Cent percent Tech

Hub is the most simple networking device which is used to connect all network devices on an internal network. It detects whether a device is physically connected to it or not. It is a Layer 1 device in OSI reference model and is best for small and simple local area networks. It is not intelligent because it does not filter any data. When a packet is received by one port, the data is copied to all other ports and is seen by all connected devices. It has 4/12 ports . Drawbacks of Hubs are:- Rebroadcast- Forwards packets across all ports. Creates Security concerns- Traffic could not be safeguarded. Unnecessary traffic which reduces bandwidth.   

Application Layer(Layer 7): This layer lies at the top of the OSI model. It enables the user, human or software to access the network. It is responsible for providing services to the user. High-level APIs including resource sharing, remote file access. Services provided by Application layer: Network Virtual terminal: A network virtual terminal is a software version of a physical terminal. This layer is responsible for facilitating the user to log on to a remote host through setting up network virtual terminal. File transfer, access, and management: It allows a user to access files    in a remote host(to make changes or read data), to retrieve files from a remote computer for use in the local computer 

Presentation Layer(Layer 6):  It is concerned with the syntax and semantics of the information exchanged between two systems, translation of data between a networking service and an application; including character encoding, data compression, and encryption/decryption.  Functions of the Presentation layer include: Translation: As different computers use different encoding systems, the Presentation layer is responsible for the interoperability between these different encoding methods. The Presentation layer at the sender changes the information from its sender dependent format to a common format. The Presentation layer at the receiving machine changes the common format into its receiver dependent format. Encryption: Encryption means sender transforms the original information to another form and sends the resulting message out over the network. Compression: Data compression reduces the number of bits contained in the information which is particularly important ...

Session Layer(Layer 5): This layer lies between the Transport layer and the Presentation layer. It allows users of different machines to set sessions between them. It establishes, maintains and synchronizes the interaction among communicating devices. It manages communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes. The functions of the session layer are: Dialog Control: The session layer allows two systems to enter into a dialog. It allows the communication between the two processes in either half-duplex or full duplex. Synchronization: It allows long transmissions to resume after a checkpointing.

Transport Layer(Layer 4):  The transport layer is responsible for the delivery of an entire message from one process to another. It ensures that the whole message arrives intact and in order, overseeing both error control and flow control at the source-to-destination level.  Functions include: Service-point Addressing: Computers often run more than one program at the same time. For this reason, source-to-destination delivery means delivery not only from one computer(source) to another(receiver), but also from a specific process on one computer to a specific process on the other. The transport layer header, therefore, must include a type of address, called service point address(port address). The Network layer is responsible for sending each packet to the correct computer; the transport layer gets the message to the correct process on that computer. Segmentation and Reassembly: A message is divided into transmittable segments, each segment containing a sequence numbe...

Network Layer(Layer 3):  It is responsible for the source-to-destination delivery of packets across multiple links(networks).It is also responsible for structuring and managing a multi-node network, including addressing, routing, and traffic control. Functions include: Logical Addressing: IP addressing is defined at the Network Layer of the OSI model. This layer adds a header to the packet coming from the upper layer that, among other things, indicates the logical addresses of the sender and receiver. IP addressing is also known as logical addressing. Routing: When independent networks are connected together to create a large network, the connecting devices(routers/gateways) route the packets to their final destination. The decision which route/path should be followed to reach from source to destination is handled by the network layer. 

Data link Layer(Layer 2):  It makes the raw transmission facility, reliable and error-free to the upper layer. It is responsible for moving the frames from one hop to the next, reliable transmission of data frames between two nodes connected by a physical layer. Functions  include: Framing: This layer divides the stream of bits from the network layer and organizes into manageable data units called frames. Physical Addressing: The data link layer adds a header to the frame in order to define physical address of the sender or receiver of the frame, if the frames are to be distributed to the different systems on the network. Flow Control: If the data rate, at which the data is transmitted by the sender is greater than the rate at which data is received by the receiver, this layer imposes a flow control mechanism to prevent overwhelming the receiver. This prevents traffic jam at the receiver side. Error Control: This layer adds reliability to the phys...

Physical Layer(Layer 1): This is the lowest layer of the OSI model that physically gets connected to the communication channel. It is responsible for movements of individual bits from one node to next i.e. transmission and reception of raw bit streams over a physical medium. Functions include: Physical characteristics of interfaces and medium: The physical layer defines the characteristics of the interface between the devices and the transmission medium. Bit Representation: To be transmitted, the bits must be encoded into signals, so this layer is responsible for defining which type of encoding is to be used. Data Rate: Physical layer defines the number of bits which are to be sent each second. Bit Synchronization: It ensures synchronization between the sender and the receiver at the bit level. Physical Topology: It defines how the devices are connected to make a network. M ode of transmission  Physical layer is responsible for defining the transmission mo...

The OSI(Open System Interconnection) model is a layered framework to implement protocols. It consists of seven separate but related layers, each of which defines a part of the process of moving information across a network.  The International Standards Organisation(ISO) developed the Open Systems Interconnection(OSI) model .  An open system is a set of protocols that allows any two different systems to communicate regardless of their underlying architecture. The OSI model is not a protocol. It is a model for understanding and designing a network architecture that is flexible, robust and interoperable. The Seven Layers of OSI are:- 7.Application 6.Presentation 5.Session 4.Transport 3.Network 2.Data Link 1. Physical

What is a Network ? A Network is defined as an arrangement of a set of devices connected together by communication links for the purpose of sharing data. Each device may be called as a node which can be a computer, printer or any other devices capable of sending or receiving data generated by other nodes or devices on the network. Following are the types of Network:- 1. Local Area Network(LAN): LANs are privately owned networks defined within a small physical area such as in a single office, building or campus. LAN size is limited to a few kilometers for which the network management is simple.   Most common LAN topologies are bus, ring, star and have data rates in the range of 4 to 16 megabits per second. LANs often use a transmission technology consisting of a single cable to which all the machines are attached. LANs are mostly used to allow resources to be shared among personal computers or workstations. 2. Metropolitan Area Network(MAN): A MAN is des...

Modes of Data Communication refers to the direction of data flow from sender to receiver or vice-versa. There are basically three modes of data communication:- 1. Simplex: In this mode the communication is unidirectional . Only one of the two devices on a link can transmit and the other can only receive .i.e data travels in one direction. Example: radio, television, loudspeaker 2. Half-Duplex: In this mode, each device on the link has   the ability to both transmit and receive, each at a time . When one device is sending, the other can only receive and vice versa. Example: walkie-talkie 3. Full-Duplex: In full-duplex mode, both the devices can transmit and receive simultaneously .i.e data can travel in both directions at the same time. Here the communication is bidirectional . Example: Telephone

Data Communication refers to the exchange of data between the sender and the receiver.There are basically five elements of data communication:- 1. Message: It is the information or the data to be communicated.It may be in the form of text, numbers, pictures, sound, video or any other physical quantities. 2. Sender: It is the device which sends the data.It can be computers, workstations, telephone etc. 3. Receiver: It is the device which receives the message.It can be computers, workstations, television etc. 4. Transmission Medium: It is the physical path by which the message travels from sender to the receiver.It could be a twisted pair cable, fibre optic cable, microwaves, infrared waves etc. 5. Protocol : A protocol is a set of rules that govern data communications. It establishes an agreement between the communicating devices. Without a protocol, two devices may be connected but cannot communicate with each other. The protocols are being embedded wi...

Wireshark is the world’s foremost and widely-used network protocol analyzer . It is used for network troubleshooting, analysis, software and communications protocol development, and education. It is a free and an open-source packet analyzer.It is cross-platform. To trace the packets first of all download and install Wireshark in the windows operating system. Open Wireshark and then choose the interface. 1.Tracking FTP Packets Step 1:   $sudo apt-get install vsftpd  command on Ubuntu terminal Step 2: Start Wireshark and open command prompt in windows. In the command prompt enter the IP address of Ubuntu Machine. It asks for username and password authentication for the Ubuntu  machine. Step 3 : Start capturing by clicking the green button in Wireshark.   Step 4: In the filter of Wireshark ,  enter ftp followed by IP address to track. Step 5 : Press the red button to stop capturing. ...

A load balancer is a device that distributes the traffic across a cluster of servers. In computing, load balancing improves the distribution of workloads across multiple computing resources, such as computers, a computer cluster, network links, central processing units, or disk drives.As a result, it improves responsiveness and increases the availability of applications.  For load balancing, we need to install LAMP server on backend servers and HAProxy on the load balancer. HAProxy is a free, open source software that provides a high availability load balancer and proxy server for TCP and HTTP based applications that spread requests across multiple servers. Here we will make two backend servers and one load balancer. At two backend servers enter the following commands— $sudo apt-get install apache2 $sudo apt-get install mysql-server $sudo apt-get install php libapache2-mod-php php-mysql $sudo gedit /var/www/html/index.html (Mak...

There are several commands which can help to diagnose the computer networking in Linux. ifconfig Command Interface configuration(ifconfig) is a command-line interface tool used for configuring, controlling and querying TCP/IP network interface parameters.It is used to initialize an interface, set the IP address and netmask of a network interface and enabling or disabling an interface on demand.  This command is mainly used to know the IP address and MAC address assigned to an interface. -->ifconfig command with no arguments will display will display all network interfaces currently in operation. $ifconfig -a  It will display all available details of the system irrespective of status.It doesn't bother whether the interface is inactive or active.  $ifconfig eth0 It will show the configuration of a specific interface i.e. it will display the configuration of eth0 only. We can change the status of a specif...

To ensure the proper network connection in the system, we do the following three types of checking: ---   Check the NIC card --- Check whether we have an IP or not or our gateway is active or not by a ping test -----  Check if the port no or the service is active or not To check the connection go to command prompt and enter the commands >ping localhost  then NIC  working. >ping 172.29.0.1 then gateway working >ipconfig In computing, ipconfig (internet protocol configuration) is a console application (command line tool) in Microsoft Windows used to control the network connections on windows.It displays all current TCP/IP network configuration values and can modify DHCP and DNS settings. Usually, ipconfig command is used with the command-line switch  /all. > ipconfig /all This command shows the various network configurations, MAC address, default gateway and IP addresses of different servers on the ne...