QOS over DMVPN w/ GRE

Unanswered Question

Hi all,

I have a need to apply QOS for Voip in my SOHO network. the spokes are 871's with DMVPN set up to 3845 NHS's.


we have GRE tunnels between each site and need to provide some sort of QOS to support the VOIP traffic. Most of the documentation out there discusses Pre-shared IPSec with GRE but not DMVPN.


I found this link

http://www.cisco.com/en/US/customer/products/ps6558/prod_bulletin0900aecd803f93d6.html

and the contact e-mail bounced back as undeliverable. :)


I would love to use auto qos voip trust but its not supported on GRE tunnels.


I have also looked at qos pre-classify but found the following...


In addition to the usual considerations for QoS over VoIP, these additional considerations need to be made:


1.Ensure that the packet marking for the IP packets is being copied to the GRE tunnel header.


The recommended way of configuring this is to issue the qos pre-classify command to the tunnel interface, and add the service policy to the physical interface.


2. Ensure that the public carrier is capable of providing QoS based on the packet marking you provide.


Why would the Carries need to provide QOS if the packets are encrypted and wrapped in GRE?


I am confused as to how exactly this will work.

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bjornarsb Wed, 05/02/2007 - 23:30
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Hi,


The Qos - Policing Support for GRE Tunnels feature allows you to set the Differentiated Services Code Point (DSCP) and IP precedence values on Generic Routing Encapsulation (GRE) tunnel packets.


This feature is essential for MPLS carriers to offer QoS on Multicast VPN services. MVPN uses GRE tunnels between PE devices, and multicast packets are placed in GRE tunnels for transmission across the MPLS core network. The Qos - policing SUPPORT for GRE Tunnels feature allows users to configure QoS for the GRE tunnel packets. Once the GRE packets accurately reflect the QoS markings of the underlying multicast packets, they may be queued accordingly as they travel across the core nodes.


In your case I believe that the underlying network is Internet and not MPLS. In this case there is no sense in using QOS since you have no guarantee of delivery !



Regards

Bjornarsb

paolo bevilacqua Thu, 05/03/2007 - 03:52
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Do not assume that since it's the Internet there is no QoS. More and more providers are implementing QoS and sometime the new devices installed do that automatically.

It is always worth to try if using the correct DSCP value there is a benefit for voice.


paolo bevilacqua Thu, 05/03/2007 - 11:00
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Hi Todd,

if you internet links are slow and lossy your best choice is to implement the ILBC codec available in the most recent IOS. Depending on you application you may need to do transcoding and this can be a little complicated as well.


Hope this helps, please rate post if it does!

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