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choppy voice

HI, have a couple of sites that are experiencing voice quality issues.

both on the end of E1 cct's. Policy map on routers all show no drops in the priority queue, phones show no transmit or receive errors on their statistics. The local switch show no issues either, yet client keeps complaining, any ideas on where to look next.

ta

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Re: choppy voice

The problem could be any one of these issues:

Fragmentation:

This issue can be removed from consideration with tests that only include voice. If choppy voice continues, check for the next issue. If the choppy voice symptom is eliminated when data is removed, check the fragmentation. For more information on Frame Relay fragmentation, refer to these documents:

The Fragmentation (FRF.12) section of VoIP over Frame Relay with Quality of Service (Fragmentation, Traffic Shaping, LLQ / IP RTP Priority)

Frame Relay Fragmentation for Voice

Queuing:

This issue can also be removed from consideration with tests that only include voice. If choppy voice is not eliminated, continue resolving the issue elsewhere. If the choppy voice symptom is eliminated when the data is removed or when such a test is not viable, check the queuing configuration. For more information, refer to the Strict Priority for Voice Traffic (LLQ or IP RTP Priority) section of VoIP over Frame Relay with Quality of Service (Fragmentation, Traffic Shaping, LLQ / IP RTP Priority).

Frame Relay Traffic Shaping (FRTS):

In this example, no BECNs or DE bit packets are being received at either end. Therefore, traffic shaping appears to be operating correctly. Problems experienced with 0K CIR services and services with inappropriate shaping to CIR ratios would manifest themselves differently. For more information on FRTS for voice, refer to these documents:

The Traffic Shaping for Voice section of VoIP over Frame Relay with Quality of Service (Fragmentation, Traffic Shaping, LLQ/IP RTP Priority)

Frame Relay Traffic Shaping for VoIP and VoFR

Lack of bandwidth and Connection Admission Control (CAC):

Ensure that the required number of calls are supported for the codec being used. Also check assumptions regarding the use of compressed RTP (cRTP) and Voice Activity Detection (VAD). For more information on bandwidth consumption, refer to Voice over IP - Per Call Bandwidth Consumption.

Delay or packet drop in the path of the call:

In this example, the round trip ping time is excessive. In addition, there are no drops on router interfaces. These facts lead to the conclusion that packets are either being delayed or dropped in the Frame Relay network.

Check with the carrier and ask them to check the round trip delay and drop characteristics of their network with reference to Loopback Tests for T1/56K Lines.

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