RTC Magazine

Suppliers and consumers of telecom equipment are aggressively adopting the AdvancedTCA (ATCA) and AdvancedMC (AMC) architectures defined by PICMG. One key reason is that these architectures include an advanced hardware platform management infrastructure based on the Intelligent Platform Management Interface (IPMI). This infrastructure is a key enabler for the stringent service availability requirements that are typically mandated in telecom equipment and the mix and match interoperability that is crucial to the promised reductions in capital and operating expenses.

Implementing the relevant aspects of this platform management architecture in each type of ATCA/AMC component is not a trivial matter, however. Even the challenge of thoroughly understanding the management aspects of the relevant specifications is substantial. The IPMI specification is over 400 pages long; the management parts of the ATCA and AdvancedMC specifications account for hundreds of additional pages.

Building Block Candidates

Figure 1 shows the logical elements of an example ATCA shelf, focusing on the platform management aspects. An ATCA shelf manager communicates inside the shelf with IPM controllers, each of which is responsible for local management of one or more Field Replaceable Units (FRUs), such as boards, fan trays or power entry modules. Management communication within a shelf occurs primarily over the Intelligent Platform Management Bus (IPMB), which is implemented on a dual-redundant basis as IPMB-0.

ATCA boards that are AMC carriers add another level to the management hierarchy. Carrier IPMCs handle on-carrier management, including communication over a local IPMB-L with the Module Management Controllers (MMCs) that provide onboard management for the AMC modules.

An overall System Manager (typically external to the shelf) can coordinate the activities of multiple shelves. A System Manager communicates with each shelf manager over an Internet Protocol (IP)-capable transport, usually Ethernet.

As shown in Figure 1, the key interoperability interfaces in the ATCA/AMC architecture include IPMB-0, which connects the shelf manager (or more precisely its shelf management controller or ShMC) to the IPM controllers in the shelf. In addition, IPMB-L connects a Carrier IPMC to the MMCs on the AMCs installed on the carrier. There is also a system manager interface, by which a system manager communicates with one or more shelf managers.

The ATCA/AMC management architecture uses IPMI-based messaging across all these interfaces. PICMG has extended IPMI with dozens of commands to cover the unique needs of a modular platform designed for high availability. A key goal of this architecture is to ensure that independently implemented building blocks can communicate seamlessly across these interfaces, enabling coherent management of the entire shelf.

Compliant and Interoperable Across Key Interfaces

To achieve the necessary compatibilities, management building block suppliers must be thoroughly familiar with the specifications they’re implementing. Ideally, they are directly involved in the PICMG subcommittees that create the specifications. Although there are some moves in that direction, there are currently no formal compliance processes for PICMG specifications. In the meantime, building block suppliers must thoroughly test their products for compliance.

In addition to internal compliance testing, independently implemented management building blocks must be compatible across the interoperability interfaces shown in Figure 1. Since 2002 (even before the ATCA specification was initially adopted), PICMG has been running ATCA/AMC Interoperability Workshops (AIWs) to help ensure this compatibility. AIWs happen about three times a year and typically involve 15-30 PICMG member companies. Each company brings instances of their products for testing. During the AIW, participants systematically apply dozens of test scenarios (see sidebar “ATCA/AMC Interoperability Workshop Scenarios”) with different combinations of components. For instance, each distinct board type is tested with each distinct shelf manager type.

Experience in AIWs has directly resulted in improvements in the ATCA and AMC specifications. For instance, independent implementers interpreted early specification requirements for FRU state transitions differently. Those and many other similar areas of potential incompatibility are now clarified in the specifications, but more will undoubtedly be found as testing gets broader and more intensive. Management building block suppliers must actively participate in AIWs to help ensure interoperability of their components and their customers’ products as well as to help uncover any specification ambiguities that remain.