WINS significantly predates Active Directory, and has its roots in MS-DOS and Windows for Workgroups. It is not a part of Active Directory. WINS operates completely separate and apart from Active Directory. However, for many current Microsoft products, such as Exchange Server 2003, WINS is still an important part of the operational and functional environment.

It is worth reminding you at this point of the number one difference between WINS and DNS – WINS supports a flat namespace and DNS supports a hierarchical namespace.

For example: in any given WINS environment, there can only be one computer named bill. In any given DNS environment, there can be many computers named bill. To wit: bill.domain1.com, bill.domain2.com, etc. ad infinitum.

WINS is based on NetBIOS, and continues several (many) of the limitations of NetBIOS, perhaps most importantly that computer names must be less than 16 characters and that all computer names must be unique within those characters.

For NetBIOS, this is true within a broadcast domain (basically, a LAN). However, WINS is a mechanism of interconnecting multiple NetBIOS broadcast domains together to have unified name resolution across all of those broadcast domains. Thus, all computer names must be unique in a WINS environment.

Exchange Server 2003 (and before) stores server names (and other things, but the server names are arguably the most important) in the configuration naming context (i.e., Active Directory) based on their short name (i.e., their WINS or NetBIOS name). This means that for Exchange 2003 to resolve (find the IP address for) those server names, it will use NetBIOS.

In some ways, using NetBIOS names was a good resolution to the particular problem of tracking down Exchange Servers, where there may be many versions of Exchange in the Exchange organization. In other ways, it has caused (and continues to cause) problems for many organizations.

What this means to you as an Exchange administrator is this: if you only have a LAN, you don’t require WINS because NetBIOS broadcasts will likely handle all name resolution issues. In any larger environment using Exchange 2003 and/or clustering, Microsoft requires that WINS be installed and properly configured to deal with all name resolution issues.

Please refer to Microsoft KB 837391 (Exchange Server 2003 and Exchange 2000 Server require NetBIOS name resolution for full functionality) for more information on this issue. Also be aware that ESM (if there are multiple administrative groups) and the clustering functionality of Exchange also require WINS.

In regards to Exchange 2007, you only require WINS if you are running clustered servers on Windows Server 2003. According to pre-release documentation, WINS is not needed with Windows Server 2008 clustering.

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