Abstract
This chapter addresses what Windows Internet Name Service is, how WINS works, advantages and disadvantages of WINS, setting up WINS servers and clients, configuring and maintaining WINS, static routing with Windows NT, and WINS in the enterprise.
In this chapter, we address the following issues:
What Windows Internet Name Service (WINS) is
How WINS works
Advantages and disadvantages of WINS
Setting up WINS servers and clients
Configuring and maintaining WINS
WINS in the enterprise
Static routing with Windows NT
In a concept similar to that of IP address and a port number (the socket), NetBIOS applications offer their services based on a NetBIOS name. Before clients can access an application service, the NetBIOS name has to be claimed by the computer offering the service. This is name registration, as we discussed in Chapter 6.
Because any computer on the network can claim NetBIOS names, existing names must be defended. There are two different ways of resolving existing NetBIOS names — broadcasts and point-to-point messages, (defined in RFCs 1001 and 1002, respectively). As we discussed in Chapter 6, two additional ways — a combination of broadcast first and point-to-point second and vice versa also exist.
Point-to-point NetBIOS name resolution is accomplished through NetBIOS name servers, and Windows Internet Name Service (WINS) is one of the most popular NetBIOS name servers. Because WINS significantly reduces broadcasts associated with NetBIOS name resolution, you should always consider using WINS servers in your networks. You can use the WINS that is included with NT Server, or if you prefer to use Unix systems for critical services, SAMBA does a very good job as a WINS server on a variety of hardware platforms and operating systems, including Solaris and Linux.
Special Note: In our industry, anything is possible. For example, it is possible, though not recommended, to make NetBIOS networks work in a WAN with broadcasts alone. You simply configure the routers so that any broadcast packets from TCP/IP ports 137, 138, and 139 are forwarded. We repeat, this isn’t recommended. However, we have seen this happen accidentally in a large and complex network, even with extremely knowledgeable and professional network personnel.
To resolve problems related to a specific human resource application, someone mentioned to the person in charge of frame relay networks that NetBIOS broadcasts should be forwarded. The broadcasts were forwarded, resulting in serious performance problems across frame relay and T1 circuits.
WHAT IS WINS?
WINS is a proprietary Microsoft name resolution service that provides dynamic NetBIOS name-to-IP address mapping. It is designed to solve the problem of locating network resources that understand NetBIOS API calls in a TCP/IP network. WINS servers maintain computer names (NetBIOS names) and IP addresses automatically. In most cases, it is used with Dynamic Host Configuration Protocol (DHCP) and can be considered to be a complementary service that provides dynamic name registration. Often, WINS is used to dynamically provide an NT-based domain name server with the names and IP addresses of Windows computers.
Unlike many other services that run on NT, more isn’t better when it comes to WINS. Microsoft recommends using just one WINS server for up to 10,000 computers. Therefore, it is usually not a good idea to have a WINS server on each network or subnetwork.
HOW DOES WINS WORK?
As soon as a WINS client obtains the IP configuration from the DHCP server (or on bootup if the WINS server’s IP address was statically assigned), the WINS client issues a NameRegistrationRequest message to the WINS server. Unlike standard NetBIOS behavior, this message isn’t a broadcast. It is a message sent only to the primary WINS server and includes the client’s computer name and IP address.
The WINS server checks to see whether the computer name is listed in its database. If it isn’t listed, the WINS server assumes that it’s unique on the network and responds with a positive WINS name registration response. The registration response includes a period called the time-to-live (TTL) during which the registration is valid. If the name isn’t unique, a negative response is sent to the client, and the WINS server sends a challenge to the name’s current owner. Typically, the computer that currently owns the name acknowledges that it is alive on the network and the negative response message informs the new computer that there is a conflict.
To configure DHCP and WINS in an NT network, DHCP options 44 and 46 must be configured. Recall from Chapter 8 that option 44 is the IP address of the WINS/NBNS server, and option 46 is the Node Type of the WINS/NBNS server. As we explained in Chapter 6, there are four possible node types, three of which are applicable in this instance:
P node (point-to-point)
M node (mixed — broadcasts then point-to-point)
H node (hybrid — point-to-point then broadcast)
H node is the default configuration and is suitable for most networks. If you have a small network or if your WINS server is located across a router, you may want to consider M node. This may provide some network-traffic optimization if most of your resources are local and not across the router.
Special Note: H nodes do more than just reverse the order of resolution methods to use point-to-point first and then broadcasts. If a client is an H node and the WINS server becomes unavailable — for example it may be across a router and the link fails or, more likely, someone has turned it off — the H node client continues to look for the WINS server, using ARP if the WINS server is on the local subnetwork or a UDP message if it is across a router. As soon as it finds the WINS server, it stops using broadcasts to resolve names and changes back to P node behavior.
ADVANTAGES AND DISADVANTAGES OF WINS
There are many advantages to using WINS. It provides dynamic NetBIOS name resolution, thereby reducing or eliminating the administrative effort required to update HOSTS, LMHOSTS, and/or DNS files. WINS reduces the number of IP broadcasts, thus reducing network traffic. It also provides a centralized management scheme for a NetBIOS computer name database, and it allows replication of that database to other WINS servers.
The disadvantages of using WINS include
WINS is a proprietary Microsoft service. Only Windows-based computers or computers that understand SMB (Server Message Block) networking or Common Internet File System (CIFS) can be clients. Your options include computers running NT Server, NT Workstation, Windows 95/98, Windows for Workgroups, LAN Manager 2.x, or systems running products like SAMBA. However, a WINS proxy can be used to help resolve NetBIOS name queries for non-WINS enabled computers.
Usually, only NT servers can be WINS servers. However, you can create a WINS server using SAMBA; this method is discussed in “WINS Servers — Unix and Linux” later in this chapter.
WINS adds one more level of complication to the Microsoft name resolution service. 2000 Server is striving to eliminate the need for WINS by adopting dynamic DNS and encouraging the elimination of NetBIOS traffic. However, because many applications use NetBIOS, eliminating NetBIOS is probably not a practical solution in the short term.
SETTING UP WINS SERVERS
The following sections describe WINS server setup and operation in NT 4.0 networks, 2000 Server networks, and heterogeneous Unix/NT networks.
WINS Servers — NT 4.0
Normally only NT 4.0 and 2000 Server computers can be set up as WINS servers. To add the WINS service to an NT 4.0 computer, click Start, and select Settings, Control Panel, and Network. Switch to the Services tab and click Add. Select Windows Internet Naming Service, insert the NT CD-ROM and select {drive letter}/I386. (If you are installing on an Alpha-processor-based server, go to the Alpha directory instead of I386.) Only administrators, by default, can add the WINS (or any) service to an NT computer. After you install WINS, reboot the computer and you are in business. Once the WINS service is installed, your Administrative Tools list contains WINS Manager option, and you can use this to configure WINS.
WINS Servers — 2000 Server
WINS servers are typically not required with 2000 Server because most of the NetBIOS-related services are gone. However, if you have clients like Windows 95, Windows for Workgroups, NT Workstation and Server 3.x and 4.0, you may want to set up a WINS server on your 2000 Server. Click Start and select Settings, Control Panel, Add/Remove Programs, Configure Windows. Click Components and select Networking Options. Check the WINS server box.
With NT 4.0, when the statistics pane of WINS Manager window is grayed, the WINS server isn’t running. If the service is running, it shows the server start time. WINS Manager user interface in 2000 Server uses the Microsoft Management Console (MMC) and, as a result, is more intuitive. For example, it is easier to determine the server status.
WINS Servers — Unix and Linux
One of the most popular and well-written networking programs is SAMBA, an SMB server for Unix and Unix-like operating systems. Versions of SAMBA run on VMS, NetWare, MVS, MPE/ix, and other operating systems. SAMBA can be configured as a WINS server. Typically this is recommended only if you don’t use an NT Server as a primary domain controller (PDC). In situations where you have a large number of Windows computers but no NT Servers — for example, a remote office or a department that won’t use NT Servers — you could consider using this free product.
After you install SAMBA, all you have to do to have a Unix-based WINS server is edit the smb.conf file, usually located in the /etc directory. Look for the entry “wins support = yes.” By default this is a comment. Uncomment this line by removing the semicolon, and you have a WINS server that runs on a Unix computer. Make sure that the entry “wins server = a.b.c.d” remains a comment because SAMBA can’t be a WINS server and a WINS client simultaneously.
Special Note: You can download SAMBA from http://samba.anu.edu.au/samba/ or any number of mirror sites around the world. Some of them are given below:
Because the original author of the software, Andrew Tridgell, is still nurturing this program and because a large number of developers are actively involved in supporting it, bug fixes and product enhancements appear rapidly.
You can download the binaries for your specific platform or, if the binaries are not available, you can download the source code and compile it. The high-quality documentation and explanations make this job very easy.
Special Note: WINS proxy servers are sometimes used to resolve requests from clients that don’t have WINS enabled. The WINS proxy server listens to broadcasts from these computers and checks its cache to try to resolve the name. If it can’t resolve the name, the WINS proxy server forwards the request to a WINS server, which can be located either on the subnetwork or across a router.
To configure a WINS proxy server on NT 4.0, set to one the EnableProxy Registry parameter, found under
HKEY_Local_Machine\System\CurrentControlSet\Services\Netbt\Parameters.
If you want to use a SAMBA server as your WINS proxy server, edit the smb.conf file so that wins proxy is set to yes. Simply uncomment the entry “wins proxy = yes.”
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