The Protocols That Make The Internet Work
When the US DOD (Department of Defense) or to be more exact DARPA (Defense Advanced Research Projects Agency) created the Internet they came up with the TCP/IP Model. Transmission Control Protocol (TCP) model is responsible for the end-to-end transportation of data from point A to point B on the internet. Internet Protocol (IP). The protocol used for data to be sent over the internet from one device (after it gets an IP Address) to another device with an IP address. Remember devices like PC,Tablet,Smartphone, VOIP Phone, etc without an IP Address can not send or receive data but once it gets an IP Address its now called a HOST.
TCP and IP are by no means the only protocols that are in the TCP/IP model but rather they are the most well known Protocols. International Organisation for Standardization (IOS) also came up with a similar model called the OSI Model, Open Systems Interconnection model. They look different but achieve the same purpose, these models are just there to describe the protocols that make the Internet work and what happens to your data e.g Email as it leaves your device until it reaches the destination device. PROTOCOLS A protocol is a set of predetermined rules.We will start with the protocols in the Application Layer (Layer 4 of OSI Model).
The application layer is the layer were data is originated and received.This the the interface were us the humans get to originate the message or receive the message.A PDU or Protocol Data Unit is the generic name for our data as it is going through the various layers. In the Application layer the PDU is called a Data Stream or Datagram.The protocols at work in the Application Layer include TELNET , Secure Shell (SSH) , File Trasnfer Protocol (FTP), DNS , SNMP etc.I will explain how one Protocol DNS works. DNS – Domain Name System resolves your domain (website) name to an IP Address.
When you type www.facebook.com your networking devices (routers,switches, …) and end devices, PC,Tablet,Smartphone, VOIP (Voice Over Internet Protocol) Phone, do not know what that is all about as the language they understand is binary & IP address.So good old Domain Name Server (DNS) is there to resolve whatever domain name you want to reach to an IP Address that your end & networking device can send and receive data to. In later posts we will move into the other Layers explaining one protocol from each layer.
Source: Funtech Systems