QoS with rate limiting / shaping

[darkmagex]

We have a point to point data connection at 30Mbps. Our QoS does not seem to be working since the line appears to think the connection is 100Mbps. The ethernet does come up as 100Mbps but the circuit is limited on the backend by the network provider.

What would be the proper way to tell the Cisco routers on both ends (2811s) that the connection out that ethernet interface is only 30Mbps so it calculates the QoS properly? We tried to add in a shaping command and it appears to have an effect but if you copy a large file during say, a video conference after 10 seconds or so that traffic starts to drop.

The output QoS policy is below, reserving 17% of the bandwidth for one class and a flat 3Mb for another.

class-map match-any A-traffic

match ip precedence 5

class-map match-any B-traffic

match ip precedence 4

!

!

policy-map LinkQOS

class A-traffic

  priority percent 17

class B-traffic

  priority 3072 2000000

policy-map Shaping

class class-default

  shape average 10000000

  queue-limit 128 packets

  service-policy LinkQOS

[d-schuemann]

I believe you want to change your shape average under the class-default to 30 Meg's


Sent from Cisco Technical Support iPad App

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained  within this   posting without consideration and with the reader's  understanding that   there's no implied or expressed suitability or  fitness for any  purpose.  Information provided is for informational  purposes only and  should not  be construed as rendering professional  advice of any kind.  Usage of  this posting's information is solely at  reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever   (including,  without limitation, damages for loss of use, data or   profit) arising  out of the use or inability to use the posting's   information even if  Author has been advised of the possibility of such   damage.

Posting

As Schuemann noted, you might want to shape closer to your 30 Mbps; 10 Mbps is rather low.  Also Cisco documentation is a bit conflicting whether you need to allow for L2 overhead, so you may want to shape 5 to 15% lower than nominal bandwidth.

Depending what IOS you're running on the 2811s, you may also want to configure tx-ring-limit smaller on the outbound interfaces and/or you might need to configure the shaper's Bc to reduce the Tc.  (Earlier IOSs defaulted to 25 ms.)

Video can be very bursty so you may want to increase your queue-limit.  (When you note traffic is being dropped, do you know why/where?  [It's also not unknown for providers to have a misconfiguration too.])