拓扑图

We all know that the Internet has changed our lives. We now use the Internet for many things. Email, surfing the web, online banking, and most recently, social media, have given us almost unlimited access to information and people. But what about the infrastructure that makes the Internet work? What does the underlying layout of the Internet look like?
The answer lies in the Internet's "topology", or map, which describes how the different computers, servers, and networks are connected. It is like a picture of the complex network that exists all around us.
At the most basic level, the Internet consists of two main components: end-users and Internet Service Providers (ISPs). End-users can be people, businesses, or organizations that use the internet to access information and data, while Internet Service Providers (ISPs) provide the infrastructure that allows those users to access the Internet.
The Internet topology is based on a hierarchical system, with ISPs at the top and end-users at the bottom. This means that ISPs typically maintain regional, or even global, control over their networks and also provide technical support and access to their networks.
At the regional or local level, ISPs are typically divided into tiers. Tier 1 ISPs are usually large, multi-national companies that own their own fiber-optic networks or have agreements with local telephone companies to provide service. Tier 2 ISPs are smaller and are usually focused on specific geographical areas or services such as cable or satellite.
Below the ISP tiers, individual customers can connect to the Internet through their home or business. This is usually done by purchasing an internet package from one of the ISP tiers. This package will include a modem, router, and other equipment, as well as an agreement with the ISP.
By understanding the Internet's underlying topology, we can better understand how the Internet works, how our data travels around the world, and how the Internet enables us to share information, conduct business, and connect with people. It's a complex web of networks and systems that makes the modern world possible, and it's all powered by the Internet.