[c-nsp] VOIP QoS problem

[Eric Kagan]

We have several customers that utilize service with a 3rd party VOIP
provider.  We have applied a very simple QoS policy (below) to several
customers interfaces on our Cisco 7206VXR's as well as the CPE.  One
customer in particular is complaining of frequent problems.  We could not
find anything real obvious of why they are having issues.  Traffic on the
norm is about 200-300k on a full T1 which should not even warrant needing
the QoS in place.  From what I understand and have read on the Qos config
below - it will only get applied as the circuit starts to get congested. We
put some real time traffic monitors on the customers interface and saw a few
real short spikes almost maxing out the circuit.  Is it possible for the
circuit to experience a really quick burst of traffic that doesn't allow the
QoS policy to "kick-in" quick enough so the customer experiences some drops
?  Anyone have any ideas on how to best troubleshoot or determine this
problem ?  Should we consider reserving a fixed amount of bandwidth vs the
config below.  Could the output drops be contributing to this problem ?  Any
pointers would be appreciated.
 
Thanks
Eric
 
 
class-map match-any VOIP
  match protocol rtp
  match protocol sip
!
policy-map voice
  class VOIP
   priority percent 65
   set ip precedence 5

interface Serialx/x/x
 bandwidth 1544
 ip address x.x.x
 ip flow ingress
 ip nbar protocol-discovery
 service-policy output voice
 encapsulation ppp
 no clns route-cache

 
show int Sx/x/x
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 5222
Queueing strategy: weighted fair
Output queue: 0/1000/64/5222 (size/max total/threshold/drops)