QoS Bandwidth Allocation Calculator
Split a link into voice, video, business and best-effort classes and check the 33% low-latency queue guideline.
Inputs
Best-effort Bandwidth Left
35.00Mbps
Voice Guarantee
10.00Mbps
Video Guarantee
20.00Mbps
Business Data Guarantee
30.00Mbps
LLQ Guideline
Within the 33% priority-queue guideline
Policy Sums to 100% or Less
Yes
Step by step
Values used
Link rate = 100 Mbps; Voice (EF) share = 10 %; Interactive video (AF4) share = 20 %; Business data (AF2/AF3) share = 30 %; Scavenger (CS1) share = 5 %
QoS Bandwidth Allocation
class bandwidth = link rate × class share; best-effort = link rate × (100% − sum of all guaranteed shares).
Best-effort Bandwidth Left
= 35.00 Mbps
Voice Guarantee
= 10.00 Mbps
Video Guarantee
= 20.00 Mbps
Business Data Guarantee
= 30.00 Mbps
LLQ Guideline
= Within the 33% priority-queue guideline
Policy Sums to 100% or Less
= Yes
How it works
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.
Formula
QoS Bandwidth Allocation
class bandwidth = link rate × class share; best-effort = link rate × (100% − sum of all guaranteed shares).
- class share
- Percentage reserved for a traffic class by the scheduler
- LLQ
- Strict-priority queue, conventionally capped at a third of the link
Frequently Asked Questions
How is QoS Bandwidth Allocation calculated?
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.
Why does QoS Bandwidth Allocation matter?
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.
What values do I need to enter?
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.