[Design View / Design Solution]
Consider An ATCA-Based Design For Carrier-Grade OSs
The Advanced Telcom Computing Architecture offers designers coveted features such as high speed, scalability, open standards, and robust system management.
DESIGN VIEW is the summary of the complete DESIGN SOLUTION contributed article, which begins on Page 2.
Managing the design and development of a carrier-grade operating system (CGOS) is a major undertaking at any time. However, it's even more difficult in these economically challenging times, when lean teams race to meet looming deadlines under restrictive budgets that have been stretched thin. Add to this mix the plethora of emerging switched-fabric architecture options.
Where does one begin? Commercial off-the-shelf (COTS) standards-based hardware and software is one objective, because it's cost-effective and helps meet time-to-market. However, currently available COTS products don't offer a viable solution due to various performance-limiting drawbacks, such as insufficient board space, narrow board spacing, limited backplane throughput, and lack of scalability.
The advent of the Advanced Telecom Computing Architecture (ATCA) offers compelling reasons to select it as the platform for a CGOS: high-speed scalability to 2.5 Tbits/s, high availability, open standards, robust system-management features, scalability, and cost-effectiveness.
Based on PICMG 3.0, the ATCA shelf has up to 14 slots in a standard 19-in. rack, or up to 16 slots in a 23-in. or ETSI rack. Other features include front boards with a form factor of 8U by 280 mm, 1.2-in. (6HP) board spacing with a 0.1-in. board offset, a high-speed (5-Gbit/s) connector, and cooling for up to 200 W per slot. ATCA PICMG subspecifications exist for Ethernet, InfiniBand, StarFabric, and PCI Express.
This article focuses on ATCA's shelf mechanicals, including the backplane. Adopting a step-by-step design methodology and using a comprehensive specification like PICMG 3.0 for ATCA can ultimately be a springboard to the successful development of a CGOS.
HIGHLIGHTS:
Selecting A Thermal-Management Solution
Cooling is a major concern with an ATCA shelf design. Dissipating 200 W per slot for a total of 2800 W in a 19-in. rack-mount shelf is no small feat when employing air-moving devices like fans and blowers. Thus, the following decisions should be made before arriving at a thermal solution:
Board and shelf dissipation
Impedance to airflow offered by the boards
Air-filter requirement
Maximum chassis height
Redundancy characteristics in cooling
Topology Considerations
The key topologies of the ATCA specification are Dual-Star, Dual Dual-Star, and Mesh. Ultimately, the topology can have a great impact on overall system cost because the cards, backplane, etc., will be affected.
Shelf Management
Shelf managers developed for the PICMG 3.0 specification use the Intelligent Platform Management Interface (IPMI). Incorporating a shelf manager that individually controls the fans in the chassis will help maximize efficiency. For redundancy, the shelf manager can be designed as dual units in a hot-swap redundant mode. An interface board can be used for direct shelf-manager plugging.
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