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June 30, 2008

Designing Multi-Function IMS Systems

By Anuradha Shukla, TMCnet Contributor

In its whitepaper, Strategies for Developing Multi-function IMS Systems, RadiSys (News - Alert) elaborates on the various benefits of IP multimedia subsystems (IMS) technology that helps telecom and mobile operators and other service providers to offer rich media services across packet-switched and traditional circuit-switched networks.
IMS is an open standard, and thus hardware and software components from multiple vendors are compatible and interoperable. Few equipment manufacturers are searching means to make system components more universal and going beyond multi-function devices. These techniques expedite and simplify the integration of the components, which greatly increases reuse opportunities.
By using design practices that facilitate the seamless scaling of capacity and functionality, IMS system developers minimize one-off requirements, like non-standard chassis and custom circuit cards, which can occur at any system level. The elimination of special situations helps equipment manufactures to streamline system assembly, configuration and test operations.
The whitepaper describes how design practices that maximize component integration and interoperability are particularly relevant in multifunction system design. There are several ways by which developers can maximize cost savings and reusability associated with system partitioning, legacy integration, HA middleware, development tools and commercial off-the shelf components.
Partition the System Wisely
RadiSys explains that IMS systems are relatively complicated to develop. These systems require the participation of different development teams including systems, hardware, software and validation engineering. Well-defined interfaces are required so that components, both hardware and software, can interoperate properly. Often system designers make system partitioning decisions that significantly impact integration, especially for multi-function systems.
The whitepaper refers to Tyson Browning, assistant professor at Texas Christian University, who emphasizes that without cautious system partitioning the number of required interfaces and thus the number of iterations required to converge on an acceptable solution can increase exponentially with system complexity. The following sections include some practices in system partitioning.
Consolidate functionality  — Designers can successfully eliminate system-level interfaces by consolidating as much functionality as possible onto a single component. A system with a single board media gateway for instance may benefit from terminating the line on the board in contrast to going out to a line card. The elimination of line cards may free up slots in the chassis and reduce backplane traffic. In some cases it is required to maintain individual line cards in large systems. But, this approach could unnecessarily burden smaller, cost-sensitive configurations.
Drive functionality to the lowest level  — By implementing features at the lowest possible system level developers can help save cost and increase efficiency. RadiSys cites the example of cyclic redundancy checking (CRC), which is much cheaper and faster to calculate a CRC in hardware, like a network interface card (NIC (News - Alert)), than in application software. A multi-function system can also use a networking driver to handle redundancy. The whitepaper discusses how a Linux bonding driver can also detect link failures and reroute network traffic around failed links in a manner transparent to the application. Through this capability, the application no longer has to be aware of network topology when the system is required to quickly switch from one LAN connection to another.
Keep options open: networking speed  — Designers of multifunction systems must plan for10 Gigabit Ethernet (GE) and all systems should be prepared to run 10 GE across the backplane to handle packet-processing intense networking elements. Businesses may find it cost effective to maintain different speed versions (1 GE and 10 GE) of the same module, such as a networking blade, as long as the reconfiguration effort is minimal.
Weigh Legacy Integration Options
According to RadiSys, IMS systems must still offer ways to integrate legacy functionality even though IP is becoming the prevalent end-to-end transport for nearly all types of service. Given the huge legacy base, telecom equipment manufacturers are driven to merge existing capabilities with next-generation-systems for financial, time-to-market and competitive reasons.
Maintain competitive advantage  — The development of proprietary technology creates a competitive advantage in the telecommunications industry. Equipment manufacturers may thus want to propagate different functionalities to their NGN multi-function system such as a unique media processing card, management software or a module that facilitates hardware failover.
Designers can re-engineer the features that rely on specific hardware into open standards-based form factors like an ATCA (Advanced Telecom Computing Architecture) board, a COM Express module or an advanced mezzanine card (AMC). Because these form factors are supported by comprehensive specifications it simplifies the task of laying out a new board. In addition to saving space in compact IMS systems, the modules and cards can present new scalability alternatives.
Transition: evolutionary, not revolutionary  — Although IPTV is driving broadband remote access servers (B (News - Alert)-RAS) to perform IP-based services, B-RAS equipment historically delivered broadband data traffic using Asynchronous Transfer Mode (ATM) and Synchronous Optical Network (SONET). RadiSys says that equipment manufacturers still have to respect the past and support ATM and SONET, as well as GE and 10 GE. The white paper refers to the DSL Forum’s Technical Report (TR) 59 that published B-RAS requirements for implementing IP-based services over DSL using ATM as the underlying transport mechanism. The transition to IP-based multi-media systems will in fact be evolutionary, not revolutionary.
Consolidate legacy interfaces  — The developers can consolidate legacy interfaces (e.g. ATM) and Ethernet onto special-purpose gateway blades, which can ease integration and save board slots in multi-function IMS systems. A single gateway component can lower system complexity by eliminating interconnects and protocol conversions that are spread across multiple boards.
Anuradha Shukla is a contributing editor for TMCnet. To read more of Anuradha’s article, please visit her columnist page.

Don’t forget to check out TMCnet’s White Paper Library, which provides a selection of in-depth information on relevant topics affecting the IP Communications industry. The library offers white papers, case studies and other documents which are free to registered users. Today’s featured white paper is  Jim Cossetta, President, CEO, 4What Interactive, Creators of The VoIPTrainer, brought to you by 4What Interactive (News - Alert).


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