Internet is not a single technology. Instead it’s a stack. A group of technologies working together. These technologies form what is known as internet protocol suite. Which powers computer networks. Many such computer networks work together to form what we know as the global internet.
[ Please note that the explanation below is by no means an exhaustive guide just an overview that’ll quickly help you understand how different networking technologies work together.]
Let’s quickly go through the internet protocol suite (or TCP/IP stack as it’s commonly known)
It consists of 4 layers
-
The link layer
-
The internet layer
-
The transport layer
-
The application layer
The link layer provides the foundation for communication within a network. This may consist of physical wires like ethernet/fiber optics. Or wireless medium like wifi. Besides providing the physical medium it’s also responsible for giving access to the channel.
This is the layer that is responsible for implementing MAC address required to transmit information between two devices.
—
The internet layer is responsible for providing communication between networks. It is at this layer internet protocol is implemented. The process of moving data between networks is called routing.
-
Each host on the network is identified by an IP address.
-
Data packets are sent from source by passing them from one router to another until they reach their destination.
The transmission of data through the internet layer is unreliable. It provides no guarantee that the source packet will reach the destination.
[This is because it is difficult to know beforehand what path data will take as it’s routed to destination. ]
[ It may be said that the Internet protocol is stateless. All of the effort is spent in forwarding if packets. None is spent on verifying whether the individual packet was successfully delivered. And due to this property it’s able to address billions of hosts.
And this type of communication is known as connection less communication. ]
—
The transport layer implements the transmission control protocol (or TCP).
The actual data packets that are transmitted by the internetworking layer over the link layer are generated here. Here they are called segments. Once generated segments are forwarded to internet layer where they are assembled into a packet and stamped with IP address.
TCP layer defines the communication channel using ports. It is at these ports that applications and services are running.
Client devices can connect to these applications using the link layer as defined above. The TCP facilitates communication between the client and the application server over network ports.
TCP is a reliable and connection oriented protocol.
While the internet layer provides routing. TCP layer manages the communication process. Making sure it’s reliable, efficient and standardized.
—-
Application layer is the is the place where the services (that a client uses) are running.
Services like
-
Domain name system
-
Dynamic host configuration protocol
-
Simple mail transfer protocol
-
HTTP servers
run on application layer.
These protocols are used for process to process communication. A client device having a web browser can access the website using http protocol.
An email client like an Android app can access emails using SMTP protocol.
Data encoded by the application layer is passed on to the transport layer where it’s assembled into segments.
Application layer is the one using which we interact with the internet. It’s also the one with which most people are familiar with. We don’t need to know about any other underlying layers. As far as we’re concerned it may not even exist.
But it does.
And this illustrates the core principle of the internet stack. The abstraction of layers. A layer does not need to concern itself with how the other layers perform or work. It only has to make sure that it’s protocol is fulfilled.
——-
That is the gist of how the network works. If you want more specific details into the protocols involved please check out this Wikipedia index
https://en.m.wikipedia.org/wiki/Outline_of_the_Internet
[It’s important to note that the internet is more than just the web. There are many other services running on it that are defined by their own protocols.]
[ Finally TCP/IP and OSI are conceptual models to help understand how things work. In real world layers are not stacked as neatly as the model expects. But it’s much simpler nevertheless]
How it all comes together?
To best understand the internet consider a wireless router in your home connected to the internet via your service provider.
When your router is on and connected to the internet
-
It gets an IP address by your ISP.
-
It assigns a local IP address to each one of your connected devices using DHCP
-
On request of client it establishes a connection with a service provider. Like a web server or an email server.
-
It then routes the client request using the internet layer to a service provider. The web server processes the request and sends the response to the router.
-
The router sends the response to the device that requested it using the IP address it assigned.
Application
Practically speaking the logical components TCP/IP model are coded into the operating system. Like Debian. So if you buy an appropriate hardware like PC with a network card and some Ethernet cables you can create your own data center.
There is a huge demand for local services that the internet is not able to satisfy. Applications that don’t need global internet to work. That can run offline so to speak.
These services are critical to digitization of processes. Both business and administrative. They don’t require to be available anywhere. But are context sensitive.
Wireless data centers running in colleges, and public places can fulfill this demand. Localized social networks, e-commerce, document management systems that are only needed where they are. Eg in a hospital or a court. To reduce the administrative burden. To improve the information flow.
Such portable data centers present a new opportunity to entrepreneurs, researchers and individuals to create rich and efficient local networks.
References
https://en.m.wikipedia.org/wiki/Internet
https://en.m.wikipedia.org/wiki/Outline_of_the_Internet
OSI and TCP video explanation
workrock 