12-10-2012 02:11 AM - edited 03-07-2019 10:30 AM
Dears
I hava a question and would like your assitance please
If my BW is larger than traffic I receive (voice + Internet traffic), in this case is it a must to put voice traffic in SP queue or mapping to different WRR queues would be fine ?
I know it will be better to put voice in SP queue and internet traffic in different WRR queue, but I am just asking from learning point of view
One opinion says says it is not a must to have SP queue ; i.e. both can be in different WRR queue as long as BW is larger that traffic I receive as QoS will only works in case of congestion
Another opinion says I should use SP queue, cause even if there is no congestion a large packet may already be in queue being served so during that time voice packet has to wait till schedular finishes serving this packet
What do you think ?
Many Thanks
Sherif Ismail
12-10-2012 09:08 AM
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One opinion says says it is not a must to have SP queue ; i.e. both can be in different WRR queue as long as BW is larger that traffic I receive as QoS will only works in case of congestion
Is a SP queue always a must? No, but it helps to deal with jitter that can arise even in cases where bandwidth is not oversubscribed.
Yes, QoS only engages when there's congestion, but congestion is whenever there's queued elements. "Larger" bandwidth, alone, does not guarantee there won't be queuing if there's multiple ingress streams, as more than one element can arrive at the same time.
Another opinion says I should use SP queue, cause even if there is no congestion a large packet may already be in queue being served so during that time voice packet has to wait till schedular finishes serving this packet
It's not quite as you describe. Scheduler determines next item to transmit, once selected and it's being transmitted your stuck waiting on it regardless of whether there's a SP queue or not. If this is an issue, and it can be, the solution is to not allow large items (as a single physical frame) to be transmitted at all.
SP queue insures whenever the scheduler is selecting, SP queued elements are selected first.
12-11-2012 03:23 AM
Many Thanks Joseph
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