Because services for emergency contact resolution may differ depending on local or service needs, this document only specifies the "wire format" for LoST services and explicitly leaves open the possibility for many different types of deployment. For instance: During discovery, a client may be directed to issue all queries to an LoST service completely authoritative for a given jurisdiction. A client may be directed to issue queries to an LoST server that acts as a reflector. In such a case, the LoST server analyzes the query to determine the best server to which to refer the client. Or the client may be directed to a server that performs further resolution on behalf of the client. A LoST service may also be represented by multiple LoST servers, either grouped together or at multiple network locations. Using U-NAPTR, clients may be given a list of multiple servers to which queries can be sent for a single service. For instance, the service at emergency.example.com may advertise LoST service at local1.emergency.example.com, local2.emergency.example.com, and master.emergency.example.com. Each server may given a different preference. In this case, 'local-1' and 'local-2' may be given a lower preference (more preferred) than 'master', which might be a busier server or located further away.

+ | | client |------ | local-1 | | |--- \ | | +-----------+ \ \ +-----------+ \ \ \ \ +-----------+ \ \ pref 10 | | \ --------->| local-2 | \ | | \ +-----------+ \ \ +-----------+ \ pref 20 | | ------------------------->| master | | | +-----------+ ]]>