I am experiencing phone/voice quality issues recently at a couple remote locations, users are reporting voice choppiness during conversation and phones reponding slow, like when they pickup the phone it takes a few seconds before they can hear the dialtone. And I noticed WAN traffic load was high when users reported the issue, so I am confident the issue is QoS related. Below is what I have configured on my WAN routers. Could someone help me clearify some questions or if there is anything wrong with my config ?
class-map match-any voice-signaling
match ip dscp cs3 af31
match protocol h323
match protocol mgcp
match protocol skinny
match access-group 101
class-map match-any Critical
match ip dscp ef
match protocol rtp audio
match ip precedence 5
class-map match-any Flash-Override
match ip precedence 4
priority percent 40
set dscp ef
bandwidth percent 30
bandwidth percent 5
With the policy-map I have in place and with the "priority percent 40" for critical traffic. does this mean that I always have 40% of the link for critical traffic ? if yes, then what would cause the issue ?
I have T1 link at all remote sites and I noticed the issue happens when the link is at 90-95% utiliized.
It means you set LLQ for voice traffic which is matched as RTP audio or dscp EF or precedence 5. Means this traffic will have priority over any other traffic and will take MAXIMUM 40% of your link. Anything over this number will be dropped means choppy voice.
I would check bandwidth configuration on your link as first thing. Maybe other unwanted traffic is marked as EF or precedence 5 before reach your router. This could cause some issues for your voice traffic.
Last thing could be more than 40% bandwidth usage for phone calls.
Use NBAR to check your traffic patterns on this link it can help in early stage of defining problem.
You may want to try increasing your priority percentage to see if that helps. If you're dropping packets a 'show interface' and 'show policy-map interface' should help you figure that out.
What is also helpful on your T1 circuits is to change the tx-ring-limit to 2:
What happens is that QoS is only applied to software queued packets. If you have a large tx-ring, you may have packets sitting in the ring holding up your priority packets. By reducing this, you put your packets in software and allow your router to more articulately determine which packets go out first.
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