfer frequently needed, protocol related data between UE and network.
Specific 3GPP related error code	LMA → MAG	It can indicate that no access is given to an APN.
Connection Set Identifier (CSI)	LMA → MAG MAG → LMA	Contains one or more CSIs. It is generated for each new PDN connection and used in case of partial node failure to identify the PDN.
PDN type indication	LMA → MAG	Used to indicate the decision of the PDN GW.
PDN GW IP address	MAG → LMA	Used in case of chaining on S2a/S2b to transfer to the intermediate LMA.
DHCPv4 address allocation indication	LMA → MAG	Indicates that IP at allocation through DHCPv4 is to be used by the UE.