How Does MPLS-TE Interact with QoS

MPLS Traffic Engineer is sometimes promoted as a QoS solution (it seems bandwidth calendaring is a permanent obsession of some networking engineers, and OpenFlow is no more a solution than MPLS-TE was ;), but in reality it’s pretty hard to make the two work together seamlessly (just ask anyone who had to implement auto-bandwidth MPLS-TE in a large network).

Not surprisingly, we addressed the topic during our MPLS Tech Talk (now part of MPLS Essentials webinar).


  1. One more automated mechanism is to used class-based tunnel selection (called PBTS I believe in newer XR) and class-based forwarding in Junos. Each will map incoming traffic to a specific LSP based on class of service. Typically you should use auto-bandwidth and also use different setup/hold priorities along with preemption to ensure the high priority traffic always takes precedent at an LSP level. Below that you would still make sure EXPs are marked correctly so per-hop QoS can drop what it needs.

    DS-TE makes your interface-level QoS configuration and LSP configuration congruent. The IGP will advertise specific amounts of bandwidth as configured in the QoS configuration for each hop along the network. So if your lower path is configured for 0% BE and 100% EF, the data LSP would never traverse it during a failure. I've rarely seen anyone implement DS-TE in a production network.
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