Many challenges were found during this project, many were solved and some are as yet not completely resolved. We examine key challenges in this section including user perceptions of voice quality, softphone QoS issues, and voice quality impact resulting from security and reliability issues.

User Perceptions of Voice Quality

When requesting a user community to report all voice quality issues, you can expect many normally unreported instances to find their way into the report. This presents a challenge. The question is how to separate the real quality issues from the minor issues or those quality issues that have always existed. We did this by utilizing good proactive measurements of the network, evaluating the QoS usage and load along with making regular test calls and qualitatively measuring the quality through user feedback.

Softphone Quality Issues

This is an area where a number of challenges exist and are not all solved at this time. Some of these issues relate more to the quality the user perceives for the voice call than anything technical. The application gaining higher priority of the PC resources is one aspect that still needs to be solved, although many CPU management tools exist. The system should provide QoS for VoIP traffic out of the LAN interface card on the PC itself. The QoS packet scheduler on the PC is a step in the right direction, but a user can place all his/her client traffic in the voice (expedited forwarding) queue and so a centrally managed system is required before the client QoS can really be trusted. There were many areas where we found attractive and simple solutions. For example, it was easy to replace headsets where quality and user acceptance was much better when we used headsets with DSP.

Security and Reliability Issues and QoS Impact

There can be many potential security issues relating to a VoIP design and deployment and some of these played a role in this case study. First there was the question regarding what happens to VoIP if there is a worm or a Denial of Service (DoS) attack on the network. This problem was significantly reduced by providing a dedicated QoS protected VLAN for all the hardware IP phones. This keeps the data traffic separate from the voice traffic and therefore would allow the voice traffic guaranteed access to the network during a DoS attack.

Another area of IT concern is privacy. IP phone calls are much easier to tap and listen in on. If end-to-end encryption is used to protect the content then it makes it more difficult for the network to distinguish and prioritize voice. Also, encryption can introduce latency. One possible solution is to not converge voice on the LAN and instead install a private voice network. However, that approach significantly degrades the business value of converged networks.