CONCEPT Cited by 2 sources
Autonomous System (AS)¶
An Autonomous System is an administratively-unified network
that speaks BGP with its neighbors under a
single routing policy. Each AS is identified by a globally-
unique AS Number (ASN) — 16-bit (e.g. 8048) or 32-bit
(e.g. 269832) — allocated by one of the five Regional
Internet Registries (ARIN, RIPE NCC, APNIC, LACNIC, AFRINIC).
See Wikipedia's Autonomous system (Internet) for the canonical definition.
Unit of BGP routing¶
BGP speaks at the AS granularity, not the router granularity: advertisements carry an AS path of ASNs, not router IDs; policy (accept / deny / prefer / prepend) is applied at the AS boundary. This is why route-leak attribution and forensics operate on ASN pairs — "AS8048 leaked AS21980's routes to AS52320" — and why tools like BGPKIT monocle are built around ASN-pair queries.
Relationship types between ASes¶
The two primary relationship types are:
- customer→ provider — one pays the other for transit
- peer↔peer — settlement-free traffic exchange
These drive export policy and are the constraints that valley-free routing emerges from.
Examples in the wiki¶
- AS8048 — CANTV, Venezuela's state-run ISP; leaker in the 01-02 route-leak event.
- AS6762 — Sparkle (Telecom Italia Sparkle); Tier-1 transit-free network.
- AS52320 — V.tal GlobeNet; Colombian network service provider.
- AS21980 — Dayco Telecom; Venezuelan originator whose prefixes were leaked.
- AS13335 — Cloudflare.
Seen in¶
- sources/2026-01-08-cloudflare-a-closer-look-at-a-bgp-anomaly-in-venezuela — four ASes (AS8048, AS6762, AS52320, AS21980) with distinct roles drive the entire forensic argument.
- sources/2025-06-20-cloudflare-how-cloudflare-blocked-a-monumental-7-3-tbps-ddos-attack — attack traffic sourced from 5,433 ASes across 161 countries; ASNs as the unit of traffic-origin attribution.