Kontron
InterphaseATCA
ATCA: A Practical Perspective
Using ATCA, system designers can build multiple types of communications products using the same basic chassis/ backplane scheme.
GEORGE SHENODA, RADISYS
Advanced Telecommunications Com-puting Architecture, known as ATCA, is a new system form-factor defined by the PCI Industrial Computers Manufacturers Group (PICMG) and was created with a number of objectives in mind. The main objectives of the ATCA standard are to enable building carrier-grade convergent systems—systems that include computing and communications products for myriad applications.
Specifically, it is aimed at converging telecom access and edge equipment functions with data center and storage equipment functions in a modular fashion. This modular approach enables both equipment producers and users to employ the same chassis/backplane for multiple types of products, using different modules, as explained later. As such, the ATCA standard was developed with the following attributes, among others, as the main guiding principals:
- Scalable Capacity of up to 2.5 Tbits/s (per chassis) with a centralized switching hub interconnected to all module slots in a star (radial) or a full mesh configuration
- Redundancy throughout the system configuration to achieve over 99.999% availability (Carrier Grade), while allowing less demanding applications to utilize a non-redundant configuration for lower cost
- Modularity and configurability to enable multiple modules with various interfaces and different technologies, such as DSPs, NPUs, CPUs and storage media to be mixed and matched for diverse applications in the same platform
- Specifications that support strict regulatory requirements such as NEBS with long life components and advanced power distribution and cooling concepts
- Specifications that support multiple types of Switching Fabrics (the core of the platform), such as Ethernet (GbE), PCI Express and others
The result is a standard that offers definitive advantages over its predecessors such as Compact PCI. ATCA supports regulatory requirements such as NEBS, as well as high-availability enabling requirements. The architecture’s higher power allowance and more advanced power distribution mean designers can pack more functionality and higher performance per shelf. ATCA provides higher capacity and the ability to mix various types of modules and technologies to enable the convergence of multiple types of equipment and multiple applications in one platform. It also allows rear-mounted modules permitting added functionality per slot or rear interface cabling. Figure 1 depicts an outline of the physical attributes of the platform.
Additional software—or middleware—specifications to support high-availability platform infrastructure are under development by organizations such as the Service Availability Forum. Such high-availability infrastructure middleware enables building robust ATCAs, as well as other platforms such as CompactPCI, which provide a standard foundation for high availability, distributed computing and system management capabilities across the industry. A distinct advantage of such standards is the ability to build multivendor embedded systems that simplify building higher-layer applications by NEPs (Network Equipment Providers) in a shorter time-to-market.
Three Avenues for Differentiation in ATCA There are three fundamental areas in which the system architecture based on an ATCA platform could be different. Difference in Switching Fabrics Configuration The switching fabric is the heart of the system in that it transports all the traffic between the different modules of the system, both within a chassis and between chassis. One architecture could use a single switching fabric to handle all traffic—user information as well as control and management information—in some cases even storage modules may be interconnected through the same fabric. Another architecture may use separate switching fabrics for each different class of data, such as control data, user data and storage data. A hybrid approach could separate storage from user and control flows via two separate fabrics. Difference in Switching Fabrics Technologies There are many switching fabric technologies that can be used as an ATCA switching fabric, such as 10/100 bT Ethernet, GbE, Fibre Channel, PCI Express, Infiniband and Cell-Based fabrics to name a few. Furthermore, they can be mixed as base and extended fabrics, where the base is used for one purpose and the extended for another in the mixed fabric architectural model discussed in the last paragraph. This leaves multiple choices from which to select the appropriate fabric for the appropriate application as well as a path of evolution as fabrics evolve. While changing a fabric will require new modules to support the interface to such fabric, the main chassis and backplane remain intact and capable of simultaneously supporting two fabrics at a time in any given chassis. This provides an added advantage of utilizing an ATCA platform without a “forklift” approach to evolution. Difference in Processing System and Shelf Management There are architectures that combine the processors that handle the system and shelf management with the switching fabric in one hardware module. Others use a separate CPU module for management. In this case, the former architecture offers definite economic and simplified implementation advantages over the latter. |