摘要：So what are Autonomous System Numbers (ASNs), and what role
do they play in the technology of the Internet? This article explores
the role of ASNs as a critical element of the Internet routing architecture.
We will first explore how the AS number space is structured,
examine how ASNs are used in the interdomain routing environment
and then look at the consumption rate of these numbers, and finally
examine our options when we get to the point of likely ASN pool exhaustion.
However, in order to put this into context, a brief overview
of Internet routing architecture follows.
