Architecture Atlas

company · explainer · draft

SpaceX / Starlink (LEO access)

Starlink is a LEO NGSO broadband access network: user terminals ↔ satellites ↔ gateway earth stations and/or optical inter-satellite links (laser mesh), with Community Gateways for local ISP redistribution. Public depth is FCC filings + Progress materials — not a hyperscaler DC Clos or published terrestrial BGP TE paper.

In one sentence. Teaching Starlink’s published access/space-segment design without inventing ISL TE algorithms, terrestrial anycast PoP maps, or treating PeeringDB ASN notes as SpaceX primary.

Why it exists

Deliver Internet where fiber is scarce via phased-array user links, Ka gateway links, and optical ISLs for continuity (FCC Gen1 technical narrative; Progress Report 2025; Community Gateway product page). This is access + space segment teaching — cross-link Clos pages only as contrast, not as Starlink disclosure.

Visual walkthrough

Walkthrough

User terminal → constellation → gateway

Published access path themes from FCC Gen1 narrative and Progress/Community Gateway materials. ISL algorithms and terrestrial BGP TE remain unknowns.

Step 1 / 3
User linkUser terminalLEO satelliteOptical ISL meshKa gatewayLocal ISP / Internet

The user terminal links to LEO satellites (phased-array / Ku user-link themes in Gen1 filing materials). This is access RF — not a DC Clos.

Control vs data plane

Control plane

Filings describe onboard digital processing / beam steering themes. No primary SpaceX document in the curated set discloses a terrestrial BGP anycast strategy or WAN TE controller comparable to Cloudflare posts.

Data plane

User terminal ↔ satellite (Ku user links in Gen1 narrative) ↔ optical ISL mesh and/or Ka gateway earth stations ↔ terrestrial Internet. Community Gateway traffic transits the laser mesh to dedicated Ka gateways; local providers do last mile (Progress 2025 + product page).

Request / packet path

North–south

Subscriber → user terminal → constellation → gateway / Community Gateway handoff → public Internet. Gen2 authorization (FCC-22-91) grants in-part authority for up to 7,500 Gen2 satellites at specified altitudes/inclinations — cite the order date; do not invent “today” satellite counts from outdated filings alone.

East–west

Optical ISLs interconnect satellites (filings note optical links are not wire/radio under FCC’s cited framing). Exact ISL routing algorithms remain known unknowns.

Scaling & math

Progress 2025 cites >100 gateway sites in the US alone and 1,500+ antennas — marketing/progress figures, not a full global inventory. AS14593 on PeeringDB is secondary until corroborated by SpaceX primary text.

When it breaks

  • Service degraded when gateway connectivity is impaired.

    Cause. Ka gateway / earth-station path unavailable; laser mesh may still need gateway egress.

    Mitigation. Progress materials emphasize gateways and laser mesh — do not invent unpublished failover TE.

  • Path continuity depends on ISL behavior under failure — internals unpublished.

    Cause. Exact ISL routing / capacity / failure handling not in public primaries reviewed.

    Mitigation. Keep ISL algorithms in Known unknowns; cite filings only for existence themes.

  • Local ISP redistribution fails after Community Gateway handoff.

    Cause. Last-mile provider path issues beyond Starlink space segment.

    Mitigation. Community Gateway product: local providers do last mile — separate those failure domains.

Misconceptions

  • “PeeringDB AS14593 is a SpaceX primary ASN disclosure.” — Secondary until SpaceX-owned primary text confirms.
  • “FCC Gen1 filing satellite counts are today’s live constellation inventory.” — Cite order/filing dates; Gen2 authority is separate (FCC-22-91).

Reference expression

Primary: FCC Gen1 tech attachment; FCC-22-91 Gen2 order; Progress Report 2025; Community Gateway page. Secondary: PeeringDB AS14593 (labeled). review: draft.

Standards & sources

Known unknowns

  • Exact ISL routing algorithm, failure handling, and capacity per link.
  • Terrestrial backbone / IX peering design, anycast, and DNS steering — not documented at Cloudflare-like depth.
  • Authoritative primary ASN statement from SpaceX (PeeringDB AS14593 is secondary).
  • Full global gateway inventory and non-US counts beyond progress/marketing summaries.
  • Direct-to-Cell network architecture details beyond high-level progress mentions.
  • User-terminal ↔ constellation MAC/scheduling internals.

Check yourself

  1. Starlink as published is primarily…

    • A hyperscaler DC Clos paper like Jupiter
    • A LEO NGSO broadband access network (terminals ↔ satellites ↔ gateways/ISLs)
    • Azure Front Door VIP rings
    • Airbnb SmartStack

    Answer: A LEO NGSO broadband access network (terminals ↔ satellites ↔ gateways/ISLs). FCC + Progress: LEO access + space segment.

  2. FCC-22-91 (as cited) authorizes in part…

    • Unlimited unlabeled PoP maps
    • Up to 7,500 Gen2 satellites at specified altitudes/inclinations
    • AS13335 anycast
    • Service Fabric for all Azure

    Answer: Up to 7,500 Gen2 satellites at specified altitudes/inclinations. Cite the Gen2 order; do not invent live counts.

  3. Community Gateway traffic as published…

    • Bypasses space segment entirely
    • Transits the laser mesh to Ka gateways; local providers do last mile
    • Uses only Netflix OCAs
    • Requires invented terrestrial anycast TE

    Answer: Transits the laser mesh to Ka gateways; local providers do last mile. Progress + Community Gateway product pages.

  4. AS14593 from PeeringDB should be treated as…

    • SpaceX primary forever without caveat
    • Secondary until corroborated by SpaceX primary text
    • Proof of ISL TE algorithms
    • Identical to AS8075

    Answer: Secondary until corroborated by SpaceX primary text. Phase 7 ship rule: ASN secondary until primary.