NEC Nortel Alcatel-Lucent Bell Labs This document specifies a mechanism which enhances Proxy Mobile IPv6 protocol signaling to support the creation of a transient binding cache entry which is used for inter-MAG handover optimization. This mechanism is applicable to the mobile node's inter-MAG handover while using a single interface or different interfaces. The handover problem space using the Proxy Mobile IPv6 base protocol is analyzed and the use of transient binding cache entries at a mobility anchor is described. The specified extension to the Proxy Mobile IPv6 protocol ensures optimized forwarding of downlink as well as uplink packets between mobile nodes and the network infrastructure and avoids superfluous packet forwarding delay or even packet loss.