Carrier Grade Server Features in the Linux Kernel Towards Linux-based Telecom Plarforms Ibrahim Haddad Ericsson Research [email protected] Abstract significant changes in the communication in- dustry, such as the convergence of data and Traditionally, communications and data ser- voice technologies. The transition to packet- vice networks were built on proprietary plat- based, converged, multi-service IP networks forms that had to meet very specific availabil- require a carrier grade infrastructure based on ity, reliability, performance, and service re- interoperable hardware and software building sponse time requirements. Today, communica- blocks, management middleware, and appli- tion service providers are challenged to meet cations, implemented with standard interfaces. their needs cost-effectively for new architec- The communication industry is witnessing a tures, new services, and increased bandwidth, technology trend moving away from propri- with highly available, scalable, secure, and etary systems toward open and standardized reliable systems that have predictable perfor- systems that are built using modular and flex- mance and that are easy to maintain and up- ible hardware and software (operating system grade. This paper presents the technological and middleware) common off the shelf com- trend of migrating from proprietary to open ponents. The trend is to proceed forward de- platforms based on software and hardware livering next generation and multimedia com- building blocks. It also focuses on the ongo- munication services, using open standard car- ing work by the Carrier Grade Linux working rier grade platforms. This trend is motivated group at the Open Source Development Labs, by the expectations that open platforms are go- examines the CGL architecture, the require- ing to reduce the cost and risk of developing ments from the latest specification release, and and delivering rich communications services. presents some of the needed kernel features Also, they will enable faster time to market and that are not currently supported by Linux such ensure portability and interoperability between as a Linux cluster communication mechanism, various components from different providers. a low-level kernel mechanism for improved re- One frequently asked question is: ’How can we liability and soft-realtime performance, sup- meet tomorrow’s requirements using existing port for multi-FIB, and support for additional infrastructures and technologies?’. Proprietary security mechanisms. platforms are closed systems, expensive to de- velop, and often lack support of the current and upcoming standards. Using such closed 1 Open platforms platforms to meet tomorrow’s requirements for new architectures and services is almost impos- The demand for rich media and enhanced sible. A uniform open software environment communication services is rapidly leading to with the characteristics demanded by telecom 256 • Linux Symposium 2004 • Volume One applications, combined with commercial off- 2 The term Carrier Grade the-shelf software and hardware components is a necessary part of these new architectures. In this paper, we refer to the term Carrier Grade The following key industry consortia are defin- on many occasions. Carrier grade is a term ing hardware and software high availability for public network telecommunications prod- specifications that are directly related to tele- ucts that require a reliability percentage up to 5 com platforms: or 6 nines of uptime. 1. The PCI Industrial Computer Manufactur- ers Group [1] (PICMG) defines standards • 5 nines refers to 99.999% of uptime per for high availability (HA) hardware. year (i.e., 5 minutes of downtime per year). This level of availability is usually 2. The Open Source Development Labs [2] associated with Carrier Grade servers. (OSDL) Carrier Grade Linux [3] (CGL) working group was established in Jan- • 6 nines refers to 99.9999% of uptime per uary 2002 with the goal of enhancing the year (i.e., 30 seconds of downtime per Linux operating system, to achieve an year). This level of availability is usually Open Source platform that is highly avail- associated with Carrier Grade switches. able, secure, scalable and easily main- tained, suitable for carrier grade systems. 3 Linux versus proprietary operat- 3. The Service Availability Forum [4] (SA ing systems Forum) defines the interfaces of HA mid- dleware and focusing on APIs for hard- ware platform management and for appli- This section describes briefly the motivating cation failover in the application API. SA reasons in favor of using Linux on Carrier compliant middleware will provide ser- Grade systems, versus continuing with propri- vices to an application that needs to be HA etary operating systems. These motivations in- in a portable way. clude: • Cost: Linux is available free of charge in the form of a downloadable package from the Internet. • Source code availability: With Linux, you gain full access to the source code allow- ing you to tailor the kernel to your needs. • Open development process (Figure 2): Figure 1: From Proprietary to Open Solutions The development process of the kernel is open to anyone to participate and con- tribute. The process is based on the con- The operating system is a core component in cept of "release early, release often." such architectures. In the remaining of this pa- per, we will be focusing on CGL, its architec- • Peer review and testing resources: With ture and specifications. access to the source code, people using a Linux Symposium 2004 • Volume One • 257 wide variety of platform, operating sys- Linux in the telecom space, OSDL established tems, and compiler combinations; can the CGL working group. The group specifies compile, link, and run the code on their and helps implement an Open Source platform systems to test for portability, compatibil- targeted for the communication industry that ity and bugs. is highly available, secure, scalable and easily maintained. The CGL working group is com- • Vendor independent: With Linux, you no posed of several members from network equip- longer have to be locked into a specific ment providers, system integrators, platform vendor. Linux is supported on multiple providers, and Linux distributors. They all platforms. contribute to the requirement definition of Car- • High innovation rate: New features are rier Grade Linux, help Open Source projects usually implemented on Linux before they to meet these requirements, and in some cases are available on commercial or propri- start new Open Source projects. Many of etary systems. the CGL members companies have contributed pieces of technologies to Open Source in order to make the Linux Kernel a more viable option for telecom platforms. For instance, the Open Systems Lab [5] from Ericsson Research has contributed three key technologies: the Trans- parent IPC [6], the Asynchronous Event Mech- anism [7], and the Distributed Security Infras- tructure [8]. There are already Linux distri- butions, MontaVista [9] for instance, that are providing CGL distribution based on the CGL requirement definition. Many companies are also either deploying CGL, or at least evaluat- Figure 2: Open development process of the ing and experimenting with it. Linux kernel Consequently, CGL activities are giving much momentum for Linux in the telecom space Other contributing factors include Linux’ sup- allowing it to be a viable option to propri- port for a broad range of processors and etary operating system. Member companies of peripherals, commercial support availability, CGL are releasing code to Open Source and high performance networking, and the proven are making some of their proprietary technolo- record of being a stable, and reliable server gies open, which leads to going forward from platform. closed platforms to open platforms that use CGL Linux. 4 Carrier Grade Linux 5 Target CGL applications The Linux kernel is missing several features that are needed in a telecom environment. It The CGL Working Group has identified three is not adapted to meet telecom requirements main categories of application areas into which in various areas such as reliability, security, they expect the majority of applications imple- and scalability. To help the advancement of mented on CGL platforms to fall. These appli- 258 • Linux Symposium 2004 • Volume One cation areas are gateways, signaling, and man- customer is authorized to use). Typi- agement servers. cally, management applications are data and communication intensive. Their re- sponse time requirements are less strin- • Gateways are bridges between two dif- gent by several orders of magnitude, com- ferent technologies or administration do- pared to those of signaling and gateway mains. For example, a media gateway per- applications. forms the critical function of converting voice messages from a native telecommu- nications time-division-multiplexed net- 6 Overview of the CGL working work, to an Internet protocol packet- group switched network. A gateway processes a large number of small messages received The CGL working group has the vision that and transmitted over a large number of next-generation and multimedia communica- physical interfaces. Gateways perform tion services can be delivered using Linux in a timely manner very close to hard based open standards platforms for carrier real-time. They are implemented on ded- grade infrastructure equipment. To achieve this icated platforms with replicated (rather vision, the working group has setup a strat- than clustered) systems used for redun-