Saturday, August 8, 2009

Voice quality of service

Complaints were coming in about poor voice quality and dropped calls.

The challenge in managing VoIP (Voice over IP) deployments is that voice traffic can take a variety of paths across the network and problems anywhere along the path can affect call quality. In the diagram, the voice traffic is shown by the RTP (Real-time Transport Protocol) connections between the phones and computers.

Fortunately, the network switches support sFlow and the network management team had recently installed an sFlow analyzer (Traffic Sentinel), providing them with network-wide visibility. The sFlow analyzer alerted the team to excessive broadcast traffic affecting a large part of the network (see Link utilization to see how sFlow provides network-wide interface statistics). The packet header and packet path information provided by sFlow allowed the analyzer to rapidly locate the source of the broadcasts to a single server. A call to the server administrator identified the cause of the recent broadcast activity; they were testing a new application for distributing software on the network and the application was generating the broadcast traffic. Shutting down the application resolved the problem.

This example demonstrates how sFlow monitoring can assist in ensuring quality of service (QoS). Proactively managing traffic allows network managers to act before service levels deteriorate to the point where users are complaining. The paper, Managing Quality of Service Using sFlow, provides a detailed discussion of this approach.

Finally, the example illustrates the challenges created by network convergence and virtualization. Typically, different teams manage voice, data, computing and storage services using their own management tools. The example shows how the "siloed" approach to management fails as services converge to share the same network resources. As well as creating challenges, convergence offers the opportunity to dramatically simplify management. Instrumenting the converged network, by selecting network equipment with sFlow support, reduces the number of tools needed to provide visibility into each of these areas (voice, data, computing, storage) and delivers the shared visibility into the network infrastructure essential for avoiding conflicts.