RTC Magazine

During the last decade standardization empowered the enterprise computing industry to put together systems using Commercial Off-the-Shelf (COTS) building blocks designed by a variety of hardware, operating system and applications providers. Enterprises were relieved to have an alternative to vertically integrated systems that locked them into proprietary architectures from individual vendors. This successful transition from the vertical to horizontal business model is now showing up in other markets as well–especially in the telecommunications industry.

Building a system using COTS building blocks still has its challenges. System developers may have to deal with issues like inadequate software APIs, overlapping functionality, duplicate data stores and memory footprint constraints. To unleash the benefits of a COTS ecosystem, pre-integration and testing among suppliers and adherence to industry standards and open specifications is required.

The encouraging news is that the industry is recognizing this need and key alliances are being formed in response. Let us first look at the anatomy of a highly available and managed network element. The essential set of services required to create such a system can be broadly classified into four categories (Figure 1).

High-Availability Services

Forming the centerpiece of any highly available and managed platform, high-availability services typically comprise a sophisticated availability management framework and key functionality, that in combination, ensure continuous service availability in the presence of failures–hardware or software. The Availability Management Service (AMS) implements two key functional areas: a comprehensive system model of all managed resources, and an associated state model that defines and governs the state of these resources. Managed resources can include applications, operating system, chassis, I/O cards, redundant CPUs, networks, peripherals, clusters and other software.

The availability system model represents each system resource to be managed as a managed object in the system model. It also captures resource dependencies, including critical relationships that form a given service. It manages objects with attributes for health, operational state, administrative state, role, availability status and dependencies and also has methods for access/control, monitoring and configuration. It is also responsible for implementing powerful recovery policies, such as 2N, N+1, N+M, Active/Active, etc. The AMS state model determines the state of each object, such as healthy/failed/shutting down, active/standby, locked/unlocked and enabled/disabled. Intelligent recovery decisions are made by the AMS based on detailed information about each resource’s attributes and methods to apply during a failure.

The presence of redundant resources is a critical requirement for highly available systems. Redundant resources can be configured in various ways to provide standby for active resources in case of a failure. Clustering is responsible for such a configuration. The AMS manages the service availability of hardware and software resources in the cluster. The clustering service is responsible for discovering, incorporating and monitoring the nodes within the cluster along with their associated network interfaces. An efficient messaging engine communicates the addition or failure of nodes and their network interfaces to AMS and any other relevant management applications. The clustering service also works with AMS to provide manager node redundancy to eliminate the manager node as a possible single point of failure.

Stateful failover is a key attribute of highly available systems, especially those required to provide seamless, often real-time, processing failover. Checkpointing capabilities allow such systems to collect state information about the applications (e.g., any in-progress calls on an active node) and replicate it to a standby node to take on call processing should the active node fail.

Management Services

Effective monitoring, access and control of various hardware and software resources in a highly available platform require sophisticated management. The SA Forum’s Hardware Platform Interface (HPI) specification has greatly facilitated the standard implementation of hardware platform resource management capabilities. The HPI provides a set of APIs for discovering, monitoring and managing hardware resources on compliant platforms. Implemented by hardware platform providers and used by the developers of management middleware, the HPI significantly reduces the time required to design and develop the system model representation of hardware resources via default resource management capabilities. Additionally, the Platform Resource Management Service (PRMS) provides a framework for developers to create custom alarm and hot swap management policies to enhance manageability and availability of their target platform.