VoIP is on the rise with companies anxious to take advantage of the cost savings. Still, questions remain about its reliability and overall quality. Viola Networks recently took steps to help improve the situation when it introduced NetAlly Lifecycle Manager 5.1. The latest release includes a new algorithm for aggregating voice quality measurements among groups of VoIP network calls, referred to as the Service Level Index (SLI).

NetAlly uses a combination of active and passive monitoring to collect data for VoIP service level analysis. In performing active monitoring, NetAlly uses agents to simulate VoIP calls and examine the range of factors that can cause voice quality problems, such as packet loss, jitter, delay, and echo. NetAlly then converts the collected data to a Mean Opinion Score (MOS). A widely accepted measurement for assessing VoIP service quality, MOS is not without challenges. As a pure measurement, MOS lacks insight to the actual causes behind quality issues, and as a mean score, doesn’t account for discrepancies between divergent assessments of the same data point.

MOS is a subjective measurement, aggregating and averaging performance; in the process, the calls that fail to meet service level agreements may drop off the radar. Despite its imperfections, MOS is useful as a generic measurement of call quality. Viola’s SLI incorporates MOS, and similar subjective quality assessment methodologies, but rather than settle on an average assessment that minimizes poor performance, SLI weights the group experience by examining the distribution of MOS calls.

Although a degree of extrapolation is still involved in the SLI metric, NetAlly dashboards highlight the weighted score provided by the SLI, helping companies see at a glance their group call performance, and even predict network degradation. Since companies can define their VoIP networks’ own level of acceptability — according to SLAs, user groups, geography, or however they choose to segment their networks — the SLI metric is significant in identifying call quality events related to entities that are important to the organization.

Viola faces considerable competition from players such as NetIQ, Brix Networks, Apparent Networks, Fluke Networks, and many others. Both Viola and NetIQ integrate with IP PBX vendors (Cisco, Avaya, and Mitel), giving them a competitive edge in the managed service provider market. Lacking partnerships with most equipment manufacturers, Brix and Apparent tend to compete with Viola in pre-deployment assessments. Like Viola NetAlly, Fluke OptiView addresses the VoIP lifecycle, from pre-deployment assessment through optimization. Fluke’s strength is in passive monitoring, whereas Viola shines in active testing. As both vendors round out their products, Fluke will become a key competitor for Viola.

Denise Dubie is senior editor with Network World.