* Network managers struggle with how to manage the performance of VoIP
My office has a VoIP system. It’s…small business solution…Vonage…not happy with it, because…calls…punctuated…gaps of silence…call is like a strobe light. The other party…talking, but…no idea that I can’t hear the full conversation.
It’s very frustrating, and given that we don’t run a very sophisticated network in our small office, we don’t have good tools to diagnose the exact problem. We’ve tuned things as best as we can, but we still suffer from lost packets and poor quality calls at times. And I suspect we aren’t alone in our misery.
As Denise Dubie pointed out a few months ago, network managers are struggling with how to manage the performance of VoIP. She cited a Network Instruments customer survey in which one-third of the 275 respondents say they don’t have the ability to monitor VoIP performance. The top concerns of those surveyed are: being able to monitor the QoS of the VoIP application, ensuring reliability of VoIP applications to perform under heavy use, and ensuring the network can adequately handle the added VoIP traffic.
To get some advice on successful VoIP implementations, I talked with Ivan McDuffie, an area engineering manager with NEC Unified Solutions. His company provides customized solutions for networking and communications, and McDuffie has been involved in many of the customer engagements for VoIP installation. He holds several technical credentials, including Cisco Certified Network Professional, Cisco Certified Design Professional, and Certified Network Instruments Administrator, giving him a good foundation for understanding the challenges that VoIP poses to a network.
His top advice for anyone considering a VoIP installation: Do your groundwork to ensure that the network is fully ready to support the added traffic of VoIP before you begin the implementation.
For the past 10 months, McDuffie has been using a GigaStor retrospective network analysis appliance from Network Instruments to conduct his network assessments. In a typical implementation, he might use VoIP management tools from NetIQ to generate VoIP calls and use GigaStor and its related monitoring tool Observer to capture, view and analyze the traffic.
One of the reasons McDuffie likes the GigaStor and Observer tools is that they are not VoIP-specific; rather, they are all-purpose networking monitoring tools. Having analysis tools that monitor both VoIP and overall network traffic is very helpful during the deployment phases of VoIP. In the predeployment stage, the tools help McDuffie track bandwidth utilization parameters that identify bottlenecks and specific points of contention on the network. During the deployment, VoIP traffic is generally segmented to its own VLAN; Observer then provides extensive metrics on the performance of each VLAN.
McDuffie also uses these same network analysis tools in the daily troubleshooting of VoIP issues. Their metrics for monitoring bursts, gaps, and jitter allow him to quickly identify and gauge the seriousness of a VoIP performance problem. In addition, Observer automatically correlates and assembles the multiple unique VoIP connections into a complete call. This means McDuffie can easily view and analyze the entire call rather than having to view each individual call component. If need be, he can drill down into the components of the call for in-depth troubleshooting.
“The Network Instruments tools let me reconstruct an entire VoIP conversation and hear it real-time,” says McDuffie. “By listening to that, I get a feel of the user’s experience. VoIP is still sort of a new technology, so you want to make sure when it is deployed, you take the appropriate steps. This tool set allows me to have eyes into a customer’s network. I know that if the Network Instrument tool points to delay on the network, I can look at the current bandwidth on the network or if QoS is properly configured.”
In McDuffie’s experience, the most important part to deploying VoIP is ensuring that QoS is properly configured. “I know a lot of my customers say ‘I have a 1 Gig backbone and my utilization is usually low.’ However, how are they measuring that utilization and what sample intervals are used? Are they measuring the traffic every five minutes? If so, the bandwidth can spike for one minute during that sample five minute period and you would never know. And what happens when a user downloads a large file from the Internet across your network? Without QoS properly configured, your voice packets will have to wait until that download is done, which can cause significant voice quality problems.” Analyzing the data from the GigaStor appliance helps uncover such scenarios quickly so the right parameters can be tuned for better performance.
Once NEC Unified Solutions has completed the VoIP installation for a customer, NEC leaves a GigaStor appliance on the customer’s network in order to aid remote troubleshooting and support. If the customer reports any kind of problem, an NEC technician can analyze the specific sequence of captured traffic to see exactly what has happened.
