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DLSw is a standard for encapsulating and tunneling IBM SNA (Systems Network Architecture) and NetBIOS traffic across IP (Internet Protocol) networks. The protocol is the result of a need to integrate SNA and non-SNA networks (i.e., Token Ring and Ethernet LANs), rather than deploy two separate networks or use a variety of proprietary schemes to tunnel SNA data over non-SNA networks.

As LANs became more popular throughout the enterprise, IBM and other vendors saw the benefits of using these networks for interconnecting SNA devices and as a way to allow network-connected PC users to access SNA mainframes. APPN (Advanced Peer-to-Peer Networking) was IBM's solution for building router-connected internetworks, but TCP/IP has since become more popular. DLSw was developed to meet the needs of sending SNA traffic over IP networks.