ENVS 1000 Chapter 17: ENVS 1000 Chapter 17 Notes
10 May 2018
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ENVS 1000 Chapter 17 Notes – Summary
Introduction
• The routing capabilities of interconnected networks, TCP/IP, routers and gateways, plus
appropriate data link layer software and physical connections.
• And indeed, the Internet is a gigantic partial mesh network, connecting a high
percentage of all the computers in the world.
• In practice, though, the number of intermediate nodes, measured as hops between
nodes, would make this scheme impractical.
• The connections would be too slow, the order of arrival of packets too erratic, and the
traffic too heavy, to sustain the effort for long.
• Although the Internet concept postulates that such connections can occur, it is more
practical to provide fast connections between distant points to reduce the time it takes
to traverse long distances, to reduce the number of hops to just a few, and to reduce
the traffic on the local connections.
• The Internet can be compared to a structure of roads and highways.
• We travel on long distance, high-speed, limited access superhighways for the longest
legs of a journey and use the local roads for initial access to the highways and for the
final access to our destination.
• There might even be a middle tier of medium-speed highways that provide a means to
get from the nearest superhighway exit to the network of local roads.
• In the United States, for example, Interstate highways provide the long legs of the
journey, national and state highways the connections to the local roads of cities and
towns, and local roads to start and finish our journeys.
• Although there is no official central backbone for the Internet and no official guidance
for its development, the Internet has developed similarly.
• All access to the Internet is provided by ISPs—Internet Service Providers.
• The arrangement is approximately hierarchical.
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