Current SUNet Backbone Infrastructure
The SUNet backbone consists of two backbone switch/routers which provide interconnection between a set of routers which serve user networks. The user routers make use of virtual networks (VLANs) on the routers to provide individual router interfaces for each network which can then be distributed using ethernet trunking technology. Each user router is connected to both backbone routers to provide reliability. The only protocol routed on SUNet is the Internet Protocol (IP). All of the links at the backbone level are currently deployed using 1-Gigabit ethernet. User networks on-campus are connected using either 1-Gigabit or 100-megabit ethernet, depending on the equipment at the user's building entrance.
For off-campus connections in the Palo Alto area, it is possible to make high-speed fiber-optic connections by contracting for the use of the fiber plant run by the City of Palo Alto Utilities. Where fiber is not available, connections back to campus can be made using serial lines provided by the phone company (aka ATT/SBC/Pac*Bell). Typically these lines run at DS1 (T1) speeds, around 1.5 megabits per second. For home connections, IT Services has a Stanford-managed DSL offering, which provides the home users a direct connection to SUNet.
The SUNet backbone can be considered to have four areas. Three areas are for the user network routers and the fourth is the "border" area where connections to the off-campus internet are made. For user networks, there is the main campus area, the School of Medicine area, and the student residential area. Routers within an area exchange IP packets directly, using the switching capability of the backbone equipment. Between areas, the IP traffic utilizes the routing capability of the backbone.
