QoS on remote site ethernet

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Jul 29th, 2008
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I have a remote site that is having voice quality issues. They have a T1 connection that has QoS concfigured to give priority to the voice traffic and shape the data traffic to 768k.

Is it necessary to have QoS configured on the trunked ethernet port that connects to the switch?

The port on the router is currently configured to remark dscp/cos markings on the packets, but no priority.

Could this be causing the voice quality issues?


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Justin Brenton Tue, 07/29/2008 - 13:10
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Hi pmccloud,

Yes this is your issue, if you do not have the proper configuration on your trunk ports your prioritization is not working.

Hope this helps, please rate if so



pmccloud Thu, 07/31/2008 - 11:05
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What is the best way to apply QoS on a trunk port with sub-interfaces? The only traffic that needs Priority is voice, all the rest of the traffic is just internet traffic that can be best effort.


okuehn Tue, 07/29/2008 - 22:29
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please, can you clarify your network setup more detail. do you have the following router connection:


HQ ---T1----| TRUNK


if so, you only have to mark traffic at trunked ethernet in. the bottleneck here is the T1 interface for outgoing traffic, hence you have to configure shaping here.

additionally you have to configure shaping for outgoing traffic at the Headquater T1 interface

hope this helps!

pmccloud Thu, 07/31/2008 - 04:35
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That is the correct layout. I am assuming that since the traffic is hitting the router with voice coming in priority, there should be enough bandwidth on the thernet side. But the voice quality issues that have been reported seen to say otherwise. There is choppy audio inbound to the site, but outbound to the PSTN is fine.

okuehn Thu, 07/31/2008 - 04:59
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regarding your problem description it seems that you have an QoS problem at the headquater outside direction or T1 leased line. since you cannot prioritize incoming traffic, your router at the branch office cannot supply QoS to incoming traffic.

first you can check the interfaces involved to ensure CRC or leased line errors. then you can look at the service policy output at HQ to see if you have drops at class LLQ

pmccloud Thu, 07/31/2008 - 07:15
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The T1 looks good on both ends, and the HQ side shows 5 dropped packets from the priority queue total. The same QoS is configured on both ends.


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