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Notes:
The twelve considered providers are large T1 ISPs :
AS2914 : Verio
AS3257 : TISCALI
AS1239 : Sprint
AS7911 : Williams
AS3561 : C&W USA
AS1668 : AOL
AS7018 : ATT
AS5511 : FT Backbone
AS3549 : GLBIX
AS3356 : Level3
AS1 : Genuity
AS293 : ESnet
For these ISPs that are in majority tier 1, the figure shows that the number of
common routes is very high varying between 96.9 and 98.1% of the full BGP table except for AS2914 having on average 85% of the routes in common with the 11 other peers. The figure also shows that between 56033 and 69735 routes are selected in a non-deterministic manner by the BGP decision process of our stub AS. A closer look at those routes reveals that 80% of them have an AS-Path length of 3 to 4 AS-hops. On average, for all considered pairs, almost 62% of the routes are chosen in a non deterministic manner. This result implies that the length of AS-Path is not always a sufficient condition to select BGP routes and that ISPs could easily influence their outgoing traffic by defining additional criteria to prefer one provider over the other.