How do Packets Travel? What's the Force behind the Internet or WAN?
A mystery-seeking mind often wonders how does the internet work? What causes the packets to travel? What is it that pushes the packets or causes the spark, if you will? Well the answer lies in the basics of Network Communications & the depths of Laws of Physics. Here is a scenario: you open up an internet browser & type in a URL. Here is what happens from Network/Physics perspective -->
As soon as you open the browser & type in the URL, a slue of network packets travel from your PC to the Local Area Network or LAN. Here it is piece by piece, in terms of what happens:
Application Layer (Layer 5, 6 & 7) sends a request to Transport Layer i.e. Layer4 of the OSI Model (http://en.wikipedia.org/wiki/Osi_model)
Layer4 creates a network socket by combining source ip, destination ip and a TCP or UDP Port # associated with the request. (http://en.wikipedia.org/wiki/Network_socket)
Layer3 on the LAN segment gets the request from Layer4 & sends the IP information down to the LAN device (switch).
LAN Switch grabs the info & processes the data by forwarding it to the WAN device i.e. Router (could be DSL modem, cable modem, t1 etc.)
Router grabs the Layer3 info & forwards the request over to Layer2 device i.e. WAN device on the provider network. It could be an ATM or a Frame Relay switch.
The provider then forwards the request to the requested host on the internet i.e. a server you are trying to access. That's the server you requested to connect to when you typed in the URL in your browser.
The server replies back to the provider, then the provider forwards the reply back to you.
The Router (WAN device) in your network forwards the information back based on the network socket info & eventually you get to see the site you requested.
Now the above-mentioned explanation is a very high-level overview of basic internet (WAN) communication. However, there is a big mystery about Layer1 that typically remains un-explained. I will try to address this here to the best of my knowledge:
The information, keeping the OSI Model in mind, travels from Application Layer (Layer 5, 6 and 7) to Layer4, down to Layer3, to Layer2 & eventually Layer1.
Layer1 deals with nothing but bits, 0's & 1's. The Binary language or the Universal language, if you will. (http://en.wikipedia.org/wiki/Binary_numeral_system)
The information on Layer1 travels in the form of electrical signals, with a specific combination of 0's & 1's that make up a particular piece of information. (http://en.wikipedia.org/wiki/Signal_(electronics))
These Electrons are actually the Force behind the Internet/WAN Communications.
There you go. Here is an answer to the mystery force causing the information to flow through wires across the globe. If you want to dig even deeper & zoom into each electron to get a sub-atomic picture, go for it. Here is the link: http://en.wikipedia.org/wiki/Sub-atomic_particle
If you grab a magnifying glass & zoom into each sub-atomic particle (like Electron) you will find out that there is something called "energy flakes or strings" that compose the Electron to define its physical characteristics. Everything in this world that physically exists on a super-microscopic level is made up of these energy strings. Here is the link for the curios: http://en.wikipedia.org/wiki/String_theory