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Network
1. What is a network?
2. How are networks classified?
3. What is a network topology?
Can you find the word? (bus, topology, optical fibres, infrared)
1. A flexible transparent fiber of extremely pure glass or plastic, generally between 10 and 200 micrometers in
diameter, used especially to carry light signals for telecommunication purposes. _________________
2.
Electromagnetic radiation having a wavelength just greater than that of red light but less than that of microwaves.
__________
3.
4.
The arrangement in which the nodes of a LAN are connected to each other. _______________
A parallel circuit that connects the major components of a computer, allowing the transfer of electric
impulses from one connected component to any other. ______________
Translate the following definition into English.
Ένα δίκτυο είναι μια συλλογή υπολογιστών και συσκευών που συνδέονται μεταξύ τους. Το δίκτυο
επιτρέπει στους υπολογιστές να επικοινωνούν μεταξύ τους και να μοιράζονται πόρους και πληροφορίες.
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………….
Computer networks can also be classified according to:
a. the hardware and software technology that is used to interconnect the individual devices in the
network, such as Optical fibre, Ethernet, wireless LAN, HomePNA, or Power line
communication.
Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches,
bridges and/or routers.
Wireless technology is designed to connect devices without wiring. These devises use radio waves or
infrared signals as a transmission medium.
b. their scale as Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area
Network (MAN), Personal Area Network (PAN), Virtual Private Network (VPN), Campus Area
Network (CAN), Storage Area Network (SAN), etc.
c. the functional relationships which exist among the elements of the network, e.g. active
networking, Client-server and Peer-to-peer (groupwork) architecture.
Network topology
Computer networks may be classified according to the network topology upon which the network is
based, such as bus network, star network, ring network, mesh network, star-bus network, tree or
hierarchical topology network. Network topology signifies the way in which devices in the network see
their logical relations to one another. The use of the term “logical” here is significant. That is, network
topology is independent of the “physical” layout of the network. Even if networked computers are
physically placed in a linear arrangement, if they are connected via a hub, the network has a star topology,
rather than a bus topology. In this regard, the visual and operational characteristics of a network topology
is not necessarily the same as the physical layout. Networks may be classified based on the method of
data used to convey the data; these include digital and analogue networks.
Network configurations.
Complete the paragraphs with the words below
terminals – remote – central – directly - configuration
Star: In the star configuration, the ____________ computer performs all processing and control
functions. All ___________ are connected to a central computer, controller or hub. The star
_______________ has two limitations; it is sensitive to failure and the ___________ devices are not able
to communicate ____________; they communicate via the central computer only.
Ring: In a ring communications system including a plurality of the concentrations that are connected in
the form of a ring and the terminal stations connected to the line concentrators are connected to the main
ring via ring subsidiaries. Devices may send information only when they are in control of the “token”,
which is a package of data which indicates the device that has control.
avoidance – clients – transmit – communications
Bus: It is a network architecture in which a set of clients are connected via a shared _______________
line, called a bus. They are the simplest way to connect multiple __________________, but may have
problems when two clients want to ______________ at the same time on the same bus. Thus systems
which are bus network architecture normally have some scheme of collision handling or collision
_________________ for communication on the bus.
Match the phrases in the columns according to the text
1.
2.
3.
4.
Wireless connection
Infrared signal
Ethernet
Network topology
a.
b.
c.
d.
Independent of the physical layout
Transmission medium
Physical wiring
Radio waves
The columns below describe characteristics of the bus, star and ring configurations. Which column
refers to which configuration?
A ……………………..
B. …………………………
C. ……………………
Simple multi-connection
The device having control
Control by the central computer
Clients connected in a line
A network in the shape of a loop Easy to fail
Collision problems
Only one device may send data at No direct communication
a given moment
Which configuration is presented in each picture?
Vocabulary
Avoidance = αποφυγή
Classify = ταξινομώ
Collision = σύγκρουση
Configuration = διάταξη, δομή
Convey = μεταφέρω
Deploy = αναπτύσσω
Hub = κεντρικός κόμβος
Indicate = δείχνω, δηλώνω
Layout = στήσιμο, διαρρύθμιση
Limitation = περιορισμός
Router = δρομολογητής
Switch = μεταγωγέας
Sensitive = ευαίσθητος
Significant = σημαντικός
Signify = υποδηλώνω
Transmit = στέλλω
Wiring =καλωδίωση
Below is a list of the most common types of computer networks. Can you identify their name?
A ___________ is a computer network used for communication among computer devices close to one
person. Some examples of the devices that are used are printers, fax machines, telephones and scanners.
The reach of the network is very short.
A ___________ is a computer network covering a small physical area, like a home, office, or small group
of buildings, such as a school, or an airport.
A ___________ is a computer network made up of an interconnection of local area networks within a
limited geographical area. It can be considered one form of a metropolitan area network, specific to an
academic setting.
A ___________ is a network that connects two or more local area networks or campus area networks
together but does not extend beyond the boundaries of the immediate town/city. Routers, switches and
hubs are connected to create this network.
A ___________ is a computer network that covers a broad area, uses routers and public communication
links. The largest and most well-known is the Internet. It is a data communications network that covers a
relatively broad geographic area (i.e. one city to another, one country to another) and that often uses
transmission facilities provided by common carriers, such as telephone companies.