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.