=========================================================== Routeviews Prefix-to-AS mappings (pfx2as) for IPv4 and IPv6 =========================================================== * Overview This Dataset contains IPv4/IPv6 Prefix-to-Autonomous System (AS) mappings derived from RouteViews data (http://www.routeviews.org). --------------------------------------------------------------------------- * Creation Process Files are generated with straightenRV using a single BGP table snapshot (that is, a RIB file) provided by RouteViews. In order to avoid truncated or otherwise problematic BGP snapshots, we choose the median-sized BGP snapshot file from all the snapshots available on a given day. For IPv4, we've used two different collectors over time, oix and rv2: - The pfx2as files with "oix" in the name were generated from route-views.routeviews.org (aka route-views.oregon-ix.net) snapshots. The "oix" collector is one of the oldest RouteViews collectors, and it had the most peers until its deactivation in late Mar 2008. - The pfx2as files with "rv2" in the name were generated from route-views2.routeviews.org snapshots. We switched over to "rv2" in late Mar 2008. The "rv2" collector has a slightly different set of peers than "oix", but for prefix-to-AS mapping, the two collectors should be comparable. For IPv6, we use rv6 (route-views6) collector. --------------------------------------------------------------------------- * New File Creation Log We have tried to make it easy for you to set up an automated process to download new pfx2as files as they are produced. The best way to do this is to download the file pfx2as-creation.log once a day. Whenever we provide a new file for download, we add a new line to this log file. Simply download and examine this log file to discover which new files have been added since your last batch of downloads. See the comments in the log file for further details. NOTE: There are two separate log files, one for IPv4 at http://data.caida.org/datasets/routing/routeviews-prefix2as/pfx2as-creation.log and one for IPv6 at http://data.caida.org/datasets/routing/routeviews6-prefix2as/pfx2as-creation.log --------------------------------------------------------------------------- * File Naming The file naming convention is routeviews--.pfx2as.gz For example, a pfx2as file generated from an rv2 snapshot taken on 20080401-0907 would be named routeviews-rv2-20080401-0907.pfx2as.gz The snapshot time is in UTC. --------------------------------------------------------------------------- * Data Format Once unpacked (with gunzip or gzip -d for example), these files can be used directly with CAIDA's ASFinder and various CoralReef tools (such as the t2_convert -R option). For more information about these tools see http://www.caida.org/tools/measurement/coralreef/ The file format is line-oriented, with one prefix-AS mapping per line. The tab-separated fields are * IP prefix * prefix length * AS The AS can be a single AS number, an AS set (e.g. {32,54} ), or a multi-origin AS (e.g. 10_20 ). From the documentation of AS links files (http://www.caida.org/data/active/ipv4_routed_topology_aslinks_dataset.xml), which use pfx2as files for mapping to ASes: In all places where an AS number can appear in this file format, there can also be an AS set or a multi-origin AS (MOAS). An AS set is a valid component of BGP AS paths. They are usually printed as a list of comma-separated AS numbers enclosed in curly braces; for example, {32,54}. In this file format, AS sets are printed without the curly braces: 32,54. AS sets will never have spaces around the comma separator. A multi-origin AS occurs when a given BGP prefix is announced by more than one AS. Suppose some prefix 10.0.0.0/8 is announced in the BGP table by both AS 10 and AS 20. Then an address in that prefix, like 10.0.0.1, will map to both AS 10 and AS 20. This is indicated by using the pseudo AS number 10_20. If AS 30 also announces that prefix, then you would see 10_20_30. If the AS set {32,54} also announces the prefix, then you would see 10_20_30_32,54 where the grouping is AS 10, AS 20, AS 30, and the AS set {32,54}. ========================================================================= NOTE: The file format changed slightly beginning with the 2010-10-27 prefix-to-AS file. Previously, ASes were listed in sorted order in MOASes (for example, we said "10_20_30" and never "30_10_20"). Now, we sort the ASes according to their frequency of appearance as an origin AS in the source BGP table. For example, suppose 10.0.0.0/8 is advertised by the ASes 10, 20, and 30, and suppose 7 RouteViews peers saw AS 10 as the origin AS, 4 saw AS 20 as the origin AS, and 29 saw AS 30 as the origin AS. Then the MOAS recorded in the prefix-to-AS file will be 30_10_20, according to descending frequency of appearance as an origin AS. If there is a tie in frequency, then we sort by lexicographical order. With the new sorting order, users who wish to choose "the best" mapping for simplicity (with full understanding of the caveats) can simply pick the first listed AS. ========================================================================= # $Header: /cvs/Production/datasets/pfx2as/README,v 1.6 2013/04/16 00:56:13 youngh Exp $