The Mobile Internet Protocol (Mobile IP) is an extension to the Internet Protocol proposed by the Internet Engineering Task Force (IETF) that addresses the mobility issues. In order to support un-interrupted services and seamless mobility of nodes across the networks (and/or sub-networks) with permanent IP addresses, handover is performed in mobile IP enabled networks. Handover in mobile IP is source cause of performance degradation as it results in increased latency and packet loss during handover. Other issues like scalability issues, ordered packet delivery issues, control plane management issues etc are also adversely affected by it. The paper provides a constructive survey by classifying, discussing and comparing different handover techniques that have been proposed so far, for enhancing the performance during handovers. Finally some general solutions that have been used to solve handover related problems are briefly discussed.