I have taken this excerpt from the QOS SRND for Campus Design: "Queueing algorithms are activated only when a device is experiencing congestion and are deactivated when the congestion clears" my question is - What if you have a Gig interface that is not overutilized but has n x 1500 byte packets waiting to be processed before your voice packet? So Im guessing the voice packet will have to wait and incur the delay right and only if the interface is 100% (bandwidth) utilized then the queues come into play and place voice packets into a priority queue, or am I understanding this wrong? M
let say without QoS enable on our network, the default is FIFO, first in, first out and the switch is not priotizing your voice from data.
With Qos, depending on what you want to do, you have different queuing method or congestion management you can use. With priority queuing for example you can always prioritize voice traffic from data. Some of the QoS mechanism will not work until congestion happens and the bandwidth you reserve is used by other queues until congestion kicks in
see this for different QoS mechansim http://www.cisco.com/en/US/tech/tk543/tk544/tsd_technology_support_protocol_home.html