On some managed systems, notably blade server systems, the serial ports on the managed computers are not normally connected to a traditional serial port socket. To allow users to access applications on these computers via the serial port, the input/output of the serial port is redirected to the network. For example a user wishing to access a blade server via the serial port can telnet to a network address and log in. On the blade server the login will be seen as coming through the serial port.
SOL is implemented as a payload type under the RMCP+ protocol in IPMI.