QoS Shaping Enforcement

[whistleblower14]

Hi all,

for my better understanding and in order to be able to get the configuration right in the end, I´d like to hear your opinions and recommendations about the following question!

Let`s assume you`ve in front of an SD-WAN capable device (cEdge Router) also another CPE-Router which terminates a MPLS Access Line - e.g. refered in the attachment!
As far as I understand, the QoS Shaper should be relocated from the MPLS CE router back to the cEdge Router so that the QoS is handeled on the edge, correct?
Do you all see that the same way or not? If yes - how should the QoS configuration look like to achive the results which would be needed to get no problems on the 20M line?
MPLS CE-Router QoS Configuration:

policy-map PM-CLASSES
 class CLASS-VOICE
  priority
  police cir percent 25
  set cos 5
 class CLASS-SIGNALING
  bandwidth percent 25
  set cos 3
 class class-default
  bandwidth percent 50
  random-detect
  set cos 0
  queue-limit 1000 packets
!
policy-map PM-SHAPING
 class class-default
  shape average 20000000
  service-policy PM-CLASSES
!
interface FastEthernet0/0
 bandwidth 20000
 service-policy output PM-SHAPING

Should/Could the same parameters be used or should they be set to a lower value as on the MPLS WAN Interface, is there anything other e.g. Hold-Queue`s, etc. that has to be kept in mind?

[Flavio Miranda]

Hi

 s far as I understand, the QoS Shaper should be relocated from the MPLS CE router back to the cEdge Router so that the QoS is handeled on the edge, correct?

Answer:  Incorrect.

 QoS is, for sure, an end-to-end concept and therefore, needs to be configured across any device in between. But, you are missing the fact that, SDWAN is divided in two parts:  Underlay and Overlay.  From the QoS point of view, only the Overlay matters and the Overlay dont care about MPLS. You could be using any technology. Imagine that you are connecting your cEdge at your home ISP. Could you setup QoS on the broadband router that they provide to you? Dont think so.

  Keep in mind that when you stablish SDWAN you are creating a tunnel over the MPLS network.

 Take a look on this paper:

https://www.cisco.com/c/en/us/support/docs/routers/vedge-router/213408-implement-qos-in-cisco-sd-wan.html 

[whistleblower14]

@Flavio Mirandathank you very much for your respond and input on that topic!

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@Flavio Miranda wrote:

QoS is, for sure, an end-to-end concept and therefore, needs to be configured across any device in between. But, you are missing the fact that, SDWAN is divided in two parts:  Underlay and Overlay.  From the QoS point of view, only the Overlay matters and the Overlay dont care about MPLS.

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please allow me to explain my thoughts about this in more detail... because I´m not sure if I`d agree with that you`ve said

Due to the fact that the ToS values are taken over in the respective IPsec Header fields it`s in my opinion important to consider also the underlay - more precisely when the underlay transport is an MPLS Network!

As you´ve mentioned QoS should be End-to-End to function properly/at all, so without the necessary reservations and prioritization in the underlay everthing configured for QoS in the overlay will not bring the desired added value and also no advantage in comparison to an internet connection - which you´´ve also shown as an example!

For me it`s interessting to know and understand what will e.g. happen, when the ISP MPLS CE-Router has an LLQ configured and drops traffic rigorous - and how I can avoid any problems and facilitate the troubleshooting if performance issues occur!
I think this topic is not only relevant for Cisco Viptela and would argue that all (SD-WAN) overlay solutions have to deal with that