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1.1.2.1 Network of Networks
Computer network (referred to as network) : consists of several nodes (Node) and links (Link) connecting these nodes . The nodes in the network are computers, hubs, switches, and routers.
Networks can be interconnected through routers to form a computer network with a larger coverage, called the Internet , which is also a network of networks (networks of networks) . This also achieves the connectivity .
Sometimes for the convenience of discussion, the computer is drawn outside the cloud, and the computer connected to the network is called a host (host) , and only routers and links remain in the cloud.
To sum up, the network connects computers, the Internet connects networks through routers, and those connected to the network are called hosts.
For network interconnection, it is not simply a physical interconnection, but also a lot of software should be installed so that computers can exchange information with each other.
Internet (Internet) : It is a general term that generally refers to a computer network formed by interconnecting multiple computer networks. The communication protocol can be chosen arbitrarily, not necessarily TCP/IP.
Internet (Internet, Internet) : is a professional term, referring to the current largest Internet. The TCP/IP protocol family is used as the communication rule.
2.1.2.2 Three Stages of Internet Infrastructure Development
The basic structure of the Internet has roughly gone through three stages of speech.
The first stage is the process of developing from a single network ARPANET to the Internet. APRANET was originally a packet-switching network, and later began to study a variety of network interconnection technologies, which was the prototype of the Internet. In 1983, the TCP/IP protocol became the standard protocol of ARPANET. Computers using this protocol can communicate with each other through the Internet. 1983 is called the first year of the birth of the Internet.
The second stage is characterized by the establishment of a three-level structure of the Internet. Divided into backbone network, regional network, campus network (or enterprise network) . Subsequently, the backbone network of the Internet will be handed over to private companies for operation.
The third stage is characterized by the formation of the Internet with a multi-level ISP structure . When government agencies were no longer responsible for the operation of the Internet, Internet Service Providers (ISPs, Internet Service Providers) emerged, both as commercial companies.
ISPs apply for a lot of IP addresses from Internet management agencies. When they need to surf the Internet, individuals or companies obtain the required IP addresses from ISPs, and then access the Internet through the IP addresses.
ISPs are also divided into different levels: backbone ISPs, regional ISPs, and local ISPs.
The figure below is an overview of an Internet with a three-tier ISP structure.
Among them, if host A wants to communicate with host B, it must go through the following ISPs:
A-local ISP-Regional ISP-Backbone ISP-Regional ISP-Local ISP-B
Because the local ISP is connected to the regional ISP through the router, and the regional ISP is connected to the backbone ISP through the router, through the cooperation between ISPs, all packet forwarding tasks can be completed. However, if the ISP on the same layer switches directly without going through the ISP on the upper layer, the packets can be forwarded faster. The Internet exchange point IXP (Internet eXchange Point) realizes such a function. The function of IXP is to allow two networks to connect directly and exchange packets. As shown in the figure above, the two regional ISPs on the right are connected through an IXP, so that host A and host B do not need to go through the uppermost backbone ISP when exchanging, and directly establish a high-speed link peer-to-peer exchange packet between the two regional ISPs.
The rapid development of the Internet began in the 1990s. The World Wide Web (World Wide Web) developed by CERN was widely used on the Internet, which facilitated the use of the Internet by non-network professionals. This is also the reason for the rapid increase in the number of Internet users. main driving force.
3.1.2.3 Internet standardization work
Internet standards are open to the public, and all RFC documents can be downloaded from the Internet for free.
Internet Society (ISOC) : The international organization that governs the Internet in general.
Internet Architecture Board (IAB) : The technical organization under ISOC that manages the development of Internet-related protocols.
There are two engineering departments under the IAB:
Internet Engineering Department (IETF) : Responsible for researching short-term and medium-term engineering issues
Internet Research Department (IRTF) : Researching issues that require long-term consideration
All Internet standards are published on the Internet in the form of RFCs.
Not all RFC documents are Internet standards, and only a small part of RFC documents can eventually become Internet standards.
Formal standards for the Internet go through the following three stages:
(1): Internet draft: This stage is not yet an RFC document.
(2): Suggested document: This stage begins to become an RFC document.
(3): Internet standards: