The obvious solution is a system like IP addresses. Every system has an address like universe.galaxy.region.system or whatever, then the system is subdivided in

The obvious solution is a system like IP addresses. Every system has an address like universe.galaxy.region.system or whatever, then the system is subdivided in whatever way is logical for that system. That way you can route ships or data or whatever to a specific system in a logical way. Each system decides how to allocate addresses. Since most systems won’t have anything or anyone to care, something like NASA or registrars would just allocate a block to the system and give large things like planets an address.