Mobility management is a key issue in mobile hotspots which enable ubiquitous Internet services while onboard a vehicle. In this paper, we compare two representative mobility management schemes for mobile hotspots: the network mobility (NEMO) basic support protocol at the network layer and the session initiation protocol (SlP)-based network mobility support protocol at the application layer. We evaluate their salient features and quantify their handoff latency over a wireless fading channel. It is shown that the SIP-based network mobility support protocol can be easily deployed and can reduce the tunneling overhead incurred in the NEMO basic support protocol. However, it can increase the handoff latency due to longer message length.