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latency issue for Voip


We have a latency issue relative to voice traffic and we need your help to lower the latency.

Here?s the situation:

we have a Cisco router (c2801-entservicesk9-mz.124-8.bin) connected to an agilent hardware that?s a traffic generator. The Cisco router is an access router for customers who are connecting to the ISP. This access router needs to apply marking and shaping for different products that the ISP is selling. For example, we have a multimedia product that needs to service both voice and data, please look at the policy named ?product_MUL_128?. When we use the traffic generator to simulate traffic for both voice and data we get latency of 50ms for voice while both equipments are directly connected. This is not acceptable for our customers since once we add others equipments the latency might end up being over 200ms!! . He?s the config on the router:

policy-map product_MUL_128_sub

class VO

set dscp ef

set cos 2

priority 45

police 50000 4000 1000 conform-action transmit exceed-action drop

class D1

set dscp af12

set cos 5

bandwidth 51

class class-default


random-detect dscp-based

set dscp default

policy-map product_MUL_128

class ALL

shape average 128000

service-policy product_MUL_128_sub

We believe the problem is due to the shaping we?re doing on the router to limit the BW the customer can use. Please let us know how we can improve the latency taking into consideration our configuration.

Note : when we use 'shape peak 128000' for example it shapes on 256000 (because peak = cir * (1+be/bc)).

Regards, Ahmed.