Data-Link Switching (DLSw) is a tunneling protocol designed to tunnel unroutable, non-IP based protocols such as IBM Systems Network Architecture (SNA) and NBF over an IP network.
DLSw was initially documented in IETF RFC 1434 in 1993.
Cisco Systems has its own proprietary extensions to DLSw in DLSw+.
[1] Some organisations are starting to replace DLSw tunneling with the more modern Enterprise Extender[2] (EE) protocol which is a feature of IBM APPN on z/OS systems.
[3] Cisco deploy Enterprise Extender on their hardware via the IOS feature known as SNAsW (SNA Switch).