CBWFQ and LLQ on the policed link

[ctam]

Is there any QoS technique that can be applied on the following scenario?

I have two routers in two sites connected by the MetroEthernet link with 2Mbps subscribed bandwidth. As I know, the MetroE provider just applies policer to drop the packet when more than 2Mbps is transmitted.

<Site 1> --- Router A --- (Eth, 2Mbps) MetroE (Eth, 2Mbps) --- Router B --- <Site 2>

I have data and voice to be transmitted between two sites, so I want to apply LLQ and CBWFQ for voip and two classes of data traffic respectively. In this case, the interface speed (10Mbps) and the actual throughput (2Mbps) are different. The voip traffic would be dropped by the policer on the MetroE provider side when the 2Mbps throughput is exceeded.

I am sure that the CBWFQ and LLQ can be applied on the WAN link because the interface clock rate and actual throughput are the same. Thus, the packet can be queued up for bandwidth assignment.

How to configure the router in this scenario that can have the bandwidth assignment like WAN link?

Thank you very much.

[Georg Pauwen]

Hello,

for your voice traffic, the CBWFQ with LLQ would look like this:

Router(config)#class-map voice

Router(config-cmap)#match access-group 101

Router(config)#access-list 101 permit udp any any eq range 16384 32767

Router(config)#policy-map policy-llq

Router(config-pmap)#class voice

Router(config-pmap-c)#priority 200 --> this would create 200k of bandwidth matching access-group 101

Router(config)#interface ethernet 0

Router(config-if)#service-policy output policy-llq

The rest of your traffic would go into the default class, but you said that you wanted to create two classes of data traffic in addition to the voice; which additional traffic do you need to classify ?

Regards,

Georg

[ctam]

Hello Georg,

Thank your for your information.

Actually, I understand how to configure the CBWFQ and LLQ. The problem is that the voip packet and data packet are dropped by the policer set at metroe provider side.

For example, one of the sites sends 3Mbps mixed with data and voip packet. Then, it is dropped by the policer, because the metroe provider does not aware traffic type.

Thanks,

Cliff.

[marcusl]

Hi Cliff,

You can configure your own policing to rate-limit the egress traffic to 2Mbps, with that setup the service provider _should_ not drop any important traffic ..

Best regards,

/M

[ctam]

Hi M,

In this way, it would drop the voip packet at my side.

To put it another way, I can set 3 policers for 2 classes of data and voip as follows.

first class data: 1Mbps

second class data: 512kbps

voip: 512kbps

However, the data traffic alway cannot consume more than the policed data. In CBWFQ used in WAN interface, each class of traffic can efficiently use the bandwidth more than the specified till the congestion.

Best regards,

Cliff.

[Georg Pauwen]

Hello Cliff,

the problem is that no matter what traffic is sent, everything over 2MB is dropped. The only solution I can see is to configure the priority scheme for VoIP traffic, in order to make sure that VoIP traffic is always transmitted. Then again, if there is more than 2MB of voice traffic, it will be dropped as well. I guess queuing and prioritizing will not do you much good if the required bandwidth actually and constantly exceeds the 2MB, unless you can get your provider to allow a certain burst exceed rate.

Regards,

GP

[ctam]

Hi GP,

Actually, priority scheme cannot help. The provider drops the packet in random manner. They do aware the order of the packet being sent.

For example, the overall bandwidth (data + voip) exceeds 2Mbps. the provider would drop the exceeded packet independent of the time order. The packet firstly sent may be the packet being drop.

I know that packetshaper can do it. I am not sure how to do it in Cisco router.

Regards,

C.