Page 84 - M. Abrahim Thesis

CHAPTER 4

NETWORK DESIGN

4.1 Internet Architecture
Although the Internet is complex, some basic ideas underlie its operation. This section
investigates the basic architecture of the Internet—a deceptively simple idea that, when repeated
on a large scale, enables nearly instantaneous worldwide data communications between anyone,
anywhere, at any time. In Figure 4-1, X and Y represent computers that are connected and that can
communicate with each other from across the world.

Figure 4-1 shown a Routers Connecting Two Networking Methodology

One limitation of LANs is that they do not scale

• Beyond a certain number of stations

• Beyond a certain geographic separation

Astonishing progress is being made in the number of stations that can be efficiently attached
to a hierarchical LAN, and there have been advances in technologies such as Metro Optical and
Gigabit Ethernet and 10 Gigabit Ethernet. However, ultimately stations must make recourse to a
long-distance, WAN-like, packet-switching network.

One assumption of the Internet’s architecture is that the details of host computers, and the
LANs on which they reside, are separate from the details of getting messages from one network to
another. One approach to the big-picture architecture for the Internet was to focus on the
application layer interactions between the source and destination computers and any intermediate
computers. Identical instances of an application, put on all the computers in the network, could
facilitate delivery of messages across the large network. However, this does not scale well.
New software functionality would require new applications to be installed on every computer
in the network; new hardware functionality would require modifying the software. Failure of an
intermediate computer or its application would break the chain on which the messages are passed.
Instead, the Internet uses the principle of network layer interconnection.

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