to perform route optimization the ha sends a binding update message bu u2032 to the cn 1 the bu u2032 is a normal correspondent binding update message except that the source address of the ipv6 header is set as the address of the ha and the message contains alternative care of address option in which the mn 39 s care of address is stored 7 the cn 1 sends binding acknowledgement to the ha optional note that the binding acknowledgement is sent back not to the mn but to the ha as the source address of the binding update was ha 39 s address fig4 and 5 illustrate movement of a mobile node between a pmip network and a cmip network when a ha performs proxy correspondent binding reception the ha performs proxy correspondent binding reception by receiving a correspondent bu message from the cn on mn 39 s behalf referring to fig4 the procedure of proxy correspondent binding reception when the mn moves from a pmip network to a cmip network is illustrated in fig3 mn 1 is served by ha 1 mn 2 which is a communicating peer with mn 1 is served by ha 2 ha 1 responds to a correspondent.