Data transmission using TCP/IP [closed]

Question

When a file is sent over Internet in the form of packets of data, and when it travels through cable wires, fibre optics, or wireless device, how exactly it is sent in binary form? For example, what represents 1's and 0's when it travels through wires using electric current, radiowaves, light? Is it high and low voltage?

Answer 1

It depends on the physical medium. The ISO OSI model provides an abstraction of a communication system made up of layers. Each layer depends on the one below it to facilitate communication. For something like TCP/IP, what you're talking about is:

• Layer 4 (Transport): TCP
• Layer 3 (Network): IP
• Layer 2 (Link): IEEE 802.3 (for example)
• Layer 1 (Physical): 100BaseTX Ethernet

When you're talking about physical representation of data bits, you're talking about Layer 1. Note that there probably wont be a 1:1 correlation between the bits in your TCP/IP packet and those on the wire, because there'll potentially be error correction and control signals in there too.

If your network cable is a bunch of copper wires, you'll be dealing with electrical coding schemes like Manchester Encoding, where a low-to-high signal transition represents a 0 and a high-to-low transition represents a 1.

For other mediums, have a look through the Physical Layer entry on Wikipedia

Answer 2

If you would like to know what data are in packets when they're sent, then you should use a network analyzer/packet sniffer such as Wireshark. Then you can see the data that packets contain when being transmitted. For what represents 1's and 0's when it travels through different mediums, you should consult Wikipedia, because they may all differ. It should usually be a "off" for 0's, and "on" for 1's. I use Wireshark for my company, and it works as an excellent network analyzer.