After your SNA Server-to-host connection is determined, you must choose the protocol(s) to use for two additional SNA Server communication paths: client-server communication and server-server communication. You can use one protocol for both, or you can use a combination of different protocols, provided that all servers share at least one client-server protocol and use it for server-server communication.
Deploying a single protocol across your WAN is the easiest way to manage your communications. Figure 4.8 shows a network in which TCP/IP is used for all types of communication involving SNA Server servers and clients:
Figure 4.8 One protocol for all communication between servers and clients.
You may decide to gradually implement SNA Server throughout your enterprise, in which case you may need to use existing protocols for certain connections. The following figure shows a LAN in which two protocols are used. For server-server communication, NetBEUI is used; for client-server communication, IPX/SPX is used.
Figure 4.9 Two protocols (NetBEUI and IPX/SPX) in a subdomain.
Similarly, other combinations of protocols can be used, provided that all the SNA Server computers share one protocol and use that protocol for server/server and client/server communication.