With the rapid development of Internet and mobile communication technology, portable mobile devices such as mobile phones and laptops have been used widely. More and more people want to access Internet in any place and keep communication continuous while moving. So IETF group brings forward Mobile IPv6 protocol. But when Mobile node enters a new subnet, the handover procedures may lead long delay and high packets losses, the correspondence will be interrupted and the Qos will be descended as well. How to retain the continuity and reduce delay to ensure the real-time applications such as Voice over IP becomes the most important work in Mobile IPv6 research.In order to optimize the handover delay in standard Mobile IPv6, IETF group brings out several improved handover protocol.Fast handover for Mobile IPv6 (FMIPv6) registers in advance by obtaining the information of the new subnet, and keep the communication continuous after finishing the handover. In this way, the handover delay in standard Mobile IPv6 can be decreased. Hierarchical Mobile IPv6 (HMIPv6) divide the whole network into many fields, each field will be managed by a new entity called mobility anchor point (MAP). When the mobile node moves inside a field, the MAP will transmit the data packets with correspondent nodes instead of home agent.
