Page 83 - Handout Computer Network.

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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