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ASR9000 QoS

I have my first QoS policy to write for ASR9000 running MPLS VPN, and have a few questions.

The requirement is to protect router control plane traffic on the egress links (PE-PE/P) from user traffic for a throughput test. Currently, if I load up the router with simulated customer traffic from a test set not surprisingly I can get BFD etc to run into problems when the PE-P egress load approaches 100% utilisation.

I need to protect ISIS, BGP, LDP and BFD from the user traffic.

So far I understand ISIS uses CLNS so falls outside of MQC and IP QoS, this is prioritised by an internal process on the router. Do I have to do anything else to protect the ISIS traffic?

Can I mark BGP, LDP and BFD within the appropriate configuration sections in the router, or do I have to use ACL's class-maps etc to mark packets generated by the router?

I'll be plowing through the QoS guide and the documents on this forum again today, any head up info appreciated.


  • XR OS and Platforms
New Member

Re: ASR9000 QoS

Hi Andy,

For routing protocols like ISIS, BGP, OSPF and LDP for MPLS you dont need to set the QoS class manually, this is done automatically. Nevertheless, in your outgoing service policy you still need to do the bandwidth allocation for that. You implement this by matching on EXP 6 and EXP 7 if you run MPLS on the interface or by matching on PREC 6 and PREC 7 on interfaces running plain IP. After matching the control traffic you allocate e.g. a minimum interface bandwidth of 1%, depending on how much control traffic you expect. Normally on Gig and 10Gig interfaces, 1% is sufficient IMHO.

For BFD, see the following document:

In this case you need to set and match the priority bits manually on the echo packets.




ASR9000 QoS

Hi Florian,

Thanks, as the IP based protocols have the predence and EXP bits set by default, it will make this easier, I think this is the same as in IOS.

But I still need to define an egress queue policy right? I must have to do that as in testing without any QoS when I try to forward 10G of traffic across the router BFD breaks on the PE-PE links.

There is an excellent document on BFD in the documents section on this forum, I've used information in that as the basis for my policy, hopefully it will get tested this afternoon.