In the hieararchical BGP paper by Gao and Rexford, three conditions are given for stability: (i) the
Question:
In the hieararchical BGP paper by Gao and Rexford, three conditions are given for stability:
(i) the provider-customer graph is acyclic,
(ii) export policies are restricted , and
(iii) Guideline A is implemented at each node (customer paths are preferred over peer or provider paths). We saw an example where (i) and (ii) hold, but (iii) does not hold, and the system diverges.
a) Show me an SPP instance where (i) and (iii) hold but not (ii), and the system diverges
b) Show me an SPP instance where (ii) and (iii) hold, but not (i), and the system diverges.
Hint: although a) and b) could have multiple answers, of course, there are simple (relatively) answers for the graph with 4 nodes (0 in the center, and 1, 2, 3, around it, forming a triangle)