L2 Controller - Silicon Graphics Origin 3900 User Manual

8: System Control

L2 Controller

116
The L2 controller, which is a standard component of the Origin 3900 server, is a
single-board computer that runs an embedded operating system out of flash memory. It
performs the following functions:
• Controls resource sharing.
• Controls all L1 controllers.
• Maintains controller configuration and topology information between the L1 and
L2 controllers.
• Routes data between upstream devices and downstream devices.
Upstream devices (for example, rack display, console, and modem) provide control
for the system, initiate commands for the downstream devices, and act on the
messages that they receive from downstream devices.
Downstream devices (for example, the USB hub of the R-brick, and L1 controllers of
the bricks) perform the actions specified by the L2 controller commands, send
responses to the L2 controller that indicate the status of the commands, and send
error messages to the L2 controller.
• Allows remote maintenance via a modem.
In a system with more than one L2 controller, all L2 controllers are peers. Each L2
controller monitors its associated L1 controllers and propagates this information to the
other L2 controllers via the Ethernet.
Note: For L2 controller commands, see the SGI L1 and L2 Controller Software User's Guide
(007-3938-xxx).
007-4653-001