The LocalDiscoveryServer is useful for networks where the host names can be discovered. However, this is typically not the case in large systems with multiple servers on multiple subnets. For this reason there is a need for an enterprise wide DiscoveryServer called a GlobalDiscoveryServer.
The GlobalDiscoveryServer (GDS) is an OPC UA Server which allows Clients to search for Servers within the administrative domain. When compared to the LDS, the GDS provides an authorative source for Servers which have been verified by administrators and accessed via a secure communication channel.
The GDS provides Methods that allow administrators to register applications and allow applications to search for other applications.
Some GDS implementations may provide a front-end to an existing DirectoryService such as LDAP (See Annex E). By standardizing on an OPC UA based interface, Clients do not need to have knowledge of different DirectoryServices.