computer networks
Connection between two or more systems with the ability to transfer information between them
In terms of size:
1. PAN (Personal Network)
2. LAN (local area network)
3. WAN (Wide Network)
4. Internet work (connected network)
PAN: The smallest type of network and is dedicated to one user. It covers an area of approximately 10 meters. For example, wireless mouse, feature headphones
Bluetooth and TV control are of this type.
LAN: The scope of a building (school, university, office, Internet cafe, etc.). In this type of network, between 2 and 16 million connection systems are established
Be. Establishing this network does not require a license. The connection is made with a few meters of cable and network card and switch.
Network card: A piece of hardware that connects the computer and the transmission environment (cable, etc.). On today's computers, there is a motherboard
Yes, but it does not exist on older computers and must be installed on the motherboard. In fact, the network card is responsible for receiving, transferring, organizing and temporarily storing
Information is networked.
Switch: A hardware capable of centralizing
Setting up this network is very cheap and its speed is good, there is a possibility of errors and low problems and quick troubleshooting.
MAN: The area of this network is the level of a city and its connections are with fiber optics. Connecting several LANs to each other is called a MAN. Setting up
This network needs to get a license from telecommunications and so on.
Example: Suppose a company has several branches. MAN is used to connect employees of these branches.
The network is slower, more error-prone, more difficult to troubleshoot, and more expensive to set up than smaller networks.
WAN: The range of this network is between several provinces or a country or even a continent and allows the connection between MANs and LANs. In the WAN network
The transfer speed is low, the coverage range is wide, the error is very high and the troubleshooting is difficult.
The broad scope of coverage means that, for example, one user in Iran can communicate with another user in another country.
Internet conversations such as Viber, Telegram, etc. are in this category.
Internetwork: The largest WAN network and there are three types.
Intranet: This type of network is controlled by a management entity and allows certain users to access the data network.
It is mostly used in organizations to share files and resources. Like the National Intelligence Network in Iran
Extranet: Sharing information is used within a group whose members are not in the same place.
For example, employees of an office can access the network from outside the office, with a username and password from anywhere, even abroad.
Have .
Internet: A large network for sharing information publicly and in the form of web pages.
The geometric pattern used to connect computers is called topology, which is available in the following two types:
Type 1: Point to Point
The second type: Broad Cast. This type of connection has different shapes, which are:
1. Bus
2. Star
3. Ring
4. Mesh
5. Tree
6. Daisy Chain
7. Wireless
8. Hybrid
The main components of a network are:
1. Endsystems: Any tool that can use the network and is located at the end of the network. Such as: printer, tablet, laptop and computer
A) Host or Server (Servers) b) Terminal or Client (Servers)
2. IMPs: A tool for communicating
A) Layer 1: Only the task of communicating (like Hub)
B) Layer 2: In addition to communication, it is possible to manage data. (Like Swich)
C) Layer 3: Allows communication between two or more different networks. (Like Router)
D) Layer 4: Has the ability to control the inputs and outputs of a network. (Like Firewall)
Hub: A device that connects multiple computers on a local network. It is not able to separate input and output addresses. So packages
Receipt from one port is sent to all available ports.
Switch: A device that connects multiple computers on a local area network. Unlike Hub, they can differentiate between different computers on the network.
Router: Connects two or more networks and transfers information packets from one network to another.
Firewall: Hardware or software that protects resources within the network from unauthorized external access.
3. Media
3.1 - Cable
A) coaxial
B) Twisted pair (TP)
C) Isdn
D) X25
E) Fiber iptic (optical fiber)
3.2 - Wireless
A) Infrared
B) Microwave
C) Wimax
D) Wifi
E) Laser
Advantages of using a computer network:
1. Share information
2. Sharing hardware resources (for example, in Internet cafes, several computers use one printer.)
3. Save time
4. Reliability of safe access to information
5. Reduce postage costs
6. Nature-friendly computer network (due to not using paper)
7. Ability to develop (the ability to connect all computers in the world together)
8. Ability to create new solutions (Possibility of connecting all people in the world with one phone with all people in the world)