Bandwidth Restriction for Specific Subnet during Congestion on link only

[Muhammad Hassan]

Dear All,

I need to restrict the traffic for specific subnet up to 10% of total bandwidth when there is congestion on link while no restrictions is applied during non-congested period. Please someone help me on this. Thanks.

Router Cisco 877 with Advance IP services License.

[mvsheik123]

Hi Muhammad,

Check the below link. It does not exactly provide what you are looking for, but may give you some idea.

https://supportforums.cisco.com/discussion/12550001/qos-bandwidth-limit

hth

MS 

[Muhammad Hassan]

Hi..

Thanks for sharing the useful information.

As per my understanding, Police/Shape will limit the traffic all the time and through bandwidth command we can set minimum guaranteed at the time of congestion.

In my case, I want to know is there any option to apply the maximum limit for specific subnet at the time of congestion only. thanks.

Regards,

[Joseph W. Doherty]

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Posting

The only feature, that often works like you desire, is a LLQ's (implicit) policer.  When there's congestion it polices, but when there's no congestion, it doesn't.

Otherwise, I'm unaware of such a feature.

[Muhammad Hassan]

Dear Joseph,

Thanks for the response.

Can you please share the sample config. thanks.

Regards,

Hassan Khan

[Muhammad Hassan]

Below configuration will work? is it restrict upto 128kbps when there is congestion on the link? Please confirm. thanks.

class-map match-all ABC
match access-group name ABC-SUBNET
exit
policy-map TRAFFIC-POLICY
class ABC
Priority 128
class class-default
fair-queue

ip access-list extended ABC-SUBNET
permit ip 192.168.1.0 0.0.0.255 any

WAN Interface
service-policy output TRAFFIC-POLICY

[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 wha2tsoever (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

Yes, that's how it appears to work on most platforms.  (NB: the implicit policer only engaging when there's congestion appears "odd", but Peter Paluch confirmed, with testing, some time back.)

Keep in mind, when there's congestion, class ABC will dequeue first.

[Erico Verissimo]

Hi Muhammad,

I was searching some materials and I found a table that describe what you want to do, I guess..

Command	Congestion	Non-Congestion
bandwidth Command	Allowed to exceed the allocated rate.	Allowed to exceed the allocated rate.
priority Command	Cisco IOS meters the packets and applies a traffic measurement system via a token bucket. Matching packets are policed to the configured bps rate, and any excess packets are discarded.	The class can exceed its configured bandwidth.

In this case, when it is used priority, the traffic will be dequeue first due to the LLQ.

Regards.

[Erico Verissimo]

Hi Muhammad,

You can try to use the feature "shape average" . This feature will buffer  the traffic, when there is congestion, and it will try to transmit them when the link is not congestion. In this feature, the subnet marked will experience high delay when the link is congestion. In fact there is a limit of the BW for the subnet but the algorithm will buffer the excess traffic and transmit them when the congestion period was over.

Regards!

[Muhammad Hassan]

Dear Erico,

Thanks for the response.

Actually, i dont want to buffer the excess traffic. Its ok with us if its discarded during congestion period. 

Regards,