互联网（internet）的基本组成

一般而言，互联网被认为由三个部分组成：

Edge Network

Devices and Endpoints: This part consists of all the devices at the periphery of the network that users directly interact with. It includes personal computers, laptops, smartphones, tablets, and various Internet of Things (IoT) devices like smart thermostats, security cameras, and wearable devices. These devices are the sources and destinations of data in the network.
Applications and Services: At the edge, there are numerous applications and services that users rely on. This includes web browsers for accessing websites, email clients for sending and receiving messages, video conferencing tools for virtual meetings, and social media platforms for communication and sharing. Online gaming platforms, cloud storage services, and streaming services like Netflix also operate at the edge.
Function: The edge network's main role is to generate and consume data. It allows users to access and utilize various network resources, such as retrieving information from websites, uploading files to the cloud, or streaming videos. It serves as the interface where users interact with the digital world.

Access Network

Technologies and Infrastructure: The access network provides the connection between end-user devices and the core network. Common access technologies include Digital Subscriber Line (DSL), which uses existing telephone lines to transmit data; Cable Modem, which utilizes cable TV infrastructure; and Fiber to the Home (FTTH), which offers high-speed data transmission through optical fibers directly to the user's premises. Wireless access technologies like Wi-Fi (WLAN) and cellular networks (such as 4G and 5G) are also part of the access network.
Connection and Transmission: Its primary function is to enable users to access the broader internet. It receives data from end devices and transmits it to the core network, and vice versa. For example, when a user sends an email from their smartphone, the access network picks up the data and routes it towards the core network for further transmission.
Service Providers: Internet Service Providers (ISPs) play a crucial role in the access network. They manage and maintain the infrastructure that provides users with network access. Examples of ISPs include Comcast, Verizon, and AT&T in the United States, and China Telecom, China Unicom in China.

Core Network

Components and Architecture: The core network is the central and most critical part of the internet, often referred to as the "backbone" of the network. It consists of high-performance routers, switches, and high-capacity communication links such as optical fibers. These components are interconnected in a complex architecture to handle large volumes of data traffic.
Data Routing and Switching: The core network is responsible for routing and switching data packets across different parts of the internet. It uses advanced routing protocols like Border Gateway Protocol (BGP) and Open Shortest Path First (OSPF) to determine the most efficient paths for data to travel. It ensures that data from a user in one part of the world can be quickly and accurately delivered to the intended recipient in another part.
Interconnection and Scalability: It connects different access networks and enables communication between various regions and networks. The core network is designed to be highly scalable to accommodate the ever-increasing amount of data traffic and the growth of the internet. It serves as the foundation that allows the entire internet to function smoothly and efficiently.

简而言之

网络边界（Edge Network）就是大家使用的物联网终端，比如常见的个人电脑、笔记本电脑、智能手机以及物联网设备比如安全摄像头、智能家电等。

网络接入（Access Network）则是网络边界和和网络核心的连接部分—— Digital Subscriber Line (DSL)，比如大家使用的SIM卡，其内置的通信模块（如4G/5G模块）会搜索并连接到最近的移动网络信号基站，信号基站接收到设备通过SIM卡发送的信号后，会通过移动网络运营商的通信网络，将设备连接到网络核心。再则大家使用的宽带网络，通过购买宽带服务，家里的电脑通过网线接入光纤，即可实现接入互联网，从而访问另一个网络边界（比如你现在正在访问博客园的服务器资源）。通俗概念的WIFI、手机信号网络（cellular networks）都属于无线网络技术，利用不同频率的波来实现终端与网络接入端的信息传输。

网络核心（Core Network）是互联网的核心和最关键部分，常被称为网络的“骨干”。它由高性能路由器、交换机以及诸如光纤之类的高容量通信链路组成。这些组件以复杂的架构相互连接，以处理大量的数据流量。这一部分则是网络通信（网络信息传输）的物理路径，这样的设计是基于高复用性、高荷载的实现，确保了全球范围内的信息传输既高效又可靠。

从某种程度而言，整个网络架构类似于高速公路系统，网络边界通过付费接入后可传输信息至全球各地的另一个网络边界。