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QoS: (Strict) Priority Queue without congestion

Hi,

I still have a doubt about Priority Queue comportment in case of non congestion. I have readen that the software queue is used only in case of congestion. However, the aim of Priority Queue is to reduce delay and jitter. Then, in case of non congestion on an interface, but high load (let's say, 70%), because of serialization delay, packets (such as voice) which need low delays can wait more or less time before other paquets in the hardware queue being serialized. Because of that, it would be logical that low packets are serialized as soon a they arrive on the router, befor any other packets, even if there is not congestion.

Thanks for any clear answer.

1 ACCEPTED SOLUTION

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Beginner

If there is no congestion on the interface, it means that any packet will be transmitted as soon as it is received. This is true for data as well os voice packets. If there is congestion it means packets have to be queued as there are currently packets being transmitted and others in queue. In this case packets that are in the priority queue will be transmitted first before packets in other other queues. How quickly this happens is dependent on the size of the packet being transmitted and the speed of the interface. Low speed interfaces you will need to fragment packets to minimize serialization delay.

Bill

Sent from Cisco Technical Support iPad App

View solution in original post

1 REPLY 1
Highlighted
Beginner

If there is no congestion on the interface, it means that any packet will be transmitted as soon as it is received. This is true for data as well os voice packets. If there is congestion it means packets have to be queued as there are currently packets being transmitted and others in queue. In this case packets that are in the priority queue will be transmitted first before packets in other other queues. How quickly this happens is dependent on the size of the packet being transmitted and the speed of the interface. Low speed interfaces you will need to fragment packets to minimize serialization delay.

Bill

Sent from Cisco Technical Support iPad App

View solution in original post