Windows NT WINS
WINS converts Windows computer names to IP addresses but does not do name lookups based on IP addresses. The use of Windows Explorer or NET commands invokes the NetBIOS interface. NetBIOS names, if repeated on another domain that is on the network, may cause a problem since there is no way to distinguish NetBIOS names between two domains. Each computer, when booted, sends a name registration broadcast. If there is no response, the computer will use the name it registered. A NetBIOS broadcast releases the computer name when the computer is shutdown gracefully.
WINS reduces this broadcast traffic when using NBT. The registration and release is sent to the WINS server rather than being broadcast. The clients have the IP address of the WINS server and they are configured to use WINS before using NetBEUI broadcasts. A backup WINS server may be available on the network for fault tolerance.
On the WINS server, there is a NetBIOS name for each service a NetBIOS computer offers. This uses the 16th hidden character of the NetBIOS names. The characters and their meanings are:
- 00 - Workstation service (Domain name) or (Workgroup name) or (Computer name)
- 03 - Messenger service (Computer name) or (User name)
- 06 - RAS server service (Computer name)
- 1B - Primary domain controller (Domain name)
- 1C - Domain controller or PDC or BDC (Domain name)
- 1D - Master browser (Domain name)
- 1E - Only is on servers, indicates the computer would become a browser if requested.. (Domain name) or (Workgroup name)
- 1F - NetDDE service (Computer name)
- 20 - Server service (Computer name)
- 21 - RAS client (Computer name)
- BE - Network Monitoring Agent service (Computer name)
- BF - Network monitor utility service (Computer name)
Most computers such as workstations have a minimum of Computer name (00) and Workgroup name (00). Also the Messenger service computer name and user name are registered.
WINS service is installed from the control panel network applet services tab. The computer must be restarted after the installation. The Microsoft WINS Manager which may be run from any NT computer on the network is used to configure WINS. To configure WINS, only statically assigned IP addresses on your network must be entered. This is done by selecting "Mappings" from the menu and clicking on the "Add Mappings" button.
The purpose of WINS is to allow a NetBIOS name to be converted to an IP address. Therefore computers using WINS must be using NBT (NetBIOS over TCP/IP). WINS was originally put in place to compensate for a shortcoming of NetBEUI which is the fact that it is not routable. Therefore on large Networks IP is used to transport NetBIOS and rather than using broadcasts, information is sent to the WINS server. In fact, although WINS overcomes a shortcoming in Microsoft networking, it can actually be used to solve another problem.
The problem concerns the dynamic allocation of computer addresses with DHCP. When DCHP allocated addresses to computers, that information is not currently sent to DNS servers. Therefore it is not possible using doman name service (DNS) to get an IP address based on a computer name for a computer that had its IP address assigned using DHCP. WINS solves this problem since when NetBIOS computers come up, they send their name and IP address information to the WINS server. The WINS server keeps this information updated and responds to name queries with IP addresses similar to DNS. Under the DNS configuration tab in the networking control panel, "Enabling DNS for WINS Resolution" allows DNS to ask the WINS server to help resolve IP addresses that DNS cannot resolve. This can be more easily implemented on the DNS server side by allowing the DNS server to use WINS. See the DNS section for details.
When a NetBIOS broadcast is to go out, a computer sends over TCP/IP to a WINS server to resolve NetBIOS names. WINS dynamically builds its database. When a client uses WINS it announces to the WINS server over TCP/IP rather than broadcasting to all computers. WINS Message Modes:
- Client Name Registration - When a client service is started, the appropriate NetBIOS name for that service (Using the hidden 16th byte) is sent to the WINS server. If the primary WINS server fails to respond, the request is sent to the secondary WINS server after three tries. If no WINS server responds, B-node broadcasts are used by the client. When contacted, the WINS server returns a time to live (TTL) field containing the length of time the client may use that name. If a duplicate name is received, a challenge is sent by the server to the registered client. If the current owner responds, the new client request is rejected.
- Client Lease Renewal - When the name lease is at 50%, the client sends a name renewal request to the WINS server with its name and IP address. When the lease is 7/8 up, the client will try again then attempt a lease with the secondary WINS server. After 4 attempts with the secondary WINS server, it attempts lease renewal with the primary WINS server again.
- Client Name Release - The client sends a name release message with its name and IP address. the server responds with a positive release message. If no confirmation is received by the client a NetBIOS broadcast release is sent up to three times.
- Server Name Query and Name Resolution response - With WINS server on the network, resolution is done using H-node on UDP port 137 (NetBIOS Name Service). Name query order:
- Local cache
- WINS server (primary then secondary, two times).
- Lmhosts file
- Hosts file
Pentium, 200Mhz computer can process 1500 name registrations and 750 queries per minute. 10,000 clients can be serviced with two WINS servers. Non-WINS clients names and IP addresses must be added to the WINS server lmhosts file.
The WINS manager inport function can import lmhosts files. Keywords other than "#DOM" are ignored. #DOM lines are added to a group for the specified domain. WINS Manager mappings menu, "Static Mappings" selection. Tyoes of mappings:
- Group - Domains and workgroups are specified
- Domain Name
- Internet Group
A menu selection is "Mapping", "Show Database". Static mappings can be added to WINS for clients that are static and /or are not Windows clients or servers. WINS database replication may be manually performed using the WINS manager.
WINS Client Support
- NT Server 5.5+ and 4.0
- NT Workstation 3.5+ and 4.0
- Windows 95
- WFW with TCP/IP-32
- Microsoft Network Client 3.0 for DOS
- Lan Manager 2.2c for DOS
No OS/2 Lan manager support.
Client Configuration types:
- 044 - WINS/NBNS Servers
- 046 - WINS/NBT Nde to 0x8 (H-node)
A WINS proxy agent can be configured to act as a relay for non-WINS clients. One WINS proxy is used on each subnet that has non-WINS clients. This means that machines that are not using WINS (Even Windows machines such as those without TCP/IP) can use a proxy agent to let them find resources on other subnets. There should be a maximum of two proxy agents per subnet. The agent must be a Windows based client, not a server. When NetBIOSs names are registered, both the proxy agent and the WINS server checks the name. The proxy agent is configured at the following registry location:
Set the EnableProxy parameter to REG_DWORD value of 1 and restart the computer.
When two WINS servers are configured to communicate with each other replication occurs any time the data base on one of them changes. Servers are configured as a push or pull partner. A server can be both a push and pull partner. Push partners send update notices when a database change is made. A pull partner asks push partners for database entries more recent than their current listings. Only changes are replicated. Pull servers are used across slow links since pull requests can be set for specific times.
- A pull server will pull updates when it is started, then at chosen times thereafter.
- A push partner will send updates when a change threshold is reached. A thershold and update interval may be set.
WINS database replication may be manually performed using the WINS manager. If multicasting is supported on the network WINS servers can multicast to 126.96.36.199 every 40 minutes. WINS server partnerships are on by default. The values "UseSelfFndPnrs" and "McastIntvl" are used to set partnership on or off and the multicast interval.
To add replication partners, the munu item "Server" and "Replication Partners" is selected using the WINS Manager. The "Configure" button is used to set replication intervals, retry counts, and the number of changes before sending updates. The WINS Configuration menu controls the following:
- Renewal interval - Default of 96 hours, sets the amount of time between which a client must renew its name.
- Extinction Interval - Default of 96 hours - Time between when a name is released and marked as extinct.
- Extinction Time-out - Default of 96 hours with a 24 hour minimum. Time between when a name is marked as extinct and removed from the database.
- Verify Interval - Default of 576 hours (24 days). - The interval between which WINS entries owned other WINS servers are verified.
The "Advanced" button allows the following selections:
- Logging enabled - WINS database events are logged
- Log Detailed Events - The amount of detail in the database is set.
- Replicate Only with Oartners - Enabled by default, this will allow a pull server to send to WINS servers it is not set as a partner to.
- Backup On Termination - When WINS Manager is closed, the database is backed up.
- Migrate On/Off - Static entries are changed to dynamic when a conflict between a static and dynamic entry is found.
- Starting Version Count - Only needet if the database becomes corrupt, this is an ID number for the database.
- Database Backup Path - A local path for the database to be backed up to.
Database entry types:
- \\Comupter name 00h - Workstation service
- \\Comupter name 03h - Messenger service
- \\Comupter name 20h - Server Service
- \\User Name 03h - The logged on user name
- \\Domain name 1bH