Tag: QoS
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RTP, Jitter and audio quality in VoIP
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In this article we will briefly look at what RTP is and how it is used to stream VoIP audio. The article then considers how certain network transmission characteristics may introduce jitter or packet loss and the measures that are used in VoIP equipment to mitigate the effects. Other phenomenon which have a bearing on the audio quality on VoIP calls, along with the features used on VoIP equipment to overcome them, are also briefly discussed.…
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VoIP QoS in practice: About Network Congestion
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My previous two articles explored QoS tagging of voice data packets using ToS/DiffServ values and of Ethernet frames using CoS or Priority values. QoS is often advocated as an essential part of any self-respecting VoIP solution and there is no doubt it can make a big difference in the right circumstances. However, it would be a mistake to expect too much of QoS or to assume that it will always make a difference no matter what.…
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VoIP QoS Settings – part 2
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In part 1, we examined the Layer 2 QoS settings available on most VoIP equipment. In this second part, I will explore the Layer 3 parameters and offer practical suggestions for the values that should be assigned to them. We will briefly look at the history and structure of the ToS and DSCP fields and their place within the DiffServ packet prioritisation model. Recap I explained in part 1 how Layer 2 data can be tagged…
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VoIP QoS Settings – part 1
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The QoS settings on VoIP phones and related equipment can be perplexing. Here, I will attempt to explain what parameters like CoS, ToS, DiffServ and DSCP really mean and offer practical suggestions for the values that should be assigned to them. Part 1 of this article starts with a broad overview and then focuses on Layer 2 network QoS settings; i.e. the settings associated with the VLAN tag in 802.1 Ethernet protocols. If you are looking…
