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Migration to ATCA: An Open Modular Architecture

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					White Paper

Migration to ATCA
An Open Modular Architecture

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© 2007 Aricent™, Inc. All rights reserved.

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e-mail: info@aricent.com Visit us at: http://www.aricent.com February, 2007

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CONTENTS

1. Introduction 2. Evolution of ATCA 3. ATCA: A Technical Summary 3.1 Mechanicals 3.2 Power Distribution 3.3 Backplane 3.4 Shelf Management 4. Trends in ATCA Products 4.1 Trends in Application - Ready Platforms 4.2 Trends in Solutions 5. Case Study - Aricent’s Experience at Migrating A Legacy System to ATCA 5.1 Motivation for Migrating to ATCA 5.2 Steps involved in Migration 5.3 Key Factors of Migration 6. Conclusion 7. Acronyms

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1. INTRODUCTION

This white paper traces the evolution and presents a technical summary of the Advanced Telecommunication Communication Architecture (ATCA) technology. In addition, it lists the current market trends in ATCA products. The white paper begins with a detailed look at how Compact PCI (cPCI) evolved over the years until it lead to the genesis of ATCA. It also discusses the mechanical, power distribution, Backplane, and shelf management aspects of ATCA.

In the end, the white paper discusses the current trends in the ATCA industry that cover the availability of different ATCA components in market today; as well as how these components are being used in various solutions. This white paper also provides a case study on the use of ATCA. The case study highlights the migration of a legacy telecommunication system to an ATCA-based platform. This section lists the motivations for migrating a legacy system to an ATCA-based platform and describes the strategy, steps, and challenges involved in the migration.

2. EVOLUTION OF ATCA The PCI Industrial Computer Manufacturers Group (PICMG) Forum adapted the PCI Bus for industrial computing environment. The specification for the same was released in 1995 as PICMG 2.0. This specification supports Passive Backplane that supports the PCI Bus and allows front-loading of boards. The PICMG 2.0 specification also standardized the form factors of the boards (3U or 6U) and the interface of the front boards with Backplanes (P1, P2, P3, P4, and P5 connectors). Later, the PICMG Forum introduced several other subsidiary specifications in the PICMG 2.x series while the PICMG 2.0 specification continued to be the core specification for all the subsidiary specifications. All the specifications contained in the PICMG 2.x series are collectively called cPCI. Some of the major specifications that lead to the evolution of cPCI from 1995 to 2004 are listed below: . PICMG 2.1: Defined the Hot Insertion and Removal feature for the PCI Bus. This specification is considered essential for all industrial products and technologies. . PICMG 2.5: Introduced support for H.110 Bus in cPCI, which can be used for real-time data transfer, such as voice and media, between cPCI shelf boards. . PICMG 2.9: Introduced the system management aspects of cPCI . PICMG 2.10: Introduced the electronic keying support for cPCI . PICMG 2.11: Added the Power interface to cPCI . PICMG 2.16: Provided support for Ethernet-based packet switching in the cPCI Backplane. Products supporting the PICMG 2.16 subsidiary specification had Ethernet-based switching connectivity in the Backplane in addition to a PCI Bus that can co-exist with Ethernet-based connectivity. . PICMG 2.17: Enabled support for the StarFabric switching fabric in the cPCI Backplane. StarFabric is a serial switch technology that supports various next-generation features, such as priority and the isochronous traffic class. . PICMG 2.20: Added support for the mesh topology in the cPCI Backplane. This specification is based on the serial switching However, during 2000-2001, despite this phased evolution, a need was felt for a new modular architecture, which showcases all the features of cPCI and can cater to the future requirements of all telecommunication nodes. During this period, the PICMG Forum started standardizing the ATCA architecture. ATCA is an open modular architecture developed by the PICMG Forum and is covered in the PIC.MG 3.x series of specifications. This architecture standardizes the interfaces and the functionality of various hardware components of a telecommunication node. These hardware components include shelf, Backplane, power supply, front boards, and the Rear Transition Module (RTM) boards. ATCA’s modular architecture and standardization of various interfaces enable vendors effectively build and customize various hardware components of this architecture, which can then be used in a single solution. This significantly reduces time-to-market as well as the cost of the solution. As evident from the preceding list of evolving specifications, the PICMG Forum incorporated several changes in cPCI in sync with technological advancements Backplane technologies, system management, power distribution, and electronic keying. technology and uses the CSIX protocol for message transport among node boards.

The ATCA architecture standardizes the interfaces and the functionality of various hardware components of a telecommunication node, such as shelf, Backplane, power supply, front boards, and the Rear Transition Module boards.

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3. ATCA: A Technical Summary ATCA is based on the experience gained in cPCI. Based on this experience, the ATCA architecture standardizes the following: 3.1 MECHANICALS 3.1.1. Chassis ATCA supports a 12U chassis and 14/16 slots variants. The following diagram depicts an ATCA chassis:

Illustration 2: The ATCA Front and RTM Board

3.1.4. The Advanced Mezzanine Card (AMC) The AMCs are child cards that can be plugged into the ATCA Carrier card to extend the Carrier card features. Carrier cards support a
Illustration 1: ATCA Chassis

new connector using which AMC cards can be plugged into the Carrier cards. AMCs support the hot plugging feature and provide I/O interconnect either using the faceplate or via the

3.1.2. Front Boards ATCA supports 8U x 280 mm size for the front board (as compared to 3U/6U x 160 MM in cPCI) and 200W of heat dissipation per board. ATCA has selected parameters, such as “the size of the board” and “heat dissipation allowed per board” to enable more devices to be fit into a single board. The front boards connect to the Backplane using zone1 and zone2 connectors and may optionally connect to the RTMs directly using zone3 connectors. 3.1.3. The Rear Transition Module ATCA supports an RTM of the size 8U x 70 mm. These boards can optionally be used in ATCA to terminate the I/O cables. The RTM simplifies the process of servicing the front boards as it does not require disconnection/reconnection of I/O cables while replacing the front boards. The RTM connects to the front boards using non-standardized zone3 connector(s). The RTM does not connect to the Backplane using zone1/zone2 connectors.

Backplane/RTM. ATCA supports a maximum of 8 single-width and half-height AMCs.

Illustration 3: The ATCA AMC Board

ATCA supports: . 12U chassis and 14/16 slots variants . 8U x 280 mm size for front board . 8U x 70 mm size for RTM . A maximum of 8 single-width and half height AMCs . Redundant 48VDC and 60VDC power supplies . Redundant power distribution via Zone1 connectors

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3.2 POWER DISTRIBUTION ATCA supports redundant 48VDC and 60VDC power supplies. Electrical power is supplied to each board of the shelf by using the zone1 connector of the Backplane. 3.3 BACKPLANE The Backplane is divided into the following zones. . The Power Connector (zone1) . The Data Transport Connector (zone2) . The Rear I/O Access (zone3)

. PICMG 3.3 (StarFabric): StarFabric is a serial switch interconnect technology developed by the Starfabric Forum (www.starfabric.org). This technology uses four pairs of 622 Mbps LVDS in its physical layer. StarFabric support 5Gbps bi-directional bandwidth between two nodes. In addition, StarFabric supports several next-generation protocol features, such as multiple traffic classes (asynchronous, isochronous, and multicast), high availability features (fault detection and isolation, redundant paths, and failover management), and QoS support. This makes StarFabric suitable for applications involving real-time data transfer. . PICMG 3.4 (PCI Express and Advanced Switching): The PCI Express protocol is developed by the PICSIG Forum (www.picsig.com). This protocol is software compatible with the PCI protocol but uses different physical and lower layers. The PCI Express protocol uses a serial-switched technology for point-to point connection in its physical layer as compared to the shared Bus technology (for point-to-multi point connection) in the PCI protocol. The PCI Express protocol allows up to 32 pairs to be used in a single link between two PCI Express devices, each pair capable of supporting up to 1.25 Gbps. . PICMG 3.5 (S-RapidIO): The S-RapidIO protocol is developed by

Illustration 4: The ATCA Backplane

the Rapid I/O Forum (www.rapidio.org). This technology supports serial as well as parallel bus-based physical interfaces. The serial interface is being used in the ATCA Backplane. This technology allows four pairs to be used in a single link between two devices, each capable of 1.25 Gbps. This technology has protocol support for distributed memory, Port-based message passing, and memory mapped I/O programming models. The following table compares the various subsidiary specifications:
Features
Bandwidth (each direction) Topology

ATCA supports redundant power distribution via zone1 connectors. The ATCA zone3 interface is not standardized intentionally. This allows vendors to select their own interconnect mechanism between the front and the rear boards. The ATCA Data Transport Zone (zone2) is designed to allow multiple switching technologies to be used for data transport between the front boards. The PICMG core specification (PICMG 3.0) is independent of the switching technology to be used; it just provides a mechanism through which a switching technology of choice can be used. Currently, the following subsidiary specifications are defined for Backplane technologies in ATCA: . PICMG 3.1 (Ethernet and Fiber Channel): ATCA supports Ethernet (10/100/1000 Mbps) based interconnect via the Base Channel interface in the Backplane. This support is available through P23 and P24 connectors. ATCA allows 2 hub and 14 node slots in a 16-slot shelf. The Dual Star topology is supported for Ethernet based interconnect. . PICMG 3.2 (InfiniBand): InfiniBand is a interconnect technology developed by the Infiniband Forum (www.infinibandta.org), primarily for data center applications. This technology unifies the computing, communications, and storage fabrics in a data enter by using a single I/O fabric for various existing interconnects, such as Ethernet, Fiber Channel, and SCSI.

Ethernet
1 Gbps

Infiniband Star fabraic PCI Express S-Rapid IO
10Gbps 2.5Gbps Dual Star Mesh Optional 10Gbps Dual Star Mesh Optional 12.5Gbps Dual Star Mesh Optional

Dual Star

Dual Star

Need for Fabric Board Suitability for Control Plane Applications Suitability for High Bandwidth Data Plane Applications Suitability for Real Time Traffic

Mandatory

Mandatory

High

High

High

High

High

Low

High

Medium

High

Highest

Low

Low

Highest

Low

Low

Suitability for Shelf to Shelf Interface

Low (Small b/w)

Highest

Medium

Low (Small max distance) Medium

Highest

Market Acceptability

Highest

Medium

High

Low

Table 1: Backplane Subsidiary Specifications Comparison

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3.4 SHELF MANAGEMENT The shelf management feature in the ATCA chassis enables multi-level management of multiple components of the chassis. The complete management strategy can be divided into three logical components: . The Shelf Manager provides the low-level management of ATCA boards . The System Manager: Controls the complete system, which may consist of multiple shelves, using a TCP/IP interface for communicating with different Shelf Managers. The System Manager can also optionally interface with the ATCA boards directly for IP-based management, such as software upgrades and remote reboot. . The Managed Component

system that connects the System Manager to different devices, enabling an IP-based management of these devices, if required. Shelf Managers are recommended to be in redundant pair though the specification does not mandate it. While the Shelf Manager manages a single shelf, the System Manager may manage multiple shelves. The Shelf Manager carries out the following functions: . Monitoring the managed intelligent devices and reporting to the higher level System Manager . Hot swap control by detecting the removed and new devices . Controlling the managed Field Replaceable Units (FRUs) for recovery actions . Power cycle or reset of devices . Negotiating with and allocating to other FRUs the power budget . Fan-level changes for proper cooling as per temperature events received from various devices

The architecture of ATCA shelf management consists of the following logical entities: . Managed devices: These are either intelligent devices or represented by an intelligent device, such as ATCA boards . The Shelf Manager . The System Manager
IPM Controller (IPMC) Shelf -External System Manager Shelf Management Controller (ShMC) Advanced ATCA Board Shelf Manager W Dedicated ShMC Shelf Manager (Active) Shelf Manager (Active) Fan Tray Power Entry Module Power Entry Module Implementation Dependent Connection Other Field Replaceable Unit (FRU)

. Controlling the enabling/disabling of ports for each board with respect to the levels of compatibility between different boards in the system

The Sensor Data Record (SDR) refers to information regarding devices. The Shelf Manager/the System Manager can access the data available in the SDR from the IPMC via the IMPB-0 bus. With the help of the SDR, it knows all the resources for that device. In case of AMC boards on a Carrier boards each AMC board acts as a managed device for the Shelf Manager. The IPMC on the Carrier board represents the AMC board and provides separate information for every AMC. Every IPMC logs the events related to its devices and sends this log to the ShMC (Shelf Manager). It is recommended

ShMC

ShMC

IPMC

IPMC

IPMC

IPMC

IPMC

IPMC

IPMC

IPMC

IPMC

that a log of these events is stored on non-volatile media on the FRU, a step that will be useful while repairing the FRU.

ATCA Board

ATCA Board

ATCA Board

ATCA Board

ATCA Board

ATCA Board

ATCA Board

ATCA Board

2x Redundant Radial Internet-Portocol-Capable Transport

4. TRENDS IN ATCA PRODUCTS Independent research and consulting organizations estimate the market for ATCA-based network equipments to be in the order of

Illustration 5: The Architecture of ATCA Shelf Management

Each entity in the architecture is a logical entity. Physically, the Shelf Manager can be a separate board or can be implemented as a part of some board. Similarly, the System Manager may be a stand-alone unit outside the shelf or implemented as a part of some board within the chassis. Interconnection between the Shelf Manager and the managed devices is through a redundant pair of the Intelligent Platform Management Bus (IPMB). These buses are termed as IPMB-A and IPMB-B. Together, they are known as the IPMB-0 Bus. Each device implementation contains an Intelligent Platform Management Controller (IPMC) to connect to the IPMB whereas the Shelf Manager contains the ShMC as the controller of the bus. Interconnection between the Shelf Manager and the System Manager is carried out through a redundant IP-based transport

billions of dollars. 4.1 TRENDS IN APPLICATION - READY PLATFORMS As vendors of ATCA products move towards integration, an emerging concept is that instead of users purchasing and integrating blade level building blocks, application-ready platforms are emerging. These platforms are built on standards-based, off-the-shelf hardware and software building blocks. From a user’s standpoint, these platforms are ready for application-specific software. Hardware building blocks include components covered in the previous paragraph and current trends ensure that users need not worry about blade, Backplane, and switch compatibility. Software

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components include high availability platforms and operating systems that are suitable for telecommunication node requirements (Carrier-grade and real-time). A Service Availability Forum (SAF) specification has gained market acceptance for high availability middleware. Similarly, the Carrier-Grade Linux (CGL) specification has gained market acceptance as the preferred operating system. Vendors, such as Force Computers, Radisys, and Continuous Computing are already offering application-ready product solutions targeting various network elements. 4.2 TRENDS IN SOLUTIONS Many leading Telecommunications Equipment Manufacturers (TEMs) are already developing solutions based on ATCA or are in the process of migrating their existing solutions from proprietary architecture to ATCA. NEC Corporation, Huawei, Alcatel, and Siemens Mobile are some of the major equipment manufacturers who are already developing ATCA-based solutions: . NEC has developed a new platform using the ATCA architecture, CGL, and a proprietary middleware. NEC has already delivered Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) products based on this new platform. . Siemens Mobile has also announced the introduction of its “Next Generation Telecom Architecture”, an ATCA-based platform model designed to speed development and simplify mobile service deployment for the Carriers. . Alcatel has demonstrated its SGSN product working on the ATCA platform and has endorsed ATCA as the preferred architecture for the evolution of its mobile and fixed network infrastructure systems.

. Smaller Footprint of the Devices: Would enable more devices on a single board. The ATCA platform is attuned to these developments and has set the mechanical size and average power consumption per board to be 8U and 200W, respectively. Adding more devices on a single board would reduce the number of boards needed for the complete system and hence, the total size of equipment would reduce considerably. This reduction in size would result in a lowered real estate requirement for the equipment in the field as well as the operating cost for the Operator. . Reduced Power Consumption: Of each device would lead to a considerable reduction in the total power consumption of the complete system. This would go a long way to cut down the operating cost of the equipment for the Operator. . Decreased Cost of the Devices: Indicates that the equipments could be manufactured at lower prices and therefore reduces the CAPEX as well as the OPEX for the Operators.

Most legacy systems involve considerable manual Backplane inter-connection, within a single shelf and between multiple shelves. This level of connectivity can be achieved only on-site, thereby increasing the complexity associated with installation as well as maintenance of the equipment. The ATCA platform reduces this complexity by enhancing the Backplane functionality by using advanced interconnection features. This minimizes the need for manual interconnection and hence makes installation/maintenance easy.

Most legacy telecommunications systems are built using proprietary hardware designs. Usually, telecom vendors manufacture these systems in-house. To reduce the cost of systems, several vendors

5. CASE STUDY - ARICENT’s EXPERIENCE AT MIGRATING A LEGACY SYSTEM TO ATCA This section provides an example, which deals with migrating a legacy system to an ATCA-based platform. The term “legacy system” is used for a telecommunication node that runs on proprietary hardware and software components. These components were designed and manufactured locally by a TEM. This section discusses the motivations, steps, and challenges involved in migrating a legacy system from a proprietary hardware/software to one, which is based upon the ATCA architecture platform, where open/standardized hardware and software components are used. 5.1 MOTIVATION FOR MIGRATING TO ATCA The hardware components used in legacy systems are based on old technologies and are unable to fully utilize the latest technological advancements. These developments ensure that devices can easily add more capabilities, such as:

are opting for COTS components rather than manufacturing them in-house. There are significant cost benefits associated with using COTS components due to the scale economy involved in manufacturing them. The modular architecture and specifications of the various interfaces in the ATCA platform has enabled new COTS components to be manufactured. For example, different vendors can now produce shelf, Backplane, control, and data processing boards, and FRUs. This helps reduce the cost of the system, as various inter-operable components are available at a lower cost. One of the most important factors for migrating a system to a new architecture is the remaining lifetime of the technology that the system is serving. For example, if it is foreseen that a technology is going to be obsolete after a year and hence no new systems of this technology are going to be deployed, there is no benefit of migrating a legacy system to a new architecture. This is particularly true for the GSM technology. With the slow penetration of 3G technologies,

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lifetime of GSM has increased. This has resulted in many vendors migrating their legacy GSM systems to an ATCA-based architecture. 5.2 STEPS INVOLVED IN MIGRATION . Selection of the Hardware Platform: The first step involves selecting an appropriate hardware platform. There are several solution options to choose from, which include ones based on the chassis, such as cPCI, ATCA, and VME; or those, which are based on a stack of Sun servers. We assume that the ATCA platform is chosen after a careful analysis of the pros and cons associated with each solution. . Selection of the Hardware Architecture: This step involves decomposing the existing node functionalities into multiple logical units, which would run on different hardware components; defining the interconnection mechanism between these hardware components (the Backplane technology as well as the topology). This step defines the hardware architecture for the system. . Selecting Vendors for the Hardware Components: Depending on the functionality, hardware components of the system can be any of one of the following two categories: . Off-the-Shelf Components: Some of the hardware components could be taken off the shelf, as these components are not application-specific. These include shelf, Backplane, general purpose processing boards, switch fabric boards, power supply, and fans. Vendors may support various product lines for the above component types. Detailed specifications of the component are required to make a decision about suitability of a vendor product in the system. . Proprietary Components: Some hardware components would be application-specific and for them no COTS components may be available. These components would have to be designed and manufactured in-house. Most of the components should be procured off the shelf. . Defining the Software Migration Strategy: Objective of software migration would be to reduce the change in existing application as far as possible. Changes are expected in the following types of modules: . Modules Closely Tied with the Hardware Components: These modules are non-reusable and have to be replaced with newer modules with similar functionalities, based on the new hardware components. . Modules Implementing the Abstraction Layer: For reducing the impact to the application while migrating to new platform, an abstraction layer should be added to the system. This layer|should reproduce the environment and interfaces that were provided by the legacy system. . Modules Getting Impacted Due to the New Hardware

Architecture: Some existing modules may be impacted due to the changed hardware architecture. 5.3 KEY FACTORS FOR MIGRATION . Minimizing the impact on the existing software: The software migration strategy should try to minimize any changes in the existing software components. These components have been stabilized over a period of time and any changes to them affect the entire new system. . Application Impact v/s the Peak Performance: The new hardware components would provide significant additional capabilities, which might require changes in the software components. A balance has to be achieved between the two components in order to attain the peak performance levels for the new system.

6. CONCLUSION In the wake of the explosive growth of wireless communication over the recent decades and the lead-time required for introducing new technologies, time has come to migrate to an architecture that standardizes interfaces and the functionalities of various hardware components of a telecommunication node. Even in today's challenging economic conditions, migrating to the ATCA architecture will benefit OEMs by enabling functional scalability, more choice of suppliers and components, and interoperability of components at multiple levels.

Having executed projects on ATCA and migration of client platforms to ATCA, Aricent possesses the ability to help migrate the infrastructure nodes at faster time-to-market and reduced development costs.

Aricent has the capability and a vast experience in building the following solutions on ATCA: . Application Servers . Base Station Controllers . Call State Control Functions . Charging Gateway Functions . Enhanced Service Platforms . GPRS Service Nodes . Home Location Registers . Intelligent Peripherals . Media Gateways/Media Servers . Media Resource Functions . Node Bs . Radio Network Controllers . Service Control Points . SIP Application Servers . Softswitches . Session Border Controllers

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7. ACRONYMS AMC: Advanced Mezzanine Card ATCA: Advanced Architecture for Protocol Engineering CPCI: Compact PCI COTS: Components Off the shelf PCI: Peripheral Component Interface PICMG: PCI Industrial Computer Manufacturers Group TEM: Telecommunications Equipment Manufacturers RTM: Rear Transition Module 3U/6U: Board Sizes for Compact PCI 8U: Board Sizes for ATCA

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Aricent is a global leader in communications software, providing strategic solutions that empower billions of people. By delivering the best and most innovative communications software in the industry, we’re helping our clients change the world. Aricent has an extensive portfolio of services and products covering the full spectrum of communications software—from strategic design to implementation in the field. Our uniquely talented team of designers, consultants and engineers work to solve the most complex, high-impact challenges for our clients—the world’s leading equipment manufacturers, device manufacturers and service providers.

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Description: This white paper traces the evolution and presents a technical summary of the Advanced Telecommunication Communication Architecture ATCA technology. In addition, it lists the current market trends in ATCA products.
Chiru Gabriel Chiru Gabriel
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