Add a comment
The underlying network metrics that affect VoIP call quality are packet loss, jitter, and latency, and if you have good network performance for traditional networked applications, it is not a guarantee that performance will be good for VoIP applications. The real-time characteristics of voice create very strict requirements for network performance.
For example, an inappropriately configured network could have calls that are delayed, dropped, or just plain sound bad. These call quality issues would quickly affect the end-user experience because telephone usage is very user-intensive.
The upshot is that you could end up with a lot of calls to the Help Desk to fix the problem. Or, at least you would, if the phones were working.
On the other extreme, you could have your VoIP traffic perform very well, but other data applications critical to the business, such as e-mail, would suffer.
When you add VoIP traffic to the network, you need to take a careful look at the performance, and not only the performance of the VoIP traffic. You need to carefully measure the impact the VoIP traffic is having on your other enterprise applications.
Jim McQuaid (Sr. Product Manager at NetQoS), recently did an interesting video blog post here titled “Nice Guys Finish Last – The impact of voice/video on data applications”, where he explains that the differences in the UDP and TCP protocols can have an interesting impact on the performance of all applications when VoIP traffic is added to the network mix.
Specifically, the adaptive nature of TCP can result in cases where TCP application performance degrades when faced with additional UDP traffic. TCP plays nice and backs off: the window sizes shrink, and less data is sent and received. But UDP, and VoIP in particular, continue to send data with no regard to congestion. Even though VoIP applications send data at a fixed, relatively slow rate, if enough calls are present, each with two unidirectional streams, the VoIP UDP traffic might create congestion and crowd out the TCP application traffic, creating longer transaction times and impairing the performance of TCP applications.
The goal in managing a converged network is to tune it so that many types of application data traffic can coexist and perform well. QoS mechanisms are necessary, as well as visibility into the underlying metrics that affect end-user quality of experience.
--------------------------------
More Information:
On VoIP Management
On VoIP Monitoring
Download the VoIP eBook on managing VoIP
 |
