February 2001

BY ANNE BROWN AND PHILIPPE CHEVALLIER

CompactPCI -- such a small word for the large role it plays. But, don't let this simple name fool you, CompactPCI is just as brimming with features and capabilities as it is compact. This seemingly innocent standards-based technology has played a large role in revolutionizing today's telecommunication network infrastructures by converging high-power computing with telecommunication equipment. It quickly achieved notoriety within the telecommunications industry and has been credited as the leading backplane technology from the plethora of platforms used in today's communication networks and infrastructures.

The reasons for CompactPCI's success in telecommunications are boundless. It affords flexibility in the implementation of rugged, fault-tolerant, reliable, and high-density applications and provides the ever-so-important hot-swap capabilities, front and rear I/O, and interconnectivity -- making it an ideal board-interconnect base technology on which to build high-availability systems. Because of its versatility and high bandwidth, it has become the standard of choice in high-speed data communication applications like routers, converters, and switching platforms.

Taming The Networks
CompactPCI's flexibility, scalability, and versatility has made it one of the best standard architectures available that solves the issue of interconnecting different networks from within the communication infrastructure, such as ATM, IP, Packet over SONET, frame relay, SS7, and the PSTN. The ever-evolving Internet and the relentless demands for more bandwidth largely drive the need for this interconnectivity.

Each of these networks exists on a medium of optical fiber, copper, or radio wave spectrum (wireless) or a combination thereof. The medium used is important because it can be substantially problematic in interconnecting the different networks. However, with the power of CompactPCI technology embedded into platforms, this problem can be virtually eliminated.

CompactPCI has become an integral component of carrier-grade, high-availability platforms that are rugged, scalable, and versatile. With CompactPCI, off-the-shelf components are readily available, making these platforms more cost-efficient than traditional telecom platforms, such as VME, and reducing time-to-market. However, the consequence of CompactPCI becoming a commodity product is lack of integration and interconnection between available cards. This problem can be resolved within the CompactPCI chassis.

A chassis is a chassis is a chassis, right? Well, not really. To interconnect the various types of networks, a CompactPCI chassis or platform must provide connectivity as well as the interworking functions so that the different networks can communicate, regardless of their medium or application. This means that a CompactPCI platform solution can interconnect, for example, ATM to IP, frame relay to IP, or TDM to IP. The type of CompactPCI platform used also depends upon the application, medium and functionality within the network. It could be a CompactPCI platform performing simple network monitoring, or a highly customized, complex HA platform performing multiple functions within the network.

Migration To IP Networks
Consider the edge of the network where VoIP platforms are popular and CompactPCI plays its biggest role. In looking at the edge from a high-level perspective, it could be argued that the edge has basically three main types of platforms: the Media Gateway, Signaling Gateway, and the Edge Gateway.

Media Gateway
The Media Gateway acts as the main voice transformation between a legacy PCM over a TDM trunk to a packetized voice such as G.711, G.723.1 or G.729. This platform is typically an H.110, CompactPCI solution where one card provides connectivity to the access network via T1/E1 or ATM. It then routes the voice channels to the TDM bus (H.110). Once packetized within the platform, the voice traffic is sent to the host processor via the CompactPCI bus, which in turn, routes the voice packets to the Ethernet network.

Until recently, DSP cards provided a maximum of 120 voice channels, or four E1 trunk lines. Therefore, on an eight-slot CompactPCI chassis, there were two eight-port E1 and four DSP cards for a total of 480 voice channels per CompactPCI chassis where the CompactPCI bus could easily sustain the payload.
Today, DSPs have doubled in density to process up to 240 voice channels, thereby doubling the voice capacity. DSP cards also have built-in Ethernet ports that can be directly connected to the IP network, bypassing the process of transferring voice packet to the host processor via the CompactPCI bus. This connectivity prevents PCI bus latency and host processor overload as the payload reaches a high number of voice calls.

A new (PCI Industrial Computer Manufacturers Group) PICMG working group, PICMG 2.16, was formed late this year to propose a "hybrid" backplane solution. The solution would incorporate H.110 on J4 and dual-star Ethernet on J3 to route all the IP traffic into a single GigEthernet switch CompactPCI card for aggregation creating a "hostless" backplane solution. This backplane presents advantages, such as cost and host processor dependency. However, by creating a hostless environment, availability and chassis management, such as power control, fans, alarms, fault detection and fault management, no longer exist. The trade-off between costs and a carrier-grade solution is left to the user.

Evolution Of IP Networks
A new generation of DSP card that supports up to eight T1/E1 ports and eliminates that need for a trunk CompactPCI card is beginning to trickle into the marketplace. The function traditionally done by the CompactPCI bus is being executed entirely within the same slot and H.110 bus is no longer needed for such a platform. Take for example, a new backplane that provides high-speed Ethernet connectivity within a 5NINES-ready architecture. In this platform example, a dual host processor and a dual IP switch card provide the necessary elements for a carrier grade media gateway solution with up to 240 voice channels per card times 12 cards, or 2,880 voice channels per chassis.

Signaling Gateway
The Signaling Gateway provides VoIP signaling such as SS7 for the PSTN. This is the first next-generation technology to fully incorporate an all-IP backplane. It does this by providing signaling translation between SS7 and Sigtran as specified by the International Engineering Task Force under RFC2719. This can be accomplished by using a single one or multiple CompactPCI IP resource cards equipped with an SS7 PMC controller.

Edge Gateway
Then there is the Edge Gateway, which is a key platform for next-generation CompactPCI solutions. This is one of the most interesting gateways as it is responsible for inserting traffic into the transport network with the QoS intact and minimum overhead. This is accomplished by header compression, traffic shaping, tag switching (or MPLS), encryption, and virtual path network establishment. It can interface an optical network such as PoS or ATM without any additional hardware.

An Edge Gateway can be as simple as a single CompactPCI card with Ethernet 10/100BT on both ends or as complex as multiple 10/100BT connections on one end and an optical network connection on the other side for a high-end solution. New derivatives of CompactPCI backplanes allow up to 20Gbps of aggregate bandwidth and 12 high-powered CPU PowerPC 7400 engines loaded with a pair of PrPMC750 modules to provide the maximum power needed for a platform of this nature.

Converging H.110 And IP CompactPCI Platforms
After considering the IP evolution in the telecommunications infrastructure, including the applications, mediums, the impact of the Internet, and some of the significant functional elements, such as gateways, there is more evidence to support the argument that CompactPCI has been and will continue to be a versatile form factor. It accommodates and cost-effectively maximizes legacy equipment investments and continues to evolve into new derivatives to support next-generation technologies.

With the versatility and longevity of CompactPCI, telecommunication infrastructures will continue to evolve from legacy to next-generation equipment and provide innovative, revenue-generating services to end-users. The momentum of this evolution is evident as the H.110 backplane divests itself into two paths, a "hybrid" or H.110 / IP backplane (Media Gateways) and an all-IP, fully-meshed backplane (Signaling and Edge Gateways). While the industry witnesses these two backplanes diverge from H.110, a future convergence is most certain. As IP solutions improve and the momentum continues, the H.110 / IP backplane will eventually morph to an all-IP solution. The ripple effect will join the once separate Media Gateway technology with the Signaling and Edge Gateway technology, providing flexible and scalable CompactPCI platform solution without incurring expensive "fork lift" upgrades to the network infrastructure. 

Anne Brown is strategic marketing manager and Philippe Chevallier is a system architect for Motorola Computer Group. Motorola Computer Group is a business unit of Motorola Integrated Electronic Systems Sector. The organization is a leading supplier of embedded computing platforms to original equipment manufacturers for use in telecommunications, network storage, imaging, medical equipment, and semiconductor production and test equipment applications. 

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