2821 question

Unanswered Question

Hello guys,

We have 2821 router in the company that moves the traffic (data/voice) between the US and Europe via two T1's. We have QoS configured that gives priority to the Voice over the data on both T1's that we have. The board Installed on the router is vwic2-2mft t1/e1. When I issue sh int sum I see a lot of packets dropped from the outgoing queue (under OQD). When I issue sh int serial x/x/x:x I see the same number of packet dropped in "Total output drops" row. My questions are: Is QoS responsable for these dropped packets or the buffer of the outgoing queue is very small and can't take all the packets sent?? Can a call(voip phone call) be dropped caused by these packets. Are these droppes problem at all?

Can these packets affect the quality of all the calls trought the T1's??

Thank you in advance!!

I have this problem too.
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guruprasadr Fri, 10/05/2007 - 02:50


If you have implemented the QOS using CBWFQ ie., which normally uses the rate-limit feature in the Configuration.

If the rate-limit is configured in such a way like: exceed action as drop means then once the max burst is reached the exceeded packets will be dropped.

Pls Post the QOS Configuration to explain further.

PLS RATE if Helps

Best Regards,

Guru Prasad R

guruprasadr Fri, 10/05/2007 - 04:27


QOS "Marking" should be same at both the end. Is it configured that way ?

Was there any "shape average" command used in the configuration.

With this INFO its quiet difficult to provide more inputs.

Pls Rate if HELPS


Guru Prasad R

guruprasadr Fri, 10/05/2007 - 05:28



Possible reason for Packet Drops:

1. Noisy Circuit

2. CRC errors in the Interfaces (connected to Service Provider)

3. Possibly during Peak Line Over Load Situation

4. Bandwidth Rate-limitation / Reservation / Traffic Shapping using QOS

5. Verify CPU Load : for eg: if the CPU load reaches more than the Normal (approxi: 85%) means possibility to Packet Loss

6. Check the Reliability of the Link with the Carrier.

Pls Rate if HELPS

Best Regards,

Guru Prasad R


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