Setting QOS Is Important for VoIP

There are many threats that can jeopardize voice traffic on a network.

1. Bandwidth/Packet Loss- The first key to having voice run on your network is having enough bandwidth to handle the amount of voice trffic you will typically have on your network. The IPitomy system typically uses the G.711 codec which uses about 160kbps for each active call. It is mportant to calculate the maximum amount of simultaneous calls you will have to ensure your bandwidth will meet your requirements, otherwise you will experience packet loss.

2. Latency- Latency is another term for delay. As packets pass through the network they are often delayed by network congestion. This is not as big of a problem for data as it is for voice traffic. Anything more than a 250ms roundtrip delay for voice traffic will most likely be noticeable to the caller. Common symptoms of this problem may be echo.

3.  Jitter- Jitter is how much variation there is in that packet delay over a period of time. As the delay time changes it causes what is known as jitter. For example poor LAN connections are a common source of jitter. Setting Quality of Service on the data switch ensures that voice packets have priority on the LAN.

The QOS Solution

Quality of Service gives preferential delivery to your VoIP traffic on your network. This substantially reduces latency, jittter and packet loss. The IPitomy system is capable of many QOS settings. Default it comes set up for DSCP 24 (CS3). On your Netgear Switch, turn on DSCP and then go to DSCP mapping and set CS3 to the highest setting. This will match up your default IPitomy QOS setting (PBX setup/SIP/Advanced) to your Netgear.

 

Note: Not all Netgear GUI interfaces will be the same.