Determining Domain Migration Strategies

Using NetBIOS with Windows 2000

NetBIOS is a high-level network-programming interface that has been used in pre–Windows 2000 networking components. Network resources are identified in the NetBIOS namespace by unique NetBIOS names. WINS is a service that was supplied as part of Windows NT Server 4.0 to support registration of dynamic mappings of NetBIOS names to IP addresses, and to provide NetBIOS name resolution.

With the release of Windows 2000, support for the NetBIOS naming interface is required only for cluster servers. For this reason, coupled with the use of DNS and the advent of Active Directory, the use of NetBIOS will decline over time.

Note that upgrading your domain to Windows 2000 does not necessarily remove the need for NetBIOS support on your network, nor does it affect the degree of support you currently have. For example, if your network is multisegmented, WINS is required to create the NetBIOS browse list. Without WINS the network must rely on Active Directory for browsing resources. This could have a significant impact on pre–Windows clients.

You can discontinue the use of NetBIOS and WINS after upgrade if the following conditions are met:

There are no clients (such as Windows for Workgroups, Windows 95, Windows 98, or Windows NT) and no servers running Windows NT that use NetBIOS. However, clients running earlier versions of Windows operating systems might still require NetBIOS names to provide file and print services and as support for legacy applications.
In your testing plan, be sure you assess the impact of legacy applications and services. For more information about testing, see "Building a Windows 2000 Test Lab" in this book.
You have a pure Windows 2000 network and are certain that all computers and applications on your network can function using another naming service, such as DNS. Network naming is a vital service for locating computers and resources throughout your network, even where NetBIOS names are not required.
The Windows 2000 WINS client caches resolved names locally and uses a component called the Caching Resolver to look in the cache before submitting a query to DNS. The HOST file is cached as soon as the client starts running, and any updates to the HOST file are reflected immediately in the cache. The name resolution sequence is as follows:
1. Client attempts name resolution from the client cache.
2. If resolution from the client cache fails, the client attempts name resolution through DNS.
3. If DNS name resolution fails, the client attempts resolution through WINS.

If these criteria are met, the move away from NETBIOS and WINS is seamless, as long as you have removed all legacy conditions and implemented sufficient change control over your newly upgraded clients.