# Global IoT Mobility: A Path Based Forwarding Approach
## 2 Mobility Management Solutions in Different Access Technologies
### Wireless IP Networks  
Mobile IP in its two versions MIPv4 [10] and MIPv6 [12] is the Internet Engineering Task Force (IETF) standard mobility solution that is designed to allow Mobile Nodes (MNs) to keep their IP address while moving. This enables forwarding traffic destined to MNs when they change their point of attachment to the network, hence providing mobility support. Mobile IP is a host-based mobility solution, where the MN takes part in the mobility management process. The solution has witnessed several enhancements leading to the Proxy Mobile IPv6 (PMIPv6) [17; 18]. PMIPv6 is a network-based mobility management solution that separates the mobile node from the involvement of the handover procedure as compared with host-based mobility protocols [19; 20]. PMIPv6 promises easier deployment and better handover performance and is aimed at accommodating various mobile access technologies such as WiMAX, 3 GPP, 3 GPP2, and WLAN.  
PMIPv6 introduces two network entities, namely the Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG) as shown in Figure 1. The LMA is responsible for maintaining the MN's reachability and acts as a topological anchor for the MN's home network prefix(es). The MAG has the responsibility of performing mobility management on behalf of the MN and resides on the access link where the MN is attached [21]. It detects the MN's movement to and from the access link and coordinates with the LMA to make sure that the MN will be able to obtain the same address configuration from its home network prefix(es) even after connecting to a different MAG with the PMIPv6 domain [17].  
In PMIPv6, the LMA discovery can be achieved as follows: First, the MAG receives the LMA's Fully Qualified Domain Name (FQDN) from the Authentication, Authorization, and Accounting (AAA) infrastructure during the network access authentication. Then, the MAG resolves the FQDN to the LMA's IP address through a DNS lookup.  
Upon an IP handover from one MAG to another, the LMA is notified about the MN's change of location, and the MN's binding at the LMA is updated according to the following procedure. The previous MAG (pMAG) sends a Proxy Binding Update (PBU) message to the LMA to de-register the MN, and the new MAG (nMAG) sends a PBU message to the LMA to register it. The LMA replies to each of the PBU messages by a Proxy Binding Acknowledgement (PBA) message. All the data traffic of the MN passes through the LMA and a bi-directional tunnel is established between the LMA and the MAG that serves the MN [19]. An advancement of PMIPv6 is the Proxy-Based Fast Mobile IPv6 Protocol  
Figure 1: Proxy mobile IPv6 domain.  
(PFMIPv6) by IETF [22], where an additional bidirectional tunnel is established between the previous and new MAG to tunnel packets meant for the MN during handover as shown in Figure 2. There are two modes of operation in PFMIPv6: (a) a predictive mode where the tunnel between the serving and the target MAG is established prior to the MN's attachment to the New MAG, and (b) a reactive mode where tunnel establishment takes place after the MN attaches to the New MAG [23].