The Three Components of VoIP QoS

Today’s enterprise networks provide many services and fulfill several important functions. They carry different types of data with voice being the latest addition, thanks to VoIP technology. The shift from PSTN based systems to IP-based technology has had a profound effect on businesses. Organizations have found that there are more benefits to upgrading than the initial cost savings.

While voice has become the latest addition to the network, it is quite different from other types of data. VoIP is real-time traffic and as such it is sensitive to delays or interruptions. Every data network suffers from some combination of delay and packet loss. In normal situations it is not noticeable and does not affect the performance of applications. But these factors will affect voice calling.

For instance, network congestion is a common issue for most organizations. If the congestion exceeds a certain level, packets may be dropped. This is not a problem for most data packets (emails, opening documents etc) as they can be retransmitted. However packet loss impacts voice calls and users can see this in the form of missing words, echoes and other artifacts.

What Is Quality of Service in VoIP?

Quality of Service is an important concept in VoIP phone systems. It is the idea that there is a way to guarantee voice calls will not be dropped or delayed due to network conditions. Certain aspects of data networks can be measured and quantified such as error rates, time delays etc. QoS is all about minimizing any potential problems with data packets and assuring a minimum level of quality.

Nowadays QoS assurances are a part of the service level agreements between providers and clients. Configuring the appropriate QoS settings on your network equipment is a crucial part of providing quality telecom services. If you are troubleshooting any issues with your phones, checking the QoS should be the first step. Many organizations are unaware of this concept and are bewildered when faced with audio quality issues. Fortunately service providers are quite willing to work with clients in setting up QoS, especially if you don’t have any experts on the payroll.

Components of VoIP QoS

There are many components to implementing quality of service on your data infrastructure. It includes congestion management, packet classification and marking, policing and shaping traffic, avoiding congestion, link efficiency etc. Let us take a closer look at a few components in particular.

Congestion Avoidance and Management

Network congestion is a reality for most organizations. The only difference lies in how much and how often your network experiences it. Avoiding congestion is a preventative measure but it doesn’t always work. There are a few techniques you can implement to avoid congestion and prepare the network on how to handle bottlenecks as they appear. Many of these involve dropping low priority traffic during peak times, so that real-time applications like voice calling are not affected as much.

Congestion management techniques are meant to control the traffic during congestion. Traditionally data packets were handled using the FIFO method i.e. first in first out. The first packet to reach a particular waypoint is transmitted first to the next relay station and so on. However it becomes obvious that we cannot use the same technique when adding time sensitive traffic to the mix. Now there are many types of queuing methods in use such as priority queuing, weighted queuing and so on.

Classification and Marking Data Packets

Classification and marking data packets is an important part of QoS. You can identify certain types of packets or traffic flows as more important than others. The default label for most data is set to low. So any traffic you designate as high priority will automatically get precedence at routers and other network points. There are different ways of marking data packets so that network equipment can identify them and handle the traffic correctly. For instance you can set voice packets to high-priority so that traffic bottlenecks and congestion will not impede transmission.

Policing and Shaping

Policing and shaping techniques are implemented on traffic flows rather than individual packets. It usually involves regulating traffic when it exceeds a certain threshold. You can drop, delay or queue traffic so that congestion doesn’t overwhelm your phone systems. For example, you can delay the transmission of large documents to a later time when the network is not as congested.

As you can see, all these components of QoS work together to ensure that voice traffic is not adversely affected by network issues. You can mark individual packets to have higher priority. You can shape overall traffic flows to reduce congestion at key bottlenecks. You can manage voice traffic and give them priority queuing over all other types of traffic. All of these measures aid in ensuring high quality audio and fewer dropped connections. Every organization with VoIP should set up QoS and review it periodically to minimize potential problems.