RTC Magazine

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.

Multiple Product Possibilities

The capabilities built into the ATCA specifications enable a compliant platform to support a number of products for multiple applications following the building blocks concept discussed below. To create multiple products utilizing the same platform, it is necessary to understand which basic common building blocks are shared among the products, create modules that meet the requirements for such building blocks and use the proper mix of the building blocks to create each specific product.

Consider for example three telecom products: a blade server, an SGSN and a Media Gateway.

Blade Server. A blade server is a modular computing platform composed of multiple blades/modules that can span one or more chassis depending on the capacity required and the type of performance needed. A blade server can also use embedded storage media as part of its own infrastructure or external network-based storage, both of which are supported by the ATCA platform.

Note that a blade server has many applications such as softswitches, HLRs, SCPs and network management/OSSs, not to mention data center processing equipment including data bases and web servers. A basic blade server can be achieved by building a switching fabric (as the heart of the platform inter-module and inter-chassis communication), different types of computing modules—which can be modular themselves—and I/O modules such as GbE interfaces. Add storage modules and a versatile blade server platform is born

SGSN. The Serving GPRS Support Node is the network element in a mobile wireless network that supports user data communication functions within the network. Depending on the generation of the network (2.5 or 3 G), the data is separated from the voice by the Base Station Controller (BSC) or the Radio Network Controller (RNC) and forwarded to the SGSN to perform data packet processing such as authentication, forwarding, SS7 signaling and user plane protocols such as tunneling over ATM. An SGSN platform requires computing capability and network interface modules to handle the protocol processing and interface to the other network elements.

Clearly the computing and switching fabric elements are common with the blade server. However, different interface modules are required, e.g., a blade server may only require Ethernet interfaces, while an SGSN requires Ethernet in addition to standard network interfaces such as E1/DS1 and SONET/SDH interfaces (OC-3c/STM-1). This brief description illustrates how the SGSN utilizes certain modules/building blocks common with the blade server while requiring another set of different modules/building blocks.

Media Gateway. Media Gateways (MGs) are widely used in service provider and enterprise networking applications. An MG is a good example of how an ATCA platform may be utilized in more than one market segment and a variety of applications with satisfactory economical and technical results. An MG is also a good example of employing the building block concept to achieve re-use of modules/building blocks common with other equipment. Of the many applications of a media gateway, multiple protocol conversions for voice services can be used as an example.

Because of the variety of service interfaces between TDM and Packet Voice services, it is necessary to provide interworking functionality between the different interfaces to create seamless services among the different subscribers. Of course the media gateway is simultaneously required to support signaling, which could also be multiple types of signaling at the same time.

To achieve that, the media gateway requires the use of CPUs (for signaling and/or packet processing) as well as specialized processors to deal with the interworking functionality, which is typically between voice over TDM and packet voice over ATM or IP, but could also be between ATM and IP. This indicates that an MG can use the switching fabric and CPUs utilized by the blade server (for inter-module and inter-chassis communications, management and signaling/control functions) while requiring specialized modules for interworking and voice packet processing.

The latter could be DSPs or NPUs depending on the system architecture and design as well as the requirements. For example, if compression/decompression/silence suppression are required, it would be best if DSPs are employed. Otherwise, NPUs will do the job for interworking.

As the above description illustrates, it should be clear that there are common elements between all three types of products and some unique elements in each. Of course the higher layer applications may be quite different, but those are achieved via software that is integrated with the embedded system platform based on ATCA. Figure 2 illustrates, in color code, the similarities and differences in building blocks among the three product examples just discussed.

Technology and Products Status

Currently there are a few platforms available from different sources, including RadiSys. Some suppliers offer one element only, such as a chassis or a processing module. Others offer a more complete solution including the chassis and processors. Mass Storage media (other than a few Gbytes on the processors) will be available in early 2004. The products available today are not at a production released, GA, level but are expected to reach that state in the first quarter of 2004. Additionally those are products that are more suitable for blade servers. Products appropriate for other network elements (mentioned above and shown in Figure 2) are expected to be available for lab trials in the first half of 2004, and GA, one to two quarters later depending on performance and trial results.

ATCA is a clear winner as it will provide economies of scale coupled with scalability and high performance for multiple critical network elements in both wireless and wire-based networks. Early availability products are currently undergoing lab trials by early adopters, and multiple interoperability workshops are held every year by the PICMG members to ensure multivendor compatibility, another winning proposition for the industry.

RadiSys
Hillsboro, OR.
(503) 615-1100
[www.radisys.com].