SNA Server Installation Guidelines (DC or Member Server)

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SNA Server logs users on to the Windows NT domain before allowing any requests to be processed, regardless of the transport used by the client to connect to SNA Server. If SNA Server logs users onto the domain over named pipes, the users is not prompted for the domain password or username. For other client server protocols (IPX/SPX, TCP/IP, Banyan, and AppleTalk), the user is prompted for the domain password and username. As a result, each new client connection to SNA Server results in a winlogon transaction which, in the case of a member server, needs to be authenticated across the network by a PDC or BDC. A Windows NT member server does not maintain the domain user database, and therefore must rely on a BDC or PDC to validate the user over a secure channel.

If the PDC or BDC spend a large percentage of CPU time servicing winlogon requests, and the clients generally stay connected to SNA Servers for a long time, then the administrator should install SNA Server on a member server. If clients connect and disconnect frequently from SNA Server, and the Windows NT domain is primarily used for SNA access (as is likely the case when you install in an existing NetWare or Banyan environment), you should install SNA Server on the PDC or BDC.

SNA Server to SNA Server Communication Issue:

1. SNA Server Versions 2.11 SP1 and earlier:
   
   If SNA Servers in the same domain are located across routers, an administrator must install SNA Server on a primary domain controller (PDC) or backup domain controller (BDC). SNA Server to SNA Server communication is mailslot or datagram based. SNA Server uses the winlogon protocols when sending messages across routers.
2. SNA Server 3.0 and 4.0:
   
   SNA Server 3.0 and 4.0 systems in the same domain that are separated by routers do not have to be installed on Windows NT domain controllers. SNA Server 3.0 and 4.0 Setup prompts for the primary SNA Server's name if it is unable to dynamically locate the primary SNA Server based on a UDP broadcast datagram.