Unanswered Question
Sep 19th, 2007

hii, i have a problem with the implmentation of the QoS in my router and the remote router, below the policy-map:

policy-map xxx

class voice

priority 200

set dscp ef

the problem is that when i apply the QoS there is disconnect in the vocie, but when i don't apply it the voice quality is good, i remplaced the priority command by the bandwidth command, and the QoS is very good, here i understand that the problem is the priority command, but i must apply this command to the voice, i don't understand this illogical problem. Thnks for your help

I have this problem too.
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ruesch-eng Wed, 09/19/2007 - 11:15

Are you using G.711 or G.729 for your calls across the WAN? The priority command strictly limits the amount of bandwidth for the voice calls. Any traffic above the specified bandwidth limit will be dropped. If you are using G.711, then perhaps you have too many calls at one time and the voice packets are being dropped. A priority queue of 200 will only support 3 calls at one time.

a.rayen83 Wed, 09/19/2007 - 23:47

hii, i use the default compression G711, but i do the test with one call, i'm sure that the problem is not 200Kbp because i did the test with one call only, the problem is the priority command, probably the IOS... i remember you that without the QoS one call is very good, and with the QoS (priority 200), i can't hear good. now i did the QoS with the bandwidth 200 ans set dscp EF, but it's not the good solution. Thanks

ruesch-eng Thu, 09/20/2007 - 01:36

When you defined your class map voice, what parameters are you matching on to specify what traffic should be sent to the priority queue? If you defined the class map too broadly, it is possible that you are sending data as well as voice to that queue and are going above the priority limit of 200 kbps. In which case, the router will drop all packets above the 200 kbps. With the bandwidth command, the router will allow you to send more than 200 kbps to the queue as long as bandwidth is available. Please post your class-map voice config. Thanks.

ruesch-eng Thu, 09/20/2007 - 01:49

Here is a sample config for you. First, I defined an access-list to match only voice traffic. I specified the ports used by CCM, QoS markings that the phones apply, and my voice vlans in the access list. I do not have any data in the or vlans.

access-list 102 permit udp any any range 16384 32767

access-list 102 permit udp any any precedence critical

access-list 102 permit ip any any dscp ef

access-list 102 permit udp

Next, I defined my class-map, which I called gold, to match on any traffic markings applied by the phones or to match on my access list.

class-map match-any gold

match ip precedence 5

match ip dscp ef

match access-group 102

Next, I defined my policy-map which includes the priority queue for my class-map gold and also a default queue for all other traffic. Your posted config did not specify whether or not you defined a default class. You must do so to tell the router what to do with all the other traffic.

policy-map voip

class gold

set ip dscp ef

priority 256

class class-default


Finally, you should consider using G.729 between sites so that you can send more calls at one time.

a.rayen83 Thu, 09/20/2007 - 02:28

hii, below my class map ans policy-map

class-map match-all voice

match ip rtp 16384 16383

policy-map BNP-QOS

class voice

set dscp ef

bandwidth 260

class class-default



ryancantor Wed, 09/19/2007 - 11:47

Sounds like you may be pumping more than 200kbps of voice traffic onto the interface. The priority command implicitly applies a policer to the interface. If you pump more than 200kbps onto the interface, voice traffic will be dropped in excess of 200kbps. All calls will suffer, not just 1 in particular.

Now if you just have the bandwidth statement configured, then calls are not policed if they go over the configured limit, assuming there is bandwidth available on the interface.

When you have the policy-map configured, run the command "show policy-map (policy-map name) interface (interface) and see if packets are getting dropped. If so, you have too much voice going over the interface and need to implement some type of call admission control technology.

a.rayen83 Wed, 09/19/2007 - 23:51

hii, i will use the last command to verify the dropped packets. Thanks

kdsmith Thu, 09/20/2007 - 06:51

Your problem is that the priority rate is specified in bps, not kbps, and the minimum is 8000. Add 3 zeros and you should get the reservation you want.

kdsmith Thu, 09/20/2007 - 07:05

I just noticed that in the cmd ref. I've been dealing with police statements too long :)


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