IP Telephony - Jitter Issue

[karthick.2.subramanian]

Hi,

I am implememting IP Telephony in one of my customer site. For testing i connected one IP phone to a switchport which has auto qos config. The switch is directly connected to the WAN router which has 15% strict priority QOS enabled for EF traffic.

Issue - While i do testing for QOS to the IP phone connected, i see no issues with packet drop, Round trip delay. But the report says Jitter is the issue and which may cause issue to the voice quality.

Steps taken:

1. I have checked the QOS config in router and switch.

2. Service provider adviced they also have 15% QOS config. Also they observe the WAN link getting fully utilised intermittently. But still my QOS should take care of the Voice and jitter.

3. No errors on ports of switch and router.

Kindly someone advice what could be the other steps that would resolve my Jitter issue.

[jyoung]

What type of QOS are you using? Does your policy map show hits on the voice traffic. QOS does not necessarily fix jitter. QOS fixes bandwidth and latency issues that can cause jitter. Jitter can also be caused by unstable connectivity. Can you explain the situation in more detail?

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[karthick.2.subramanian]

I have configured Low latency Queueing - LLQ in WAN QOS. In my scenario, 15% is for strict priority voice class and rest of the traffic is in default class. Yes, the policy map shows hits of voice traffic.

Eventhough if latency issue is present due to intermittent high WAN link utilisation, QOS should take care of my Voice traffic in prioritising it.