Intelligent Platform Management

Managing hardware is critical to the functioning of any enterprise. The management of hardware includes monitoring the various physical characteristics of the equipment such as the temperature, humidity and the state. State information could be whether the equipment is on or off, whether the fan is running and so on. 

The second part of managing hardware is taking an action, based on the information provided by this monitoring process. For example, powering on the fan in case of high CPU temperature or sending a shutdown signal if things get really out of hand. The characteristics to monitor and the action to be taken can (ideally) be configured.

Traditionally all manufacturers have used proprietary interfaces and techniques to monitor and control the hardware. These techniques might involve using dedicated hardware for the process or they might use system's hardware to run a software solution. The latter, however, provides limited capability and reliability as compared to a dedicated hardware

solution.

Vendors have been pretty much on their own in terms of making a call between the two solutions as well as sorting out the details of communication

between the various components. This means that solutions by different vendors have, by and large, not been interoperable which makes the task of having a singular management platform for all over hardware in a multi-vendor hardware environment, next to impossible. 

IPMI, or Intelligent Platform Management Interface, is an attempt to standardize the interface used by manufacturers to

monitor and control their hardware. It is 'Intelligent' because it has a brain of it's own, ie, incorporates a dedicated processor for monitoring. This processor is functional all the time, even when the system itself is off (as long as the 'mains' are plugged in of course). Vendors are encouraged to adopt IPMI and build on top of it to add features specific to their requirements. The underlying IPMI core ensures that the solutions are interoperable.

How IPMI works



At the heart of each IPMI implementation is the BMC (Baseboard Management Controller) which is responsible for interacting with all IPMI-aware components and acts as the central point for all

communication with the non-IPMI world. The BMC is generally a small, not so costly but highly reliable processor. In addition to interacting with the components on the main-board via the system interface, BMC also interacts with sensors either directly or via one or more smaller MCs (Management Controllers). This communication is done either over IPMB (Intelligent

Platform Management Bus) or ICMB 



(Intelligent Chassis Management Bus) interfaces or an external interface such as Ethernet.

The heart of any IPMI implementation is the BMC or Baseboard Management Controller chip that interacts with all IPMI-aware components

The term IPMB interfaces refers to the standard interfaces defined by the IPMI specification that can be used to connect devices to the BMC. SMIC or Server Management Interface Chip is the oldest of these interfaces. KCS or Keyboard Style Controller is similar to the standard PC keyboard controller of the old days and is perhaps the most popular IPMB interface out there thanks largely due to the availability of cheap hardware. Both these interfaces suffer from slow speed because they transfer data one byte at a time. Further, while SMIC doesn't support interrupts, KCS does. BT or Block Transfer is the newest interface and as the name suggests, it supports transferring entire messages at a time and, thus, offers much greater performance.

In addition to IPMB, the MCs might be connected using ICMB, which is nothing but a serial bus between chassis.

I2C or Inter Integrated Circuit or simply Inter IC is a bus developed by Philips in the early 1980s for efficient inter-IC communication. Most of the sensors used in computer hardware sit on top of I2C. A smaller MC is often attached to monitor devices attached to I2C and this MC

reports back to the BMC either via bus, if both the MC and the BMC are on the same board, or via Ethernet or any other interface where the MC and BMC sit in different boxes. 

A BMC may directly monitor I2C devices in some cases eliminating the need for an additional MC but increasing the load on the

BMC.

MCs are capable of performing basic state change operations upon the devices they are controlling. For example, the chassis MC has the ability to power it on or off or reset. The MCs also maintain FRU

(Field Replaceable Unit) data. FRU refers to the current state of the system in terms of user replaceable cards and other things such as power supplies & memory 



modules. The serial number, manufacturer etc. of these components are also read and stored in EEPROMs. This can be termed as 'inventory management' within the system. 

MCs also maintain a Sensor Device Record containing sensor information for the device they are monitoring. An IPMI setup may have as many device level SDRs as there are MCs. However, there is only one system level SDR that is managed by the

BMC.

SEL refers to System Event Log and, in case it isn't self-explanatory, is the log for system level events.

Advantages



IPMI ensures increased server reliability, availability and serviceability. It

also goes one step forward by bringing the much needed standardization in a sphere typically dominated by proprietary solutions. Customers can now buy servers from different vendors knowing that they'll be interoperable as far as managing them from a central console is concerned -as long as all the servers implement the IPMI specification, of course. This results in lower TCO (Total Cost of Ownership) for the solution as well as prevents vendor lock-in.

What's new?



IPMI is not a new standard and has been around for some time. Recently version 2.0 of the specification was released and it offers many new features such as increased security through Secure Hash Algorith-1 (SHA-1), Advanced

Encryption Standard (AES) and packet data encryption. 

Also added is support for Virtual LANs. Also added is improved support for IPMI over LAN and a brand new feature called SOL (Serial Over LAN).

Who is it for?



IPMI is obviously for OEMs looking to add increased reliability in their system. Manufacturers of cards and controllers can also look to make their components IPMI aware. But IPMI isn't all about hardware. Application suites that can speak IPMI are also necessary to sit on top and act as the bridge between the user and the underlying hardware.

Kunal Dua