network.pptx

COMPUTER NETWORK INTRODUCTION A computer network is a group of devices connected with each other through a transmission medium such as wires, cables etc. These devices can be computers, printers, scanners, Fax machines etc. The purpose of having computer network is to send and receive data stored in other devices over the network. Data communication: is nothing but the exchange of data between any two devices via transmission media. Components of Data Communication: Message: A message is a piece of information that is to be transmitted from one person to another. It could be a text file, an audio file, a video file, etc. Sender: It is simply a device that sends data messages. It can be a computer, mobile, telephone, laptop, video camera, or workstation, etc. Receiver: It is a device that receives messages. It can be a computer, telephone mobile, workstation, etc. Transmission Medium / Communication Channels: Communication channels are the medium that connect two or more workstations. Workstations can be connected by either wired media or wireless media. Set of rules (Protocol): When someone sends the data (The sender), it should be understandable to the receiver also otherwise it is meaningless.

COMPUTER NETWORK Therefore, there are some set of rules (protocols) that is followed by every computer connected to the internet and they are: TCP (Transmission Control Protocol): It is responsible for dividing messages into packets on the source computer and reassembling the received packet at the destination or recipient computer. It also makes sure that the packets have the information about the source of the message data, the destination of the message data, the sequence in which the message data should be re-assembled, and checks if the message has been sent correctly to the specific destination. IP (Internet Protocol): Do you ever wonder how does computer determine which packet belongs to which device. What happens if the message you sent to your friend is received by your father? Scary Right. Well! IP is responsible for handling the address of the destination computer so that each packet is sent to its proper destination.

COMPUTER NETWORK Type of data communication: As we know that data communication is communication in which we can send or receive data from one device to another. The data communication is divided into three types: 1.Simplex Communication: It is one-way communication or we can say that unidirectional communication in which one device only receives and another device only sends data and devices uses their entire capacity in transmission. For example, IoT, entering data using a keyboard, listing music using a speaker, etc. 2.Half Duplex communication: It is a two-way communication or we can say that it is a bidirectional communication in which both the devices can send and receive data but not at the same time. When one device is sending data then another device is only receiving and vice-versa. For example, walkie-talkie.

COMPUTER NETWORK 1. Full-duplex communication: It is a two-way communication or we can say that it is a bidirectional communication in which both the devices can send and receive data at the same time. For example, mobile phones, landlines, etc. Communication Channels: Communication channels are the medium that connects two or more workstations. Workstations can be connected by either wired media or wireless media. It is also known as a transmission medium. The transmission medium or channel is a link that carries messages between two or more devices. We can group the communication media into two categories:  Guided media transmission  Unguided media transmission Guided Media: In this transmission medium, the physical link is created using wires or cables between two or more computers or devices, and then the data is transmitted using these cables in terms of signals. Guided media transmission of the following types:

COMPUTER NETWORK Unshielded Twisted Pair (UTP): It is used in computers and telephones widely. As the name suggests, there is no external shielding so it does not protects from external interference. It is cheaper than STP. Shielded Twisted Pair (STP): It offers greater protection from crosstalk due to shield. Due to shielding, it protects from external interference. It is heavier and costlier as compare to UTP. Coaxial Cable: It consists of a solid wire core that is surrounded by one or more foil or wire shields. The inner core of the coaxial cable carries the signal and the outer shield provides the ground. It is widely used for television signals and also used by large corporations in building security systems. Data transmission of this cable is better but expensive as compared to twisted pair. 3. Optical fibers: Optical fiber is an important technology. It transmits large amounts of data at very high speeds due to which it is widely used in internet cables. It carries data as a light that travels inside a thin glass fiber. The fiber optic cable is made up of three pieces: Core: Core is the piece through which light travels. It is generally created using glass or plastic. Cladding: It is the covering of the core and reflects the light back to the core. Sheath: It is the protective covering that protects fiber cable from the environment.

COMPUTER NETWORK Unguided Media:The unguided transmission media is a transmission mode in which the signals are propagated from one device to another device wirelessly. Signals can wave through the air, water, or vacuum. It is generally used to transmit signals in all directions. Unguided Media is further divided into various parts: Microwave: Microwave offers communication without the use of cables. Microwave signals are just like radio and television signals. It is used in long-distance communication. Microwave transmission consists of a transmitter, receiver, and atmosphere. In microwave communication, there are parabolic antennas that are mounted on the towers to send a beam to another antenna. The higher the tower, the greater the range. Radio wave: When communication is carried out by radio frequencies, then it is termed radio waves transmission. It offers mobility. It is consists of the transmitter and the receiver. Both use antennas to radiate and capture the radio signal. Infrared: It is short-distance communication and can pass through any object. It is generally used in TV remotes, wireless mouse, etc.

Line configuration A network is two or more devices connected through a link. A link is a communication pathway that transfers data from one device to another. Devices can be a computer, printer, or any other device that is capable to send and receive data. For visualization purposes, imagine any link as a line drawn between two points. For communication to occur, two devices must be connected in some way to the same link at the same time. There are two possible types of connections:  Point-to-Point Connection  Multipoint Connection A point-to-point connection provides a dedicated link between two devices. The entire capacity of the link is reserved for transmission between those two devices. Most point-to-point connections use an actual length of wire or cable to connect the two ends, but other options such as microwave or satellite links are also possible. Point to point network topology is considered to be one of the easiest and most conventional networks topologies. It is also the simplest to establish and understand. Example: Point-to-Point connection between the remote control and Television for changing the channels.

COMPUTER NETWORK Multipoint Connection : It is also called Multidrop configuration. In this connection, two or more devices share a single link. If more than two devices share the link then the channel is considered as a ‘shared channel’. With shared capacity, there can be two possibilities in a Multipoint Line configuration: Spatial Sharing: If several devices can share the link simultaneously, it’s called Spatially shared line configuration. Temporal (Time) Sharing: If users must take turns using the link, then it’s called Temporally shared or Time Shared Line configuration.

What is Topology? Topology defines the structure of the network of how all the components are interconnected to each other. There are two types of topology: physical and logical topology. Physical topology is the geometric representation of all the nodes in a network.

Bus Topology  The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable.  Each node is either connected to the backbone cable by drop cable or directly connected to the backbone cable.  When a node wants to send a message over the network, it puts a message over the network. All the stations available in the network will receive the message whether it has been addressed or not.  The bus topology is mainly used in 802.3 (Ethernet) and 802.4 standard networks.  The configuration of a bus topology is quite simpler as compared to other topologies.  The backbone cable is considered as a "single lane" through which the message is broadcast to all the stations.  The most common access method of the bus topologies is CSMA (Carrier Sense Multiple Access

Bus Topology Advantages of Bus topology: Low-cost cable: In bus topology, nodes are directly connected to the cable without passing through a hub. Therefore, the initial cost of installation is low. Moderate data speeds: Coaxial or twisted pair cables are mainly used in bus-based networks that support upto 10 Mbps. Familiar technology: Bus topology is a familiar technology as the installation and troubleshooting techniques are well known, and hardware components are easily available. Limited failure: A failure in one node will not have any effect on other nodes. Disadvantages of Bus topology: Extensive cabling: A bus topology is quite simpler, but still it requires a lot of cabling. Difficult troubleshooting: It requires specialized test equipment to determine the cable faults. If any fault occurs in the cable, then it would disrupt the communication for all the nodes. Signal interference: If two nodes send the messages simultaneously, then the signals of both the nodes collide with each other. Reconfiguration difficult: Adding new devices to the network would slow down the network. Attenuation: Attenuation is a loss of signal leads to communication issues. Repeaters are used to regenerate the signal.

Ring Topology:  Ring topology is like a bus topology, but with connected ends.  The node that receives the message from the previous computer will retransmit to the next node.  The data flows in one direction, i.e., it is unidirectional.  The data flows in a single loop continuously known as an endless loop.  It has no terminated ends, i.e., each node is connected to other node and having no termination point.  The data in a ring topology flow in a clockwise direction.  The most common access method of the ring topology is token passing.  Token passing: It is a network access method in which token is passed from one node to another node.  Token: It is a frame that circulates around the network.

Ring Topology: Advantages of Ring topology:  Network Management: Faulty devices can be removed from the network without bringing the network down.  Product availability: Many hardware and software tools for network operation and monitoring are available.  Cost: Twisted pair cabling is inexpensive and easily available. Therefore, the installation cost is very low.  Reliable: It is a more reliable network because the communication system is not dependent on the single host computer. Disadvantages of Ring topology:  Difficult troubleshooting: It requires specialized test equipment to determine the cable faults. If any fault occurs in the cable, then it would disrupt the communication for all the nodes.  Failure: The breakdown in one station leads to the failure of the overall network.  Reconfiguration difficult: Adding new devices to the network would slow down the network.  Delay: Communication delay is directly proportional to the number of nodes. Adding new devices increases the communication delay.

Ring Topology: Star Topology:  Star topology is an arrangement of the network in which every node is connected to the central hub, switch or a central computer.  The central computer is known as a server, and the peripheral devices attached to the server are known as clients.  Coaxial cable or RJ-45 cables are used to connect the computers.  Hubs or Switches are mainly used as connection devices in a physical star topology.  Star topology is the most popular topology in network implementation.

Ring Topology: Advantages of Star topology  Efficient troubleshooting: Troubleshooting is quite efficient in a star topology as compared to bus topology. In a bus topology, the manager has to inspect the kilometers of cable. In a star topology, all the stations are connected to the centralized network. Therefore, the network administrator has to go to the single station to troubleshoot the problem.  Network control: Complex network control features can be easily implemented in the star topology. Any changes made in the star topology are automatically accommodated.  Limited failure: As each station is connected to the central hub with its own cable, therefore failure in one cable will not affect the entire network.  Familiar technology: Star topology is a familiar technology as its tools are cost-effective.  Easily expandable: It is easily expandable as new stations can be added to the open ports on the hub.  Cost effective: Star topology networks are cost-effective as it uses inexpensive coaxial cable.  High data speeds: It supports a bandwidth of approx 100Mbps. Ethernet 100BaseT is one of the most popular Star topology networks. Disadvantages of Star topology A Central point of failure: If the central hub or switch goes down, then all the connected nodes will not be able to communicate with each other. Cable: Sometimes cable routing becomes difficult when a significant amount of routing is required.

Tree topology  Tree topology combines the characteristics of bus topology and star topology.  A tree topology is a type of structure in which all the computers are connected with each other in hierarchical fashion.  The top-most node in tree topology is known as a root node, and all other nodes are the descendants of the root node.  There is only one path exists between two nodes for the data transmission. Thus, it forms a parent-child hierarchy.

Tree topology Advantages of Tree topology  Support for broadband transmission: Tree topology is mainly used to provide broadband transmission, i.e., signals are sent over long distances without being attenuated.  Easily expandable: We can add the new device to the existing network. Therefore, we can say that tree topology is easily expandable.  Easily manageable: In tree topology, the whole network is divided into segments known as star networks which can be easily managed and maintained.  Error detection: Error detection and error correction are very easy in a tree topology.  Limited failure: The breakdown in one station does not affect the entire network.  Point-to-point wiring: It has point-to-point wiring for individual segments. Disadvantages of Tree topology  Difficult troubleshooting: If any fault occurs in the node, then it becomes difficult to troubleshoot the problem.  High cost: Devices required for broadband transmission are very costly.  Failure: A tree topology mainly relies on main bus cable and failure in main bus cable will damage the overall network.  Reconfiguration difficult: If new devices are added, then it becomes difficult to reconfigure.

Mesh topology  Mesh technology is an arrangement of the network in which computers are interconnected with each other through various redundant connections.  There are multiple paths from one computer to another computer.  It does not contain the switch, hub or any central computer which acts as a central point of communication.  The Internet is an example of the mesh topology.  Mesh topology is mainly used for WAN implementations where communication failures are a critical concern.  Mesh topology is mainly used for wireless networks.  Mesh topology can be formed by using the formula: Number of cables = (n*(n-1))/2;

Mesh topology Mesh topology is divided into two categories:  Fully connected mesh topology  Partially connected mesh topology Full Mesh Topology: In a full mesh topology, each computer is connected to all the computers available in the network. Partial Mesh Topology: In a partial mesh topology, not all but certain computers are connected to those computers with which they communicate frequently.

Mesh topology Advantages of Mesh topology:  Reliable: The mesh topology networks are very reliable as if any link breakdown will not affect the communication between connected computers.  Fast Communication: Communication is very fast between the nodes.  Easier Reconfiguration: Adding new devices would not disrupt the communication between other devices. Disadvantages of Mesh topology  Cost: A mesh topology contains a large number of connected devices such as a router and more transmission media than other topologies.  Management: Mesh topology networks are very large and very difficult to maintain and manage. If the network is not monitored carefully, then the communication link failure goes undetected.  Efficiency: In this topology, redundant connections are high that reduces the efficiency of the network.

Hybrid Topology  The combination of various different topologies is known as Hybrid topology.  A Hybrid topology is a connection between different links and nodes to transfer the data.  When two or more different topologies are combined together is termed as Hybrid topology and if similar topologies are connected with each other will not result in Hybrid topology. For example, if there exist a ring topology in one branch of ICICI bank and bus topology in another branch of ICICI bank, connecting these two topologies will result in Hybrid topology.

Hybrid Topology Advantages of Hybrid Topology  Reliable: If a fault occurs in any part of the network will not affect the functioning of the rest of the network.  Scalable: Size of the network can be easily expanded by adding new devices without affecting the functionality of the existing network.  Flexible: This topology is very flexible as it can be designed according to the requirements of the organization.  Effective: Hybrid topology is very effective as it can be designed in such a way that the strength of the network is maximized and weakness of the network is minimized. Disadvantages of Hybrid topology  Complex design: The major drawback of the Hybrid topology is the design of the Hybrid network. It is very difficult to design the architecture of the Hybrid network.  Costly Hub: The Hubs used in the Hybrid topology are very expensive as these hubs are different from usual Hubs used in other topologies.  Costly infrastructure: The infrastructure cost is very high as a hybrid network requires a lot of cabling, network devices, etc.

OSI Model  OSI stands for Open System Interconnection is a reference model that describes how information from a software application in one computer moves through a physical medium to the software application in another computer.  OSI consists of seven layers, and each layer performs a particular network function.  OSI model was developed by the International Organization for Standardization (ISO) in 1984, and it is now considered as an architectural model for the inter-computer communications.  OSI model divides the whole task into seven smaller and manageable tasks. Each layer is assigned a particular task.  Each layer is self-contained, so that task assigned to each layer can be performed independently. Characteristics of OSI Model:

OSI Model  The OSI model is divided into two layers: upper layers and lower layers.  The upper layer of the OSI model mainly deals with the application related issues, and they are implemented only in the software. The application layer is closest to the end user. Both the end user and the application layer interact with the software applications. An upper layer refers to the layer just above another layer.  The lower layer of the OSI model deals with the data transport issues. The data link layer and the physical layer are implemented in hardware and software. The physical layer is the lowest layer of the OSI model and is closest to the physical medium. The physical layer is mainly responsible for placing the information on the physical medium. Functions of the OSI Layers There are the seven OSI layers. Each layer has different functions. A list of seven layers are given below:  Physical Layer  Data-Link Layer  Network Layer  Transport Layer  Session Layer  Presentation Layer  Application Layer

OSI Model Physical layer  The main functionality of the physical layer is to transmit the individual bits from one node to another node.  It is the lowest layer of the OSI model.  It establishes, maintains and deactivates the physical connection.  It specifies the mechanical, electrical and procedural network interface specifications.

OSI Model Physical layer Functions of a Physical layer:  Line Configuration: It defines the way how two or more devices can be connected physically.  Data Transmission: It defines the transmission mode whether it is simplex, half-duplex or full-duplex mode between the two devices on the network.  Topology: It defines the way how network devices are arranged.  Signals: It determines the type of the signal used for transmitting the information

OSI Model Data-Link Layer  This layer is responsible for the error-free transfer of data frames.  It defines the format of the data on the network.  It provides a reliable and efficient communication between two or more devices.  It is mainly responsible for the unique identification of each device that resides on a local network.  It contains two sub-layers

OSI Model Data-Link Layer •Logical Link Control Layer • It is responsible for transferring the packets to the Network layer of the receiver that is receiving. • It identifies the address of the network layer protocol from the header. • It also provides flow control. •Media Access Control Layer • A Media access control layer is a link between the Logical Link Control layer and the network's physical layer. • It is used for transferring the packets over the network. Functions of the Data-link layer Framing: The data link layer translates the physical's raw bit stream into packets known as Frames. The Data link layer adds the header and trailer to the frame. The header which is added to the frame contains the hardware destination and source address.

OSI Model Data-Link Layer  Physical Addressing: The Data link layer adds a header to the frame that contains a destination address. The frame is transmitted to the destination address mentioned in the header.  Flow Control: Flow control is the main functionality of the Data-link layer. It is the technique through which the constant data rate is maintained on both the sides so that no data get corrupted. It ensures that the transmitting station such as a server with higher processing speed does not exceed the receiving station, with lower processing speed.  Error Control: Error control is achieved by adding a calculated value CRC (Cyclic Redundancy Check) that is placed to the Data link layer's trailer which is added to the message frame before it is sent to the physical layer. If any error seems to occurr, then the receiver sends the acknowledgment for the retransmission of the corrupted frames.  Access Control: When two or more devices are connected to the same communication channel, then the data link layer protocols are used to determine which device has control over the link at a given time.

OSI Model Network Layer  It is a layer 3 that manages device addressing, tracks the location of devices on the network.  It determines the best path to move data from source to the destination based on the network conditions, the priority of service, and other factors.  The Data link layer is responsible for routing and forwarding the packets.  Routers are the layer 3 devices, they are specified in this layer and used to provide the routing services within an internetwork.  The protocols used to route the network traffic are known as Network layer protocols. Examples of protocols are IP and Ipv6.

OSI Model Functions of Network Layer:  Internetworking: An internetworking is the main responsibility of the network layer. It provides a logical connection between different devices.  Addressing: A Network layer adds the source and destination address to the header of the frame. Addressing is used to identify the device on the internet.  Routing: Routing is the major component of the network layer, and it determines the best optimal path out of the multiple paths from source to the destination.  Packetizing: A Network Layer receives the packets from the upper layer and converts them into packets. This process is known as Packetizing. It is achieved by internet protocol (IP).

OSI Model Transport Layer  The Transport layer is a Layer 4 ensures that messages are transmitted in the order in which they are sent and there is no duplication of data.  The main responsibility of the transport layer is to transfer the data completely.  It receives the data from the upper layer and converts them into smaller units known as segments.  This layer can be termed as an end-to-end layer as it provides a point-to-point connection between source and destination to deliver the data reliably.

OSI Model Transport Layer: The two protocols used in this layer are: Transmission Control Protocol  It is a standard protocol that allows the systems to communicate over the internet.  It establishes and maintains a connection between hosts.  When data is sent over the TCP connection, then the TCP protocol divides the data into smaller units known as segments. Each segment travels over the internet using multiple routes, and they arrive in different orders at the destination. The transmission control protocol reorders the packets in the correct order at the receiving end. User Datagram Protocol  User Datagram Protocol is a transport layer protocol.  It is an unreliable transport protocol as in this case receiver does not send any acknowledgment when the packet is received, the sender does not wait for any acknowledgment. Therefore, this makes a protocol unreliable.

OSI Model Transport Layer: Functions of Transport Layer:  Service-point addressing: Computers run several programs simultaneously due to this reason, the transmission of data from source to the destination not only from one computer to another computer but also from one process to another process. The transport layer adds the header that contains the address known as a service-point address or port address. The responsibility of the network layer is to transmit the data from one computer to another computer and the responsibility of the transport layer is to transmit the message to the correct process.  Segmentation and reassembly: When the transport layer receives the message from the upper layer, it divides the message into multiple segments, and each segment is assigned with a sequence number that uniquely identifies each segment. When the message has arrived at the destination, then the transport layer reassembles the message based on their sequence numbers.  Connection control: Transport layer provides two services Connection-oriented service and connectionless service. A connectionless service treats each segment as an individual packet, and they all travel in different routes to reach the destination. A connection-oriented service makes a connection with the transport layer at the destination machine before delivering the packets. In connection-oriented service, all the packets travel in the single route.  Flow control: The transport layer also responsible for flow control but it is performed end-to-end rather than across a single link.  Error control: The transport layer is also responsible for Error control. Error control is performed end-to-end rather than across the single link. The sender transport layer ensures that message reach at the destination without any error.

OSI Model Session Layer:  It is a layer 3 in the OSI model.  The Session layer is used to establish, maintain and synchronizes the interaction between communicating devices. Functions of Session layer:  Dialog control: Session layer acts as a dialog controller that creates a dialog between two processes or we can say that it allows the communication between two processes which can be either half-duplex or full-duplex.  Synchronization: Session layer adds some checkpoints when transmitting the data in a sequence. If some error occurs in the middle of the transmission of data, then the transmission will take place again from the checkpoint. This process is known as Synchronization and recovery.

OSI Model Presentation Layer  A Presentation layer is mainly concerned with the syntax and semantics of the information exchanged between the two systems.  It acts as a data translator for a network.  This layer is a part of the operating system that converts the data from one presentation format to another format.  The Presentation layer is also known as the syntax layer.

OSI Model Presentation Layer Functions of Presentation layer:  Translation: The processes in two systems exchange the information in the form of character strings, numbers and so on. Different computers use different encoding methods, the presentation layer handles the interoperability between the different encoding methods. It converts the data from sender-dependent format into a common format and changes the common format into receiver-dependent format at the receiving end.  Encryption: Encryption is needed to maintain privacy. Encryption is a process of converting the sender-transmitted information into another form and sends the resulting message over the network.  Compression: Data compression is a process of compressing the data, i.e., it reduces the number of bits to be transmitted. Data compression is very important in multimedia such as text, audio, video.

OSI Model Application Layer Functions of Application layer: File transfer, access, and management (FTAM): An application layer allows a user to access the files in a remote computer, to retrieve the files from a computer and to manage the files in a remote computer. Mail services: An application layer provides the facility for email forwarding and storage. Directory services: An application provides the distributed database sources and is used to provide that global information about various objects.

Transmission media  Transmission media is a communication channel that carries the information from the sender to the receiver. Data is transmitted through the electromagnetic signals.  The main functionality of the transmission media is to carry the information in the form of bits through LAN(Local Area Network).  It is a physical path between transmitter and receiver in data communication.  In a copper-based network, the bits in the form of electrical signals.  In a fiber based network, the bits in the form of light pulses.  In OSI(Open System Interconnection) phase, transmission media supports the Layer 1. Therefore, it is considered to be as a Layer 1 component.  The electrical signals can be sent through the copper wire, fibre optics, atmosphere, water, and vacuum.  The characteristics and quality of data transmission are determined by the characteristics of medium and signal.  Transmission media is of two types are wired media and wireless media. In wired media, medium characteristics are more important whereas, in wireless media, signal characteristics are more important.  Different transmission media have different properties such as bandwidth, delay, cost and ease of installation and maintenance.  The transmission media is available in the lowest layer of the OSI reference model, i.e., Physical layer.

Transmission media Some factors need to be considered for designing the transmission media: •Bandwidth: All the factors are remaining constant, the greater the bandwidth of a medium, the higher the data transmission rate of a signal. •Transmission impairment: When the received signal is not identical to the transmitted one due to the transmission impairment. The quality of the signals will get destroyed due to transmission impairment. •Interference: An interference is defined as the process of disrupting a signal when it travels over a communication medium on the addition of some unwanted signal. Causes Of Transmission Impairment:

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