Page 86 - M. Abrahim Thesis

Chapter (4) Network Design

Figure 4-2 shown a connection between Local and Remote Networks

One way would be for the router to keep a list of all user computers and the paths to them.
The router would decide whether and where to forward data packets based on this table of all users,
forwarding based on the destination computer. However, this would quickly become problematic as
the number of users grows—it is not scalable. What if the router could instead keep a list of all
networks, leaving the local delivery details to the local physical networks?

This solution is better and more scalable—forwarding based on the destination network. In
this case, the routers relay messages.

In principle, if the routers can share some information about which networks they are
connected to, doing so can scale this idea to many routers.
Figure 4-3 shows the results of this extension, showing the user’s desired view: universal
interconnections, with a minimum of details required by the end users to get their packets across
the “cloud.” Yet the physical/logical structure to accomplish this can be extremely complex. Indeed,
the Internet cloud has grown exponentially, with devices and protocols constantly being improved
to allow more users. The fact that the Internet has grown so large, with more than 90,000 core routes
and more than 300,000,000 end users, is testimony to the soundness of the basic Internet
architecture. Thus, two computers, anywhere in the world, following certain hardware, software,
and protocol specifications, can communicate reliably
(“anyplace/anytime/anyone”).

Even when they are not directly connected (or even not close to being directly connected),
cooperation and procedures for moving data across this network of networks have made the Internet
possible.

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