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Intelligent Platform Management Interface

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The Intelligent Platform Management Interface (IPMI) is a standardized computer system interface used by system administrators to manage a computer system and monitor its operation.

The development of this interface specification was led by Intel Corporation and is supported by more than two hundred computer systems vendors.[1]. Dell, Hewlett-Packard, Intel, and NEC Corporation announced IPMI v1.0 on 1998-09-16, v1.5 on 2001-03-01, and v2.0 on 2004-02-14. The technology is now considered a de-facto standard for computer system management.[citation needed]

Functionality

An IPMI sub-system operates independently of the operating system and allows administrators to manage a system remotely in the absence of an operating system or of the system management software. The monitored system may be powered off, but must be connected to a power source and the monitoring medium, typically a local area network connection. IPMI can also function after the operating system has started, and exposes management data and structures to the system management software. IPMI prescribes only the structure and format of the interfaces as a standard, while detailed implementations may vary.

An implementation of IPMI version 1.5 can communicate via a direct serial connection or via a side-band local area network (LAN) connection to a remote client. The side-band LAN connection utilizes the board network interface controller (NIC). This solution is less expensive than a dedicated LAN connection but also has limited bandwidth. Systems compliant with IPMI version 2.0 can also communicate via serial over LAN. System administrators can then use IPMI messaging to query platform status, to review hardware logs, or to issue other requests from a remote console through the same connections. The standard also defines an alerting mechanism for the system to send a simple network management protocol (SNMP) platform event trap (PET).

Side-band and out-of-band

IPMI implements what is often called a side-band management LAN connection. This connection utilizes a System Management Bus (SMBUS) interface between the BMC (Baseboard Management Controller) and the board Network Interface Controller (NIC). This solution has the advantage of reduced costs but also provides limited bandwidth – sufficient for text console redirection but not for video redirection. For example, when a remote computer is down the system administrator can access it through IPMI and utilize a text console. This will be sufficient for a few vital functions, such as checking the event log, accessing the BIOS setup and perform power on, power off or power cycle. However, more advanced functions, such as remote re-installation of an operating system, may require an out-of-band management approach utilizing a dedicated LAN Connection.

IPMI components

An IPMI sub-system consists of a main controller, called the baseboard management controller (BMC) and other management controllers distributed among different system modules that are referred to as satellite controllers. The satellite controllers within the same chassis connect to the BMC via the system interface called Intelligent Platform Management Bus/Bridge (IPMB) — an enhanced implementation of I²C (Inter-Integrated Circuit). The BMC connects to satellite controllers or another BMC in another chassis via the Intelligent Platform Management Controller (IPMC) bus or bridge. It may be managed with the Remote Management Control Protocol (RMCP), a specialized wire protocol defined by this specification.

IPMI architecture diagram shows BMC sideband via SMBUS.
Interfaces to the baseboard management controller

Several vendors develop and market BMC chips. A BMC utilized for embedded applications may have limited memory and require optimized firmware code for implementation of the full IPMI functionality. Highly integrated BMCs can provide complex instructions and provide the complete out-of-band functionality of a service processor. The firmware implementing the IPMI interfaces is provided by various vendors. A field replaceable unit (FRU) holds the inventory, such as vendor ID and manufacturer, of potentially replaceable devices. A sensor data record (SDR) repository provides the properties of the individual sensors present on the board. For example, the board may contain sensors for temperature, fan speed, and voltage.

Baseboard management controller

The baseboard management controller is the intelligence in the IPMI architecture. It is a specialized microcontroller embedded on the motherboard of a computer, generally a server. The BMC manages the interface between system management software and platform hardware.

Different types of sensors built into the computer system report to the BMC on parameters such as temperature, cooling fan speeds, power status, operating system (OS) status, etc. The BMC monitors the sensors and can send alerts to a system administrator via the network if any of the parameters do not stay within preset limits, indicating a potential failure of the system. The administrator can also remotely communicate with the BMC to take some corrective action such as resetting or power cycling the system to get a hung OS running again. These abilities save on the total cost of ownership of a system.

Physical interfaces to the BMC include SMBus busses, an RS-232 serial console, address and data lines and an Intelligent Platform Management Bus (IPMB), that enables the BMC to accept IPMI request messages from other management controllers in the system.

A direct serial connection to the BMC is not encrypted as the connection itself is secure. Connection to the BMC over LAN may or may not use encryption depending on the security concerns of the user.

See also

References

  1. ^ IPMI adopter list
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