Some important questions in computer networking

Some important questions

Q1. What do you mean by Network? …

A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications.

Q2. What do you mean by Node? …

A node is a basic unit of data structures. Any system or device connected to a network is also called nodes.

Q3. What do you mean by Network Topology?

A network topology is the arrangement of nodes -- usually switches, routers, or software switch/router features -- and connections in a network, often represented as a graph.

Q4. What is Routers? …

A router is a networking device that forwards data packets between computer networks.

Q5. What is the OSI model? …

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.

Q6. Explain the Different layers of the OSI model?

1. Physical layer:- The physical layer is the first layer of the Open System Interconnection Model (OSI Model). The physical layer deals with bit-level transmission between different devices and supports electrical or mechanical interfaces connecting to the physical medium for synchronized communication.

2. Data link layer:- Data Link Layer. ... It makes sure the appropriate physical protocol is assigned to the data. The data link layer is the second layer in the OSI Model. The three main functions of the data link layer are to deal with transmission errors, regulate the flow of data, and provide a well-defined interface to the network layer.

3. Network layer:- The network Layer controls the operation of the subnet. The main aim of this layer is to deliver packets from source to destination across multiple links (networks).

4. Transport layer:- The network Layer controls the operation of the subnet. The main aim of this layer is to deliver packets from source to destination across multiple links (networks).

5. Session layer:- the session layer is the fifth layer, which controls the connections between multiple computers. ... This layer establishes, controls and ends the sessions between local and remote applications.

6. Presentation layer:- The presentation layer is layer 6 of the 7-layer Open Systems Interconnection (OSI) model. It is used to present data to the application layer (layer 7) in an accurate, well-defined and standardized format. The presentation layer is sometimes called the syntax layer.

7. Application layer:- The application layer is a layer in the Open Systems Interconnection (OSI) seven-layer model and in the TCP/IP protocol suite. It consists of protocols that focus on process-to-process communication across an IP network and provides a firm communication interface and end-user services.

Q7. Describe Hub, Switch and Router?

Hub:- hub is the most basic networking device that connects multiple computers or other network devices together.

Switch:- A network switch (also called switching hub, bridging hub, officially MAC bridge) is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device.

Router:- A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet.

                

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Network Security tutorial

Network Security

Network Security refers to the measures taken by any enterprise or organization to secure its computer network and data using both hardware and software systems. 

This aims at securing the confidentiality and accessibility of the data and network. Every company or organization that handles large amount of data has a degree of solutions against many cyber threats.

 Network Security has become the central topic of cyber security with many organizations inviting applications of people who have skills in this area. The network security solutions protect various vulnerabilities of the computer systems such as:

1. Users

2. Locations

3. Data

4. Devices

5. Applications 

Network Security : Working

The basic principle of network security is protecting huge stored data and network in layers that ensures a bedding of rules and regulations that have to be acknowledged before performing any activity on the data.

1. Physical

2. Technical 

3. Administrative 

1. Physical Network Security:

This is the most basic level that includes protecting the data and network though unauthorized personnel from acquiring the control over the confidentiality of the network. These includes external peripherals and routers might be used for cable connections. The same can be achieved by using devices like bio-metric systems.

2. Technical Network Security:

It primarily focuses on protecting the data stored in the network or data involved in transitions through the network. This type serves two purposes. One, protection from the unauthorized users and the other being protection from malicious activities.

3. Administrative Network Security:
   

This level of network security protects user behavior like how the permission has been granted and how the authorization process takes place. This also ensures the level of sophistication the network might need for protecting it through all the attacks.

Types of Network Security:

Access Control: Not every person should have complete allowance to the accessibility to the network or its data. The one way to examine this is by going through each personnel’s details. This is done through Network Access Control which ensures that only a handful of authorized personnel must be able to work with allowed amount of resources.

Antivirus and Anti-malware Software:

This type of network security ensures that any malicious software does not enter the network.

 The malicious software like Viruses, Trojans, Worms are handled by the same. This ensure that not only the entry of the malware is protected but also that the system is well equipped to fight once it has entered.

          Cloud Security:

Now a day, a lot many organizations are joining hands with the cloud technology where a large amount of important data is stored over the internet. This is very vulnerable to the malpractices that few unauthorized dealers might pertain. This data must be protected and it should be ensured that this protection is not jeopardize over anything. This type of security ensures in creating gaps in visibility of the data.

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TCP/IP MODEL tutorial

                       TCP/IP MODEL

The OSI model we just look at in just a reference/logical model. It was designed to describe the functions of the communication system by dividing the communication procedure into smaller and simller components.

           But when we talk about the TCP/IP model, it was designed and devoloped by DEPARTMENT OF DEFENSE (DOD) in 1960s and is based on standard protocol, It stands for Transmission Control Protocol/Internet Protocol. The TCP/IP model is a concise version of the OSI model.

             LAYERS IN TCP/IP MODEL

It contains four layers, unlike seven layers in the OSI model.

• Process/Application layer.
• Host-to-Host/Transport layer.
• Internet layer.
• Network Access/Link Layer.

• Application Layer:- To allow access to network resources.

• Transport Layer:- To provide reliable process massage delivery and error delivery.

• Internet Layer:- To move packets from source to destination to provides internetworking.

• Network Interface:- Responsible for the transmission for the between two device on the same network.

            NETWORK ACCESS LAYER

• This layer corresponds to the combination of data link layer and physical layer of the OSI model.
• It looks out for hardware addresing and the protocols present in this layer allows for the physical transmission of data.
• It helps you to defines details of how data should be sent using the network.
• It also includes how bits should optically be signaled by hardware devices which directly interface with a network medium, like COAXIAL,OPTICAL,FIBER or TWISTED-PAIR CABLES.

                       INTERNET LAYER

• An internet layer is a second layer of the TCP/IP model.
• It is also known as a network layer.
• The main work of this layer is to send the packets from any network, and any computer still they reach the destination.
• The main protocols resinding at this layer are………….

                      1. IP,   2.ICMP, 3.ARP.

                HOST-TO-HOST LAYER

• This layer is analogous to the transport layer of the OSI model.
• It is responsible for end-to-end communication and error-free delivery of data.
• The two main protocols present in this layer are……………..

                    1.TCP (Transmission control protocol)

                    2.UDP (User datagram protocol)

                     TRANSPORT LAYER

• Transport layer helps you to control the reliability of a link through flow control, error control and segmentation on de-segmentation.
• The transport layer also offers an acknowledgment of the succesful data transmission and sends the next data in case no errors occurred.

                  APPLICATION LAYER

• This layer performs the functions of top three layers of the OSI model…...APPLICATION, PRESENTATION and SESSION layer.
• It is responsible for node-to-node communication and controls user-interface specifications.
• Some of the protocols present in this layer are…….HTTP, HTTPS, FTP, TFTP, Telent, SSH, SMTP, SNMP, NDP, DNS, DHCP.

The diagrammatic comparison of the TCP/IP and OSI model---------

TCP/IP model                             OSI model

                                                         Application layer

1. Application layer                   Presentation layer

                                                    Session layer

2.Transport layer                       Transport layer

3.Internet layer                           Network layer

4.Network access layer             Data link layer

                                                     Physical layer

 Difference between TCP/IP and OSI model…

TCP/IP model                       OSI model

1.TCP refers to transmission  1.OSI refers to open           

   Control protocol                     system interconnection.

2.TCP/IP has 4 layer.                   2.OSI has 7 layer.

3.TCP/IP is more reliable.            3.OSI is less reliable.

4.TCP/IP does not have very       4.OSI has strict 

   Strict boundaries                       boundaries.

5.TCP/IP develop protocols       5.OSI developed model 

   Than model                                than protocol.

6.TCP/IP follow a horizontal.      6.OSI follows a vertical   

                                                         approach.

What is protocol?

• A protocol is a standard set of rules that allow electronic devices to communicate with each other.
• These rules include what type of data may be transmitted, what commands are used to send and receive data, and how data transfers are confirmed.

SOME IMPORTANT PROTOCOLS………

• IP:- It's stand for internet protocol and it is responsible for delivering packets from the source host to the destination host by looking at the IP addresses in the packet headers.

• ICMP:- Stands for internet control massage protocol. It is encapsulated with in IP datagrams and is responsible for providing hosts with information about network problems.

• ARP:- Stands for address resolution protocol. It job is find the hardware address of a host from a known IP address.

• TCP:- It is known to provide reliable and error-free communication between end system.

1. It performs sequencing and segmentation of data.
2. It also has acknowledgement feature and controls the flow of the data through flow control mechanism.

• UDP (user datagram protocol):-

1. It is the go to protocol if your application does not require reliable Transport as it is very cost effective.
2. Unlike TCP which is connection-oriented protocol, UDP is connection less.

• HTTP and HTTPS:-

1. HTTP stands for Hyper Text Transfer Protocol. It is used by the world wide to manage communication between web browsers and servers.
2. HTTPS stands for HTTP-SECURE. It is a combination of HTTP with SSL (secure socket layer).
3. It is efficient in cases where the browser need to fill out forms sign in, authenticate and carry out bank transactions.

• TELNET:- Telnet is a protocol. That allows you to connect to remote computer, called host over a TCP/IP network.

• SSH:-

1. SSH stands for SECURE SHELL. It is a terminal emulations software similar to Telnet.
2. The reason SSH is more preferred is because of its ability to maintain the encrypted connection.

• NTP:-

1. NTP stands for NETWORK TIME PROTOCOL .
2. It is used to synchronize the clocks on our computer to one standard Time source.
3. It is very useful in situations like bank transaction.

• FTP:- FTP is a network protocol used to transfer files from one computer to another over a TCP network.

• SNMP:- It stands for SIMPLE NETWORK MANAGEMENT PROTOCOL is an application layer protocol used to manage and monitor network devices and their functions.

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Collision Domain and Broadcast tutorial.../

Collision Domain and Broadcast 

Domain in Computer Network

1. Collision Domain –
                   A Collision Domain is a scenario in which when a device sends out a message to the network, all other devices which are included in its collision domain have to pay attention to it, no matter if it was destined for them or not. This causes a problem because, in a situation where two devices send out their messages simultaneously, a collision will occur leading them to wait and re-transmit their respective messages, one at a time. Remember, it happens only in case of a half-duplex mode.

2. Broadcast Domain –
           A Broadcast Domain is a scenario in which when a device sends out a broadcast message, all the devices present in its broadcast domain have to pay attention to it. This creates a lot of congestion in the network, commonly called LAN congestion, which affects the bandwidth of the users present in that network.

From this, we can realize that more the number of collision domains and more the number of broadcast domains, the more efficient is the network providing better bandwidth to all its users.

• HUB – it neither breaks a collision domain nor a broadcast domain,i.e a hub is neither a collision domain separator nor a broadcast domain separator. All the devices connected to a hub is in a single collision and single broadcast domain. Remember, hubs do not segment a network, they just connect network segments.

• SWITCH – Every port on a switch is in a different collision domain, i.e a switch is a collision domain separator. So messages that come from devices connected to different ports never experience a collision. This helps us during designing networks but there is still a problem with switches. They never break broadcast domains, means it is not a broadcast domain separator. All the ports on the switch are in still in a single broadcast domain. If a device sends a broadcast message, it will still cause congestion.

• ROUTER – A router not only breaks collision domains but also break broadcast domains, means it is both collision as well as broadcast domain separator. A router creates a connection between two networks. A broadcast message from one network will never reach the other one as the router will never let it pass.

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