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Table 1 (Source: skitter-f.isc.org (204.152.184.98) - 8 october 1999)

Preliminary analysis of the data gathered by the CAIDA skitter host located with the F DNS root server in Palo Alto, CA, USA. Skitter probes were sent to a target list of approximately 36,000 customers of the F root server. Probes are sent about every half hour; each returns the round trip time to the destination and the path that the packets took to reach it.

Table 1: probability of changing autonomous systems along a path

Table 1 sorts paths by path length (shown vertically) and for each length, lists the links in the path and shows the probability of a path crossing a boundary between Autonomous Systems (ASes) at that link. Probabilities are colored to help highlight their values: low (blue), medium (green) and high (red). We can infer some peering and routing policy relationships from these data.

path length in hops num of paths
found
link 1 link 2 link 3 link 4 link 5 link 6 link 7 link 8 link 9 link 10 link 11 link 12 link 13 link 14 link 15 link 16 link 17 link 18 link 19 link 20 link 21 link 22 link 23 link 24 link 25 link 26 link 27
2 3 0.00 0.00
3 2 0.00 0.50 0.00
4 16 0.00 0.12 0.94 0.81
5 60 0.00 0.12 1.00 0.75 0.22
6 369 0.00 0.00 1.00 0.78 0.04 0.11
7 411 0.00 0.00 1.00 0.71 0.06 0.14 0.25
8 772 0.00 0.00 1.00 0.56 0.09 0.21 0.28 0.23
9 1134 0.00 0.00 1.00 0.40 0.13 0.34 0.36 0.28 0.22
10 2967 0.00 0.00 1.00 0.19 0.09 0.18 0.24 0.15 0.15 0.29
11 3859 0.00 0.00 1.00 0.22 0.13 0.13 0.33 0.18 0.17 0.33 0.15
12 4940 0.00 0.00 1.00 0.13 0.14 0.13 0.39 0.17 0.14 0.38 0.17 0.15
13 3922 0.00 0.00 1.00 0.15 0.18 0.09 0.33 0.18 0.10 0.44 0.23 0.19 0.13
14 3850 0.00 0.00 1.00 0.11 0.20 0.08 0.31 0.16 0.09 0.43 0.25 0.28 0.15 0.14
15 2774 0.00 0.00 1.00 0.09 0.20 0.08 0.27 0.18 0.09 0.43 0.21 0.23 0.23 0.17 0.14
16 2190 0.00 0.00 1.00 0.09 0.19 0.07 0.25 0.15 0.08 0.48 0.23 0.20 0.22 0.23 0.16 0.12
17 1544 0.00 0.00 1.00 0.06 0.14 0.07 0.30 0.18 0.10 0.45 0.19 0.18 0.23 0.24 0.24 0.17 0.07
18 1224 0.00 0.00 1.00 0.06 0.17 0.07 0.33 0.18 0.07 0.46 0.15 0.18 0.23 0.23 0.21 0.21 0.10 0.09
19 691 0.00 0.00 1.00 0.07 0.11 0.08 0.32 0.16 0.10 0.45 0.17 0.14 0.22 0.24 0.23 0.17 0.11 0.13 0.08
20 436 0.00 0.00 1.00 0.06 0.13 0.13 0.32 0.14 0.12 0.45 0.17 0.15 0.18 0.28 0.22 0.15 0.12 0.19 0.13 0.11
21 244 0.00 0.00 1.00 0.07 0.11 0.11 0.38 0.19 0.09 0.45 0.17 0.11 0.16 0.23 0.27 0.14 0.18 0.18 0.11 0.16 0.12
22 95 0.00 0.01 1.00 0.14 0.14 0.12 0.44 0.20 0.06 0.31 0.15 0.15 0.15 0.16 0.37 0.08 0.17 0.18 0.16 0.20 0.19 0.06
23 45 0.00 0.00 1.00 0.13 0.18 0.16 0.40 0.20 0.04 0.38 0.27 0.13 0.31 0.04 0.33 0.20 0.11 0.22 0.07 0.16 0.18 0.20 0.16
24 15 0.00 0.00 1.00 0.07 0.13 0.07 0.67 0.13 0.07 0.27 0.13 0.00 0.20 0.47 0.27 0.00 0.13 0.13 0.27 0.07 0.07 0.33 0.07 0.00
25 18 0.00 0.00 1.00 0.06 0.06 0.11 0.89 0.06 0.06 0.00 0.17 0.00 0.06 0.83 0.17 0.06 0.00 0.06 0.06 0.00 0.11 0.83 0.11 0.00 0.00
26 6 0.00 0.00 1.00 0.17 0.17 0.17 0.83 0.00 0.00 0.33 0.17 0.00 0.00 0.50 0.33 0.17 0.00 0.00 0.17 0.17 0.17 0.50 0.17 0.00 0.00 0.00
27 3 0.00 0.00 1.00 0.33 0.33 0.33 0.67 0.33 0.33 0.33 0.33 0.33 0.00 0.33 0.33 0.33 0.00 0.00 0.00 0.33 0.67 0.33 0.33 0.33 0.33 0.33 0.33
Table 1: probability of changing autonomous systems along a path

For the first few links (two, in this particular example) the probability of an AS switch is zero, since these first hops are internal to the site where the skitter host is located. Then, in this example at hop 3, all packets change to the autonomous system (AS) of the source site's upstream providers. Upon identifying the actual ASes in the paths, we see that longer paths often have a block of consecutive hops in the middle within the same AS, and then fan out to many individual ASes closer to the destination. This is more readily seen in Table 2, where we record the AS switched to and the percentage of paths that switched to it.

The level of aggregation of the data displayed makes drawing any more specific conclusions difficult.

Related Objects

See https://catalog.caida.org/details/software/skitter/ to explore related objects to this document in the CAIDA Resource Catalog.
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