Summary

  • RFC 9914 defines DAO Projection: an RPL Root, or an external controller acting through the Root, can install Projected Routes that need not follow the main DODAG.
  • A PCE can calculate paths against topology and constraints such as path length, battery state and reservable buffers; the Root then projects the selected result into the RPL domain.
  • The mechanism covers Storing-Mode and Non-Storing-Mode P-Routes, hybrid situations, acknowledgement, maintenance, expiry, replacement and removal.
  • The result is not a promise that every projected path is shorter or safer. It is a route-state design in which central computation and lifecycle assurance matter as much as path quality.

RFC 9914 is an IETF Proposed Standard published in April 2026. It updates RFC 6550, RFC 6553 and RFC 8138. The base RPL architecture remains the DODAG: the principal RPL Instance is expected to pre-exist in Non-Storing Mode, while projected routes can create hybrid mode situations. In Storing Mode, projected state is installed through the relevant nodes; in Non-Storing Mode, the source-routing representation and its projected state follow the rules of the specification. Operators must validate the interaction rather than assume that one mode erases the other.

The important shift is control-plane responsibility. A PCE may use policy and constraints, not merely hop count, to compute a directional route. The Root signals a Projected DAO toward selected participants. Nodes acknowledge installation where required, maintain the state, and later process refresh, expiry, replacement or removal. A separate, higher-precedence RIB can let projected state win over ordinary alternatives. That precedence is useful for a point-to-point shortcut, a protection path, or a route interleaved into a 6TiSCH Track, but it can also make stale state authoritative until it is withdrawn or expires.

This is RPL source routing and RPL option processing, bounded by RFC 6553 and compressed by RFC 8138 where applicable; it is not SRv6. Nor is it a universal optimization. A path can be longer, less robust or more expensive under a different constraint set, and a partial installation can produce behavior unlike the PCE's complete graph. The decision therefore belongs to the operator's state-assurance process, not only to the path calculator.

Sources

Claim-to-RFC evidence ledger

Claim Evidence
DAO Projection and P-Routes RFC 9914, Abstract and Sections 1–6
RPL DODAG foundation RFC 6550
RPL information signalling RFC 6553
Compressed RPL routing header boundary RFC 8138
Tracks and constrained-network context RFC 9030
Recovery-graph and adjacent-coverage context RFC 9912
Reliability and low-latency use cases RFC 9450