Performing a defensive procedure in response to certain path advertisements

1. A method comprising:

receiving at a first routing device of a first autonomous system a path advertisement from a second routing device of a second autonomous system; the path advertisement advertising a path from the second routing device of the second autonomous system to a target autonomous system;

determining whether the second autonomous system is a stub autonomous system;

based on the path advertisement, determining whether a path length of the path is greater than one, the path length identifying a number of autonomous system in the path from the second router of the second autonomous system to the target autonomous system;

if the second autonomous system is a stub and the path length is greater than one, performing a defensive measure to decrease the possibility of an attack on the path; and

otherwise, performing a default procedure the path.

2. The method of claim 1 , the determining whether the second autonomous system is a stub further comprising:

accessing a list maintained at the first routing device, the list indicating whether an autonomous system is a stub.

3. The method of claim 1 , the determining whether the path length of the path is greater than one further comprising:

obtaining the path length from a path segment length field of the path advertisement.

4. The method of claim 1 , the performing the defensive measure for the path further comprising:

applying a filter to the path to permit or deny one or more Internet Protocol (IP) addresses.

5. The method of claim 1 :

the performing the defensive measure for the path further comprising applying a lower weight to the path; and

the performing the default procedure for the path further comprising applying a higher weight to the path, the lower weight decreasing the probability that the path is selected.

6. The method of claim 5 , the lower weight decreasing probability of an attack.

7. The method of claim 5 , the lower weight allowing the path to operate as a backup path.

8. An apparatus comprising:

a memory of a first routing device of a first autonomous system, the memory configured to store computer executable instructions; and

one or more processors coupled to the memory, the processors configured, when executing the instructions, to:

receive a path advertisement from a second routing device of a second autonomous system, the path advertisement advertising a path from the second routing device of the second autonomous system to a target autonomous system;

determine whether the second autonomous system is a stub autonomous system;

based on the path advertisement, determine whether a path length of the path is greater than one, the path length identifying a number of autonomous system in the path from the second router of the second autonomous system to the target autonomous system;

if the second autonomous system is a stub and the path length is greater than one, perform a defensive measure for the path; and

otherwise, perform a default procedure for the path.

9. The apparatus of claim 8 , the determining whether the second autonomous system is a stub further comprising:

accessing a list maintained at the first routing device, the list indicating whether an autonomous system is a stub.

10. The apparatus of claim 8 , the determining whether the path length of the path is greater than one further comprising:

obtaining the path length from a path segment length field of the path advertisement.

11. The apparatus of claim 8 , the performing the defensive measure for the path further comprising:

applying a filter to the path to permit or deny one or more Internet Protocol (IP) addresses.

12. The apparatus of claim 8 :

the performing the defensive measure for the path further comprising applying a lower weight to the path; and

the performing the default procedure for the path further comprising applying a higher weight to the path, the lower weight decreasing the probability that the path is selected.

13. The apparatus of claim 12 , the lower weight decreasing probability of an attack.

14. The apparatus of claim 12 , the lower weight allowing the path to operate as a backup path.

15. One or more non-transitory computer readable media when executed operable to:

receive at a first routing device of a first autonomous system a path advertisement from a routing device speaker of a second autonomous system, the path advertisement advertising a path from the second routing device of the second autonomous system to a target autonomous system;

determine whether the second autonomous system is a stub autonomous system;

based on the path advertisement, determine whether a path length of the path is greater than one, the path length identifying a number of autonomous systems in the path from the second router of the second autonomous system to the target autonomous system;

if the second autonomous system is a stub and the path length is greater than one perform a defensive measure to decrease the possibility of an attack on the path; and

otherwise, perform a default procedure for the path.

16. The media of claim 15 , the determining whether the path length of the path is greater than one further comprising:

obtaining the path length from a path segment length field of the path advertisement.

17. The media of claim 15 , the performing the defensive measure for the path further comprising:

applying a filter to the path to permit or deny one or more Internet Protocol (IP) addresses.

18. The media of claim 15 :

the performing the defensive measure for the path further comprising applying a lower weight to the path; and

the performing the default procedure for the path further comprising applying a higher weight to the path, the lower weight decreasing the probability that the path is selected.

19. The media of claim 18 , the lower weight decreasing probability of an attack.

20. The media of claim 18 , the lower weight allowing the path to operate as a backup path.