Cisco QoS - how to use traffic shaping for interface and bandwidth/priority for classes?

[jwayne]

I have VPLS (MPLS which looks like a layer 2 switch to me) carrier networks and I'm currently developing QoS policies for them.

I have some sites with a 1000 physical link and CIRs like 50 mb, 100 mb etc. I need to do traffic shaping on these with a service policy otherwise I get drops and less performance with many traffic types.

The challenge is that as I'm implementing various traffic classes in my QoS policy I it seems I can no longer traffic shape the entire physical interface to 50 mbps for example. Instead I have to shape per traffic class, which is really not what I want to do. I would like to be able to shape the entire interface to 50 mbps, then alot traffic types 30%, 20% of that etc and allow them to use more if it is available (I am also using the priority queue for VoIP and I know it can't use extra available bandwidth since it is the priority queue.) Is there a way to do this while also shaping the entire interface?

I appreciate any tips.

[Francesco Molino]

Hi,

Which router are you using and IOS version?

What config did you apply when saying you can't do shaping on interface? Can you share your config?

I mean, we always do HQOS with 1 policy-map shaping the physical interface and then calling a 2nd policy-map on which you define every classes.

When you're saying you can't shape the interface, do you have any error message or how you determine shaping isn't working?

[jwayne]

Francesco,

Thank for the reply.  I guess I just wasn't familier with this type of nested QoS.  I'm using mostly ISR 4Ks with IOS XE 03.16.06 and ASRs with IOS XE 03.16.03.

So is the preferred best practice method is to do something like this?

interface GigabitEthernet0/0/0

service-policy output 50mbps_Shape

!

!

policy-map 50mbps_Shape

     class class-default

          shape average 50000000

          service-policy QOS

policy-map QOS

      class VOIP

          priority percent 10
          set cos 5

      class CLASS2

           bandwidth percent 40

           set cos 4

etc....

[Francesco Molino]

Yes, this is best practices because I mean you want to shape globally but want to define different type of bandwidth per class right.

But using just the shape in class default should work also

[Joseph W. Doherty]

Your on the right track, as also confirmed by Francesco.

A couple of things to be aware of. WAN providers "count" bandwidth at L2, but It's my belief that many Cisco shapers only count bandwidth at L3. If you find this true on your device, you may want to shape at about 15% slower (or whatever you think best represents your average L2 overhead).

You might ask whether your provider is willing to tell you what they use for Bc and/or Tc. If they do, you can configure your shaper to more accurately conform with how they enforce your CIR.

Your policy is setting CoS, which is unusual unless you have a tagged VLAN handoff.

BTW for "(I am also using the priority queue for VoIP and I know it can't use extra available bandwidth since it is the priority queue.)", that's not always true on Cisco devices. On many, the implicit policer only engages if PQ packets are queued.