The WINS architecture is very different from that of DNS. WINS maintains a database of name-IP address mappings. It is not hierarchical. After a client registers a mapping, the WINS server issues a successful registration message to the client. Encapsulated in that message is a time-to-live (TTL) value, which is like a "lease" on the name, held in trust by WINS for a certain period of time.
What if the name is already registered with WINS and the client makes a new registration attempt, or another client tries to register with the same NetBIOS name? WINS does not ignore the request; it sends out a verification request to the currently registered owner of the mapping. The request goes out three times at 500-millisecond intervals. If it has more than one IP address for the client, which is often the case on NT, 2000, or Windows Server 2003 servers, WINS tries each address that it has for the registered owner. This verification regimen continues until all IP addresses are "called" or the owner responds.
If the owner responds, the client requesting the registration gets a polite decline. If the owner does not respond, however, the client requesting registration gets free passage.
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