Basic concepts of networks
Computer Network
A computer network is made up of a set of computers and some other devices, whether by physical means or not, in order to share resources.
Network Classifications.
- Local area networks. LAN (Local Area Network).
- Wide area networks. WAN (Wide Area Network).
According to the relationship between teams:
Here the egalitarian Networks enter that allow all the computers in the network to share resources without any of them having control of the network, as well as the Networks with server that exist in the network a specialized computer, called server, which is responsible for control of the network, resources, users and privileges; The rest of the teams are the customers.
According to the connection means:
Here are the cable either twisted pairs (8 wires), or fiber optic, as well as wireless. By Wi-Fi, or by Bluetooth.
According to Typologies:
Here they enter In bus and in ring that use coaxial cable with BNC connectors in T. They are in disuse because they are very slow. The cable connects the equipment directly without other devices, also in star, or tree. It is the most used today, uses 8-wire UTP Cat-5 structured cable forming twisted pairs and RJ45 connectors. The equipment is connected to a hub (or hub), or its evolution, a switch , which controls the transit of information.
BIT: (binary digit). The smallest unit of information of a machine.
BYTE: A unit of data that is usually eight bits.
LOAD: Stream a file over a network.
Encryption : Encryption is the manipulation of data to avoid that any of the users to whom the data is not directed can make an accurate interpretation.
SWITCH:
1. Device that is the central point of connection of equipment and other devices of a network, so that the data can be transmitted at full transmission speed.
2. Device for making, interrupting or modifying the connections of an electrical circuit.
DDNS: (Dynamic Domain Name System) Allows you to host a website, FTP server or email server with a fixed domain name (for example, www.xyz.com) and a dynamic IP address.
IP ADDRESS: Address used to identify a device or device in a network.
ROUTER: A network device that connects multiple networks, such as a local network and the Internet.
ETHERNET: IEEE standard network protocol that specifies the way in which data is placed and retrieved from a common transmission medium.
FIRMWARE: The programming code that runs a network device.
NODE: Network connection or connection point, usually a workstation or equipment.
ACCESS POINT: Device that allows equipment and other devices equipped with wireless function to communicate with a wired network. It is also used to extend the reach of a wireless network.
NETWORK: Series of connected devices or devices in order to share data, storage and transmission between users.
Hardware.
The network card: It is the component of the computer that allows you to connect it to a network. Also called NIC (Network Interface Card), it is connected in an expansion PCI slot, or in a USB port.
Interconnection devices: These are the devices that centralize all the wiring of the network, therefore, they must have as many ports as computers we want to connect.
Hub or Hub: Receives a data packet and transmits it to the rest of the connected equipment, which slows down. They generally work at a standardized speed of 10Mbps.
Switch or Switch: Stores the MAC address of the connected equipment, and sends the packets only to the equipment to which it is addressed. Speed is gained by efficiency.
The router or router: It is a device designed to interconnect two networks between them.
WAN or Wide Area Network: They allow to share devices and have a fast and efficient access, which the difference of the others is that it provides a means of long distance transmission of data, voice, images, videos, on large geographical areas that they can reach a country, a continent or the whole world, it is the union of two or more LAN networks.
Features:
* They operate within a large geographical area.
* Allows access through serial interfaces that operate at lower speeds.
* Provides partial and continuous speed.
* Connects devices separated by great distances, even worldwide.
* Allows access through serial interfaces that operate at lower speeds.
* Provides partial and continuous speed.
* Connects devices separated by great distances, even worldwide.
Intranet: An Intranet is a private computer network based on Internet standards. Intranets use Internet technologies to link the information resources of an organization, from text documents to multimedia documents, from legal databases to management systems. documents Intranets can include network security systems, bulletin boards and search engines. An Intranet can be extended over the Internet. This is usually done using a virtual private network (VPN).
Structured Cabling: It is the physical support or means by which the information travels. This transmission can be by electrical signals, or through light beams.
Basic Network Parameters.
Network protocols: These are the rules and technical specifications that are followed by networked devices to be able to communicate and transfer information to each other.
The IP (Internet Protocol) address: Each device connected to a network has a unique identifier, called an IP address. It is formed by 4 figures separated by a point, each one can take values from 0 to 255, that is, the same values that a byte can take.
- Reserved IP addresses.
- Configuration.
-Share a folder on the local network.
-Access to shared folders.
-Network units.
-Organization of shared folders.
Topologies
How do physical and logical topologies differ?
The physical and logical topology can be the same. In a physically connected network like "Linear Bus" (that is in direct line), the data travels in direct line from one computer to another. A network can have physical and logical topologies and that these are not equal. The cable segments can connect all computers to the central hub in star type, but within the hub the connection can vary, so the signal travels through a circle from one port to another creating a logical ring.
Bus Topology:
In the linear bus topology all computers are connected on the same line. The cable comes from one computer to the next and so on. It has a beginning and an end, the linear bus network requires a terminal at each end, so it receives the signal and therefore does not return one of the ends of a linear bus network must have a ground.
A linear bus network usually uses thick or thin coaxial cable, Ethernet 10 Base 2 and 10 Base5.
Communication in the Linear Bus Topology
In a linear bus type network, when a computer sends a message, the message goes to each computer. Each network card (NIC-Network Interface Card) examines each message address to determine to which computer it is addressed.
Advantages of the Linear Bus Topology
-This topology is very simple and easy to fix.
-It is relatively cheaper because it requires less wiring unlike the other topologies.
-The linear bus topology is especially convenient for a small and temporary network.
Disadvantages of the Linear Bus Topology
-The linear bus network is known as a passive topology because computers do not regenerate the signal.
-This makes the network vulnerable to attenuation, as it loses signal through the cable distance.Although repeaters can be used to fix that problem.
-Other disadvantages are that if the cable breaks or one of the users decides to disconnect their computer from the network the line is broken.
-This means that not only the computers on the opposite side lose communication, but then there would be two endings on the cable that would not be finished.
Star Topology:
The star topology is one of the most popular topologies of a LAN (Local Area Network). It is implemented by connecting each computer to a central Hub. The Hub can be Active, Passive or Intelligent. An active hub is just a connection point and does not require electrical power. An active Hub (the most common) is currently a repeater with multiple ports; boost the signal before passing it to the next computer. An Intelligent Hub is an active hub but capable of diagnosing, can detect errors and correct them.
Communication in the Star Topology
In a typical star network, the signal passes from the network card (NIC) of the computer that is sending the message to the Hub and it is responsible for sending the message to all ports. The star topology is similar to the Bus, all computers receive the message but only the computer with the address, equal to the address of the message can read it.
Advantages of the Star Topology
-The star topology has two big advantages unlike the Bus and Ring topology.
-It is more tolerant, this means that if a computer is disconnected or if the cable is broken only that computer is affected and the rest of the network maintains its communication normally.
-It is easy to reconfigure, add or remove a computer is as simple as connecting or disconnecting the cable.
Disadvantages of the Star Topology
-It is expensive since it requires more cable than the Bus and Ring topology.
-The cable travels separately from the Hub to each computer.
-If the Hub goes down, the network has no communication
-If a computer crashes, it cannot send or receive messages.
Ring Topology:
If you connect the last computer of a linear bus network behind the first computer, you will have a Ring Topology. In a ring network each computer is connected to two other computers, and the signal can travel through a circle. Because a red ring does not have an end point, and terminals are not necessary.
A ring network physically generally uses coaxial cable, as well as the Bus topology. A Token Ring network, which is a logical ring, uses STP cable (IBM type) and is compatible with IEEE 802.5 specifications
Communication in the Topology Ring
In a red ring, the signal travels in only one direction. Each computer receives the signal from its neighbor above and sends it to its neighbor below. The ring network is considered an active topology, because each computer regenerates the signal before sending it to the next computer.
The ring topology is commonly associated with the Token Ring architecture. In this implementation the ring is usually a "logical ring", the circle that is inside the hub of a Token Ring, is called the Multistation Access Unit (MSAU).
Advantages of the Ring Topology
-The red ring is easy to have technical problems and like the bus network, it is easy to fix.
-A physical ring topology requires more cable than a bus network and less than a star network.
Disadvantages of the Ring Topology
-One of the main disadvantages is the difficulty to add more computers to the network, because the cable runs in a closed circle and it is necessary to break the ring at a point to insert the new computer.
-That means that the network will be out of communication while the installation is done.