What is Internet’s Hierarchical Structure

Internet is the most used network in the word. Internet is made up of set of thousand networks connected to each other like national and state government agencies or non-profit organizations and for-profit companies. Internet is basically a hierarchy structure of networks that allows one internet connected device to connect to another internet connected device, both being at different geographical locations.

These networks must have access to use internet protocols and all networks must support TCP/IP. Internet has many unrestricted applications as well as content which have been developed freely all over the web.

Basic understanding of the Internet

Every computer that is connected to internet has a unique address. This address is called IP address where IP stands for internet protocol. This address is in the form of nnn.nnn.nnn.nnn where nnn can be any number in the range from 0 to 225.

This IP address is provided to your computer if you are connected to LAN or an ISP (internet service provider). Depending on what network your computer or device is connected, your IP address can be temporary or permanent. But in any case the IP address is unique.

One computer interacts with another computer connected to internet with the help of protocol stacks. These are also called IP/TCP stacks. They are built into the computer’s operating system and has four major layers i.e. application protocol layer, transmission protocol layer, internet protocol layer and hardware layer. These layers convert and send the information from one IP address to another over the internet.

What is Internet's Hierarchical Structure


Routing is basically the process of sending internet packets from one network to another. Each packet has a unique IP address and is sent through a gateway to another address. Although the process is a bit more complicated but on ground level this is what happens in the process of routing.

Domain name

Since remembering names is much easier than remembering number, the idea of domain name was created. IP numbers were replaced with a static name called domain name and they which is accessible to all the devices connected to the internet. These domains are further divided as follows

  • Generic top level domains (gTLD )
  • Sponsored top level domains (sTLD)
  • Country code top level domains (ccTLD)

The infrastructure

Connecting to an ISP makes you connected to a part of their network. The ISP might be connected to an even bigger network. The ISP is well connected to a number of modems which makes up for the back bone of the internet.

The ISPs are further divided into a three tier system.

  1. National Internet Service Providers (ISPs): NISPs are the backbone of the internet service provider and they connect to the internet directly. The NISPs have a pact to allow the traffic to flow between them for better network. They then provide their access services to regional ISPs or local ISPs. As of now, there are 5 major Internet service providers (ISPs) that come under tier 1 category and they are AT&T, Equant, British Telecom, MCI and InfoNet.
  1. Regional ISPs: these are tier 2 ISPs and are mostly regionally based. They are connected with national ISPs and have peering agreements with them and they provide ISP links to some big organizations. They also provide or sell access to Local ISPs but they do not have peer to peer connection in between them. Some of the examples of tier two organizations are Sprint, XO communications, etc.
  1. Local ISPs: these are tier 3 service providers and thus the smallest. They provide or sell services to local homes or small offices or individuals. They have a peer to peer network with tier 1 and 2 networks and are connected to them. Some of the examples are time warner cable, cablevision optimum, Verizon Fios, etc.

Network access points

Most of the big communication companies have a backbone connecting the network of various regions and is called POP (point of presence). POP helps the user(local) to connect to company’s network via a local number or a line. Though there is no network that has an overall control but there are various high-level network connected to each other via NAPs or Network access points.

Thus, NAPs connect the ISPs together and sometimes even at regional or local level.

Then there are MAEs i.e. Metropolitan Area Exchanges that connect the regional ISPs together.

The hierarchy

The internet works as a hierarchy of network and these networks are connected to each other on various levels. The network on each level are connected to each other via nodes. The structure of internet is basically like an atom where the highest number of network flows through the nodes present in the core. The nodes on the outer side are connected to these network. There are isolated network on the periphery which are connected to the core, and they can be cut off if the core is shut down.

Image Credit: cisco.com