feat(moq-net): cost-based cache-aware routing (moq-lite-06 WIP) + route-cost I-D#2179
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feat(moq-net): cost-based cache-aware routing (moq-lite-06 WIP) + route-cost I-D#2179kixelated wants to merge 5 commits into
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… routing
Replace hop count as the routing metric with an accumulated route cost.
The hop chain stays immutable per announcement (loop detection); cost is
the one dynamic routing input:
- ANNOUNCE_BROADCAST (lite-06) carries a cost: a publisher-set base
forwarded unchanged plus a per-link transit accumulated hop by hop.
Absent (older versions, plain publishes) it derives from the hop
count, so default routing orders exactly as before.
- A relay actively carrying a broadcast advertises zero transit
(marginal cost: its upstream path is already paid for), steering
peers onto already-hot routes instead of opening duplicate upstream
pulls.
- ANNOUNCE_UPDATE mutates a live announcement's cost in place, so a
hot/cold flip doesn't ride an Ended+Active pair (which aborts
in-flight subscriptions downstream). Increases hold down 30s and
decreases forward within a 1s tick (dynamic metrics must be coarse
and damped); receivers re-rank after a deterministic per-node jitter
so mutually-preferring peers don't swap simultaneously.
- Links are priced by the dialing side: a connect_api peer entry may be
{host, cost} (0 = free same-datacenter link), declared in SETUP so
the acceptor prices the link identically. Default cost 1 per link.
- Lite06Wip is negotiated via the moq-lite-06-wip ALPN but excluded
from the default version sets; endpoints opt in explicitly
(Versions::with_preferred) until lite-06 ships.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Post-merge fixups after pulling origin/dev: - dev replaced BroadcastState.tracks (HashMap) with the amortized-GC WeakCache; adapt Consumer::is_active to a new WeakCache::has_live() query (the old code iterated .values()). - Add drafts/draft-lcurley-moq-route-cost.md: the IETF I-D for the cost-based routing this branch implements, written as a moqt extension that composes with (and generalizes) draft-lcurley-moq-relay-hops -- base + transit cost, per-link costs in SETUP, the marginal-cost reset for actively-forwarded broadcasts, and in-place cost updates. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Route cost is a strict generalization of relay-hops path selection (it replaces the hop count with an additive weight and defaults back to hop count when absent), and rides the same HOP_PATH machinery, so it belongs in one draft rather than a separate overlapping one. - Delete draft-lcurley-moq-route-cost.md. - Extend draft-lcurley-moq-relay-hops.md: RELAY_HOPS Setup Option now optionally carries a Link Cost; new Route Cost + ROUTE_COST Parameter sections (base + transit, marginal-cost reset, relay forwarding rule, cost updates + damping); Path Selection made cost-primary with hop count as the fallback; Security + IANA (ROUTE_COST 0x40B59) updated. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
API feedback: the Cost cell bolted onto an otherwise-immutable Info was arbitrary — the hop list is announcement metadata too, and the criterion for tearing anything down was never "which field changed" but "did the data source change". An announcement rides a session, so a route update never changes which peer the media comes from; teardown belongs to the data plane (producer dies -> resubscribe), not to metadata. - broadcast::Info now holds one shared, mutable Route (hops + base + transit) replacing the immutable hops field and the Cost cell. Route exposes hops()/contains()/base()/transit()/cost()/set()/set_cost(). - ANNOUNCE_UPDATE is gone from the wire: a repeat Active already carries hops + cost, and the receiver now applies it IN PLACE on the same broadcast — no producer replacement, no aborted subscriptions. The lite-06 wire delta shrinks to the two cost varints on Active. - subscriber: restart_announce (publish-new + retire-old, which tore down in-flight tracks one hop below every route change) is replaced by update_announce (Route::set + damped refresh). A repeat announce whose chain now loops through us retires the broadcast as before. - publisher: the cost tick generalizes to a route tick (lite-05+): it re-announces in place when hops, cost, or activity diverge from what the peer last saw, including lifting/imposing exclude_hop suppression that an in-place hop update can toggle. Hop changes and cost decreases forward promptly; pure cost increases keep the 30s hold-down. - origin restarts now happen ONLY where the active consumer actually swaps (that relay re-announces; downstream applies it in place), so a route change no longer cascades teardowns across the mesh. - e2e: the route-cost test now also proves swap continuity — a cheaper broadcast replaces the active one at the server and the client's in-flight subscription keeps receiving frames from the original producer while its broadcast handle shows the new hops, with no re-announce events. - I-D: Cost Updates becomes Route Updates — re-advertisement is the update mechanism, applied in place; updates MUST NOT interrupt existing subscriptions; the lightweight cost-only message is dropped. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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July 18, 2026 12:20
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What
Replaces hop count as the cluster routing metric with an accumulated route cost, carried on announcements in a new (WIP, opt-in) moq-lite-06 version, specced as an extension of the relay-hops I-D (
drafts/draft-lcurley-moq-relay-hops.md).The core model: a broadcast's announcement metadata is one shared, mutable
Route(hop chain + cost). A repeat ANNOUNCE replaces it in place — same broadcast, same subscriptions, new route. Teardown belongs to the data plane (a producer dying), never to metadata: an announcement rides a session, so a route update can't change which peer the media comes from, only the advertised path/cost beyond it. Origin-level restarts happen only where the active consumer actually swaps; downstream they arrive as in-place updates, so route changes no longer cascade teardowns across the mesh.Why
Routing today is blind to what a link actually costs and to which candidate already carries the media. In a CDN deployment two relays in one datacenter each pull the same broadcast over a metered backbone (the via-sibling route is +1 hop, so shortest-hop routing never picks it), and cross-region ties break by hash rather than toward the peer already streaming it. The parallels are classic: OSPF-style per-link costs, a Babel-style damped dynamic metric, and marginal-cost advertisement for the cache signal.
How
broadcast::Info.route: Route— hops +base+transitin one kio cell shared by every clone.origin::Producer::refresh_broadcastre-ranks a path after a route mutation and restarts only if the winner changed.ANNOUNCE_BROADCASTgains two cost varints (baseforwarded unchanged,transitaccumulated per link). No new message: a repeat Active is the update, applied in place by the receiver. Old versions derive cost from the hop count, so ordering is bit-identical to the current(hops.len(), fnv)key.exclude_hopsuppression that an in-place hop update can toggle. Hop changes and cost decreases forward within a 1s tick; pure cost increases hold down 30s; receivers re-rank after a deterministic per-node jitter so mutually-preferring peers don't swap simultaneously.cluster.connect_apientries may be{host, cost}(0 = free same-DC link), declared in SETUP so both ends price the link identically.moq-lite-06-wipALPN, excluded fromVersions::all()/ALPNS; opt in viaVersions::with_preferred. Transport accept dispatch recognizes any parseable moq ALPN (is_moq_alpn).draft-lcurley-moq-relay-hops: optional Link Cost on the RELAY_HOPS setup option, Route Cost + ROUTE_COST parameter sections, and a Route Updates section — re-advertisement applied in place, MUST NOT interrupt existing subscriptions.Safety
exclude_hop) runs before ranking; a repeat announce whose chain now loops through the receiver retires the broadcast.Tests
Wire round-trips (cost on Active, version gating); model (cost-beats-hops, base cost, refresh promotes/demotes,
is_activelifecycle); real-QUIC e2e: base-cost propagation, link-cost addition, hot flip in place, and route-swap continuity — a cheaper broadcast replaces the active one at the server while the client's in-flight subscription keeps receiving frames from the original producer, its broadcast handle showing the new hops, with zero re-announce events. Full workspace suite green; clippy/fmt/doc clean; the I-D renders end-to-end.Public API (moq-net)
broadcast::Route(new),broadcast::Info { route, origin },Consumer::is_active,origin::Producer::refresh_broadcast,Client::with_link_cost,Setup.link_cost,Versions::with_preferred,is_moq_alpn,lite::RouteCost,Version::Lite06Wip. No separate Cost type, no ANNOUNCE_UPDATE message, nowith_cost_basebuilder.🤖 Generated with Claude Code