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Threshold to turn on layer 2 QoS

Network is Ethernet 100BASE-TX with switch in the middle. 8 ports.

At what point should I start to worry about QoS. Right now I do not go above 15 Mbps as being the total offered node. i.e. Worst case 15 Mbps offered to one port and clients at say two ports 7.5 Mbps at each. 50% VoIP and 20% TCP and 30% UDP.

I think I do not need QoS yet, but is there a norm or some accepted industry practice say when you need to start worrying. For the UDP and VOIP I have no reliability built in.

Note: The switch is supposed to be 100BASE-T standard.

mikecr

If you're using VoIP, QoS is mandatory, no matter what others may think or how much bandwidth your currently using. High burst traffic, even though it won't reflect on the overall throughput, will impair voice. Voice uses RTP streaming so if it get's interrupted for any reason, you'll get dead air, missing speach, or the converstation will just break up. QoS overcomes this by alloting the appropriate bandwidth and packet service needed so that VoIP takes precendenc over all other traffic. With voice being 50% of your bandwidth, it's just a matter of time before you start to have problems.

MikeDKJ

ASKER

No VOIP is not 50% of the bandwidth. 100BASE-TX on paper should be able to do full-duplex 100Mbps. I am offering 7.5 Mbps of VOIP (say 20 msec samples). If the peak is 15 Mbps - then at 15% do I need QoS? I know that turning on is always good but why try to fix it if it is not broken?

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mikecr

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