Growth of non-transit ASes, cont.


Q: Does the Internet grow mostly at the periphery?
A: Most likely, although BGP graph may not have 
       enough coverage at network edge to answer

may show transit ASes as nontransit
may undercount indegree (multi-homing)
captures only downstream, not lateral, connectivity
18%, 17%, 16% transit ASes in 1999, 2000, 2001
absolute number grows but proportion shrinks 
bidirectional part of the graph (core): 3.13%, 2.24%, 2.09%
compare to skitter (traceroute-based) AS graph: 
32% transit ASes, twice as many as BGP graph
28% ASes in combinatorial core (BGP: 2%)