Early in 2003, Six 9s Associates, Inc. conducted a qualitative market study of telecommunications equipment suppliers for Eternal Systems, Inc. The purpose of the market research was to identify and characterize data communications and telecommunications (telecom) applications that provide or need to provide very high service availability on system platforms for telecom network operators. The research included in-depth interviews with developers of applications on network elements and platforms in the telecom infrastructure. This research uncovered the following:

A very high level of Linux usage in these high-availability (HA) telecom applications The requirement for 5-Nines and 6-Nines availability A requirement for application state checkpointing The emerging use of the new IP backplane bus This article overviews these HA, Linux-based applications, the types of networks the applications run in, and where they fit in the network. Twenty-five research interviews were conducted with telecommunications application specialists and professionals. Over 50 percent of research participants are system architects and/or project managers. All have various engineering or marketing roles that gave them in-depth insight into their telecommunications infrastructure applications. Those interviewed are involved with programs with relatively large development teams with 60% of them having over 50 developers. Six of the interviewees are based in Europe, two in Canada, and the remainder in the United States. The network elements and applications represented in this study show a cross section of new and emerging telecom applications as the telecommunications infrastructure transitions from traditional circuit switching to IP-based packet switching. The applications characterized in this research study run in wireline (POTS), wireless, IP telephony, and/or Internet infrastructure networks. Some applications run in multiple networks. The telecom applications in this research have a wide range of configuration sizes with many large configurations. Approximately one-third of the configurations use two application processors, one-third use three to 25 processors, and one-third use over 25 application processors. The applications in this research also have a large number of line cards in the configurations with 60 percent using 5 or more line cards and 44 percent using more than 10 line cards. It is significant that 24 percent of these applications use communications interfaces on the application processor blades and do not have line cards in the network element. The merger of application processors and line card interfaces into application processor blades is likely to continue. Significant use of Linux Linux appears to be widely accepted for use in high-availability telecom applications. In this research sample, 44 percent of these telecom applications use Linux in their application processors leading all real-time operating systems combined and all Unix operating systems combined. It was also found that 28 percent of the applications use multiple operating systems. Embedded Linux is used on line cards by 26 percent of these applications that use line cards. Those interviewed represent Linux-based applications from three global telecommunications companies, a global wireless company, and five specialized telecommunications solutions companies. Four interviews were conducted with different business units in the larger firms representing different telecom applications. Those interviewed are involved with Linux programs with relatively large development teams with 55 percent of them having over 50 developers and 36 percent having from 26 to 50 developers. The Linux-based wireline, wireless, IP telephony, and Internet infrastructure applications represented in this research run in various roles in these networks including: Switching and routing Call control (SS7/IP gateways) Network and application services Network access and subscriber aggregation Customer premise/Service termination Here are descriptions of the new and emerging telecom, Linux-based applications found in this research: Media Gateway Controller - responsible for the call session and service control functions. A soft switch providing transition from classical TDM world (SS7, ISUP, DSS1, INAP) into the NGN (Next Generation Network - Packet Based) architecture (Megaco, SIP, SIGTRAN), while being able to serve both networks simultaneously Universal platform for many different applications Connection Processing Server / SIP application server IP Telephony Gateway - Carrier grade; IETF and ITU compliant for performance, redundancy. Module Replacement for current switch - not yet a funded project Signaling gateway Edge router for ATM, Frame Relay, Ethernet, and IP-based services Class 5 softswitch ISMSC, MMSC, Wireline SMS platform IP-PBX media server for enterprise IP telephony The Linux-based applications in this study at the platform level all have very-high service availability goals with 73 percent requiring 5-Nines and 27 percent requiring 6-Nines. To deliver these high service availability goals, these Linux-based application processors use active/standby, active/active, and N+1 redundancy schemes. The line cards use N+1, active/standby, active/active, and N+M approaches. In support of these HA redundancy schemes, 91 percent indicated that it is "Absolutely required" or "Highly beneficial" to preserve Linux-based application state information over a fail-over and recovery process. In support of application state checkpointing, 90 percent of these Linux-based applications store data and information in processor memory. This is positive for fast and efficient application checkpointing in support of the fail-over and recovery process in these HA applications. With the emergence of open and standard IP-based platform architectures, it is likely that the uses of Ethernet LAN for application state checkpointing will likely migrate to the IP backplane bus as applications evolve to the new architectures. A rich set of protocols are used in these Linux-based telecom applications: IP is used by most of these Linux applications to communicate within and between network elements. ATM and Sonet are used for routing packets through the network. SS7, the call setup and tear down protocol, is used to control calls and services in the Intelligent Network and in many of these applications. There is also a strong mix of protocol support for the interfaces between the packet, IP-based networks and the TDM and next generation wireless networks. This validates that the applications characterized in this research are representative of the growth and evolutionary segments of the telecommunications infrastructure. This qualitative research uncovered a strong presence of Linux usage in very-high availability applications in the core applications of the telecommunications infrastructure. These applications, which require 5-Nines and 6-Nines availability, are found in both the traditional telephone networks and the emerging IP Telephony and Internet networks. It is not surprising that application state checkpointing is key to the HA implementation strategies of these platforms, which heavily use IP networking for intra-processor communications. The research also found a significant use of the new IP backplane bus in these applications. This IP backplane bus usage will grow as new platforms using these new interconnect architectures are delivered to telecom development teams. Noel Lesniak is President of Six 9s Associates, Inc. (Scottsdale, AZ)