Introduction
Assume that a student at Setif University sends an email to his friend in Algiers using 4G mobile data. Which networks are involved?
University LAN (Ethernet) or WLAN (Wi-Fi): the packet is sent from the student’s laptop to the default gateway (university router).
ISP network (fiber backbone): The university router is connected to a national Internet Service Provider, for example Algérie Télécom
Mobile operator network (4G/5G): The packet’s destination address is associated with an Algiers 4G subscriber. Thus, the packet is forwarded to the Mobile Operator Network (e.g., Djezzy, Ooredoo, or Mobilis) by the backbone.
4G Radio Access: The mobile operator transmits the packet to the nearest 4G base station, which then transfers it over the air (by radio waves) to the friend’s smartphone in Algiers.
Despite using various devices, protocols, speeds, technologies, and transmission mediums, these networks work together to offer seamless communication. We refer to these networks as heterogeneous networks.
When two or more heterogeneous networks are interconnected, they form an inter-network or a network of networks (Internet)
The global network that connects several local, regional, and national networks is called the Internet.
It connects billions of computing devices around the world.
The Internet is a global network of infrastructures, and these infrastructures are organized in different hierarchical levels.
Backbone networks are at the pinnacle of the Internet structure, employing extremely high-bandwidth links and powerful routers.
Regional or national networks are at the intermediate level, typically handled by telecom operators such as Algérie Télécom, Ooredoo, and Mobilis.
At the lowest level are local networks (access networks, such as those found in homes, businesses, universities, and other organizations.
How do these heterogeneous networks actually cooperate and communicate?
The network layer Internet Protocol (IP)