Tuesday, 19 November 2019

Simplex,Half-Duplex,Full-Duplex Transmission modes


Data transmission process (Communication Channels)

There are three kinds of transmission data flows in the Telecommunication and computer Networking.  This channels can be Physical transmission media or a logical media. Basically we can say transmission flow type is transferring data between to networking devises. A brief introduction about three Data Transmission process types will be given in this part.

 Importance of data flows

  •           helps to determine how to transport the data into one end to another end.
  •           To identify the communication way between the communication devises.
  •           To learn the data flow systems and how it laid.
  •           To identify the difference of the three types of data flows and how will be data is transmitting.


01.Simplex

Image result for simplex transmission mode


-        simplex is a one direction communication. In this type there is no both way communication. For example: Radio Station, radio station is used in Simplex Transmission because it’s always transmit the signals its listeners and listeners cannot be able to reply in this way. Television setup is also can get the example to the simplex transmission. simplex mode of transmission is data bandwidth can be fully used for one direction and it is a great advantage of the that type.



02.Half-Duplex

       Image result for half duplex
-        Provides communication for both directions but only one direction at a time. The simplest real world example is a walkie-talkie. Usually, when one direction starts to communicate other side have to listen until it’s over. After the one side communication other end side can replay the other side. If two directions transmit signals at a same time, there are some collision occur between them. After that both way stop transmitting signals and wait and randomly again re transmitting .
-         Example of related networking field: E-mail



03.Full-Duplex 

Image result for full duplex transmission
-        Simultaneous transmission for the both direction. Another word is both station send and receive at the same time. It has two simplex channels it is a forward and backward channel. For a real world example is telephone conversation. Both sides can communicate in simultaneously. Increase the efficiency of communication is the main advantage of full duplex. Transmitting two ways by using full-duplex mode is Bandwidth of the channel should be decreased. It is a main disadvantage of the Full-duplex mode.





OSI Model



OSI Reference Model (Open System Interconnection)

The open system interconnection model is a conceptual framework for understanding various aspects of a computer network into seven layers  It has been developed by International Organization of Standardization (ISO) in year 1974. It maintained a ISO/IEC 7498-1. Each layer having special functionality. All layers working together to transmit the data for one end to another end 
Above mentioned seven layers can divide into 3 categories. It is the
  •       Software layer- [application, presentation, session layers]
  •       Transport layer [heart of OSI]
  •       Hardware layers [network, datalink, physical layers]


Why a layer network model


  •          Reduce complexity
  •           Standardize interface
  •           Facilitate modular engineering.
  •           Ensure inter operable technology.
  •           Simplifies teaching and learning.
  •           To allow different type of network hardware and software to communicate with each other.
  •           When we make the network devises OSI model is very important.
  •           To design network.
  •           To detect the errors of network.
  •           To breaks network communication into smaller parts that are easy to develop.


                                               Image result for osi layers

   01.Physical Layer
  •          The bottom layer of the OSI model.
  •           It is a protocol to decide physical signals and connection methods in networks.
  •           Working the interface between communication media and communication devises.
  •           The way off cable is connected to the network interface, size of connector type and number of pins and modulation technology is describing in this layer.\

    02.Data Link Layer
  •  Most important function is it provide a way for packets to be sent safely over the physical media without interference from other devices.
  •  It realizes the reliable transmission between two points based on MAC (Media Access Control) address. (transmit data between LAN or WAN network ports.)
  • Data link layer provide basic error detection and correction to ensure that data sent is the same as the data receive
  • The data from the network layer will be transmitted and framed into the physical layer to distribute trough the network.
  • Data link layer support to flow control and frame synchronization.
  • Data link layer commonly used bridge and switches.

     03.Network Layer
  • The ultimate responsibility is to determine the best way to send data to the end point and it decides appropriate communication path between two hosts based IP addresses.
  • To above purpose, logical addressing use for translate logical address to MAC (Media Access Control) address.
  • Only decides communication path and is not involved in the quality of communication.
  • Network layer provide two important functions. It is logical addressing and routing. 

     04.Transport Layer
  •  Provide basic data transfer services.
  •  TCP helps IP to move the data packet to one end to another end.
  •   Main purpose of the transport layer is handle error recovery it ultimately ensures data are received in order and free of corruption.
  •   Ensure complete data transferring.

     05.Session Layer

  • The session layer establishes conversation sessions between networked devices. Session layer be able to detect the errors of above layers.
  • Session layer tracks the dialogs between computers, which are also called sessions 
  • Session layer allows three types of transmission medias.
1.      Simplex – data flow to only one direction.
2.      Half-duplex – both way communication but at a time
3.      Full duplex – both way communication at the same time. 


 Image result for simplex duplex and half duplex
     
     06.Presentation Layer

  • Presentation layer can data Translate, Encryption and Compression
  • It responsible for how data is represented to application layer.
  • translate: convert the sender data to the public data and also public data type convert to the sender data type.
  • Encryption: the sender will translate the original data into another format to send the data foe receiver (it is security method to the data protection)
  • Compression: number of bits in the data is reduced. It is important for multimedia transport and also when we sending the large file to the receiver.




    07.Application Layer
  •          The most recent layer is for the user.
  •          Application layer represents the programing interfaces that application programs use to request network services.
  •          Provide an interface to user services of e-mail, telnet, FTP and HTTP.
  •          Application layer can data recovery procedure and error recovery procedures.
  •          Ensure the privacy
  •          More than is protocols are used in this layer 

Networking devises


Networking devises

Basically computer network is a group of multiple networking devises connect together for data sharing and all networks are made up of basic hardware building blocks to interconnected network nodes, such as NICs (Network Interface Card), routers, switches etc. when we implement the network to share the data or information through the network, it has methodological system to complete that methods. Every networking devises has its own functionalities and operations. When we consider the network devices, there are some special and main devises 

1.      Hub
2.      Switch
3.      Repeater
4.      Router
5.      Bridge


  •  Network hubs are categorized as physical layer devise in the OSI reference mode.
  • Data travel around a network in packets, hub forwards these data packets out to all the devices connected to its ports (distributes packets to every device on the network).
  • Commonly used connect segment of a LAN (Local Area Network) and Central connection point for LAN 
  • Hub contains multiple ports.
  • When data packet arrives at one port and I is copied to the other ports so that all segment of the LAN can see all packets.
  • Cannot provide routing capabilities or other advanced network services.
  •  Mainly there are 3 type hubs 





 


       SWITCH
  • Hub and Switch function is same. It used to connect multiple computers together in a LAN segment but there some different between those two devises. 
  • Function: when a switch receives data, switch identify the MAC (Media Access control) address of destination station and forward it to the correct port (Intelligent devise).
  • Switches available 4, 8, 12, 24, 48, 64 ports.
  • Switches work in Layer 2 (Data Link Layer).
  • Switch can detect the errors before forwarding data.



      REPEATERS

  • Repeater is a devise that operates only at the physical layer.
  • Function: regenerate the signal over the same network before the signal becomes too weak.
  • Repeater only regenerate not amplify the signals and also it is copy the signal bit by bit and regenerate it at the original strength.
  • Repeaters cannot be used to connect segments of different networks.


      ROUTER
  • Network layer devise.
  • Router forwards packets on the bases of their destination address. (connect multiple networks and forward packets destined either for its own network or other network)
  • Functions: connect different network segments and different media types like UTP (Unshielded Twisted Pair) and fiber optic and also router can connect different network architectures like Token Ring (Ring topology) and Ethernet.
  • Connect several small network into large network.
  • Router reduce network traffic by creating collision domain and broadcast domains


    BRIDGE

  •   Bridge work at the MAC sub-layer of the OSI model (Physical and Datalink)

    - Physical layer – it regenerates the signal it receives.
   - Data link layer – bridge can check source and destination of the data (MAC) contain in the  frame           
  •  Bridge used to divide a large network in to small segments.

  •  Bridge has per port. It means if a port force collision, other ports will not have effected of that collisions.

  • Join different media types such as UTP with fiber optic and also connect different network architecture such as Ethernet and Token ring 


What is Wi-Fi


Wi-Fi (Wireless Fidelity)


Wi-Fi is a short name for Wireless Fidelity alternative network to wired network which is commonly used for connecting devises in wireless transmission media mode. Generally, use to any type of IEEE 802.11 Wireless Local Area Network (WLAN). Wi-Fi is a wireless networking technology of enable computers and other devices to communicate over a wireless signal. Wi-Fi is the standard computers connect to wireless networks. Modern computers and devises have built connecting chips that allows users to find and connect the Wi-Fi router. The router must be connected to internet (by using DSL or cable modem) in order to provide in internet access for the connected devises.
Wi-Fi is works in hotspot is created by installing an access point to an internet connection and that access point acts as a base station. Normally a single access point can support up to 30 users and can function within a range of 100-150 feet indoors and up to 300 feet outdoors.  
There many standers in here the Wi-Fi,

802.1x

This standard improves LAN security by providing an authentication framework that allows users to authenticate to a central authority such as LDAP or Active Directory. Combined with 802.11 access technologies, it provides an efficient mechanism for controlling wireless LAN access.

802.11a

An extension of the 802.11 standard, developed by IEEE for wireless network technology. The 802.11a standard applies to wireless LANs and supports a maximum connection speed of 54 Mbps in the 5 GHz band. This specification is not backwards compatible with 802.11b / g and requires special wireless adapters.

802.11b

An extension of the 802.11 standard, developed by IEEE for wireless network technology. The 802.11b standard applies to wireless LANs and supports a maximum connection speed of 11 Mbps with a pullback to 5.5, 2, and 1 Mbps in the 2.4 GHz ISM band. This standard was ratified in 1999.

802.11g

An extension of the 802.11 standard that allows a maximum connection speed of 54 Mbps while ensuring compatibility with the 802.11b standard in the 2.4 GHz band. This specification is compatible and free for the 802.11b standard.

802.11i

An extension of the 802.11 standard that offers more security than the 802.11 extensions. This enhancement provides improved encryption methods and integration of the IEEE 802.1x authentication protocol and advanced encryption mechanisms such as the Advanced Encryption Standard (AES) for an optional and fully compatible 802.11i implementation.

802.11n

It uses multiple antennas for transmitters and receivers (MIMO) to enable higher speed and greater data width. This is not a standard ratified since December 2006. Pre-standard hardware is commercially available and is not compatible with Wireless PittNet.

 Advantages of Wi-Fi network

·       Not needed wires to access the internet because of that no wire damages and maintainers
·         Users can move around freely within the area of the network with their devises.
·         User can share files and other resources to other devises that are connected to the network without having be cabled to port.
·         It can serve a suddenly-increased number of clients with the existing equipment.
·         Easy to manage access the internet
·         Sometimes handle a large amount of users because they are not limited by a specific number of connection ports.

 Disadvantages of Wi-Fi network

  •        File sharing transfer speeds are normally slower with wireless networks than the wired network.
  •         Wireless setup sometimes bit difficult to people who are not experience with computers.
  •          General speed of a wireless network usually slower than the wired one.
  •       Less secure and can be easier to hack into.


STAR Network Topology is One of the better solutions for a client-server architecture in the Lab Environment



STAR Network Topology is One of the better solutions for a client-server architecture in the Lab Environment

Centralized network architecture of the Star Network allows easy Network management, security and resource sharing through central server. In a training lab instructor or administrator always had to have access to all the computers in the lab. In a star network central server always do necessary configurations to its clients in the network. Client’s activities monitoring is another additional feature.  If some of the students completed their practical, server will be able to correct and mark necessary activities.

When we compare the other topologies with the star topology, bus, ring have no hub or switch. In a star topology it is a possible to have all the important data backup on the hub in a private folder. And also, if the computer fails, we can still use our data using the next computer in the network and accessing the backup files. Because of the I recommend STAR topology is suitable for the client server architecture in the lab.

When working with client server architecture by using Star topology, if any cable is not working then the whole network will not be affected. Therefore, the users can access the network without any failures. And also if you want to add or remove some node in the network, it can easily add or remove without interrupting other nodes. In a star network the whole network is run on the hub so if the entire network is not working then there could be a occurred problem with the hub. Because of that easy to troubleshoot.  

When we consider the client server architecture, server can provide the limit accessing the clients for data, websites, application or any other things. It is based on the IP addresses of the nodes. If we use the STAR topology with switch, that switch can identify the IP address and helps the server. Client server architecture is more expensive and want good technical knowledge to implement it but STAR topology installation is simple, inexpensive, and fast because of the flexible cable and the modular connectors. Comparing the other topologies (ex: mesh) easy to implement and maintain.  

When we consider the LAB environment a star network topology is best suited for lab works efficiently when there is limited number of nodes. When we work in the we can do our every works by using any nodes within the network. If some day want to the develop and expand to the network of the LAB its only need to the another hub/switch and go to a ‘STAR of STAR’ topology. 

Network Topologies


Network Topology

                      Image result for network topologies
   
Network Topology defines as physical or logical layout of a network.  It is the way different nodes are placed and interconnected each other.  Most of all network topology gives a solid idea of how the data is transferred between interconnected nodes.

In the beginning there were simple computer networks. Most of the time requirement of the computer network was to transfer user data in between to computers or computer to server. But eventually when requirements are complicated need for the more complex and sophisticated networks popped up. Most of the financial companies, banks, government offices had a great deal of difficulties to back-up their daily progress. With the evolution of   network technology backing up valuable data and restoring after critical failures such as natural disasters, cyber-attacks and intellectual theft. Presently almost all companies store their valuable data within their computers, servers and data centers. In banks they have their own backup systems. As an example, when a customer withdraws or deposit money through a ATM or Cash deposit machine his bank account automatically updates necessary data same time through network. Also they have added security features and filtering systems as a network feature. If you have With day to day work stress most of the employees used to visit social media websites. In centralized networks, network administrator can block unwanted traffic as face book, twitter, Instagram in order to maintain productivity of the company. Firewalls can be added to the server and easy maintain access control by limited staff.
Networks can be design and adapt to the shape and the original design of the building, organizational structure and behavior. Some of the offices buildings require star topologies and some of them can be manage by using mesh networks.
With the evaluation of the network technologies, equipment and topological designs most of the technological giants moved to fiber optic networks. These high speed fiber networks carry more than 100 Gbps data rate without any delay in between Local Area Networks as well as Wide Ares Networks across the globe.

   
                                 Image result for bus topologies
   
Each devices or computers connected to a single cable or backbone is called as bus topology. Depending on the type of network card in each computer of the bus topology, a coaxial cable or a RJ-45 network cable to connect computers together.
Host of the bus network called as Station or Workstation. In a bus network, each and every station will receive all network traffic, and the traffic generated by every station has equal transmission priority.
A bus network forms a single network segment and collision domain. In order for nodes to transmit on the same bus simultaneously, they use a media access control technology such as carrier sense multiple access (CSMA).

Advantages and disadvantages of the BUS topology

Advantages
Disadvantages
·         Easy to implement
Network disruption when computers are added or removed
·         Not use any specialized equipment
A break in the main cable will prevent all systems from accessing the network.
·         No need technician knowledge to implement
Difficult to troubleshoot.
·         Require less cable.
Low security
·         Easy to connect computers
Limited cable length and number of stations.
·         Less expensive

·         If one node fail, other nodes are not effected



Image result for star topology
It is the most common Centralized network topology in use. In this configuration, every node connects to a central network device, like a hub, switch, or computer. The central network device acts as a server and the peripheral devices act as clients. Depending on the type of network card used in each computer of the star topology, a coaxial cable or a RJ-45 network cable is used to connect computers together.

There are two types of Star Topology

Extended Star Topology

The network based upon the physical star topology has one or more repeaters between the central node and the peripheral or spoke nodes. The repeaters being used to extend the standard maximum transmission distance between the central node and the peripheral nodes. 

Distributed Star Topology

These networks are individual networks that are based upon the physical star topology connected together in a liner fashion with no central or top level connectivity.


Advantages and disadvantages of the STAR topology

Advantages
Disadvantages
·         easily expended without disruption to the network
·         The centralized device increase overall cost of the network
·         cable failure affects only a single user
·         The nodes depend on capacity of central devise.
·         Centralized management.
·         requires more cables
·         Failure of one node or link doesn’t effect the rest of the network.

·         easy  to troubleshoot and isolate problems

·         gives better performance than BUS topology.

 



Image result for ring topology

In this types of networks each node connected to two other nodes of the network, with two connections forming a double ring. First and last node is connected to each other with two connections. Normally only one ring is active and caring date in to a single direction unless there is a failure or breakdown in active ring, data transmission will switch to protection ring and start transmitting to opposite direction.

Advantages and disadvantages of the RING topology

Advantages
Disadvantages
·         cable faults are easily located , making troubleshooting easier
·         expansion to the network can cause network disruption

·         ring network are moderately easy to install

·         a single break in the cable can disrupt the entire network.
·         Each computer from the network as equal access to resources.
·         In a packet pass to the computers its make slower than the star topology.
·         With lord of the network increases it can give a better performance than bus topology.
·         When node goes down, entire network get effected.




Image result for mesh topology

Network topology in which a node transmits its own data as well as serves as a relay for other nodes. Best and most efficient path for effective communication is provided by routers. In the event of hardware failure many routes are available to switch back and continue the network communication process.

There are two types of MESH Network topologies.

Full Mesh networks

This topology is active when each node of the network is connected to all other nodes with direct connections. This provides greater redundancy because if a node goes down, network traffic can be routed through other nodes. Each node accesses the neighboring business nodes and finds the best path for efficient and reliable communication.

Partial Mesh Networks

Partial Mesh Network topology is active when some nodes are connected to all other nodes via direct connections, while others are connected to only one or two nodes. This is less expensive than the entire mesh topology but has less redundancy.


Advantages and disadvantages of the MESH topology

Advantages
Disadvantages
·         provide redundant path between devices
·         chances of redundancy in many of the network connection.
·         the network can be expended without disruption to current uses
·         complicated implementation

·         data can be transmitted from different devises simultaneously.
·         cable cost is high
·         If one of the components fail, there is also alternative path to continue.
·         The setup and maintainers is very much complicated and difficult.



5. Tree Network Topology
                                    Image result for tree topology

Tree network is a combination of two or more star networks connected together. Each star network is a Local Area Network (LAN) and it has a central computer server which all nodes are directly connected. The servers of the star networks are connected to a main cable called the bus. Tree networks are a BUS Network of STAR Networks. 


Advantages and disadvantages of the TREE topology

Advantages
Disadvantages
·         The expansion of network possible and easy
·         Maintains process is more hard
·         Error detection and correction process is easy
·         The main  cable(back bone cable) break whole network goes break down.
·         If one segment is damage other segment are not affected.