Advanced X.25 over TCP/IP (aXOT) PXS-aXOT LayGO Client

If the X.25 connection is point-to-point, tunneling of X.25/LAPB or X.25/LAPD (whole HDLC-frame) or advanced XOT (aXOT) is an option. Instead of having one socket for each virtual circuit, one socket is used for each major X.25 device.

With aXOT the complete HDLC with LAPB or LAPD header and the X.25 packet are encapsulated into TCP/IP. The same encoding would work for SLDC type protocols, such as SNA.

(Click to enlarge) LayGO aXOT Client Protocol Stack Diagram

At the receiver, the LAPB or LAPD frame is routed to the lower edge of the link layer (frame level) using the LayGO Return Layer. They are then decoded as if they had arrived from the X.21 layer. At the transmitter, the LAPB or LAPD frames are routed from the lower edge of the X.25 link layer to the aXOT client using the LayGO Return Layer. The LayGO application is unaware that aXOT is used. In addition to aXOT, RPC can be used to support multiple local or remote simultaneous processes.