A service represents a layer four TCP or UDP service available on a device or virtual machine. For example, you might want to document that an HTTP service is running on a device. Each service includes a name, protocol, and port number; for example, "SSH (TCP/22)" or "DNS (UDP/53)."
A service may optionally be bound to one or more specific IP addresses belonging to its parent device or VM. (If no IP addresses are bound, the service is assumed to be reachable via any assigned IP address.)