Does Your Voice Over IP Network Have Quality of Service (QOS)?

Voice over IP (VoIP) is not going away. It is important that you understand how to buy services. The assumption made by most Internet Telephone Service Providers is that all networks are the same. When they sell you VoIP services, very rarely is there a discussion about your network. Truthfully, most do not care because it is a numbers game. They understand that some customers are going to have a bad experience due to having a network that is not VoIP compatible or an Internet connection that does not support the requirements of VoIP services.

Before you give anyone money for VoIP services, make sure you get a network assessment of your network to make sure VoIP will work on your network and what the limits are. We are going to focus this article on one aspect of making VoIP work correctly on your network: Quality of Service (QOS). QOS was defined by the ITU in 1994 to address network issues.

Your communications network may consist of a wireless router or even a port switching hub, bur regardless of the type and model of network equipment, your network forms the backbone of organization. Your network transports a multitude of applications and data, including high-quality video and delay-sensitive data such as real-time voice. Your network and Internet connection has limits on how much data it can process. I recently purchased a smart flat screen television that has a wireless interface to connect to my home network. The television has several apps including Netflix for streaming movies directly to the television. Bandwidth-intensive applications stretch network capabilities and resources of you network. Your networks must give secure, predictable, measurable, and sometimes guaranteed services if you want to add VoIP services. You carry out this by achieving the required Quality of Service (QoS) by managing the delay, delay variation (jitter), bandwidth, and packet loss parameters on your network. QOS is simply a set of techniques to manage network resources.

Example one: you have two or three computers on your network with a 100mb connection. You have one or two wireless devices that have 54 megabits connections. Add in two VoIP phones with 100 megabits connections and you have an obligate bandwidth total of over 600 megabits, but you cable modem is only capable of delivering 5 megabits out of your network to the Internet. Don’t panic, the good news is that only one device on your network can communicate with the Internet modem at a time. The bad news is that only one device can communicate on your network at a time. If more than one device attempt to communicate at the same time, a network collision condition is created. Your network is most likely a first come first served network. This is fine for home use and some small businesses, but it is not a good mean to manage a network.

Example two: The same devices as in example one, but organized better. First we have four networks or Virtual Local Area Networks or VLANs. VLAN number one is for the smart TV that streams Netflix, VLAN two is for my computers with a VLAN three is for all of other wireless devices and VLAN four is for all of VoIP phones. All traffic is managed by a Layer Two (L2) switch. Let me clear up something quickly about switches. I meet many people who believe they have a L2 switch, but they don’t. The device they think is a switch is a hub. It has the label of switch because the word hub has such a negative connotation. The makers of hubs can get away with calling switches because the hub is able to switch port speed from 10, 100, 1000 megabits. one a hub, only one device can talk, while on a switch, all the devices can be configured to talk at the same time. In a L2 switch, traffic is managed by the switch when multiple devices are talking at once to the Internet modem. In this example, the L2 switch prioritize the voice traffic over wireless data, and wireless data is prioritize over computer generated traffic, computer traffic is given priority over the smart television. If you amount of traffic exceeds the ability of the switch to send to the L2 switch, the L2 switch will drop data based on configured priority parameters.

In example two, voice communication is given the best chance to get out to the Internet or be delivered to the phones from the Internet. In example one, voice traffic would be delivered if the network was not being used by another device and application. The resources are strained, most computer generated traffic can be dropped without much consequence because anything not received by the other end will simply ask you resend the data. But with voice, if the third syllable is dropped from the fifth word, how do you resend that segment of speech real-time? You don’t! The word become garbled and unrecognizable.

Never believe your network is too small for QOS. It is important to implement a QOS strategy before implementing QOS. If your Internet Telephone Service Provider can not help you, find one that can.

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