Интерфейс управления интеллектуальной платформой IPMI

Interface standard
The Intelligent Platform Management Interface (IPMI) is a set of computer interface specifications 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 management of 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. Another use case may be installing a custom operating system remotely. Without IPMI, installing a custom operating system may require an administrator to be physically present near the computer, insert a DVD or a USB flash drive containing the OS installer and complete the installation process using a monitor and a keyboard. Using IPMI, an administrator can mount an ISO image, simulate an installer DVD, and perform the installation remotely. 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, and Intel.

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.

The baseboard management controller (BMC) provides 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. BMC has its dedicated firmware and RAM. 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 pre set limits, indicating a potential failure of the system. The administrator can also remotely communicate with the BMC to take some corrective actions – such as resetting or power cycling the system to get a hung OS running again. These abilities reduce the total cost of ownership of a system. 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. Physical interfaces to the BMC include SMBuses, an RS 232 serial console, address and data lines and an 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. There are rising concerns about general security regarding BMCs as a closed infrastructure. OpenBMC is a Linux Foundation Collaborative open source BMC project.

The IPMI specification has been updated with RAKP+ and a stronger cipher that is computationally impractical to break. Vendors as a result have provided patches that remediate these vulnerabilities. The DMTF organization has developed a secure and scalable interface specification called Redfish to work in modern datacenter environments.