Carrier Grade Server Features in the Linux Kernel Towards Linux-based Telecom Plarforms Ibrahim Haddad Ericsson Research [email protected] Abstract 1 Open platforms The demand for rich media and enhanced communication services is rapidly leading to 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 platforms to meet tomorrow’s requirements for new architectures and services is almost impos- sible. A uniform open software environment with the characteristics demanded by telecom applications, combined with commercial off- the-shelf software and hardware components is a necessary part of these new architectures. Figure 1: From Proprietary to Open Solutions The following key industry consortia are defin- ing hardware and software high availability specifications that are directly related to tele- com platforms: 2 The term Carrier Grade In this paper, we refer to the term Carrier Grade on many occasions. Carrier grade is a term 1. The PCI Industrial Computer Manufactur- for public network telecommunications prod- ers Group [1] (PICMG) defines standards ucts that require a reliability percentage up to 5 for high availability (HA) hardware. or 6 nines of uptime. 2. The Open Source Development Labs [2] • 5 nines refers to 99.999% of uptime per (OSDL) Carrier Grade Linux [3] (CGL) year (i.e. 5 minutes of downtime per working group was established in Jan- year). This level of availability is usually uary 2002 with the goal of enhancing the associated with Carrier Grade servers. Linux operating system, to achieve an Open Source platform that is highly avail- • 6 nines refers to 99.9999% of uptime per able, secure, scalable and easily main- year (i.e. 30 seconds of downtime per tained, suitable for carrier grade systems. year). This level of availability is usually associated with Carrier Grade switches. 3. The Service Availability Forum [4] (SA Forum) defines the interfaces of HA mid- dleware and focusing on APIs for hard- 3 Linux versus proprietary operat- ware platform management and for appli- ing systems cation failover in the application API. SA compliant middleware will provide ser- vices to an application that needs to be HA This section describes briefly the motivating in a portable way. reasons in favor of using Linux on Carrier Grade systems, versus continuing with propri- etary operating systems. These motivations in- clude: The operating system is a core component in such architectures. In the remaining of this pa- • Cost: Linux is available free of charge in per, we will be focusing on CGL, its architec- the form of a downloadable package from ture and specifications. the Internet. • Source code availability: With Linux, you high performance networking, and the proven gain full access to the source code allow- record of being a stable, and reliable server ing you to tailor the kernel to your needs. platform. • Open development process (Figure 2): The development process of the kernel is open to anyone to participate and con- 4 Carrier Grade Linux tribute. The process is based on the con- cept of "release early, release often." The Linux kernel is missing several features • Peer review and testing resources: With that are needed in a telecom environment. It access to the source code, people using a is not adapted to meet telecom requirements wide variety of platform, operating sys- in various areas such as reliability, security, tems, and compiler combinations; can and scalability. To help the advancement of compile, link, and run the code on their Linux in the telecom space, OSDL established systems to test for portability, compatibil- the CGL working group. The group specifies ity and bugs. and helps implement an Open Source platform targeted for the communication industry that • Vendor independent: With Linux, you no is highly available, secure, scalable and easily longer have to be locked into a specific maintained. The CGL working group is com- vendor. Linux is supported on multiple posed of several members from network equip- platforms. ment providers, system integrators, platform providers, and Linux distributors. They all • High innovation rate: New features are contribute to the requirement definition of Car- usually implemented on Linux before they rier Grade Linux, help Open Source projects are available on commercial or propri- to meet these requirements, and in some cases etary systems. start new Open Source projects. Many of 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 Figure 2: Open development process of the also either deploying CGL, or at least evaluat- Linux kernel ing and experimenting with it. Consequently, CGL activities are giving much Other contributing factors include Linux’ sup- momentum for Linux in the telecom space port for a broad range of processors and allowing it to be a viable option to propri- peripherals, commercial support availability, etary operating system. Member companies of CGL are releasing code to Open Source and of simultaneous connections. A signaling are making some of their proprietary technolo- server application is context switch and gies open, which leads to going forward from memory intensive due to requirements for closed platforms to open platforms that use quick switching and a capacity to manage CGL Linux. large numbers of connections. • Management servers handle traditional network management operations, as well 5 Target CGL applications as service and customer management. These servers provide services such as: a Home Location Register and Visitor Lo- The CGL Working Group has identified three cation Register (for wireless networks) main categories of application areas into which or customer information (such as per- they expect the majority of applications imple- sonal preferences including features the mented on CGL platforms to fall. These appli- customer is authorized to use). Typi- cation areas are gateways, signaling, and man- cally, management applications are data agement servers. 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- work, to an Internet protocol packet- 6 Overview of the CGL working switched network. A gateway processes a group large number of small messages received and transmitted over a large number of physical interfaces. Gateways perform The CGL working group has the