201 lines
8.4 KiB
HTML
201 lines
8.4 KiB
HTML
<!doctype html>
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<html>
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<title>Online text</title>
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<meta charset="utf-8">
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<body>
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<p dir="ltr" style="text-align: left;"></p><p><span lang="EN-IN">1.
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Data communication is defined as the exchange of data between two or more
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connected devices over some types of transmission medium, such as copper cable
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or the Internet. These devices must be capable of both sending and receiving
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data. The 5 main components of data communication are:</span></p>
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<p><span lang="EN-IN">- Sender: A sender is a device that can send data over a network,
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such as a computer, a mobile phone, a broadcaster, etc.</span></p>
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<p><span lang="EN-IN">- Receiver: A receiver is a device that can receive data from the
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network, such as a radio, a printer, etc. </span></p>
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<p><span lang="EN-IN">- Message: The data exchanged between the sender and the receiver.</span></p>
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<p><span lang="EN-IN">- Transmission medium: It is the path that the message travels
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between the origin and the destination. This path could be either wired (cable)
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or wireless (the Internet).</span></p>
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<p><span lang="EN-IN">- Protocols: It is a set of rules and agreements between devices
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that must be followed by the communicating parties in order to have successful
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and reliable data communication.</span></p>
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<p><span lang="EN-IN">2. The OSI model includes
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7 layers, from data to network:</span></p>
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<p><span lang="EN-IN">- Layer 7 – Application: The Application Layer is located at the very top of the OSI Model
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layer, where network applications run. These programs generate the data that
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must be sent across the network. This layer also facilitates access for application services to access the
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network and present information to the user.</span></p>
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<p><span lang="EN-IN">- Layer 6 – Presentation: The Presentation Layer represents the
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preparation or translation of the application format from or to the network format. In
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other words, the layer translates,
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encrypts, and compresses data, so that they could be used by upper or lower
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layers.</span></p>
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<p><span lang="EN-IN">- Layer 5 – Session: The Session Layer creates a session in which
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connected devices on a network can communicate with each other. The layer
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establishes, manages, and terminates sessions, as well as security and authentication.</span></p>
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<p><span lang="EN-IN">- Layer 4 – Transport: The layer serves the Application Layer and
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receives services from the Network Layer. It is in charge of delivering the
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entire message from beginning to end. The transport layer also provides
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reliable process-to-process message delivery and error recovery. Segments are
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the units of data in this layer. A good example of this layer is the
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Transmission Control Protocol (TCP).</span></p>
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<p><span lang="EN-IN">- Layer 3 – Network: The Network Layer is responsible for data
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transfer between hosts on various networks. It also handles packet routing,
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which is the determination of the quickest path to send the packet from the
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available routes. The network layer inserts the IP addresses of the sender and
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receiver into the header. Packets are the units of data in this layer.</span></p>
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<p><span lang="EN-IN">- Layer 2 – Data Link: The Data Link Layer is in charge of message
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transport from node to node. This layer's primary duty is to provide error-free
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data flow from one node to another over the physical layer. When a packet
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enters a network, it is DLL's obligation to send it to the Host using its MAC
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address. Frames are the units of data in this layer. The layer also organizes
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bits from the physical into frames.</span></p>
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<p><span lang="EN-IN">- Layer 1 – Physical: The Physical Layer manages the physical
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connection between the devices. Bits are the units of data in this layer. It is
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in charge of sending individual bits from one node to the next. When this layer
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receives data, it converts the incoming signal into 0s and 1s and sends them to
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the Data Link layer, which reassembles them into frames. The layer also
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provides mechanical and electrical specifications.</span></p>
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<p>
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<span lang="EN-IN">3. - Bus topology: A shared wire connects
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all devices (such as PCs in a computer network). The end systems' connection to
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the bus is passive. This implies that each end system can read data from the
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bus but is not responsible for passing it to other terminals. A data unit is
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always received by all end systems on a bus, even though the data unit is
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normally only intended for one end system. As a result, only one end system may
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transmit a data unit through the bus at any given moment. Otherwise, data units
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from multiple end systems would overlap and cannot be correctly received. A
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termination resistor is used to prevent signal reflections at the cable ends.</span></p>
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<p><span lang="EN-IN"><img src="image.png" alt="" role="presentation" class="img-fluid"></span></p>
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<p><span lang="EN-IN">- Star topology: All end systems in a star topology are connected to
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one another via an extra network component (star coupler) utilizing their own
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cables. The star coupler is not the end of the line. It just serves to send
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data units. Every communication is routed through the star coupler as a result
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of this setup. There are two kinds of star couplers: </span></p>
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<p><span lang="EN-IN">• A hub sends signals received on one port to all other ports. This
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is quite straightforward and hence inexpensive to implement because no
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addresses must be assessed, among other reasons. As a result, only one device
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may transfer data at the same time. Otherwise, collisions, such as in bus
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topology, may occur. </span></p>
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<p><span lang="EN-IN">• A switch forwards signals selectively, that is, just to the end
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system that will receive the data unit. This necessitates the evaluation of
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addresses during forwarding and the management of which end system is linked to
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which port. However, this has the advantage of allowing concurrent
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communication across end systems. For example, an end system at port 1 can
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transfer a data unit to an end system at port 2, while end systems at ports 3
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and 4 interact with one another simultaneously. The number of parallel
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communications that are actually possible is determined by the switch's
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internal capabilities.</span></p>
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<p>
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<span lang="EN-IN"> <img src="image%20%281%29.png" alt="" role="presentation" class="img-fluid"></span></p><p><span lang="EN-IN">- Tree topology: A tree topology is formed when numerous systems of
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star topology are merged to form a bigger unit by linking star couplers
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together. This structure is frequently utilized as the foundation for a
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hierarchical network, which is commonly employed in office buildings. </span></p>
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<p><span lang="EN-IN"><img src="image%20%282%29.png" alt="" role="presentation" class="img-fluid"></span></p><p><span lang="EN-IN">- Mesh topology: There are redundant connections in a mesh
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architecture to safeguard the network from breakdowns. In a completely meshed
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network, all network nodes are linked to one another. Even with a few nodes,
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this situation is just theoretical because the cost and labor for building all
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of the mesh connections grow substantially. A partly meshed network is one in
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which the possible redundant connections are only partially realized. In this
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instance, you might, for example, build the network so that each node is linked
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to at least three other nodes. Then, even if two links fail, you may continue.</span></p>
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<p></p><img src="image%20%283%29.png" alt="" role="presentation" class="img-fluid"><br clear="ALL">
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<p><span lang="EN-IN">4.- Local area network (LAN): A LAN is a network that exists inside
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the confines of an organization and can range in size from 10 m to 10 km.
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Ethernet technology has become the only option for local area networks with no
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specific requirements. The situation is similar with wireless local area
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networks, where only Wireless LAN technology is now available.</span></p>
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<p><span lang="EN-IN">- Metropolitan area network (MAN) is a network that spans between 10
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and 100 kilometers. There were formerly particular technologies (like FDDI)
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created for MANs. Instead, LAN or WAN technology is employed nowadays.</span></p>
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<p><span lang="EN-IN">-
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Wide area network (WAN): A WAN is a network that spans more than 100
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kilometers, such as a national network. Different technologies, such as IP,
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Ethernet, SDH, OTN, or MPLS, are used in these networks.</span></p><br><p></p>
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</body>
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</html> |