====== 5. Routing Behavior ======

===== 5.1 Purpose =====

This document defines how MTRP learns, stores, and selects routes.

===== 5.2 Direct Neighbor Reachability =====

A destination that is reachable directly on a registered local path MUST be treated as a neighbor candidate.

Direct-neighbor state MUST be stored in the neighbor table.

===== 5.3 Learned Route Reachability =====

A route advertisement received from another node MAY create or update a learned forwarding candidate.

Learned candidates MUST be stored in the forwarding table.

Multiple forwarding candidates for the same destination MAY exist simultaneously.

===== 5.4 Route Resolution Order =====

For unicast traffic, MTRP MUST resolve egress in the following order:

  - explicit valid egress path, if already present
  - direct-neighbor resolution
  - forwarding-table resolution
  - unroutable result if no valid candidate exists

===== 5.5 Metric Behavior =====

Metrics are additive across relayed advertisements.

A directly reachable destination SHOULD have a lower metric than the same destination learned through one or more relays, assuming all constituent path metrics are positive.

===== 5.6 Preferred Route Population =====

Preferred-route entries are populated at send-time route selection.

Preferred-route entries are not required to be created when a learned route is first stored.

As a result, the preferred route table MAY remain empty even when the forwarding table contains valid learned routes.

===== 5.7 Practical Interpretation =====

If all participating nodes are direct neighbors of one another, MTRP MAY still learn indirect candidates through re-advertisement. In such a topology, direct routes SHOULD normally be preferred over indirect candidates with worse metrics.