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Proxy Mobile IPv6 (or PMIPv6, or PMIP) is a network-based mobility management protocol standardized by IETF and is specified in RFC 5213. It is a protocol for building a common and access technology independent of mobile core networks, accommodating various access technologies such as WiMAX, 3GPP, 3GPP2 and WLAN based access architectures. Proxy Mobile IPv6 is the only network-based mobility management protocol standardized by IETF.
Network-based mobility management enables the same functionality as Mobile IP, without any modifications to the host's TCP/IP Protocol stack. With PMIP the host can change its point-of-attachment to the Internet without changing its IP address. Contrary to Mobile IP approach, this functionality is implemented by the network, which is responsible for tracking the movements of the host and initiating the required mobility signalling on its behalf. However in case the mobility involves different network interfaces, the host needs modifications similar to Mobile IP in order to maintain the same IP address across different interfaces.
The "SaMOG" (S2a Mobility) study item in 3GPP defines the interworking between mobile packet core and a trusted WLAN access network. The interface that SaMOG defines for this interworking is 3GPP S2a PMIP and GTP interfaces.
+--------+ _----_ | +--------+ _----_ | | _( )_ | | | _( )_ | |----( Internet ) | | |----( Internet ) | (LMA) | (_ _) | | (LMA) | (_ _) | | '----' | | | '----' +--------+ | +--------+ | | | -- -- --- -- -- | _----_ -- -- | _( )_ -- -- | ( internet ) -- IP Network -- | (_ _) -- -- | '----' -- -- | | -- -- --- -- -- | +-----------+ / \ | | MAG |---- +-------------+ +-------------+ | +-----------+ |--- (Session Chaining) | | | | | | LMA |---- | MAG | | MAG | | +-----------+ | | | | | | +-------------+ +-------------+ | _----_ | | | | | _( )_ +-----+ +-----+ +-----+ +-----+ | --(IP Network )-- | AP | | AP | | AP | | AP | | | (_ _) | | (L2)| | (L2)| | (L2)| | (L2)| | | '----' | +-----+ +-----+ +-----+ +-----+ | +-----+ +-----+ . . . . | | MAG | | MAG | / \ / \ / \ / \ | +-----+ +-----+ MN | /\ | MN | Proxy Mobile IPv6: Flat Domain Model | Proxy Mobile IPv6: Domain Chaining |
The PMIPv6 architecture defines following functional entities:
Mobile Operators today are facing two fundamental challenges:
To address these scaling challenges, mobile operators are exploring new technology approaches for expanding their network coverage by integrating alternative access technologies into a common mobile core. Specifically, Wireless LAN networks based on IEEE 802.11 standards is showing lot of promise.
Secondly, for addressing the issue with the massive growth in mobile data traffic, mobile operators are exploring new ways to offload some of the IP traffic flows at the nearest WLAN access edge where ever there is an internet peering point, as supposed to carrying it all the way to the mobility anchor in the home network. Not all IP traffic needs to be routed back to the home network; some of the non-essential traffic which does not require IP mobility support can be offloaded at the access edge gateway. This approach provides greater leverage and efficient usage of the mobile packet core with increased overall network capacity and by lowering transport costs. Approaches such as, Selective IP Traffic Offload Option can be provide the basic offload semantics.
|Functional Block||Requirement||Platform API Interface||Description|
|Trigger Handler||Events: MN-ATTACHED, MN-DETACHED Parameters: Mac-Address, MN-Id (if present)||Linux API - TBD||This functional block is required for detecting the triggers related to mobile node's attachment, detachment, address configuration and router discovery related events. The network triggers, ARP message for the default-router’s MAC address, Gratuitous ARP message, DHCP Request message, IPv6 ND messages are the potential triggers for the MAG to initiate PMIPv6 signaling. In some cases, trigger can also be based on detecting a new MAC address on the access link by other link-layer specific means. Refer to: RFC 5844, RFC 5213, RFC 4436, RFC 5227. The identity of the mobile node in these triggers is always the Mac address, except for DHCPv4, where the client-identifier option can potentially be the mobile node identifier (if set by the client or a transit node such as an access point, or a WLAN controller).|
|Identity Management||GET-MN-Identity. Parameters: Mac Address, MN-Id||TBD||The identity of the mobile node is tied to the access authentication. When the mobile node using 802.1x/EAP mechanisms complete the access authentication, its identity used for authentication and the corresponding Mac address of the MN is known. If access Authenticator function and the MAG are functionally collocated on the same node, it is internal to the implementation as how that mapping between the mobile node’s identity and its link-layer/Mac identifier is obtained. It is also possible these functions are hosted on different network nodes (Ex: Authenticator on the AP and the MAG on the Wireless-LAN-controller/first-hop-router), but with some protocol interface between the two nodes, that enables the MAG to obtain the mobile node's identity. Refer to Section 6.6, RFC 5213. When using Mac Address as the MN-Id, the security implications and the Mac address in the policy profile needs to be understood.|
|Policy Profile||GET-MN-Profile. Parameters: MN-Id||TBD||The mobile's node policy profile identifies the service preferences for a given mobile node. Parameters such as PMIPV6 Domain, LMA IP Address, 3GPP APN ..etc., are present in the profile. Refer to Section 6.2, RFC 5213 This profile is typically on a central policy store such as AAA, or it can also be locally configured. Refer to PMIPv6 RADIUS draft, or PMIPv6 Diameter Interface (RFC 5779).|
|PMIPv6 Signaling||PBU/PBA Messages||TBD||The options that are required in the PBU message are a.) Home Network Prefix option b.) IPv4 Home Address Request option c.) Access Technology Type option d.) Link-layer Identifier option e.) Handoff Indicator option. Other optional parameters such as Service Selection Option for carrying the 3GPP APN information, Access Network Information option, IPv4 Traffic Offload Option, and any Vendor Specific options. Refer to Section 8 (RFC 5213). Section 3 (RFC 5844), Section 3 (RFC 5094), Section 3 (RFC 5149). It is to be noted that the PBU is just MIPv6 BU message. Any of the MIPv6 Open source implementations can be used as the messaging library after adding the new options.|
|DHCPv4 Interactions||Get-IP-Address-From-LMA, Assign-IP-Address-To-MN. Parameters: MN-Id, Mac Address, IPv4 home Address, Subnet Mask, Default-router Address||Example||The mobile node obtains its IPv4 address using DHCPv4. RFC-5844 supports two modes of DHCP configurations, DHCP server collocated on the MAG and the DHCP Relay collocated on the MAG. Implementing DHCP server (minimalistic) collocation on the MAG is the simpler approach. The needed interactions are the ability to influence the DHCP server to assign an IPv4 address that the MAG obtained from LMA over PMIPv6 signaling plane. When there is DHCP Discover request from the mobile node, the DHCP server should trigger the MAG and the MAG should return the IP address after completing the PMIPv6 signaling with the mobile node's LMA. The DHCP server should assign the IP address that it obtains from the LMA. The MAG should also be able to respond to any ARP requests for the default-router address.|
|Tunnel Management||Create-Tunnel, Delete Tunnel. Parameters: Encap-Type, IP Source Address, IP Destination Address||Example||PMIPv6 specifications support GRE, IP-in-IP encapsulation modes. In other words the tunnel encapsulations can be IPv4-GRE, IPv6-GRE, IPv4 and IPv6. The payload packet can be IPv4, or IPv6, carried with the negotiated tunnel encap. The linux open source package, IPRoute2, support both these encapsulation modes.|
|IP Forwarding||Add-IPv4-Tunnel-Route, Delete-IPv4-Tunnel-Route, Add-Reverse-Tunnel-Policy-Route, Delete-Reverse-Tunnel-Policy-Route. Parameters: IPv4 Address, IPv6-Prefix, Tunnel-Interface-Id, MN-MAG-Interface-Id.||TBD||The MAG should ensure any IPv4 or IPv6 packets from the mobile node using the IP addresses assigned by the LMA, should be reverse tunneled over the PMIPv6 LMA tunnel. Typically, a PBR route tied to the MAC address, source IPv4 address, source IPv6 prefix in the packet headers can be used for selecting the packet for reverse tunneling. When local-routing is enabled, there are some optimizations needed.|
|Functional Block||Requirement||Platform API Interface||Description|
|Proxy Model||TBD||TBD||Extend open source MIPv6 Home Agent to support PMIPv6|
|Data Structures||TBD||TBD||Extend the BCE table with new parameters, define new PMIPv6 mobility options|