The Cisco 633 serial to Symmetric Digital Subscriber Line (SDSL) data service unit (DSU) is designed for small offices and branch offices to provide cost-effective access to high-speed SDSL services. The Cisco 633 preserves the customer's investment in existing business class routers, allowing them to take advantage of New World applications and Packet Telephony. The Cisco 633 provides small offices and branch offices with fast, affordable, and easy-to-use access to the Internet and corporate network. The Cisco 633 serial SDSL DSU allows DSL services and applications to be available to the office router or to the desktop. It supports an integrated SDSL WAN interface and a serial interface to the router and can operate at symmetric speeds of up to 1168 Kbps.