---------           ------             ---------
         /         \         /      \           /         \
        /           \       /        \         /           \
       | PE1 o    ASBR1 -- ASBR2    ASBR3 -- ASBR4    o PE2 |
        \           /       \        /         \           /
         \         /         \      /           \         /
          ---------           ------             ---------
          AS 100              AS 200              AS 300
       |-----------|--------|---------|--------|------------|
          segment1  segment2 segment3  segment4  segment5