Downward Dependencies:
Downward dependencies can be an obstacle for issuing ROAs.
If a prefix p originates from some AS A, but p has a subprefix p' that originates from a different AS B (belonging to a different organization), then publishing a ROA specifying A as the origin AS of p, before a ROA specifying B as the origin AS of p', would invalidate BGP advertisements of p'.
As in the example of Orange and its customers in the figure below.



We find the organizations that must issue ROAs for their own prefixes (and have not yet done so), to allow the owner of the queried IP-prefix to issue a ROA without invalidating legitimate BGP-advertisements.


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