AS556

AS556 is a legacy 16-bit autonomous system number registered under ARIN, allocated 1989-12-19 to the University of Southern California's Information Sciences Institute (USC/ISI), a research institute headquartered in Marina del Rey, California. The AS name, CALREN-AS, ties it historically to CalREN, the California Research and Education Network — a program that today operates under CENIC, a separate nonprofit consortium. Cross-checking CENIC's own public materials (its AS-numbers list, peering policy, and Settlement-Free Interconnection policy) turns up no reference to AS556 by number; CENIC's actively documented ASNs are AS2152 and AS2153. That gap means the historical CALREN name should not be read as confirmation that CENIC currently operates AS556. Present-day routing data reinforces the dormancy picture: RIPEstat reports zero currently-announced IPv4 or IPv6 prefixes and zero observed BGP neighbors for AS556, and CAIDA's customer cone for the ASN is a singleton — itself, with no downstream prefixes or addresses. One anomalous, isolated routing event appears in RIPEstat's routing-status feed: a single APNIC-block prefix, 103.102.27.0/24, briefly originated by AS556 around 2026-04-19, seen by zero of ~327 RIS peers — inconsistent with a legitimate current CalREN/USC-ISI announcement and more consistent with a route leak, misconfiguration elsewhere, or stale collector data than with active use of the ASN. No public abuse signal was found as of 2026-07-11.

Operator / registrant

USC/Information Sciences Institute (ARIN org handle USI-11), 4676 Admiralty Way, Suite 1001, Marina del Rey, CA [Confirmed] — https://whois.arin.net/rest/org/USI-11

Country / RIR

US, ARIN (16-bit block resource 1-1876, "Assigned by ARIN") [Confirmed] — https://rdap.arin.net/registry/autnum/556

Allocated

1989-12-19 — read from the RDAP autnum object's TOP-LEVEL events[] (eventAction "registration"), not the nested WP8-ARIN POC entity events (1987-12-21 registration / 2022-11-21 last-changed, correctly excluded as decoy contact-record dates); last changed 1996-06-10 (top-level) [Confirmed — corroborated independently by two angles, A2 and A3] — https://rdap.arin.net/registry/autnum/556

Org status

Unknown whether USC/ISI still actively operates AS556 in any capacity; ARIN org record (USI-11) carries no explicit status flag and was last updated 2012-10-10 with no indication of revocation [Unknown] — https://whois.arin.net/rest/org/USI-11

Website

no operator-published page specific to AS556 was found; CENIC (cenic.org) is the modern CalREN operator but does not confirm AS556 as one of its current ASNs [Unknown] — https://cenic.org/pages/as-numbers

Abuse contact

a named individual, Walt Prue (ARIN POC handle WP8-ARIN), at a University of Southern California address; his personal mailbox is not reproduced here. ARIN flags this POC as unvalidated since 2023-11-21 [Confirmed for the POC identity; Likely stale/unvalidated] — RIPEstat abuse-contact-finder for resource=556; https://rdap.arin.net/registry/entity/WP8-ARIN

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-07-11 — not in Spamhaus ASN-DROP, no NANOG archive mentions of AS556 or CALREN in an abuse/hijack context

Network & routing

Network type

historically associated with the CalREN research-and-education network name; registrant is a research institute (USC/ISI), not a commercial ISP; whether AS556 is an actively operated production network today is Unknown [Likely] — https://rdap.arin.net/registry/autnum/556

Routing/announcements

not currently announced — 0 IPv4 and 0 IPv6 prefixes in RIPEstat's announced-prefixes window (2026-06-27 to 2026-07-11); 0 of 327 (v4) and 0 of 322 (v6) RIS peers seeing it; 0 observed neighbours [Confirmed] — RIPEstat as-overview/announced-prefixes/routing-status for resource=556

Routing anomaly

RIPEstat routing-status logs a single first/last-seen event, prefix 103.102.27.0/24 (an APNIC-allocated block) originated by AS556 on 2026-04-19, seen by 0 RIS peers — flagged as an inconsistency (route leak, third-party misconfiguration, or stale cache), not treated as a legitimate current CALREN-AS announcement; not independently corroborated on bgp.he.net or bgp.tools [Confirmed as a logged event; Likely as anomaly interpretation] — RIPEstat routing-status query for resource=556

CAIDA AS rank / cone

rank 79,459; customer cone = 1 ASN (itself), 0 prefixes, 0 addresses; clique_member false; seen false [Confirmed] — CAIDA ASN Ranking dataset, asn=556

RPKI

not assessable — AS556 announces no prefixes, so there is no ROA to validate against; RIPEstat's rpki-validation endpoint was skipped (requires a --prefix) [Confirmed] — RIPEstat rpki-validation response for resource=556

Peering policy

Unknown for AS556 specifically; CENIC (present-day CalREN operator) publishes a general peering policy and Settlement-Free Interconnection policy, but neither names AS556, and AS556 is absent from CENIC's public AS-numbers page (which lists AS2152/AS2153)

[Unknown] — https://cenic.org/network/peering, https://cenic.org/pages/as-numbers

Notable usage

third-party BGP collector bgp.he.net reportedly shows AS556 with a single observed peer (AS137023, a Bangladesh-based network) and bogon-flagged origination activity — third-party observational data, not operator-confirmed, treated as low-confidence context rather than fact

[Likely, low confidence] — https://bgp.he.net/AS556

ASN / name

AS556 / CALREN-AS [Confirmed] — https://rdap.arin.net/registry/autnum/556

Status

"active" per ARIN RDAP status field, but current operational/routing activity is separately Unknown (see below) [Confirmed for the RDAP flag] — https://rdap.arin.net/registry/autnum/556

Analyst note

dormant/legacy academic ASN with a historically evocative name (CalREN) but no first-party confirmation of present-day operation by USC/ISI or CENIC; routing data across RIPEstat and CAIDA agree on zero current announcements aside from one unexplained, low-confidence historical anomaly.