There are two types of LNP Query Services provided by CenturyLink:
- LNP Default Query Services
- LNP Database Query Services
Let's take a look at Default Query Services first:
CenturyLink provides Default Query Services whenever it receives unqueried calls from service providers. These service providers may include Competitive Local Exchange Carriers (CLECs), Incumbent Local Exchange Carriers (ILECs), Interexchange Carriers (IXCs) or Wireless Service Providers (WSPs) that require a query in order to terminate calls efficiently.
If the call is being handed off at a tandem (local/toll/access), then the switch will launch a query to determine if the terminating telephone number is ported, and if so, where it was ported to. A record is created by the switch that indicates the query was done.
If the call is on a direct route to a CenturyLink end office, then the switch will first attempt to complete the call within that switch. If it doesn't find that TN as a working number, then it will launch the query. At the end office, if a number turns out to be ported, then the switch will have to redirect that call up to the appropriate tandem for it to be switched out to the correct end office.
It is because of this extra switching that the end office LNP query is more expensive than a tandem query.