Disadvantages

In a branch-based network, you cannot implement high-speed mainframe connections such as channel attachment and Ethernet. Most such networks face physical limitations or difficulty in implementing SNA protocols over a WAN connection. Traditionally, branch-based SNA gateways employ an SDLC-type solution that supports only one physical unit (PU) per host adapter, and only 254 logical units (LUs) over the connection.

If you decide to use routers to pass WAN traffic between the branch and SNA host systems, the routers must be sophisticated enough to prioritize interactive communications over the WAN, as multiple protocols besides SNA may be operating over the connection.