Client Conflicts Detected During Registration
When a client node registers or refreshes a name, the name might already exist in the WINS database. The action taken by the WINS server depends on the state of the registered name. It might be active, released, or extinct. (An extinct name is referred to as a tombstone.) The name might be a unique name or a group name, owned by the server or a replica, a database entry copied from another WINS server, with a statically or dynamically assigned IP address. The IP address might be the same as or different from that specified in the registration request of the client.
Two cases are always handled the same way: Normal group entries and static entries are never overwritten. The WINS server always returns a negative name registration response to registration requests for a name that is already in the database as a group or static name. Internet groups get additional members through the use of Internet group registration. Internet groups, or "special groups" as they are sometimes called, are used for special, user-defined administrative groups. These internet groups are sometimes used to group resources such as, file servers and printers. In this case, if the record in conflict has been released or tombstoned, the name registration request is treated as the registration of a new name.
With unique, dynamic names, if the IP addresses are the same, the WINS server returns a positive name registration response and acts as described in Table 7.3.
Table 7.3 Name Registration Responses
State of Name |
Server Action |
|---|---|
Owned and active |
Update time stamp |
Replica and active |
Update time stamp, take ownership, increment version ID |
Released |
Update time stamp, make active, increment version ID |
Owned tombstone |
Update time stamp, make active, increment version ID |
Replica tombstone |
Update time stamp, take ownership, make active, increment version ID |
If the IP address of the registration request is different from the IP address of the database record, and the existing database record is already released or tombstoned, then the name registration is treated as new. The server sends a positive name registration response and updates the entry to reflect the new time, ownership, version ID, and active state.
If the existing database entry is active and has an IP address that is different from the IP address of the registration request, the WINS server must determine whether the name and IP address in the database entry are still in use. The WINS server does this by sending a name query request to the client computer with the IP address in question. Figure 7.5 shows the initial step of a registration request sent from the client to the server, followed by a challenge sent by the server to the old IP address.
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Figure 7.5 A WINS Server Challenges an Old Address
If the server receives a positive name query response from the old IP address, it rejects the new registration by sending a negative name registration response to the client that originally requested the name registration. If the old address does not respond to the name query request, the server assumes there is no computer with that name and IP address and accepts the new name registration. In this case, the last arrow indicates a positive name registration response.