08-28-2008 09:20 AM - edited 03-15-2019 12:54 PM
Hello
I'm working in deploying QoS in a branch office
but I'm getting poor voice quality on calls.
here is the configuration of the QoS parameters
*****************************************
class-map match-all VOZ
match dscp ef
class-map match-all VOZ(SIGNAL)
match dscp af31
class-map match-all APLICACION-CRITICA
match access-group name AS400
!
!
policy-map POLITICAS-QoS
class VOZ
priority percent 60
class VOZ(SIGNAL)
bandwidth percent 5
class APLICACION-CRITICA
bandwidth percent 10
class class-default
fair-queue
*****************************************
!
!
!
interface FastEthernet0/0
description LAN
ip address 10.12.1.1 255.255.255.0
speed auto
!
interface Serial0/0
description Link to HQ
bandwidth 128
ip address 192.168.50.42 255.255.255.252
service-policy output POLITICAS-QoS
load-interval 60
compress stac
!
interface BRI1/0
no ip address
shutdown
!
ip classless
ip route 0.0.0.0 0.0.0.0 Serial0/0
ip route 16.0.0.0 255.255.255.0 Serial0/0
no ip http server
!
ip access-list extended AS400
permit ip any host 16.0.0.2
Now take a look at the Output of the show policy-map interface serial 0/0
CS-1760-PN#show policy-map interface serial 0/0
Serial0/0
Service-policy output: POLITICAS-QoS
Class-map: VOZ (match-all)
1034703 packets, 66220992 bytes
1 minute offered rate 147000 bps, drop rate 71000 bps
Match: dscp ef
Queueing
Strict Priority
Output Queue: Conversation 40
Bandwidth 60 (%)
Bandwidth 76 (kbps) Burst 1900 (Bytes)
(pkts matched/bytes matched) 1034703/66220992
(total drops/bytes drops) 530418/33946752
Class-map: VOZ(SIGNAL) (match-all)
0 packets, 0 bytes
1 minute offered rate 0 bps, drop rate 0 bps
Match: dscp af31
Queueing
Output Queue: Conversation 41
Bandwidth 5 (%)
Bandwidth 6 (kbps) Max Threshold 64 (packets)
(pkts matched/bytes matched) 0/0
(depth/total drops/no-buffer drops) 0/0/0
Class-map: APLICACION-CRITICA (match-all)
1423 packets, 84273 bytes
1 minute offered rate 0 bps, drop rate 0 bps
Match: access-group name AS400
Queueing
Output Queue: Conversation 42
Bandwidth 10 (%)
Bandwidth 12 (kbps) Max Threshold 64 (packets)
(pkts matched/bytes matched) 1423/84273
(depth/total drops/no-buffer drops) 0/0/0
Class-map: class-default (match-any)
38296 packets, 21064743 bytes
1 minute offered rate 47000 bps, drop rate 0 bps
Match: any
Queueing
Flow Based Fair Queueing
Maximum Number of Hashed Queues 32
(total queued/total drops/no-buffer drops) 11/130/0
CS-1760-PN#
As you can see there are A LOT of packets being dropped
related to DSCP ef (voice bearer packets) but there are actually 0 (ZERO!!) calls being placed at this time ?
Notice that there is also 0 packets matching DSCP af31 (voice signaling)
Can anyone tell me what might be happeing here ??
Why am I getting so many drops ?
Thanks
08-28-2008 10:49 AM
Do you have Qos enabled on your switch.
Also, you should add this to your VOZ(signalling)
class-map match-any VOZ(SIGNAL)
match cs3
match dscp af31
08-28-2008 01:41 PM
This bit of configuration allows the router bandwidth scheduler to enforce a minimum BW guarantee out of an interface capacity and to enforce a queue drop profile to any of the classes previously defined. This builds a certain âbehaviourâ for the router.
Also you should make sure it is enabled.
!
interface input_interface_name
mls qos trust dscp
!
!
The scheduler is attached to the output port and is active for the traffic leaving the router (output) by the mean of a template called âservice-policyâ containing the already defined âpolicy mapâ template.
!
interface output_interface_name
service-policy output policy_map_name
mls qos trust dscp
!
The command lines âmls qosâ deserve a paragraph on its own.
The command line âmls qosâ in the global configuration mode is needed to enable QoS on the supervisor engine while âmls qos trust dscpâ issued in the input and output interfaces is there to avoid cards to reset the dscp code of packets entering or leaving the interfaces.
08-28-2008 06:58 PM
Hi ROYCE
i agrre with i think he has a missing trustbounday for the DSCP
however
u have mentioned that mls qos trust dscp should be entered on the Router interfaces
while it should be enabled on the switch side
especially on uplink ports and port going tward the router interface !!
and the router will use this DSCP marking in its matching cratiria
and about reseting the marking this happen if the marking is on L2 COS and gose to a L3 device like layer three switch or router in this case the packet will loss its marking unless u trust DSCP marking on switch uplinks and the switch will use default COS to DSCP maping so this default maping should be altered aswell as bellow....
Glenn PLEASE, MAKE SURE UHAVE THIS CONFIG ON UR SWITCH:
When configuring an access-switch to trust/conditionally-trust CoS, then the default mapping for CoS 5
should be adjusted to point to DSCP EF (46), instead of DSCP CS5 (40). This modification is shown
below:
(config)#mls qos map cos-dscp 0 8 16 24 32 46 48 56
! Maps CoS 5 to EF
for aditional config (optional) u can remap DSCP marking to its COS marking in the returne path linke this example
ip cef ! IP CEF is Required for Packet Marking
policy-map BRANCH-LAN-EDGE-OUT ! Enables default DSCP-to-CoS Mapping
class class-default
set cos dscp
interface [interface No. connected to LAN switch]
service-policy output BRANCH-LAN-EDGE-OUT
good luck
please, if helpful rate
09-01-2008 12:58 PM
My friend!
It worked quite well!!
Thx a lot...
09-01-2008 03:56 PM
hi Glenn
i am glad its working now
but can u let us know what did u add exactly and get work
is it the trust interface on the switch and cos maping only ?
thank you
08-28-2008 10:15 PM
Are you running muticast routing and multicast MoH? That could be 2 MoH streams.
add match dscp cs3 to VOZ(SIGNAL) and see if you get some hits
Good Luck!
08-29-2008 07:56 AM
Hello friend!
I added that sentence amd I'm getting lots of hits... But why exactly is this happening ?
Thx!
08-29-2008 08:51 AM
The first thing I will try is to setup a SPAN on your switch to sniff what exactly traffic is marked as dscp ef. Or you can enable netflow on the router to look at the traffic.
08-29-2008 11:20 AM
Hello Richard
Unfortunaly I do not know how to setup a sniffer on a switch or how to enable netflow on the router(never done it before)
Do you have examples available ?
Thanks
08-29-2008 11:58 AM
To enable netflow
interface FastEthernet0/0
ip flow ingress
And then you can use 'show ip cach verbose flow' to check the netflow static.
To using SPAN, here is the link http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008015c612.shtml
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