Split a link into voice, video, business and best-effort classes and check the 33% low-latency queue guideline.
Each class gets a share of the link, and whatever is left over becomes the default best-effort queue. Voice and interactive video sit in the strict-priority queue, which industry guidance caps at roughly a third of the circuit so that starving the other classes is impossible. A policy that reserves more than the link can deliver, or puts more than a third in strict priority, will drop TCP flows in ways that look like a circuit fault rather than a config error.
QoS Bandwidth Allocation
class bandwidth = link rate × class share; best-effort = link rate × (100% − sum of all guaranteed shares).
class bandwidth = link rate × class share; best-effort = link rate × (100% − sum of all guaranteed shares). Each class gets a share of the link, and whatever is left over becomes the default best-effort queue. Voice and interactive video sit in the strict-priority queue, which industry guidance caps at roughly a third of the circuit so that starving the other classes is impossible.
A policy that reserves more than the link can deliver, or puts more than a third in strict priority, will drop TCP flows in ways that look like a circuit fault rather than a config error.
This calculator takes 5 inputs: Link rate, Voice (EF) share, Interactive video (AF4) share, Business data (AF2/AF3) share, Scavenger (CS1) share. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.