I’ve recently taken a closer look at RIFT(Routing in Fat Trees) protocol.

Some details below.

Saying about pros of the protocol I dare to quote appropriate draft-ietf-rift-rift with my personal comments.

So, the protocol:

  1. Deals with no configuration, fully automated construction of fat-
    tree topologies based on detection of links.

    Undoubtable, Zero Touch Provisioning looks fancy in this case. Probably, it beats one of the main benefit of the controller based solutions such as Cisco ACI.

  2. Minimizes the amount of routing state held at each level.

    Standard solutions were becoming to be unscalable for huge fabrics and something specific and optimized for CLOS architectures was needed.
    Hyperscalers should be satisfied, but I guess they are deploying their own customized approaches.

  3. Automatically prunes and load balances topology flooding exchanges
    over a sufficient subset of links.

  4. Supports automatic disaggregation of prefixes on link and node
    failures to prevent black-holing and suboptimal routing.

    What a nice idea, it's absolutely clear and simple.

  5. Allows traffic steering and re-routing policies.

  6. Allows loop-free non-ECMP forwarding.

    After all, It'd a solvation for restore and maintenance procedures.

  7. Automatically re-balances traffic towards the spines based on
    bandwidth available.

RIFT: Routing in Fat Trees draft-ietf-rift-rift-12