OLSRv2 Routing

jacquard-olsrv2 (engine ID jacquard.olsrv2.) implements a deterministic OLSRv2-class proactive link-state engine. It preserves the core OLSRv2 shape: HELLO-driven symmetric-neighbor learning, deterministic MPR election, TC-style topology flooding, and shortest-path next-hop derivation over the learned topology database.

The crate is not a wire-compatible RFC 7181 daemon clone. It is a Jacquard engine that consumes Observation<Configuration>, advances only during router-owned synchronous rounds, and publishes only next-hop route candidates through the shared engine traits.

Engine Overview

The engine owns five pieces of runtime state:

1. one-hop neighbor state learned from HELLO exchange
2. two-hop reachability learned from symmetric neighbors
3. local MPR and MPR-selector sets
4. topology tuples learned from TC advertisements
5. a derived shortest-path tree and best-next-hop table

The router and host own ingress draining, tick cadence, and time attachment. jacquard-olsrv2 consumes explicit ingress through the shared runtime hook and returns router-visible NextHopOnly candidates.

Internally, the engine splits route choice from protocol progression. OlsrPlannerSnapshot carries the route-choice projection used by planning. A pure round reducer owns HELLO and TC expiry, two-hop reachability derivation, MPR selection, SPF refresh, and best-next-hop projection.

A separate pure maintenance reducer owns route-health refresh and replacement decisions. The runtime wrapper is limited to ingress decode, transport emission, and router-facing integration. jacquard-olsrv2 also implements the shared RoutingEnginePlannerModel surface. The simulator executes OLSRv2 planner checks from engine-owned planner seeds instead of building OLSR control-state fixtures itself.

Jacquard-Specific Simplifications

Jacquard keeps the OLSRv2 surface deterministic and auditable:

• one deterministic decay window controls HELLO and TC freshness
• one deterministic MPR election policy is used for all nodes
• link cost is integer-only and derived from shared link observations
• all sets and maps use canonical ordering with no ambient randomness
• no async protocol loop, no host-driver ownership, and no external RFC interoperability layer
• route publication remains router-owned

The result is an OLSRv2-class baseline for comparative routing work rather than a feature-complete NHDP implementation.

HELLO Semantics

Each round, the engine may originate one HELLO message carrying the local originator ID, a monotonically increasing local HELLO sequence number, the current symmetric-neighbor set, and the current local MPR set.

Inbound HELLO processing updates the one-hop neighbor table and the derived two-hop reachability map. A link is treated as symmetric only when the inbound HELLO confirms the local node inside the neighbor’s symmetric-neighbor set. The shared topology observation constrains whether the underlying link is usable. HELLO state alone does not override a failed transport observation.

HELLO state expires when the engine-local hold window passes. Expiry uses Tick, not wall-clock time.

MPR Election

MPR election is deterministic and local. The input surface is the symmetric one-hop neighbors, two-hop neighbors reachable through those one-hop neighbors, and the integer link metric derived from the shared observation model.

The algorithm chooses a minimal covering relay set for the known two-hop neighbors. Ties break first on lower metric cost, then on canonical node order. The elected set is exported only as engine-local control state plus the local HELLO advertisement. It is not promoted into shared core vocabulary.

TC Flooding

TC advertisements carry the originator ID, a monotonically increasing local TC sequence number, and the advertised-neighbor set selected for flooding.

The engine originates a fresh TC when the advertised-neighbor surface changes or when the local topology state needs refresh. Inbound TC processing accepts only strictly fresher sequence numbers per originator, replaces older topology tuples for that originator, and expires stale tuples by the same tick-based hold window.

Forwarding is constrained by MPR-selector state. A node forwards only when the sender has selected it as an MPR and the TC sequence has not already been forwarded for that originator.

Shortest-Path Computation

The topology database is a deterministic set of directed topology tuples. Shortest-path derivation runs over local symmetric edges, accepted TC tuples, and integer link cost derived from the shared link observation.

The shortest-path tree is recomputed when HELLO or TC ingestion changes the topology database. Best-next-hop derivation collapses the tree into one NodeId next hop per reachable destination. Only destinations that advertise support for jacquard.olsrv2. in the shared service surface are eligible for route candidates.

Capability Envelope

The OLSRv2 engine declares the same conservative next-hop envelope used by the other proactive engines:

The engine keeps a full topology graph privately. It does not claim explicit-path visibility at the shared contract boundary.

Route Lifecycle And Maintenance

Planning and admission follow the standard Jacquard route lifecycle. candidate_routes emits next-hop candidates from the projected best-next-hop snapshot. check_candidate validates the candidate against the current snapshot projection. admit_route binds the candidate to router-owned identity. materialize_route installs the active next-hop record.

Maintenance returns Continued while the selected next hop remains valid. It returns ReplacementRequired when the shortest-path table selects a new next hop. It returns Failed(LostReachability) when no route remains.

There is no suffix repair or engine-owned hold mode. Route replacement is the only reconfiguration path.

Restore is router-led. On recovery, the router passes the full MaterializedRoute record back into the engine. jacquard-olsrv2 reconstructs its active route entry from the router-owned backend route record and rebuilds derived SPF state from the current topology and refreshed control tables rather than from an engine-private checkpoint payload.

Comparison Role

jacquard-olsrv2 is the in-tree full-topology proactive baseline. It answers a different question from the batman and Babel engines.

batman-classic and babel are distance-vector gossip baselines. batman-bellman is a topology-enriched BATMAN variant. OLSRv2 is the proactive link-state baseline with explicit topology flooding.

OLSRv2 is the primary comparison point for measuring how much full topology knowledge buys over gossip-style next-hop routing.

Related Pages

• Routing Engines
• Batman Routing
• Babel Routing
• Crate Architecture