The internet is of course a complex system, of many collaborating parts, and it'd be easy to get lost in the technical minutia of it's inner workings.
Keep in mind that as with all systems of great expanse, humans manage complexity with hierarchical decomposition, e.g. A CEO issues a directive, his
trusted lieutenents each apply it to their area of responsibility, and so on for every subordinate down the tree. Complex solutions are also often
emergent. Let there be towns A,B,C where roads are planned from AB, and BC. Without any forethought, we now have AC.
Getting back to the internet. Let's ignore details, and approach the problem by construction. For some parties to exchange information they must
decide on A) the medium: speech, semaphore flags, electrical signals etc.. B) The protocol. Lets assume you and a friend are each on separate
hilltops using flashlights (medium) to exchange morse code messages (protocol). It becomes confusing if you both communicate at once, so you decide
to break up the transmission time into quantum's of 5 seconds each in a round-robin fashion. During your turn to communicate, you can send as many
messages as you like, as long as you stop in time. Now we have a very simple exchange protocol.
Continuing with this analogy, imagine a scientist and an engineer hear about this communication network, and want to use it to communicate their
complex research reports across the different hills. Beforehand (probably at the local pub), they agree to write to each other in English, and
without knowing how big their reports will be, they agree to use the sentence THE-END to specify the end of their report. The scientist and engineer
have now designed an exchange protocol, at a higher level than the morsecode/flashlight scheme above.
I'm sure you can see where this is going. The scientist and engineer may now overlay their protocol on top of the hilltop morsecode/flashlight
protocol. The scientist can simply give his paper to an operator on his hill, who'll start using transmitting it according to the rules above. On
the receiving end, it's eventually turned back into an English report. Once the Engineer reads "THE-END" he can tell his flashlight operator he's done
receiving this message.
Going further, we might have multiple scientists show up, and they all want to exchange reports with different parties. To deal with this, they might
prefix the name of the recipient at the start of each message. As time goes on, the demands on the system will grow and each layer in the network may
be improved without consideration to the whole (here is hierarchical decomposition at play). The flashlight operators may want error signals to
retransmit signals, while researchers might want a protocol to tell the other to slow down (or speed up) the communication if one side cannot keep up
with the other.
The growth of the internet emerged in a very similar way. At one point, all addresses had to be known in advance before communication could take
place; when a new party joined the network their address had to be copied to everyone on the net! (now we have DNS). At the high-level end, as you
probably know, HTTP existed long before WWW.
My advice is to get the big picture sorted out, and then refine your knowledge in the areas that interest you.
edit on 4-9-2011 by bitstream
because: (no reason given)
edit on 4-9-2011 by bitstream because: grammar / added content.