Class Base weighted Fair queuing

kjanakiraman · ‎09-17-2003

We have a 2Mb leased line between location A and Location B. Location A connects to internet and to location Bthrough this leased line. We have Cisco 3640 router on both the sides and we have configured CBWFQ for prioritising voice,video and data since we have ip phones also connected for communication. We have setup priority like below

class-map match-all video

match ip precedence 6

class-map match-all voice

match ip precedence 5

!

policy-map voice-monitor

class voice

priority 900

class video

priority 500

class class-default

fair-queue

and we had access -list matching the class-map. Everything seems to work fine and we get a download speed of 110Kb/sec from location B to Location A. But when we give policing command for class video and class class-default like the one below

class-map match-all video

match ip precedence 6

class-map match-all voice

match ip precedence 5

!

policy-map voice-monitor

class voice

priority 500

class video

priority 768

police 768000 800000 800000 conform-action transmit exceed-action drop

class class-default

fair-queue

police 768000 928000 928000 conform-action transmit exceed-action drop

The download and the internet speed drops down drastically. The download is just 5-10Kb/sec and some times goes to 300bytes/Sec.

Can some one suggest me what should i do so that i could have good voice,video and data transfer through his 2mb line.

Thanks in Advance

deilert · ‎09-17-2003

One thing is your burst parameters are incorrect ,

police 768000 96000 96000

kjanakiraman · ‎09-17-2003

Thanks for your reply. IS there any specific reason to set the burst parameters as you have suggested?

Thanks in advance

deilert · ‎09-17-2003

by default cisco uses CIR/8 for the Bc

768000/8=96000

kjanakiraman · ‎09-17-2003

Thanks a lot for the information. I will check up and get back about the status.

kjanakiraman · ‎09-17-2003

When i gave police 768000 96000 96000 on both the video and class-default i am getting a download speed of about 11Kbytes/Sec. Is policing is like the Committed access rate where in 768Kbits is always stored for that particular class irrespective of being used of not?

Thanks

deilert · ‎09-18-2003

yes that is correct 768K is the limit. In CBWFQ you can utilize additional bandwidth from the other classes if it is not being used .

allan.wells · ‎09-18-2003

Im quite sure you can only use the priority for 1 que this is the PQ the other classes need bandwidth statement.

If other classes arent useing there bandwidth it is distributed the PQ will always be serviced first thats why it is the PQ and is garunteed the bandwidth ........

LLQ enables a single strict PQ within CBWFQ at the class level. With LLQ, delay-sensitive data (in the PQ) is dequeued and sent first. In a VoIP with LLQ implementation, voice traffic is placed in the strict PQ.

The PQ is policed to ensure that the fair queues are not starved of bandwidth. When you configure the PQ, you specify in Kbps the maximum amount of bandwidth available to the PQ. When the interface is congested, the PQ is serviced until the load reaches the configured Kbps value in the priority statement. Excess traffic is then dropped to avoid the problem with Cisco's legacy priority-group feature of starving the lower priority queues.