Since May 9th, 2005, CAIDA has produced a data set that maps IPv4 prefixes (and later also IPv6 prefixes) to the AS (Autonomous System) originating that prefix into the global BGP routing system, as observed via a single BGP data collector of the Route Views data collection system. We have called this data set “RouteViews Prefix to AS”. We used CAIDA’s straighten_rv script to filter the RIB (routing information base file used as input data. We will discontinue this data set on December 31st, 2022 an replace it with a new more complete data set that we call CAIDA’s Prefix-to-AS data set.

CAIDA will use the BGPStream software package (and in particular the bgpview library) to include data from all available BGP collectors from both of the primary global publicly available collection systems: Route Views and RIPE NCC Routing Information Service. We will backfill Prefix-to-AS data to 2000. As part of this transition, CAIDA will no longer use straighten_rv to preprocess AS paths. We will create two files: an annotated file with all the data observed in BGP, and a simple file that filters out data of no interest to many researchers as described below.

Annotated files. The annotated file will include information about the stability and visibility of prefixes by different peers and collectors. Individuals who wish to produce a more refined mapping can fairly easily filter this data. The table below compares the older “Routeviews2” (a single Route Views collector) and the new annotated CAIDA Prefix-to-AS dataset (all collectors from both RIPE RIS and Route Views) for 1 June 2022. Most (99.6%) ASes and (87.2%) prefixes appeared in both datasets. Note that multiple ASNs announced the prefix 0.0.0.0/0, we exclude it since it covers the entire IPv4 address space.

Simple files. The simple file will exclude very large prefixes, e.g., with mask lengths < 8, private addresses (RFC 1918), or prefixes announced exclusively by reserved ASNs (Special-Purpose ASN). The resulting simple prefix-to-ASN mapping covers 99.7% of the address space captured by the annotated file. In the table below (also reflecting 1 June 2022), 0.94% of prefixes and 0.42% of addresses had an additional origin AS that was not also observed in the Routeviews2-only dataset. This reflects the expanded visibility of more collectors and peer. 4.92% of CAIDA’s prefixes and 1.82% of addresses were not covered by Routeviews2-only prefix2as. Overall the combined data set provides visibility of 5.86% of prefixes and 2.24% of addresses not covered by routeviews2-only.

CAIDA’s Prefix to AS “simple” (99.7% of addresses observed in annotated files)

You can find the new CAIDA Prefix-to-AS Mapping Data Set here.