QoS needed for IP routing / Network Control traffic?

[brettlarkins]

When defining a QoS scheme for your network and carving up bandwidth on your router interfaces, do you need to create a classmap to specifically match IP routing protocol traffic, and then account for that traffic in your policy maps?  

I recently saw this being done in someone elses network, but always thought that Network Control (CS6) traffic was automatically protected and given a certain level of "priority"...???

[Dennis Mink]

CS6 is considered critical data, which would include routing traffic:

https://www.cisco.com/en/US/technologies/tk543/tk759/technologies_white_paper0900aecd80295aa1.pdf

[brettlarkins]

Hi Dennis,

Thanks for the prompt reply... Should I be creating a match statement for CS6, and creating a Bandwidth allocation for that traffic in my policy-maps?

[Francesco Molino]

Yes i would highly recommend to take this cs6 tagged traffic into consideration in your policy-map and assign a percentage of remaining bandwidth. If should be 5% or 10% maximum but won't use the 10%

[Joseph W. Doherty]

"I recently saw this being done in someone elses network, but always thought that Network Control (CS6) traffic was automatically protected and given a certain level of "priority"...???"

Yes and no. This is a "it depends" kind of question. Much depends on whether the CS6 traffic is source on the same devices or whether it's transit traffic.

If the router is generating the CS6 marked traffic, it may also be providing it PAK priority. It depends on the platform, if the packet has PAK priority, how the packet will be treated on interface egress. More information might be found in this old white paper: https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-congestion-management-queueing/18664-rtgupdates.html#packtag. You might also find this old thread of interest: https://community.cisco.com/t5/routing/bgp-pak-priority-and-qos/td-p/1397656.

Personally, if I feel the need to insure what bandwidth CS6 traffic obtains on an interface, my interface egress QoS policy will be configured to deal with it. (BTW, this may be especially important for transit CS6 traffic, i.e. traffic not generated on that device.)