In IPv6 mobility does not have the problem of unbalanced routing as like in IPv4 packages, so that a mobile connection is so efficient as a normal connection. This is due to there is a process through which the mobile node can inform the node which communicates to which is the address in the new network and use this address for their communication.
The field ‘Total Lengh’which is part of the IPv4 header, is not found in the IPv6 header. Its function was to count the size of the packet payload plus the size of a variable lenght header. As the IPv6 header has a fixed size, the presence of this field is unnecessary.