This article provides an update of the Carrier Grade Linux initiative, the CGL specification, distributions, platforms and deployments.

Carrier Grade Linux - The OSDL Initiative
The OSDL Carrier Grade Linux working group was established in January 2002. Its goal is to identify requirements for enhancing the Linux operating system to achieve an open source platform that is highly available, reliable, secure and scalable, and so suitable for carrier grade systems. The CGL working group has the vision that next-generation and multimedia communication services can be delivered using Linux-based platforms. To realize this vision, the WG evolved a strategy to define the requirements and architecture for the Carrier Grade Linux platform, develop a roadmap for the platform, and promote development of a stable platform for deployment of commercial components and services.

The CGL WG focuses on two areas (see Figure 1):

• Carrier Grade Linux: CGL enhancements to the operating system are related to various requirements (listed in later sections) such as availability and scalability
• Software Development Tools: Tools including debuggers and analyzers

The CGL WG also identifies existing open source projects that support the roadmap and implement required components and interfaces for the platform. When no open source project exists to satisfy a given requirement, CGL member companies either launch or support the launch of new open source projects to implement missing components and interfaces of the platform.

CGL Requirement Documents - History and Current Status
Since its formation, the CGL working group has produced three versions of a specification to define these required capabilities. In response, Linux distribution suppliers are now demonstrating that they can meet the emerging needs of telecommunications by registering (disclosing publicly) how their Linux-based software platform products address the requirements as defined in the Carrier Grade Linux Requirements Definition.

This expanded group has now released the Carrier Grade Linux Requirements Definition version 3.1. For clarity and ease of use, the specification has been split into seven separate topical documents:

• Availability: A collection of requirements that addresses the robustness of a single computing node. Clustering individual computing nodes so that a node cannot represent a single point of failure will enhance availability.
• Clustering: The clustering requirements support the use of multiple carrier server systems to provide higher levels of service availability through redundant resources and recovery capabilities, and to provide a horizontally scaled environment supporting increased throughput.
• Serviceability: The serviceability requirements specify a set of features for servicing and maintaining a system. They support servicing and managing hardware and software on carrier server systems. These requirements help support the availability of applications and the operating system.
• Performance: The performance requirements describe the needed performance and scalability of typical communications systems.
• Standards: One goal of the CGL effort is to leverage mature and well-established industry standards that are common and relevant to the carrier-grade environment and include them as part of the CGL requirements. The CGL WG is actively working with recognized standard bodies such as the Linux Standard Base and the Service Availability Forum. These organizations are producing standards and specifications that address the RAS and application portability gaps between Linux as it exists today and where it needs to be to support highly available communications applications.
• Hardware: The hardware requirements specify a set of generic requirements that are common across platform types. It includes support for blade servers, hardware management interfaces, and blade hot swap events.
• Security: The security requirements were formally introduced in CGL 3.1. Their aim is maintaining an acceptable level of security without compromising CGL goals for high availability, performance, and scalability. The requirements support the use of additional security mechanisms to protect systems against attack from both the Internet and intranets, and provide special mechanisms at kernel level to be used by telecom applications.

Figure 3 presents the path of the CGL requirements definition document: more focus and more depth in specific areas, based on the feedback from the member companies and the marketplace.

CGL Registration and Registered Distributions
CGL Registration entails the disclosure of how and if a given CGL Linux platform meets priority 1 requirements from the CGL Requirements Definition. For each met requirement, the document defines the data needed for registration disclosure. Linux distribution vendors provide the disclosure information on their Web site and on the OSDL site. If a Linux distribution vendor didn't implement a certain priority 1 requirement(s), the vendor must disclose the reason for its absence. Linux distribution vendors that have registered with full public disclosure of all priority 1 requirements may describe their product as "OSDL CGL Registered".

Currently, five Linux distribution suppliers offer CGL version 2.0 registered distributions. OSDL maintains a Web site that lists CGL registered distributions and links to their disclosure documents: www.osdl.org/lab_activities/carrier_grade_linux/registration.html.

Deployments with CGL-based Platforms
The first step in deployment is the availability of carrier grade platforms that support CGL. At the writing of this article, there were over 18 platform providers and network equipment providers that offer CGL-based platforms. The list is interesting from a geographical perspective, as CGL-based products and platforms are coming from North America, Europe and Asia.

As for deployment, two interesting stories stand out: one is from NEC, which today provides CGL-based platforms for Asian carriers, and British Telecom Global, which is successfully piloting a project providing communication services with CGL-based platforms.