Basic knowledge of the network (3)

LAN: Ethernet and Fast Ethernet

In the late 1970s, Ethernet had become very popular, and the network technologies for building local area networks (LANs) have always been relatively advanced. These technologies are often used to connect a building's internal network or stand-alone sites. The Ethernet connection is based on the CSMA/CD (multiple-entry sensing carrier signal and intelligent collision detection) standard.

An Ethernet workstation can send information to the network only when there is no data packet transmitted on the network, that is, when the network is “quiet”. Otherwise, one must wait, as if two people were talking. If one is talking, the other person can only speak after he finishes.
If multiple stations receive an "open" signal and send data at the same time, a collision occurs. At this time each workstation has to wait and try to send the data packet again. As more and more people use the Internet, the number of conflicts, the number of errors, and the number of consecutive transmissions will grow very quickly, resulting in a snowball effect.

The occurrence of conflict is normal, but too many conflicts will slow down the network. When 50% of the total network bandwidth is occupied, the collision rate can cause network congestion. It takes a long time for the file to be printed out before the application can be opened and the user is forced to wait for a long time. When 60% or more of the bandwidth is occupied, the network is extremely slow and even interrupted.

Ethernet's bandwidth or data transmission capacity (also called traffic) is about 10 megabits per second (Mbps). Fast Ethernet performs collision detection in the same way, but its bandwidth is 10 times that of the former and its traffic is 100 Mbps.

Shared Ethernet (Ethernet) is somewhat like a single-lane freeway, and speed is limited to 10Mbps. Ethernet, on the other hand, is like a multi-lane expressway. Speed ​​is limited to 100 Mbps: cars on the road have more space and can travel at faster speeds. Switched Ethernet (Ethernet) is more like a multi-lane highway. The speed of each lane is limited to 10Mbps. Switched Ethernet (Ethernet) is also a multi-lane expressway, except that the speed of each lane is limited to 100 Mbps.

Small company internal LAN (LAN)

The LAN is a simple Ethernet that connects each employee to the Internet with two servers and modems. Employees can share files, lecture notes, spreadsheets, and customer reports on various computers; they can conduct occasional searches by dialing into the Internet; they can also communicate via e-mail; and companies can share peripherals such as printers, modems, and hard disks. Save a lot of costs.
However, LAN cannot meet the needs of company expansion. Many users compete for 10 Mbps of Ethernet (Ethernet) bandwidth, and only one lucky user can connect to the Internet through a modem at a time. If there are more graphics in the files transferred between the client and server, the network will block.

The solution is to use an Ethernet switch to segment the network and connect it to the Internet through a router. This increases bandwidth for all users and allows multiple users to connect to the Internet at the same time via a single line. The company can meet the requirements of those CAD designers who are very bandwidth consuming, allowing their workstations to enjoy 10 Mbps Ethernet (Ethernet) bandwidth. When the network is upgraded, only new equipment and cables can be added to the existing equipment and cables, which greatly saves costs.

Several small websites are connected into one wide area network (WAN)
If the company wants to improve communications between headquarters and remote branches, a wide area network (WAN) can be established. The wide area network (WAN) makes the company's Internet connectivity more cost-effective and requires only a central high-speed connection to connect all the branch offices.

High-performance WAN
In different cities, a growing company generally sees growing network traffic from three perspectives. The first step is to install an advanced LAN to support the rapid growth of traffic. Secondly, it needs to provide a high-speed WAN connection so that employees in branch offices in two different cities can participate in video training held by the headquarters. In addition, because some employees work at home, this requires the company to allow them to dial into the local server directly from home.