Tips and Tricks – Quality of Service

Tips and Tricks – Quality of Service

Voice and video traffic is time-sensitive. Packets encapsulating voice and video traffic must traverse the network in a timely manner, encounter minimal packet loss, arrive in sequence, and always have adequate bandwidth. Anything short of this will result in poor voice and video quality and dropped calls. Quality of Service (QOS) is a mechanism on the network that provides voice and video traffic a higher priority over traffic that is less time-sensitive like web and email.

The network switches, routers, and VOIP equipment all need to support QOS. There are different ways to implement QOS. A best practices approach is to have your VOIP equipment use the Differential Services (DiffServe) QOS mechanism.  In this scenario, the IP packets carrying VoIP are “marked” as priority packets. All networking equipment would then be configured to honor the marking and provide priority to these packets.

Ensuring QOS end-to-end across the network is an important consideration when designing networks for VoIP and video. For example, when a WAN protocol like MPLS is used, various “marking” techniques can get lost in translation. The QOS mechanism used by your routers and switches on your Local Area Network need to translate to high-priority packets with your WAN provider. Various MPLS carriers implement QOS in different ways. You want to ensure that your provider recognizes your markings and places those packets into their own high-priority VoIP scheme.  Many WAN providers will take DiffServe packets marked with “EF” or “Express Forwarding” and place them in their “VoIP” or high priority queues.

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