High Availability ATCA

ATCA/AMC: The Backbone for Telecom High Availability

Built with telecom requirements squarely in mind, AdvancedTCA and Advanced Mezzanine Card form-factors offer a new plateau of High Availability.


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Component suppliers have been chasing telecom OEMs (TEMs) for more than two decades, trying to get them to outsource basic infrastructure such as chassis, board-level products (blades) and system software. To that end, component suppliers, through industry organizations such as VITA and PICMG, have offered a number of open architecture platforms intended to make the transition from custom hardware and software to off-the-shelf solutions, as painless and cost-effective as possible.

The problem has been that most of these platforms, such as VMEbus, CompactPCI and CompactPCI Packet Switching Backplane (cPSB, or PICMG 2.16), aren’t optimized for telecom. They’re general-purpose platforms adapted for telecom, generally lacking the performance, availability, system management, capacity, scalability and power handling capabilities essential to TEMs.

That said, a sea of change is overtaking the way telecom OEMs design and outsource their hardware and software. Even as the telecom industry rebounds, and carriers begin to spend again on new packet infrastructure and services, competition is fierce, money is tight and fast time-to-market is critical. As such, TEMs who were once inclined to build everything in-house no matter what, are now looking actively to outsource basic infrastructure, which will enable them to cut costs, reduce time-to-market and focus on more profitable value-added application software and services.

The timing couldn’t be better for AdvancedTCA (ATCA), the industry’s first open architecture platform designed from the ground up for telecom. A collaboration of component suppliers and leading telecom OEMs, ATCA provides a standard platform that makes it easy for TEMs to outsource shelf-level chassis, blades and system software. Figure 1 shows an example of an ATCA board. AMC, the first mezzanine architecture designed by telecom for telecom, makes ATCA platforms even more attractive by facilitating the design of highly modular systems that can be provisioned, serviced and upgraded with a fine degree of granularity.

ATCA: Baseline HA Platform

ATCA provides a number of unique features that make it an excellent baseline high-availability telecom platform. The first is its high-performance, multi-protocol (Ethernet PCI Express, Rapid I/O and InfiniBand), switched-fabric interface. With a point-to-point bandwidth of 10 Gbits/s, ATCA provides ten times the throughput of cPSB. Equally important, ATCA greatly enhances redundancy and availability by providing a full-mesh fabric with flexible routing that enables each board in the chassis to communicate simultaneously with every other board in the chassis in a point-to-point fashion. In contrast, cPSB supports only a dual-star topology, which gives each blade (node) at most two alternative paths to other blades attached to the fabric. As such, the entire chassis is more susceptible to single points of failure.

In addition to providing built-in redundancy, ATCA’s point-to-point switched fabric enhances availability by supporting hot-swappability, which enables individual blades to be serviced without disrupting overall system operation. Other high-availability features include redundant -48VDC power sources, redundant clocks and redundant system management, all of which make ATCA systems less vulnerable to single points of failure. ATCA further enhances availability by providing a large form-factor (8U vs. 6U for cPSB) and high-power capability (200W per blade vs. 50W for cPSB), which enables designers to build field replaceable blades that offer higher capacity and greater functionality.

One of ATCA’s most significant high-availability features is its PICMG 2.9 IPMI (Intelligent Platform Management Bus) system management interface, which enables remote shelf managers to monitor and control (i.e., shut down a dead blade or switch function/processing load to another blade) individual ATCA blades. Through IPMI, shelf managers can perform in-line diagnostic tests and monitor physical health parameters such as blade voltages, airflow, fan speed, temperature, power supply status and insertion status.

The IPMI specification also provides for automatic alert with remote system shutdown and restart—with remote logging—making it easier for system administrators to determine the system health and respond to alert conditions.

At a higher level, ATCA also provides for redundant Ethernet management. Through this higher bandwidth interface, managers can perform code updates, upgrade system features, diagnose hardware defects, and even modify the hardware function—(if it’s reprogrammable logic).

AMC Extends ATCA’s HA Capabilities

The AMC mezzanine interface extends the performance and high-availability advantages of ATCA to the module level. AMC’s hot-swappability reduces spare costs and mean-time-to-repair (MTTR) by enabling telecom operators to replace only the malfunctioning portion of an ATCA blade, not the entire blade. At the same time, its integrated IPMI interface enables carriers to provision, manage, service and upgrade individual modules without taking the entire blade off line. Figure 2 shows an example of an AMC full height card.

AMC extends ATCA’s high-performance switched fabric by providing a high-speed, multi-protocol (Ethernet PCI Express, Rapid I/O and InfiniBand) serial packet interface with up to 21 I/O channels at 12.5 Gbits/s per channel.

It supports module-to-baseboard and module-to-module data rates of up to 200 Mbits/s, five times that of OC-768. This scaleable interface enables designers to take full advantage of ATCA’s 11 Gbit/s fabric and makes AMC ideal for a broad range of applications within the telecom core, edge, access and enterprise. AMC also extends ATCA’s high-power capability—up to 200W per blade—supporting up to 60W per module.

Versatile Form-Factor

AMC’s versatile form-factors gives ATCA availability and flexibility an added boost by enabling designers to partition their blades in a way that is optimized for their scalability, upgradeability and field serviceability requirements. AMC supports four module sizes: half-height single width, half-height double width and a full-height version of both of these. The AMC spec also provides detailed guidelines for building three types of ATCA carrier boards—short, long and hybrid. The short carrier has bays for up to eight AMC modules. The long carriers provide bays for up to four AMC modules, with two thirds of the board reserved for other components. The hybrid carrier provides for portions of either long, short or no module bays along the faceplate of the board.

Architecturally, long carriers are generally perceived as baseboards that provide primary functionality, with AMCs acting as a functional extension of the onboard circuitry. This is the conventional role of mezzanine cards. The short carrier, however, is more aptly viewed as a modularly constructed blade or extension of the ATCA fabric. Here, the carrier performs generic functions such as distributing power, system management infrastructure and fabric interconnectivity, while field replaceable AMC modules provide the primary functionality.

The short carrier, in particular, facilitates the design of highly modular systems. An ATCA shelf equipped with 16 ATCA short carriers, for example, can hold up to 128 AMC modules. This high degree of modularity gives TEMs tremendous flexibility in the way they partition their systems. Using AMC modules, designers are free to create scaleable, high-density modules dedicated to a specific function, such as control, SIGTRAN signaling, transcoding, interfacing or packet processing. They can also combine multiple functions on a single blade and alter the mix as applications and/or system partitioning changes.

Figure 3 shows how an ATCA card equipped with Advanced Mezzanine Card modules might be used to implement a scaleable signaling blade. The server module runs the upper level signaling stacks such as SS7 MTP3, SCCP, ISUP, TCAP and/or MAP. The signaling modules run the lower level signaling protocol such as SS7 MTP1 and MTP2. Mass storage devices log blade and signaling link activity.

Fine-Grain Advantages

The fine granularity of modular ATCA/AMC carriers offers significant cost savings for telecom OEMs. Modular blades cost less to produce because they can be configured using generic AMC components such as network interfaces, network processors, DSP farms, mass storage devices and encryption/decryption devices that can be reused across multiple blades, thereby facilitating volume production.

Modular ATCA/AMC blades also reduce cost by reducing the number of unique blades that telecom OEMs have to purchase and stock. With ATCA/AMC, TEMs can stock a single generic carrier board that spans several products, along with the AMCs needed to configure that carrier for specific applications. This is not possible with traditional mezzanine architectures like PMC because PMC modules aren’t field replaceable. They’re typically bolted on at the factory and sold to the telecom OEM as a single unit. Thus, the TEM has to purchase and stock a unique board for each application.

Modular, field replaceable ATCA/AMC systems are also easier and less expensive to scale and upgrade, reducing equipment costs by enabling carriers to deploy the minimal hardware needed to service their subscriber base. Consider for example, an ATCA-based core router equipped with AMC-based network processor modules, or a VoIP gateway equipped with AMC-based transcoding modules. Both systems could be deployed in a minimal configuration and scaled later without replacing the whole blade or taking it off line.

Fine-grain ATCA/AMC blades also reduce provisioning cost by enabling systems to be scaled and provisioned according to actual demand. For example, consider an ATCA WAN card equipped with eight AMC cards, each providing four T1 channels. In this configuration, the T1 channels can be added and provisioned in blocks of four rather than 32. This fine granularity also reduces the cost of sparing. Regardless of the number of active channels used in the system, spare replacements—on line and on the shelf—usually require only one or two modules, not an entire 32-channel carrier board.

Lego-Like Block

In addition to reducing cost, the modular “Lego-like block” approach provides faster time-to-market. The greater the number of functional elements that are available off-the-shelf (or from prior projects), the smaller the number of functional elements that must be designed and tested from scratch. This building block approach greatly reduces overall complexity and ground-up design, thereby reducing development time.

Modular systems also enhance availability by reducing the impact of component failures. Consider, again, an ATCA WAN card equipped with eight AMC modules, each providing four T1 channels. A failure in any particular T1 channel might at most take out four T1 channels, versus all 32 for a monolithic card on which the 32 channels are mounted directly to the baseboard. Similarly, failures to any single AMC module on a multi-channel SIGTRAN signaling blade or DSLAM blade would only impact the signaling links or subscriber connections provided by that module.

AdvancedTCA baseboards equipped with Advanced Mezzanine Cards (AMCs) are poised to become the dominant platform for high-availability telecom applications. ATCA’s high throughput, multi-protocol support, high-power capability, hot-swappability and integrated system management provide a solid baseline telecom fabric. AMC extends the benefits of that fabric to individual modules, enabling designers to customize, scale, upgrade and service their systems with a finer degree of granularity. Together ATCA and AMC greatly reduce the time and cost associated with developing, upgrading and servicing high-performance, high-availability telecom systems. This will allow TEMs to outsource enabling technology and lower maintenance costs while providing a roadmap to future technologies.

Artesyn Communication Products
Madison, WI.
(608) 831-5500.