Short for High-Speed Serial Interface, HSSI is a serial interface that supports transmission rates up to 52 mbps. It is used to connect routers on local area networks with wide area networks over a 680×0 or similar high-speed line. HSSI can also be used to provide high-speed connectivity between LANs, such as token ring and Ethernet.
HSSI is a DTE /DCE interface developed by Cisco Systems and T3plus Networking to address the need for high-speed communication over WAN links.