A computer network is a digital telecommunications network that allows network nodes to share resources. In computer networks, computer devices exchange data with each other using connections (data links) between nodes. These data links are established via network cables such as wire or fiber optics , or wireless media such as Wi-Fi . Network computing devices that launch, route , and terminate data are called network nodes. [1] Nodes are often identified by network addresses and can include network hosts such as personal computers , phones , and servers , as well as network hardware such as routers and switches. Two such devices can be said to be interconnected when one can exchange information with the other, whether they are directly connected to each other or not. In most cases, application-specific communication protocols are layered (i.e., carry a payload ) over other general communication protocols . This formidable collection of information technology requires skilled network managers to keep all network systems running well.

1. Internet
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A computer network is a digital telecommunications network that allows
network nodes to share resources. In computer networks, computer
devices exchange data with each other using connections (data links)
between nodes. These data links are established via network cables
such as wire or fiber optics, or wireless media such as Wi-Fi.
Network computing devices that launch, route, and terminate data are
called network nodes. [1] Nodes are often identified by network
addresses and can include network hosts such as personal computers,
phones, and servers, as well as network hardware such as routers and
switches. Two such devices are interconnected when one can
exchange information with the other, whether they are directly
connected or not. In most cases, application-specific communication
protocols are layered (i.e., carry a payload ) over other general
communication protocols. This formidable collection of information
technology requires skilled network managers to keep all network
systems running well.
Computer networks support a large number of applications and services
such as access to the World Wide Web, digital video, digital audio,
shared use of storage and application servers, printers, and computers.
fax, and use email and instant messaging applications as well as many
other applications. Computer networks differ in terms of the
communication methods used to carry signals, communication protocols
to organize network traffic, size of the network, topology, traffic control
mechanisms, and organizational intent. network. The most famous
computer network is the Internet.
History of computers

2. Computers of the 1940s were large and fragile electromechanical
devices. The invention of the semiconductor transistor in 1947 created
the opportunity to make computers smaller and more reliable.
In 1950, mainframe computers running programs written on punched
cards began to be used in large institutions. Although this creates many
advantages for computers that can be programmed, it also has many
difficulties in creating programs based on these punched cards. [2]
In the late 1950s, people invented integrated circuits (ICs) containing
many transistors on a small semiconductor model, creating a giant leap
in creating more powerful, faster, and smaller computers. To date, ICs
can contain millions of transistors across multiple circuits. I have
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In the late 1960s and early 1970s, small computers called
minicomputers began to appear. [3]
In 1977, the computer company Apple Computer introduced computers,
also known as personal computers ( personal computers - PC). [4]
In 1981, IBM launched the first personal computer. The ever-increasing
miniaturization of ICs led to the widespread use of personal computers
in the home and business.
In the mid-1980s, users of stand-alone computers began sharing files
using modems connected to other computers. This method is called
point-to-point, or dial-up transmission. This concept is expanded by
using computers as communication centers in a dial-up connection.
These computers are called bulletin boards. Users connect to this
messaging platform, leaving or removing messages, as well as
uploading and downloading files. The limitation of the system is that
there are very few directions of communication, and only to those who
know about that notification platform. In addition, the computers on the
notice floor need a modem for each connection. As the number of
connections increases, the system cannot meet the demand.
Through the 1950s, 1970s, 1980s, and 1990s, the US Department of
Defense developed highly reliable WAN-wide area networks to serve

3. military and scientific purposes. This technology is different from
point-to-point communication. It allows multiple computers to connect
using different paths. The network itself determines how data moves
from one computer to another. Instead of being able to communicate
with only one computer at a time, it can communicate with multiple
computers at the same time using the same connection. Later, the US
Department of Defense's WAN became the Internet.
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Network computational model
Centralized computing model
All processing takes place at the central computer. Terminals are
networked to the central computer and only act as data input and output
devices allowing users to view on the screen and enter data via the
keyboard. Terminal workstations do not store and process data. The
above network computing model can be deployed on a hardware
system or software installed on the server.
Advantages: Data is safe, easy to back up, easy to remove viruses, and
low installation costs.
Disadvantages: Difficult to meet the requirements of many different
applications, slow access speed.
Distributed computing model
Computers can operate independently, and tasks are broken down and
assigned to many different computers in the network instead of
concentrating on processing on a central computer. Although data is
processed and stored locally, these computers are networked together
to exchange data and services.
Advantages: Fast access, mostly unlimited applications.
Disadvantages: Fragmented data storage is difficult to synchronize, and
back up and is very susceptible to viruses.

4. Collaborative computing model
The collaborative network computing model involves multiple computers
that can cooperate to perform a job. One computer can borrow the
computing and processing capacity of another computer by running
programs on computers on the network.
Advantages: Very fast and powerful processing, can be used to run
applications with large mathematical operations and large data
processing. For example: cracking code systems, calculating DNA,...
Disadvantages: Data is stored in different locations so it is difficult to
synchronize and back up, and the possibility of virus infection is very
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Network classification
LAN
LAN ( English: Local Area Network ), also known as "local area
network", is a private network in a building, an area (school or office, for
example) about a few kilometers in size. [5] They connect servers and
workstations in offices and factories to share resources and exchange
information. LAN has 3 characteristics:
The limited range of operation ranges from a few meters to 1 km.
They are often using a simple technique with only one cable connecting
all machines. Typical data transfer speeds are 10 Mbps, 100 Mbps, 1
Gbps, and more recently 100 Gbps. [6]
Three common LAN-type network architectures include:
Bus network or linear network. The machines are connected
continuously in a row from one machine to the other. An example is
Ethernet ( IEEE 802.3 standard ).
Ring network. The machines are connected as above and the last
machine is connected back to the first machine to form a closed loop.
For example, the IBM token ring network ( IBM token ring ).
Star network.
MAN

5. MAN ( English: Metropolitan Area Network ), also known as
"metropolitan network", is a network larger than LAN, with a range of
several kilometers. It can consist of groups of offices close together in a
city, it can be public or private and has the following characteristics. I
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There are only a maximum of two connecting cables.
Do not use transfer techniques.
Can support general data transport and voice, or even television. Today
people can use fiber optic technology to transmit signals. Current
speeds can reach 10 Gbps.
An example of this technique is a DQDB ( Distributed Queue Dual Bus )
network, also known as a distributed dual bus (IEEE 802.6 standard).

6. WAN
Types of connections in WAN
WAN ( English: Wide Area Network ) is also known as a "wide area
network", used in large geographical areas, usually for countries or
entire continents, with a range of several hundred to several thousand
kilometers. They consist of collections of machines intended to run
programs for users. These machines are often called storage machines
( hosts ) or also called servers or end systems. The main machines are
connected by communication subnets, or more simply, subnets. The
task of the subnet is to transmit messages from one server to another. I
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Subnets usually have two main components:
Transport lines are also called circuits, channels, or trunks.
Connecting devices. This is a specialized type of computer used to
connect two or more trunk lines to move data between computers.
When data arrives on the input lines, the switching device must select
(according to a predetermined algorithm) an output line to send that
data. The name of this device is a packet-switching node or
intermediate system. The computer used for the connection is called a
"path selector" or "router".
Most WANs consist of multiple cables or phone lines, each connected to
a pair of routers. If two routers are not connected to the same line, they
will communicate indirectly through many other intermediate routers.
When the router receives a data packet, it holds the packet until the
outgoing line needed for that packet is free, then it forwards the packet.
This case is called the point-to-point subnetwork principle, or the
store-and-forward subnetwork principle, or the packet-switching
subnetwork principle.
There are many types of WAN configurations using the point-to-point
principle such as star, ring, tree, complete, ring, or irregular.
Network model

7. Main article: Network topology
Star Network
There are all stations connected to a central device that is responsible
for receiving signals from the stations and transferring them to the
destination station. Depending on the communication requirements of
the network, the central device can be a hub, switch, router, or central
server. The role of the central device is to establish Point-to-Point links.
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The advantages are simple network setup, easy network reconfiguration
(add or remove stations), easy control and troubleshooting, and full
advantage of the transmission speed of the physical connection.
The disadvantage is that the transmission line length connecting a
station to the central device is limited (a radius of about 100m with
current technology).
Bus Network
Have all stations divided on a common line (bus). The main
transmission line is limited at both ends by two special connectors
called terminators. Each station is connected to the main axis via a
T-connector or a transceiver. The Bus network model operates on
point–to–m–multipoint or Broadcast links.
Advantages: Easy to design and low cost.
Disadvantages: Poor stability, just one network node fails and the entire
network stops working.
Ring Network
The signal is transmitted on the ring in only one direction. Each station
of the network is connected through a repeater, which is responsible for
receiving the signal and then forwarding it to the next station on the ring.
Thus the signal is circulated on the ring in a consecutive series of
Point-to-Point links between repeaters.
Advantages: Ring networks have the same advantages as star
networks.

8. Disadvantages: One broken station or cable means the entire network
stops working, adding or removing a station is more difficult, and the
network access protocol is complicated.
Mesh Network
Star and linear combination (Star Bus Network): This type of network
configuration has a signal splitter (splitter) acting as a central device,
and the network cabling system is configured as Star Topology and
Linear Bus Topology. The advantage of this configuration is that the
network can consist of many groups working far away from each other.
ARCNET is a combined Star Bus Network. This configuration offers
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Star and ring combination (Star Ring Network): Configure the Star Ring
Network combination, there is a communication "card" (Token) that is
transferred around a central HUB. Each workstation is connected to a
HUB - a bridge between workstations to increase the necessary
distance.
Ring network Linear network
Communication methods
Circuit Switching Network
Main article: Channel switching

9. When two stations need to exchange information with each other, a
fixed "channel" will be established between them and maintained until
one of the two parties disconnects. Data is only transmitted along this
fixed path. Circuit switching techniques are used in ATM (Asynchronous
Transfer Mode) and Dial-up ISDN (Integrated Services Digital Networks)
connections. An example of a circuit-switched network is the telephone
network.
The advantage is that the transmission channel is reserved during the
communication process, so data transmission speed is guaranteed.
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The disadvantage is that it takes time to establish a fixed connection
between two stations; The transmission efficiency is not high, because
there are times when there is no data transmission on the channel from
the two connected stations, but other stations are not allowed to use
this channel.
Message Switching Network
Unlike circuit switching, message switching does not establish a
dedicated link between two communicating stations, instead, each
message is treated as an independent block containing both a source
and destination address. Each message will be transmitted through
stations in the network until it reaches the destination address, each
intermediate station will receive and store the message until the next
intermediate station is ready to receive the message then it forwards.
relays the message to the next station; for this reason, a
message-switching network can also be called a Store and Forward
Network. A typical example of this technique is electronic mail (e-mail),
which is relayed through stations until it reaches its destination.
The advantage is to provide a more efficient management of network
traffic, by assigning priorities to messages and ensuring that higher
priority messages are circulated instead of delayed due to traffic on the
network; Reduces network congestion, and intermediate stations can
store messages until the channel is free before sending messages;
Increase the efficiency of using the channel. With this technique,
stations can share the same channel.

10. The disadvantage is that the delay caused by storing and forwarding
messages is not suitable for real-time applications. Intermediate
stations must have a very large memory capacity to store messages
before forwarding them to another intermediate station (the size of
messages is not limited).
Packet Switching Network
Main article: Packet switching
This technique is proposed to take advantage of the advantages and
overcome the disadvantages of the above two techniques. For this
technique, messages are divided into packets of variable size, each
packet includes data, source address, destination address, and
information about intermediate station addresses. Individual packets do
not always follow a single path; this is called independent routing. I
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The advantage is that bandwidth can be managed by splitting data into
different paths in case the channel is busy; If a link fails during
communication, the remaining packets can be sent via other paths; The
basic difference between message switching and packet switching is
that in packet switching, packets are limited in maximum length,
allowing switching stations to store packets. information into internal
memory without having to send it to external memory, thereby reducing
access time and increasing information transmission efficiency.
The disadvantage is that the difficulty of the packet switching method
that needs to be resolved is to gather packets at the receiver to recreate
the original message as well as handle packet loss.
Network application model
Peer–to–Peer-to-peer network model
Main article: Peer-to-peer network
Peer–to–peer networks are a very simple example of LANs. They allow
every network node to act as both an entity requesting network services
(client) and as an entity providing network services (server). In this
environment, users on each computer are responsible for operating and

11. sharing their computer's resources. This model is only suitable for small
organizations and does not care about security issues. Peer-to-peer
network software is designed so that peer entities perform the same
functions.
The characteristics of a peer-to-peer network are that a peer-to-peer
network is also known as a workgroup network and is used for networks
with ≤ 10 users working on that network. ; does not require a network
administrator; In a peer-to-peer network, each user acts as an
administrator for their workstation and chooses which resources or data
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The advantage is the simplicity of installation and relatively cheap cost.
The disadvantage is that there is no centralized administration,
especially in cases where there are multiple accounts for one user to
access different workstations; Network security can be violated with
users share the same username and password to access the same
resource and cannot centrally backup (backup) data. Data is stored
scattered on each station.
Client–Server Network / Server-Based Network model
Main article: Client-server
Client-host networking involves defining the roles of communication
entities within the network. This network determines which entities can
make service requests and which entities can service those requests.
Machines are organized into domains. Security on domains is managed
by several special servers called domain controllers. On the domain,
there is a master domain controller called PDC (Primary Domain
Controller) and a BDC (Backup Domain Controller) to prevent PDC
problems.
Network management model
Workgroup network model

12. The Workgroup network model is a group of network computers that
share resources such as data files and printers. It is a logical group of
computers that all have the same group name. There can be many
different workgroups connected on a local area network (LAN).
The Workgroup network model is also considered a peer-to-peer
network because all machines in the workgroup have equal rights to
share resources without needing to be specified by the Server. Each
computer in the group maintains and secures its local database. This
means that all administration of user accounts and security of shared
resources are not centralized. You can connect to an existing group or
create a new group.
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The advantage is that Workgroups do not require a computer running
on the Windows Server operating system to centralize security
information; Workgroups are simple to design and implement and do not
require the extensive planning and administration that a domain
requires; Workgroups are convenient for groups with a small number of
computers that are close together (≤ 10 computers).
The downside is that each user must have a user account on each
computer they want to log in to; Any user account changes, such as
changing a password or adding a new user account, must be made on
all computers in the Workgroup, if you forget to add a new user account
to a computer. within the group, new users will not be able to log in to
that computer and will not be able to access that computer's resources;
Device and file sharing is handled by individual computers, and can only
be used by users with accounts on that computer.
Domain network model
Main article: Domain name
A domain network model is a group of network computers sharing a
centralized directory database. The data directory contains user
accounts and security information for the entire Domain. This data
directory is known as the active directory.

13. In a Domain, directories only exist on computers configured as domain
controllers. A domain controller is a Server that manages all security
aspects of the Domain. Unlike Workgroup networks, security and
administration in the domain are centralized. To have a Domain
controller, servers must run a Domain controller service (a service built
into Microsoft's Windows Server versions; or on Linux, we configure the
Samba service to perform the Domain controller task). ,...).
A domain is not considered a single location or separate network
configuration. Computers in the same domain can be on a LAN or WAN.
They can communicate with each other via any physical connection,
such as Dial-up, Integrated Services Digital Network (ISDN), Ethernet,
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The advantage is that it allows centralized administration. If a user
changes their password, the change is automatically updated across
the Domain; Domains provide a simple login process for users to
access the network resources they are authorized to access; Domain
provides flexibility so administrators can create very large networks.
Typical domains in Windows Server may contain the following computer
models:
Domain controllers store and maintain directory replicas. In a domain, a
user account is created once, Windows Server records it in this
directory. When a user logs in to a computer in the domain, the domain
controller checks the directory for the user name, password, and login
restrictions. When there are multiple domain controllers, they
periodically regenerate their directory information.
Member servers: A member server is a server that is not configured as
a domain controller. The server does not store directory information and
cannot verify the user's domain. Servers can provide shared resources
such as shared folders or printers.
Client computers: Client computers run an operating system for the
user's workstation and allow users to access resources in the domain.
Unlike Workgroup, Domain must exist before users join it. Joining a
Domain always requires the Domain administrator to provide an
account for the user's computer to that domain. However, if the

14. administrator gives the user the correct privileges, the user can create
his or her computer account during the installation process.
Network parameters
Bandwidth (Bandwidth - B)
In computer technology, bandwidth is a quantity used to refer to the
amount of data that can be transmitted in a certain time. For digital
devices, bandwidth is calculated in bps (bits per second) or Bps (bytes
per second).
Latency (Latency - L)
Latency is the time it takes to transfer a message from one node to
another in the network.
Throughput – T
Throughput is the amount of data passing through a link in a unit of
time. Or throughput is the actual bandwidth used by network
applications during a specific time (throughput can be time-varying). I
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Throughput is usually much smaller than the maximum possible
bandwidth of the transmission medium used (Throughput ≤ Bandwidth).
The throughput of a computer network depends on factors such as link
distance, transmission environment, network technologies, type of data
transmitted, number of users on the network, user computers, servers,
etc.
Data communication methods
Main article: Network node
Unicast method: A source node wants to send a message to only one
destination node on the network.
Multicast method: A source node wants to send a message to a group
of destination nodes on the network.
Broadcast method: A source node wants to send a message to all other
destination nodes on the network.
Network protocols

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Main article: Communication protocol
Main article: TCP/IP
Typical network models
The following models, TCP/IP and OSI, are standards, not filters or
protocol generators.
OSI
OSI model with seven layers.
OSI, also known as the "Open Systems Interconnection Reference
Model", abbreviated as OSI Model or OSI Reference Model is a design
based on the development of ISO (International Organization for
Standardization) and IUT-T. The model includes 7 floors:
Application layer (Layer 7): allows users (human or software) to access
the network by providing a user interface, supporting services such as
remote access email and file transfer, shared database management,
and several other information services.

16. Presentation layer (Layer 6): performs tasks related to the syntax and
content of sent information.
Session layer (Layer 5): plays the role of " dialog " controller of the
network with the task of establishing, maintaining, and synchronizing
the interaction between the two parties.
Transport layer (Layer 4): receives data from the session layer, cuts
them into small units if necessary, sends them to the network layer, and
checks that these units reach the receiving end.
Network layer (Layer 3): controls the operation of the subnet.
Determines the beginning and end of a data transfer.
Data link layer (Layer 2): the main task is to convert data into data
frames according to algorithms to detect, adjust, and solve problems
such as damage and loss. and duplicate data frames.
Physical layer (Layer 1): Performs the functions necessary to transmit
data streams in the form of bits across physical media.
TCP/IP
TCP / IP is like OSI but this one has three fewer layers:
The application layer: includes many high-level protocols. Previously,
people used virtual terminal applications such as TELNET, FTP, and
SMTP. Later, many additional protocols were defined such as DNS, and
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Transport layer: the task is the same as the transport part of OSI but
there are two protocols used: TCP and UDP.
Network layer: responsible for transferring data packets from sender to
receiver. Data packets may have to go through many networks
(intermediate hops). The data link layer transfers data packets between
two devices on the same network, while the network layer ensures that
the data packet will be transferred from the sender to the correct
recipient. This layer defines a packet format and protocol called IP.
Data link layer: Used to transmit data packets across a physical
medium.
Network devices
Main article: Terminal system

17. Transmission equipment
Twisted pair cable: Twisted pair cable consists of many pairs of copper
wires twisted together to prevent electromagnetic interference emission.
Due to its low price, twisted-pair cables are widely used. There are two
types of twisted pair cables widely used in LAN: shielded and
unshielded.
Coaxial Cable
Fiber optic cable: a type of telecommunications cable made of glass or
plastic, using light to transmit signals. The fiber optic cable is long, thin,
and composed of transparent glass about the diameter of a human hair.
They are arranged in bundles called fiber optic cables and are used to
transmit signals over very long distances. Unlike copper cables that
transmit signals electrically, fiber optic cables are less susceptible to
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Connected devices
Wireless Access Point is a wireless network connection device
designed according to IEEE 802.11b standards, allowing LAN to LAN
connection, using CSMA/CA mechanism to resolve disputes, using both
Infrastructure and Network connection architectures. AdHoc, 64/128 bit
encryption. It also supports wireless transmission speeds of up to
11Mbps on the 2.4 GHz band and uses DSSS (Direct Sequence
Spectrum Spreading) radio technology.
Wireless Ethernet Bridge is a device that allows Ethernet devices to
connect to a wireless network. For example, the Linksys WET54G
Wireless-G Ethernet Bridge device. It supports any Ethernet device
connecting to a wireless network whether that Ethernet device can be a
single device or a router connected to many other devices.
A network card is a type of expansion card attached to a computer,
providing physical and logical communication between the computer
and network devices and network systems through transmission media.
A repeater is simply a signal amplifier between two ports of two network
segments. Repeaters are used in the Bus network model to extend the
maximum distance on a cable line. There are two types of Repeaters in
use: Electric Repeaters and Optical Repeaters. Used to connect two
networks with the same communication protocol
Hub is a device with the same function as a Repeater but with more
communication ports allowing many network devices to connect at one

18. point. Hubs typically have from 4 to 24 communication ports, often used
in 10BaseT Ethernet networks. Hub is just a multi-port Repeater. The
hub repeats any signal received from any one port and sends that
signal to all remaining ports on it. Hubs operate at the physical layer of
the OSI model and also do not filter data. Hubs are often used for
networking, through their plugs people connect to computers in star
form. Hubs are divided into two main types: Passive hubs and Active
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A bridge is a device that allows connecting two network branches, with
the function of selectively transferring packets to the network branch
containing the packet recipient. To filter packets and know which packet
belongs to which network branch, the Bridge must contain a MAC
address table. This address table can be created automatically or must
be configured manually. Because the Bridge understands the MAC
address, the Bridge operates at the second layer (data link layer) in the
OSI model.
A modem is a device used to convert digital format data into analog
format data for a transmission process from a digital signal medium
through an analog signal medium and then back to a digital signal
medium at the receiving end. Final. The name Modem is an acronym
composed of the first letters of MOdulator/DEModulator -
Modulator/Demodulator.
A switch is a harmonious technical combination between a Bridge and a
Hub. The operating mechanism of a Switch is very similar to a Hub
because it is a device that centralizes network connections on it. The
communication ports on the Switch are miniature bridges built on each
corresponding communication port.
A router is a router used to connect multiple network segments, or
multiple network types (usually heterogeneous in architecture and
technology) into the same interactive network. Typically there is a
processor, memory, and two or more input/output ports.
Brouter
Gateway is an intermediary device used to connect different networks in
both architecture and network environment. A gateway is understood as
the main entrance port of an internal network connecting to another
external network. It may be a specialized hardware device, but it is

19. usually a server that provides connections for the machines it manages
to communicate with another network.
Network technologies
Point-To-Point
Main article: Point-To-Point
Ethernet
Main article: Ethernet
Token Ring
Main article: Token Ring
FDDI
Main article: FDDI
In essence, FDDI is like Token Ring, but double Token Ring. That
means FDDI has 2 Token Rings, but, only 1 ring is active, and 1 ring is
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FDDI ensures LAN operates effectively, without downtime, and provides
higher security.
Subscriber network
Main article: Subscriber network
Switched network
Main article: Switched network
ATM
ATM(Asynchronous Transfer Mode) is a packet switching technology
compatible with all types of services today. It is used in both the access
network and the core network. Operates at layer 2 datalink of OSI
-The data to be sent is divided into packets with a fixed length of 53
bytes, called a cell.
X.25
X.25 is a protocol recognized by CCITT ( English acronym: Consultative
Committee for International Telegraph and Telephone). This protocol is
a very popular protocol introduced to ensure the integrity of data when
traveling in the network. It defines the interconnection of multiple
networks using packet-switching techniques with associated computers
or outputs. X.25 allows computers on many different public networks to

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Frame relay
Frame relay is a packet-switching protocol used to connect devices in a
WAN. This protocol was created for use in very fast environments with
little chance of error. In the US, it supports T-1 (or DS1) speeds up to
1,544 Mbps. Frame relay is essentially based on the old X.25 protocol.
The difference is that frame relay is a "fast-packet" technique and this
technique will not perform error correction. When an error is found, it
simply drops the packet with the error. The terminals are responsible for
detecting errors and requesting resends of aborted packets.
DSL
Main article: DSL
Main article: ADSL
Main article: HDSL
Main article: RADSL
Main article: VDSL
Novell Netware
Main article: Novell Netware
Windows NT
Main article: Windows NT
Apple Talk
Main article: Apple Talk
ARPANET
ARPANET is a WAN-style network, nse ) initiated in the early 1960s to
create a network that could survive a possible nuclear war between the
United States and the Soviet Union. The word ARPANET is a
combination of the words Advance Research Project Agency and the
word NET. This was one of the first networks to use packet-switching
technology, it consisted of subnets and multiple masters. Subnets are
designed using minicomputers called IMPs, or Interface Message
Processors, (from the word Interface Message Processor ) to ensure
communication capabilities, each IMP must connect to at least two
other IMPs and call the software of these subnets the IMP-IMP protocol.
The IMPs are connected by existing 56 Kbps telephone lines.

21. ARPANET has developed very strongly thanks to the support of
universities. Many other protocols have been tested and applied on this
network, the most important of which is the invention of the TCP/IP
protocol used in LANs connected to ARPANET. By 1983, ARPANET
had proven resilient and successful, including more than 200 IMPs and
hundreds of mainframes. Also in the 1980s, many LANs were
connected to ARPANET, and the design of DNS, or domain naming
system, (from the word Domain Naming System ) was also born on this
network first. By 1990, this network was no longer in use. This is
considered a historic network and the predecessor of the Internet.
NFSNET
In 1984, the National Science Foundation of the United States (NSF)
was designed to serve the research and information needs between
universities, including 6 supercomputers from many centers spread
throughout the United States. This was the first WAN to use TCP/IP. In
the late 1990s, fiber optics technology was applied. In December 1991,
the National Research and Educational Network was born to replace
NSFNET and used speeds up to gigabits. By 1995, NSFNET was no
longer needed.
Internet
The number of computers connected to the ARPANET increased rapidly
after TCP/IP became the sole official interface on January 1, 1983. After
ARPANET and NSFNET were connected, network development
increased exponentially. Many parts of the world began connecting to
form networks in Canada, Europe, and across the Atlantic Ocean,
forming the Internet. Since 1990, the Internet has had more than 300
networks and 2,000 computers connected. By 1995 there were
hundreds of medium-sized networks, tens of thousands of LANs,
millions of mainframes, and tens of millions of Internet users. Its size
doubles every two years. I have the Das Home Office Cash Paket
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The main fabric that holds the Internet together is the TCP/IP protocol
and the TCP/IP interface stack. TCP/IP made services ubiquitous. By
January 1992, the spontaneous development of the Internet was no

22. longer effective. The Internet Society was born to promote and manage
it. The Internet has the following main applications:
Electronic mail ( email ): provides the ability to write, send and receive
emails.
Newsgroup: forums for users to exchange information. There are tens
of thousands of such groups and each has its style and style.
Remote login: helps users anywhere can use the Internet to log in and
use or control another computer where they have an account. Famous
is the Telnet program.
File transfer: use the FTP program to transfer files over the Internet
everywhere.
Search engines, these programs over the Internet, can help people
find information in all forms and levels about anything. From finding
in-depth research documents to finding people and information about
that person, or finding directions on maps,
Wireless network
Black laptop with the router in the background
Computers are very often connected to networks using wireless links
Main article: Wireless network
Handheld or pocket-sized devices can often communicate with each
other wirelessly and in a LAN fashion. Another option used for cell
phones is based on the CDPD ( Cellular Digital Packet Data ) protocol
or digital cellular packet data.
Wireless devices can completely connect to a regular (wired) network to
form a mixed network (equipped on some passenger aircraft. I have AI
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Internet
Main article: Internet connection
Networks around the world may differ in hardware and software, so for
them to communicate with each other, a device called a gateway is
required to coordinate the task. A set of interconnected networks is
called an internetwork. The most common form of internetworking is a

23. collection of multiple LANs connected by a WAN. I have Avatar
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Main article: Internet connection
Networks around the world may differ in hardware and software, so for
them to communicate with each other, a device called a gateway is
required to coordinate the task. A set of interconnected networks is
called an internetwork. The most common form of internetworking is a
collection of multiple LANs connected by a WAN.
ISDN
Main article: PSTN
Main article: ISDN
ISDN comes from the word Integrated Services Digital Network,
meaning "digital network of integrated services". In general, ISDN is a
type of network that uses circuit-switched connection technology. ISDN
is an international standard for digital audio, data, signal, and video
communications. For example, it can be used for video conferences to
simultaneously exchange images, sounds, and text between personal
computers connected to a group of video conferencing systems.
The ISDN system uses connections over digital telephone lines to allow
multiple channels to operate simultaneously over a single interface
standard. Users at home and in economic establishments who want to
have ISDN via a digital telephone line system need to install special

24. hardware equipment called adapters. ISDN's current maximum speed is
up to 128 Kbps. Many localities that are not equipped with digital
telephone lines will not be able to install ISDN technology.
Organizations influencing network standardization
Organizations with major influence or authority on computer network
standardization:
ISO "International Organization for Standardization"
ANSI "American National Standards Institute"
IEEE "Institute of Electrical and Electronics Engineers"
ITU "International Telecommunication Union" I have Internet Money
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Social issues
Relationships between people becoming faster, easier, and closer also
bring many social problems that need to be solved such as:
Abusing the network system to do illegal or unethical things:
Organizations of human trafficking, pornography, fraud, or cybercrime,
hacking organizations to steal property of citizens and agencies,
terrorist organizations.
The larger the network, the easier the risk of spreading malicious
software (malware).
The trading system becomes more difficult to control but also creates
conditions for fiercer competition.
One problem that arises is defining the border between the control of
public employees and their private property rights. (The owner wants full
control over emails or online chats, but this can seriously violate
personal rights.)
The problem of educating teenagers also becomes more difficult
because they can participate in activities online that are difficult for
parents to control.
More than ever with fast communication media, freedom of speech or
abuse of speech rights can also have a more profound impact than
before as is the case with advertising software ( adware ) and spam
emails. junk ( spam mail ).

25. The development of computer network systems brings many benefits to
society such as. I have ChatGPT The AI all-rounder for your
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Many people can share the same utility software.
If a group of people working on a project are connected to the network,
they will share the project's data, share the project's master file, and
exchange information with each other easily.
Data is centrally managed so it is secure, exchange between users is
convenient and fast, and data backup is better.
Shared use of printers, scanners, hard disks, and other devices.
Users exchange information easily with each other through electronic
mail service (Email), Chat services, file transfer services (FTP), and
Web services.
Eliminate barriers of geographical distance between computers in the
network that want to share and exchange data with each other.
Some users do not need to be equipped with expensive computers (low
cost but strong functions).
Allows programmers in one computer center to use utility programs and
memory areas of another computer center that are idle to increase the
economic efficiency of the system.
Safe for data and software because it manages access rights of user
accounts (depending on network administrators).
References
^ Computer network definition
^ John Kopplin (2002). “An Illustrated History of Computers: Part 4” .
ComputerScienceLab.
^ “DEC released its first mini computer: PDP-1” .
^ Tom Owad (May 22, 2004). “October 1977 Price List” .
^ New global standard for fully networked home, ITU-T, 12 December
2008, Archived from the original on 21 February 2009, retrieved 12
November 2011
^ IEEE P802.3ba 40Gb/s and 100Gb/s Ethernet Task Force, accessed
November 12, 2011,
Read more
Cisco Professional Certificate
Microsoft Professional Certificate

26. Banking network system
Join-transfer technique
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Further research
Tanenbaum, Andrew S. Computer Networks. 3rd ed. Prentice Hall PTR.
ISBN 0-13-066102-3.
Shelly, Gary, et al. "Discovering Computers" 2003 Edition
Cisco Systems, Inc., (2003, March 14). CCNA: network media types.
Accessed from ciscopress.com
Wendell Odom, Rus Healy, Denise Donohue. (2010) CCIE Routing and
Switching. Indianapolis, IN: Cisco Press
Kurose James F and Keith W. Ross: Computer Networking: A
Top-Down Approach Featuring the Internet, Pearson Education 2005.
Andrew S. Tanenbaum, Computer Networks, Fourth Edition, Pearson
Education 2006 ( ISBN 0-13-349945-6 ).
William Stallings, Computer Networking with Internet Protocols and
Technology, Pearson Education 2004.
Important publications in computer networks
Vinton G. Cerf "Software: Global Infrastructure for the 21st Century"
Meyers, Mike, "Mike Meyers' Certification Passport: Network+" ISBN
0-07-225348-7 "
Odom, Wendall, "CCNA Certification Guide"
Network Communication Architecture and Protocols: OSI Network
Architecture 7 Layers Model
External links
Wikimedia Commons has media related to Computer networks.
Easy Network Concepts (Linux kernel specific)
Computer Networks and Protocols (Research document, 2006)
Computer Networking Glossary Archived 2006-08-16 at the Wayback
Machine
Networking on DMOZ