Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

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.

Kermit

Everyone's tags (3)
1 REPLY
Super Bronze

Re: COS/QOS and oversubscription

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

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".

266
Views
0
Helpful
1
Replies