Index of /datasets/topology/ark/ipv4/as-links

Icon  Name                         Last modified      Size  Description
[DIR] Parent Directory - [TXT] README.txt 01-Feb-2014 22:27 7.0K [TXT] aslinks-creation.log 19-May-2020 14:53 2.8K [   ] caida_aua.pdf 01-Feb-2014 22:28 12K Acceptable Use Agreement [   ] merge-warts-aslinks 03-Feb-2014 13:35 14K [DIR] team-1/ 03-Jan-2020 14:48 - [DIR] team-2/ 07-Feb-2018 20:48 - [DIR] team-3/ 08-Feb-2018 19:14 -
                        IPv4 Routed /24
               Autonomous System (AS) Links Dataset

  *** NOTE: Please read the Data Format section for important information
  ***       not covered by the AS links web page (all other text in this
  ***       README is the same as the web page).

This dataset is useful for studying the topology of the Internet at the
level of Autonomous Systems (ASes), which are approximately network(s)
under a single administrative control. ASes are an important abstraction
because they are the "unit of routing policy" in the routing system of the
global Internet. ASes peer with each other to exchange traffic, and these
peering relationships define the high-level global Internet topology. For
the purposes of analysis, these peering relationships are represented with
an AS graph, where nodes represent ASes and links represent peering

The IPv4 Routed /24 AS Links Dataset provides regular snapshots of AS links
derived from the ongoing traceroute-like IP-level topology measurements
that make up our IPv4 Routed /24 Topology Dataset [1]. We have collected this
IP-level topology data since September 2007 using our next generation
Archipelago (Ark) measurement infrastructure. For AS links data prior to
September 2007, please see the related Skitter AS Links Dataset [2] (skitter AS
links are no longer being collected).

Data from the IPv4 Routed /24 Topology Dataset are processed by using
RouteViews BGP data to identify the Autonomous System (AS) associated with
each responding IP address and collapsing the original probed IP paths into
a set of links between ASes. The process of converting IP addresses into
Autonomous Systems involves potential distortion due to: 

    *  No AS mapping for the IP address: some IP addresses appear in
       topology probes but are not advertised by any AS;
    *  AS Sets: an aggregated set of ASes advertises the prefix;
    *  Multi-origin ASes (aka MOASes): several separate ASes advertise the
       same prefix).

AS Sets and Multi-origin ASes are identified specifically in the AS Links
files; for more information, see the file format description in the data
file header.

Once IP addresses have been mapped to ASes, two types of AS links can be
observed: direct links, in which two adjacent IP addresses map to two
different ASes, and indirect links, in which two IP addresses in different
ASes are separated by one or more hops for which we could not identify an
AS (because some hops were non-responding or because we were not able to
identify an AS for the IP address at a given hop). Indirect links are
annotated with the size of the gap between ASes as measured in IP hops. 

The current AS Links dataset fixes a few bugs in the skitter-based
AS-links generation software:

- The previous generation technique reported the first known
  link between two ASes, so if both an indirect and a direct
  link between the ASes was observed, and the indirect link
  was seen first, only an indirect link between the ASes
  would be reported.  The new version correctly reports
  direct links.

- The previous software also reported the first gap size it saw for
  an indirect link between two ASes.  Now, if an indirect link with
  a smaller gap size is observed, the smaller gap size is reported.


The format of each AS links file is described within the header of
the file itself.  The IPv4 Routed /24 Topology Dataset from which
this AS Links data is derived uses separate teams that independently
probe every routed /24 in the IPv4 address space.  Because different
teams have different members, locations, and capabilities, each
team completes a cycle of probing every routed /24 at a different

The directory structure is organized as team-<TEAM-ID>/YEAR/FILE.
For example,


The components of the path are

  TEAM-ID: the unique identifier of the team that did measurements,

  YEAR: the year (UTC) in which the underlying topology data used
        to generate the AS links files was collected, and

  FILE: the AS links filename in the following format:



      LIST-ID is the list in use for the probing (multiple teams
              can probe the same list; list 7 is the IPv4 Routed /24
              Topology Dataset),

      TEAM-ID is the same team identifier as in the path,

      CYCLE-NUMBER is a counter of probing cycles through a list done by
              *all teams* probing that list, and

      DATE is the date in UTC of the start of that probe cycle.

We have tried to make it easy for you to set up an automated process to
download new AS links files as they are produced.  The best way to do
this is to download the file aslinks-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.


The AUA for these publicly-available data is included in pdf format as a
separate file, caida_aua.pdf, in the same directory as this README file.

When referencing this data (as required by the AUA), please use:

    The IPv4 Routed /24 AS Links Dataset - <dates used>,

Also, please, report your publication to CAIDA


    Special thanks to Matthew Luckie for development of and assistance with

The IPv4 Routed /24 AS Links Dataset was sponsored by:

    * National Science Foundation
    * Department of Homeland Security
    * Cisco Systems


[1] IPv4 Routed /24 Topology Dataset:
[2] Skitter AS Links Dataset:
[3] University of Oregon RouteViews Project:
[4] Archipelago Project