How to reserve bandwith when link speed change

[impi]

Hi,

Please let me explain where is my problem :

with QoS on routers, i know how to garanty an amount of bandwith when link speed is known :

 - create a parent policy and shape the traffic speed to 95% of the bandwith

 - create a children policy with bandwith reservation

something like that :

policy-map my-qos
 class important-to-me
  bandwidth percent 25

policy-map physical
 class class-default
  shape average 4000000
  service-policy my-qos

But here, my customer has a link that could be from 16 Mbps to 32 Mbps (depending on weather).

He only wants to reserve 2Mbps to a certain type of traffic (easy to define with ACL : IP to IP !)

I know that QoS only trigger in case of congestion, that is why there is a shaping policy, but here i do not know how to tell the router to always give 2Mbps to this traffic.

This is not important if this 2Mbps are lost for other traffic.

Thanks for your help

[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.

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Posting

Recently I came across a new Cisco feature, Adaptive QoS over DMVPN.  This might work for you.  Otherwise, the only other thing that comes to mind would be to configure on-going SLA tests, monitor the results with a script that keeps checking, and rewrite the QoS shaping value, as needed.

[impi]

Hi Joseph, and thanks for your reply.

There is no VPN, this is a direct link (radio link operated by someone else). About SLA, script and so on, this looks like a good idea but will give me some headache as i do not know much about that :)

I'm followings two other ways :

 - if the operator can split his link into 2 independant links

- if the operator can do QoS based on packets tagging, then the router will only have to mark them

If there is other ideas, i'll take them !

regards 

[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

Even if there is no VPN now, to take advantage of the new feature, you run a VPN link over your physical path.

[impi]

ok, great !

I'll see if i find some reading about that. if you have a link, that would be great.

thanks again !

[Joseph W. Doherty · Accepted solution]

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/xe-3s/qos-plcshp-xe-3s-book/qos-plcshp-adaptive-qos-dmvpn.html

[impi]

Thanks a lot for that, i'll have some reading.

I'll mark this post as "correct answer" even if i can not test that before some weeks.