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COS/QOS and oversubscription

This is really over my head so I hope I can supply enough info for the question to make sense.

We have an MPLS circuit to a remote site. 50meg access from the hub, 3 meg from the remote. It is a managed solution that carries voice and data. I'm told the last managed hope is over ATM.

We know that we're maxing the 3 meg circuit in peaks.  Basic monitoring (pings) alerts and we see 300 or greater MS response times. Callers can barely hear due to jitter and dropped packets.

We have COS configured. We tag voice traffic with EF and AT&T is seeing it. This is configured as COS1 and has priority and is set for 1meg. COS3 is where we know packets are being dropped. 

In a situation like this, where voice has priority but the entire pipe is filling up, will the slow response time cause jitter and dropped packets for voice anyway?

Thanks for any insight.


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Re: COS/QOS and oversubscription


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When you share a saturated link, even "perfect" QoS won't deliver performance exactly the same as a non-saturated link.  This mainly due to interface packet serialization, or hardware FIFO queuing, of the non-priority packets.  However, correctly configured QoS generally delivers performance that priority traffic should be within its SLA requirements.

In other words, your VoIP will be impacted, but it shouldn't be impacted to an extent it's adverse to the call.

If your is a managed solution - tell your managed service provider "fix it".