What is a lookup group?
A lookup group is a string used to identify a set of services. Groups can be used to organize services into logical sets, for example by department or floor. Any service, including a lookup service, can belong to more than one group. The default group is called the "public" group, although its name is a null string.
A group name can be used during discovery to limit the set of lookup services found; only those lookup services which are members of that group will respond to the discovery request. Lookup services will also declare their groups during announcement. By default, lookup services are members of the public group and discovery finds all public lookup services. Services may choose to register themselves only in certain groups.