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Intelligent Platform Management Interface

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The Intelligent Platform Management Interface (IPMI) specification is an Intel led standard which defines a set of common interfaces to a computer system which system administrators can use to monitor system health and manage the system. More than two hundred companies support IPMI. Dell, HP, Intel Corporation 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.

IPMI Functionality

An IPMI sub-system operates independently of the operating system and allows administrators to manage a system remotely even in the absence of an operating system or the system management software, or even if the monitored system is powered off, but connected to a power source. 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 send out alerts via a direct serial connection or side-band local area network (LAN)) connection to a remote client. IPMI uses what is called a side-band LAN connection, which utilizes the board Network Management Interface (NIC). This solution is less expensive of a dedicated LAN connection but also has limited bandwidth. Systems compliant with IPMI version 2.0 can also send alerts 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 an SMBUS (or I2C) interface between the BMC 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. In other words, 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 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 IPMB (Intelligent Platform Management Bus/Bridge) — an enhanced implementation of I²C (Inter-Integrated Circuit). The BMC connects to satellite controllers or another BMC in another chassis via IPMC (Intelligent Platform Management Chassis) bus/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 Baseboard Management Controller.

Several vendors develop and market BMC chips. Not all BMCs are created equal. A BMC utilized for embedded applications will have limited memory and require highly optimized firmware code for implementing full IPMI functionality. At the opposite side of the spectrum, highly integrated BMCs can host more complex instructions and provide the complete out-of-band functionality of a Service Processor. The firmware implementing the IPMI interfaces is provided by a number of companies. A field replaceable unit (FRU) holds the inventory (such as vendor ID, manufacturer etc.) 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.

References

See also

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