Abstract: Communication controller allowing communication between application programs running in at least one host computer and DTEs attached to a X25 packet switched network and communicating through virtual circuits (VC), the communication being provided through the X25 network and a Systems Network Architecture (SNA) network. The controller includes tables and logic for establishing predetermined SNA sessions between the application programs and the communication controller, and tables and logic for linking at least one virtual circuit on a predetermined SNA session. The controller further includes memory for storing a set of alternate session tables defining, for each of said established predetermined SNA sessions, a prioritized list of alternate backup sessions, logic for detecting the occurrence of one failure on one SNA session, and logic for switching the virtual circuits linked to said session being subject of a failure to one backup session defined in the corresponding alternate session table.