Image Processing Reference
For a start, servers and clients are situated long distances away from one another in the
geographical sense but also in the networking sense. A network is connected using a series
of smaller sub-networks joined together by routers. The router knows about other routers
that it is connected to but knows nothing of the network beyond them. A process of dis-
covery is involved when you make a connection. The number of routers that need to be
traversed from your local network to the one where the target server lives will determine
the shortest route.
The networking protocols are built using a technical structure that is referred to as a stack.
This describes the way that protocols manage different parts of the process starting at the
very lowest level where the physical cable connects two devices together. The TCP stack
is based on the ISO Open Standards Interconnect layering scheme, although some layers
are merged together in the TCP stack, so there is not a complete 1-to-1 correspondence
between the two models. They are ordered the same, however, and the counterparts are
shown in Figure 19-2.
The electrical signals along that wire are defined as voltages and impedances, and on
that a means of coding binary digits is imposed. This describes the bottom-most layers of
TCP & UDP
IP v4 & IP v6
Device & hardware drivers
Figure 19-2 TCP stack.