The Internet is a Internetwork of Internets. It is not a network!
To repeat, it has no center, and further, does not even have any edges.
that's not a useful vocabulary. try this one:
1 - Connection Taxonomy
1.1. The Internet is a "network of networks", where the component
networks are called Autonomous Systems (AS), each having a unique AS
Number (ASN).
1.2. Connections inside an AS are called "Interior" (or sometimes
"backbone"), and their security policies are set according to local
needs, usually based on business or technical requirements.
1.3. Connections between ASs are called "Border" (or sometimes
"peering"), and their security policies are set bilaterally according to
the joint needs of the interconnecting parties.
1.4. Connections between an AS and its traffic sources (generators) and
traffic sinks (consumers) are called "Edge" (or sometimes "customer"),
and their security policies are generally, by long standing tradition,
inconsistent.
that's from http://www.icann.org/committees/security/sac004.txt, fyi.
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Paul Vixie