AS4

AS4 is a legacy single-digit allocation registered under ARIN to the University of Southern California's Information Sciences Institute (ISI), one of the most historically significant institutions on the Internet. ISI was the institutional home of Jon Postel — RFC Editor and director of IANA for roughly three decades until his death in 1998 — ran IANA until ICANN was created in 1998, continued operating the RFC Editor until 2009, developed DNS (Paul Mockapetris), and operates the DNS B-root server. That weight is historical; the current holder is USC/ISI, and AS4 still actively announces about 47 IPv4 prefixes and 7 IPv6 prefixes (~67,000 IPv4 addresses), importing from AS226 (Los Nettos) and announcing to AS-LOSNETTOS. For triage, AS4, AS226 (Los Nettos), and AS47 (USC main campus) form the USC/ISI cluster; encountering AS4 indicates ISI research network space behind Los Nettos. The ARIN RegDate of 1984-02-22 is the registry date and may be an early refresh. RPKI is weak (one valid IPv6, one invalid IPv4, remainder unknown) — a hygiene note. No notable public abuse signal was found as of June 2026.

Operator

University of Southern California / Information Sciences Institute (ARIN OrgId USC-32, Marina del Rey, CA) [Confirmed] — ARIN RDAP

Country / RIR

US, ARIN [Confirmed]

Allocated

ARIN ASN RegDate 1984-02-22 (registry date; may be early refresh; org RegDate 1984-02-22) [Confirmed for shown date]

Org status

active — isi.edu

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-06-07; clean research network — bgp.he.net

Network & routing

Network type

research / education [Confirmed]

Size

~47 IPv4 prefixes, 7 IPv6 (~67,072 IPv4 addrs) — bgp.he.net / bgp.tools (2026-06)

Routing/peering

1 IX; actively announcing; imports from AS226 (Los Nettos), announces to AS-LOSNETTOS; RPKI valid 1 (IPv6), invalid 1 (IPv4), remainder unknown — bgp.he.net

Notable usage

[historical] USC/ISI — home of Jon Postel; ran IANA until ICANN (1998); ran the RFC Editor until 2009; developed DNS (Mockapetris); operates DNS B-root. [current] ISI research network routed behind Los Nettos — isi.edu

Related ASNs

AS226 (Los Nettos — upstream/peer); AS47 (USC-AS, USC main campus, OrgId USC-6 — sibling) [Confirmed]

Analyst note

Single-digit ASN with outsized historical weight (Postel/IANA/RFC Editor/B-root); still actively routed by ISI behind Los Nettos. AS4 ↔ AS226 ↔ AS47 form the USC/ISI cluster.