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Cisco STUN-SDLC
Cisco's Serial Tunnel (STUN) with Synchronous Data Link Control (SDLC) is a protocol used primarily to encapsulate mainframe SNA traffic over IP networks. It facilitates bridging traditional serial synchronous protocols across routed IP infrastructure, enabling mainframe communications over modern networking topologies without changing legacy host configurations..
Cisco STUN-SDLC is designed to transport SDLC frames, which are typically exchanged between IBM mainframes and remote devices, over IP networks. It encapsulates traditional SDLC bit streams within TCP or UDP packets, allowing these legacy synchronous protocols to pass through routed or switched Ethernet networks rather than dedicated serial lines.
This encapsulation approach maintains the integrity of synchronous data transmissions, supporting full SDLC frame control and addressing. As a result, enterprises can continue using their mainframe communications without hardware changes, leveraging existing Cisco routing infrastructure to interconnect remote SNA devices or branch controllers across their WAN.
STUN-SDLC supports both point-to-point and multipoint connections, and it is compatible with various Cisco routers implementing SNA encapsulation strategies. This technology was an important step in bridging traditional IBM networking with emerging IP-based transport during the transition from pure SNA to IP networks.