LoST² is a protocol for geographic service discovery on the Internet. The protocol allows a client to discover network services related to the client's area of interest specified as a geographic object. LoST² is a generalized version of the original LoST protocol (RFC 5222) developed for next-generation emergency calling.

A LoST² service consists of the following logical entities:

• LoST seeker: An application using LoST² to discover network services
• LoST resolver: A local service that resolves LoST² requests on behalf of seekers
• LoST server: A server entity that routes LoST² requests received from resolvers and other servers
• LoST publisher: An entity submitting service descriptors to the LoST² service
• LoST responder: An entity resolving LoST² requests to service descriptors