An individual device interface has multiple queues assigned to store packets temporarily before transmission. To determine the order to service the queues, the device uses a round-robin scheduling method based on priority and the queue's weighted round-robin (WRR) credits. Junos OS schedulers allow you to define the priority, bandwidth, delay buffer size, rate control status, and RED drop profiles to be applied to a particular queue for packet transmission.
Still confused about the order described above
Assuming all traffics are in contract.
VIDEO--Q1--Schdeuler priority low, tranmsit rate 40%
VOICE-Q2- Scheduler priority low , Transmit rate 20%
Network-CONTROl--Q3--Scheduler priority low, Transmit rate 40%
Are we saying the order will be based on Sceduler priority plus Weight of each queue? or just Scheduler' priority alone?
If all scheduler have same priority, how is this order determined just wieght or we go from q7 to q0?
In Cisco, for example for Classed based weighted fair queuing, All traffic class are serviced in round robin , but this round round robin is not fixed , it changes. For example
We have four traffic class:
Then Cisco router firts compute the sequence number using Flow ( SRC IP.DST IP, TCP/UDP PORT, etc) for each traffic class which then dictates the order the Queues are serviced. So we may have order:
You will find a very nice explanation to your question with example here
Configuring Class of Service -> Class of Service Overview -> Transmission Scheduling