The most important features that a computer network provides to users are connectivity and sharing
Connectivity is a computer network that allows Internet users to exchange information. Sharing is resource sharing.
The internet has become the world's largest computer network.
Let's start by understanding the basic concepts:
The network consists of several nodes and links connecting these nodes, the nodes in the network can be calculators, hubs and so on. Usually we use a cloud to represent a network.
Networks and networks can be connected via routers. This can be overridden into a larger network, the Internet, so that the Internet is the network in the network.
The Internet is the largest Internet network in the world, and all the computers connected to the Internet are called hosts, and the Internet is usually represented by a cloud.
The network connects many computers together, while the Internet connects many networks together.
Through years of development, gradually formed a multi-level ISP structure of the Internet. ISPs are Internet service providers.
The host on the Internet must have an IP address to access the Internet.
ISPs are divided into backbone ISPs, regional ISPs, and local ISPs.
In principle, as long as each local ISP has a router connected to a regional ISP, and each regional ISP has a router connected to the backbone ISP, in conjunction with these interconnected ISPs, you can quickly complete all the packet forwarding tasks in the Internet.
But in order to forward the packet faster, people have studied the Internet Exchange point ixp.
The main function of the Internet Exchange Point IXP is to allow two networks to connect directly and swap packets without having to forward the packet through a third network.
The internet, when it comes to setting standards, is a big feature for the public.
The composition of the Internet:
1. The edge part: consists of all the hosts connected to the Internet, which are used directly by the user for communication and resource sharing.
2. Core part: Consists of a large number of networks and routers that connect these networks. This section provides services for the Edge section.
The Edge section leverages the services provided by the core to enable multiple hosts to communicate with each other and exchange or share information.
The communication between the end systems at the edge of the network can usually be divided into two main categories: client-server (c/s), peer-peers.
The core part of the network provides connectivity to a large number of hosts in the network edge, allowing any host in the edge to communicate with other hosts.
It is the router that plays a special role in the core part of the network. A router is a key component that implements packet switching, and its task is to forward the received groupings.
Three modes of exchange:
1. Circuit switching
Establish connection, communication, release connection
During the full time of the call, two users of the call always occupy an end-to-end communication resource. Other users need to wait for the resource to be idle before they can use it again.
That is, the bitstream of the entire message is continuously flowing from the source to the end point, as if it were delivered in a pipeline.
2. Message Exchange
The entire message is first transmitted to adjacent nodes, all stored down to find the forwarding post, and forwarded to the next node.
3. Packet switching
A single grouping, which is only part of the message, is transmitted to adjacent nodes, stored down to find the forwarding post, and forwarded to the next node.
The performance index of computer network:
1. Rate
The signals sent by the computer are in digital form. A bit is the unit of data in a computer. The rate of network technology refers to the rate at which a host connected to a computer network transmits data on a digital channel, also known as a data rate or bit rate.
2. Bandwidth
The highest rate, the wider the "bandwidth" of a communication link, the higher the "maximum data rate" it can transmit.
There are throughput, delay, delay bandwidth product, round trip time, utilization and other indicators of the network performance of the computer has an impact.
Computer network Overview