Ipmi - Intelligent Platform Management Interface

The Intelligent Platform Management Interface (IPMI) is a set of computer interfacespecifications for an autonomous computer subsystem that provides management and monitoring capabilities independently of the host system's CPU, firmware (BIOS or UEFI) and operating system. IPMI defines a set of interfaces used by system administrators for out-of-band managementof computer systems and monitoring of their operation. For example, IPMI provides a way to manage a computer that may be powered off or otherwise unresponsive by using a network connection to the hardware rather than to an operating system or login shell.

The specification is led by Intel and was first published on September 16, 1998. It is supported by more than 200 computer system vendors, such as Cisco, Dell, Hewlett Packard Enterprise, Intel, NEC Corporation, SuperMicro and Tyan.

Using a standardized interface and protocol allows systems-management software based on IPMI to manage multiple, disparate servers. As a message-based, hardware-level interface specification, IPMI operates independently of the operating system (OS) to allow administrators to manage a system remotely in the absence of an operating system or of the system management software. Thus IPMI functions can work in any of three scenarios:

• before an OS has booted (allowing, for example, the remote monitoring or changing of BIOS settings)
• when the system is powered down
• after OS or system failure – the key characteristic of IPMI compared with in-band system management such as by remote login to the operating system using SSH

System administrators can use IPMI messaging to monitor platform status (such as system temperatures, voltages, fans, power supplies and chassis intrusion); to query inventory information; to review hardware logs of out-of-range conditions; or to perform recovery procedures such as issuing requests from a remote console through the same connections e.g. system power-down and rebooting, or configuring watchdog timers. The standard also defines an alerting mechanism for the system to send a simple network management protocol (SNMP) platform event trap (PET).

The monitored system may be powered off, but must be connected to a power source and to the monitoring medium, typically a local area network (LAN) 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 out-of-band local area network (LAN) or 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, whereby serial console output can be remotely viewed over the LAN. Systems implementing IPMI 2.0 typically also include KVM over IP, remote virtual media and out-of-band embedded web-server interface functionality, although strictly speaking, these lie outside of the scope of the IPMI interface standard.

DCMI (Data Center Management Interface) is a similar standard based on IPMI but designed to be more suitable for Data Center management: it uses the interfaces defined in IPMI, but minimizes the number of optional interfaces and includes power capping control, among other differences.

Side-band and out-of-band

As well as using a separate dedicated management LAN connection, IPMI also allows implementation of a so-called "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 suffices for a few vital functions, such as checking the event log, accessing the BIOS setup and performing power on, power off or power cycle. However, more advanced functions, such as remote re-installation of an operating system, may require a full out-of-band management approach utilizing a dedicated LAN connection.[citation needed]

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. RMCP+ (a UDP-based protocol with stronger authentication than RMCP) is used for IPMI over LAN.

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) repository 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.