Preventing Disaster with Redundancy Solutions

By David Weiss

With the ongoing migration of voice communications toward server-based facilities and IP networks, today’s phone system is susceptible to all of the maladies of the network world, including hacker attacks, viruses, and Trojan horses. While many companies have embraced redundancy in the data center, few have recognized the need to incorporate redundant systems into their voice technologies. As the corporate world hinges on a constant stream of data and voice communications, organizations must provide for the highest degree of fault tolerance to maintain these vital links to customers, partners and employees.

Historically, the resiliency of the voice network meant disaster planning budgets were focused in other areas of concern. Now, organizations are deploying server-based PBXs, VoIP solutions, conference bridges and call center systems. Providing new capabilities at a fraction of the cost, these services are increasingly critical to day-to-day business operations and, as such, they demand expected levels of uptime. Built more frequently from a combination of hardware and software vendors, however, the likelihood is increasing that these systems experience failures.

Failures can occur at any level. Server-based PBXs incorporate complex software, often sourced from multiple vendors; disc arrays and other hardware technologies can also fail. Network connectivity exposes the system to malicious internal and external attacks. IP phones, computer-telephony integration and Bluetooth have created additional levels of complexity for the handset, typically the most reliable part of the phone system. Phone lines are subject to occasional outages due to cable breaks and component failures at the local and long-distance carrier levels.

Redundancy solutions are a key part of planning for the inevitable. Fail-safe options on every level, including failover servers, diverse phone lines, media storage and hot sites can all minimize unscheduled downtime and prevent real disasters.

Minimizing Failures on the Line Side: A highly available solution attempts to eliminate single points of failure in all aspects of a system’s design. To minimize failure options, network planners need to evaluate both link redundancy and hardware redundancy. Carriers can also provide diversity and avoidance to help minimize risks.

Done at both the local and long-distance levels, diversity refers to redundant services and avoidance ensures that redundant services do not share common facilities. Additionally, loop diversity provides two redundant circuits from a local point-of-presence (POP) to your facility. POP diversity, having local links originate from multiple wire centers, or POPs, is an ideal solution. Interoffice diversity provides the same level of service between wire centers.

Diversity services may or may not include the customer premise equipment necessary to switch between redundant links. Protection switching for redundant T-1 or DS-3 circuits is either provided by the carrier or purchased and installed by the customer. Any service degradation or interruption is automatically detected with switchover to a spare circuit. Protection switching is either 1:1, with a standby circuit for each primary, or 1:N, with a spare circuit for one of several circuits.

Even with VoIP solutions, any gateway to the public switched network involves local loops and carrier services and it’s essential that this critical link to customers is not overlooked.

Minimizing Failures on the Equipment Side: The migration of telephony services to a server-based platform has prompted the wide acceptance of un-PBXs and IP-PBXs. Advantages such as an open and flexible architecture, standardized components, multiple sources and lower costs mean servers are now common for phone systems, voice mail, call recorders and other voice technologies. Although processors, memory, storage, power supplies, telephony boards, operating systems and application software are supplied by “best of breed” vendors, it is, however, the end user or consultant who must ensure all the pieces work together seamlessly.

For each piece then, a critical metric is its availability, or readiness to perform its stated function at any given time. Availability does not take into account downtime for scheduled maintenance. By adding lost time for maintenance, you arrive at true operational availability. To achieve the best availability possible, system engineers must look at maximizing reliability and minimizing both scheduled and unscheduled downtime. Redundancy is the key to providing both the maximum reliability and the minimum repair time.

Redundancy is commonplace for products at the component level that are most likely to fail, such as disk drives, power supplies and other mechanical items. Additionally, inexpensive redundant discs (RAID) and power supplies are standard with most systems for telephony services.

For more complex applications, system level redundancy needs to be evaluated. With hot standby systems, two complete, identical systems are installed. The standby server, SNMP manager or other management facility continuously monitors the health of the primary system and, upon detecting any failures, automatically switches the standby system into service. Deploying two systems also allows for the performance of scheduled maintenance with minimal interruption, as one server is upgraded while the other is in service. And, if a planned upgrade or new software installation goes awry, the organization has an immediate, graceful fallback.

Redundancy switches essentially perform the same function as a patch panel, but do so automatically and simultaneously for all circuits. They operate on the physical layer, moving the actual wires from phone lines and operator instruments to telephony boards in the system. With IP phone systems, switching is only required for the phone line side. As the central component of a fault tolerant solution, the redundancy switch itself cannot represent a single point of failure as magnetic latching relays provide a continuous mechanical connection in all circumstances.

Although redundancy servers are optimal solutions, several issues need to be considered. Databases must be synchronized so all configurations, securities and call logs remain identical. Licensing is also a factor. If redundant systems share the same licenses, they need to have dongles switched or require an add-on module to support automatic redundancy switchover.

Conclusion: For many types of organizations, voice technology remains critical for effective corporate communications and customer service. To maintain voice systems and ensure their optimal operation, organizations must consider the level of fault tolerance required and how redundancy solutions can help meet these objectives. Deploying diversity and avoidance services as well as protection switching, will help minimize failures on the line side. In addition, standby systems and redundancy switches will mitigate the risk of failures on the equipment side. Unplanned downtime is clearly not acceptable in most businesses, and redundancy solutions maximize uptime and allow voice communications to continue in the event of system failures.

David Weiss has nearly 20 years experience in product management, business development, sales and marketing and is an expert in the remote site management technology industry. David serves as the president and CEO of Dataprobe, a remote site management and monitoring solutions provider.

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