The FDSN data center registry contains a listing of data centers, which (web) services are offered, and which data sets are available from each.
Data centers maintain their own entries after completing the data center registration.
For more information see http://www.fdsn.org/datacenters/help/
In particular, documentation for the data set priorities and for service names.
Data center registry entries are exchanged in a JSON-based schema, which is defined using JSON Schema in this repository.
This repository contains an illustrative, reference example of a data center entry. The registry itself contains numerous entries of real examples as needed.