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Community Member

Per Site Shaping on MPLS networks

Say I have the following style configuration for a head office router connecting into an MPLS IP WAN:

class-map match-all SITE-A

match access-group name SITE-A

!

class-map match-all SITE-B

match access-group name SITE-B

!

class-map match-all SITE-C

match access-group name SITE-C

!

!

policy-map SHAPE

class SITE-A

shape average 5000000

service-policy SCHEDULE

class SITE-B

shape average 5000000

service-policy SCHEDULE

class SITE-C

shape average 5000000

service-policy SCHEDULE

!

interface Hssi1/0

bandwidth 10000

service-policy output SHAPE

The access-lists simply matches traffic destined to each site.

The child policy SCHEDULE is a standard CBWFQ policy (with priority queuing and min BW classes).

The SHAPE policy is meant to shape traffic down to 5Mbps for each site. However, the interface to which this policy is applied is clocked at 10Mbps.

The question is what happens from a QOS scheduling perspective if all 3 classes under the SHAPE policy attempt to transmit at an aggregate rate of over 10Mbps (the access speed of the interface)? What QOS policy controls the combined traffic entering the hardware buffers (TX-Ring) of the physical interface?

Daniel

1 ACCEPTED SOLUTION

Accepted Solutions
Super Bronze

Re: Per Site Shaping on MPLS networks

In your example, when the interface was congested, I would see a queue form at class SITE-A, SITE-B and/or SITE-C. When the load within the SITE-A, SITE-B or SITE-C exceeded the bandwidth configured by the shaper for that class, I would then see the traffic queue within the shaper under the corresponding class.

5 REPLIES
Bronze

Re: Per Site Shaping on MPLS networks

The combined traffic entering the Tx-ring will be controlled by the queuing mechanism which is enabled on that interface. Depending the on the router you are using, choose the best available mechanisms.

http://www.cisco.com/en/US/tech/tk543/tk544/tsd_technology_support_protocol_home.html

Super Bronze

Re: Per Site Shaping on MPLS networks

An interesting question, so I tried something similar today. What I saw was when the interface was congested, traffic appeared in the parent's class queue unless the bandwidth within that the parent's class exceeded the parent class's shaper's bandwidth, then the traffic appeared in the child's classes. This was on a 7200 -G2 running 12.4(15)T4.

Community Member

Re: Per Site Shaping on MPLS networks

Thanks for your response. Can I get further clarification from you as I'm a little confused? Can you name the classes that where queueing the traffic (as per the names in my example)?

Super Bronze

Re: Per Site Shaping on MPLS networks

In your example, when the interface was congested, I would see a queue form at class SITE-A, SITE-B and/or SITE-C. When the load within the SITE-A, SITE-B or SITE-C exceeded the bandwidth configured by the shaper for that class, I would then see the traffic queue within the shaper under the corresponding class.

Community Member

Re: Per Site Shaping on MPLS networks

Ok. That makes sense. Thanks for your input.

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