HIP stands for Host Identity Protocol. The idea is to separate a host's identity from its location. An IP address does both. It could be argued that DNS already achieves the ID/locator split: The DNS name of your host identifies it, the resolved IP address gives its current location.

Well DNS does not really split this because of the way TCP-connections are defined: The are the pair of IP and Ports of both sides. So TCP-connections are always between two locations not between two identities. That's the reason why connections get lost when changing from one network to another.

Also updating DNS entries is to slow to do it whenever you walk with your smartphone from one cell/wifi to another.

You are right. I simply wanted to illustrate the idea of id/locator split. The mapping of a fixed id to a quickly changing locator is a problem of all those schemes.