Network_BSC

Introduction:  It is the collection of computer and devices interconnected by wire or wireless that facilitated communication among users and allows users to share resources (file, printer, DVD-ROM etc) and information.

Importance of Networking:

Resource sharing: The main advantage of networking is resource sharing. Resource can be hardware and software like file, printer, operating system, scanner, hard disk etc.

Communication medium: The main goal was to established communication between autonomous devices. It is very fast and cheap to communicate long distance through network communications. We can communicate via sending text, listening online FM stations, e-commerce, Facebook.

Centralized computer: All the computer and other components of a network are managed and controlled by central computer is called server. Server data can be protected easily and the data can be transferred to all the clients through server rather than individual.

Simultaneous Access: Many organizations like banks works on same database system. This database should be modified, updated and deleted frequently. A network server is a central computer with large storage capacity and other resources that all users can share.

Backup and recovery: The server is placed in a secure place and in a good security mechanism is providing for backup of data. If the data is lost accidently or due to any other reason in client, then it is possible to restore them from the server.

Saving money: Mainframe computer are hundred times faster than personal computer. Because of this imbalance personal computer with network emerge to share data and resource through different mainframe server.

Disadvantages:

    I.          Increase Expenses: In order to install computer in network, we requires some common devices such as hubs, cable, NIC, MODEM, switch, router etc. Networking equipment and network software are expensive too.

  II.          Possibility of leakage and corruption of data: The data transmission in between the nodes can be hacked and used by third parties. This causes data corruption and leakage in networking. Hackers and computer virus are the threats to the computers in the network.

III.          Need special technical knowledge: To work in networking environment, the organization needs very high skilled manpower to install and operate it. The absence of technical manpower causes shutdown of network.

Computer network types: On the basis of geographical areas

LAN: A group of computer and other devices that are connected by communication lines in a limited geographical area such as home, campus, office building. Basically, Networks covers area up to 1 Km. LAN is faster then WAN and MAN. Twisted pair cable is the major transmission medium and in wireless radio and infrared. Ethernet is the most common used technology.

MAN: MAN is networks larger than LAN and smaller that WAN. It is called metropolitan since it normally covers the area of city or two towns up to 100 kms. Example Network of cable television.

WAN: A geographically widespread network capable for communicating and sharing all types of data and information all around the world is called WAN. It is the network of network and consists of large number of LANs and MANs. The span of WAN is in thousand KM around the world connecting countries and continents. WAN has the slowest data communication rates. The operator of WAN is by ISP (Internet Service Provider) or by Telephone Company.

Network Architecture: It refers how computer are organized in a system and how task are allocated between these computer

Two types of network architecture.

Peer to Peer Model (P2P): In this type of network, each computer has equal capabilities and responsibilities to share data and information. Each computer acts as a client as well as server i.e. all computers can both request and provide services. There is no central server to maintain. It is also called distributed network.

Advantages of peer to peer Model

1.      Less expensive and simple, easy to setup, easy maintenance.

2.      No dedicated staffs are needed for administration and controlling network. 

  

Disadvantages of peer to peer model

1.      Performance degrades as the network increase.

2.      Low security.

3.      This system is not centralized, making administration difficult.

Client/Server architecture: In client server model, all the workstations (clients) are connected to the central device (Server). The central server manages, organize control and coordinate and provide services to the entire client in the network. The clients and server computer are interconnected by hub, switch or router. In this type of network client computers requests services to the server. Example: Email Server, Web server, database server, file server, print server

Advantages of client server Model

1.      Easy to implements security policies, since the data are stored in central location.

2.      Gives better performance than p2p provide that server must be powerful computer.

3.      Simplified network administration

Disadvantages of client server model

1.      If server crashes, there is a chance of data loss.

2.      Expensive

Two tier architecture:  It is used to describe client server system where client request resources and single server computer is responsible for responding directly to the request. Server is responsible for database manipulation and processing business logic.

Advantages:

1. Easy to maintain and modification is bit easy
2. Communication is faster

Disadvantages:

1. In two tier architecture application performance will be degrade upon increasing the users.
2. Cost-ineffective

Three tier architecture: In this architecture, server is divided into 2 levels: Application and database server. A client request resources (using web browser). The application server is responsible for providing the request resource to the client. Application server processes business logic whereas database server manipulate database and provide data to the application server.

Advantages

1. High performance, lightweight persistent objects
2. Scalability – Each tier can scale horizontally
3. High degree of flexibility in deployment platform and configuration
4. Better Re-use
5. Improve Data Integrity
6. Improved Security – Client is not direct access to database.
7. Easy to maintain and modification is bit easy, won’t affect other modules

Disadvantages

1. Increase Complexity/Effort

Network topologies: Network topology is the way of connecting the computer in LAN or way of cabling in the network i.e. topology refers to the shape of network. The major goal of topology is to find out the most economical and efficient way to connect all the users to the network resources

Some of the topologies are

A.    Bus Topology: All the devices are connected to a central cable called bus/ backbone topology. This cable or bus is terminated at either end. The data sent are detected by all the nodes but accepted only those nodes which are addressed.

Advantages of Bus Topology:

       I.          Installation is cheap and easy.

     II.          Addition of nodes / new connection is easily made.

   III.          Less cable is required

  IV.          If one computer down it does not affect the network

Disadvantages of Bus Topology:

I.          It is used only for small network.

II.          Fault identification is difficult.

III.          A single fault in cable disturbs network transmission.

IV.          All computers share the same path hence performance decreases while network grows.

B. Ring Topology: In this topology, cable runs from computer to computer without any endpoint to form a loop i.e. data flows in circular manner through the ring cable. It is based on peer to peer architecture. A ring topology passes data in only one direction (either clockwise or counter clockwise). So the failure of one node can affect the entire network.

     

Advantages of Ring Topology:

  I.          It is easy to install and modify the network.

II.          The fault isolation is simplified.

III.          No signal/data loss in the ring topology.

      Disadvantages Ring Topology:

I.          Adding and removing computer disturbs the entire network.

II.          A break in the ring can stop transmission in the network.

III.          It cannot use for large scale network.

C. Star Topology: Star topology uses a central hub through which all the components are connected. Nodes communicate across the network by passing data through the hub. The central hub makes decision to transmit data around the network and make simple communication among devices.

            Advantages of Star Topology

I.          Installation and configuration of network is easy.

II.          Less expensive when compare to Mesh topology.

III.          Fault in the network can be easily tracked.

IV.          Expansion and modification of star topology is easy.

V.          Single computer failure does not affect the network

VI.          It supports multiple cable type like STP, UTP, telephone cable etc.

Disadvantages of Star Topology:

                 I.Failure of central hub brings the entire network halt.

               II.          More cabling is required in comparison to tree, bus or ring topology.

D. Mesh Topology:  In this type of topology, each computer is interconnected to all other computer in the network. A fully connected mesh network has n*(n-1) /2physical links between n devices.

 Advantages of Mesh Topology

1.      Use of dedicated links eliminates traffic problems.

2.      Failure in one of the computer does not affect the entire network

3.      Point to point link make fault isolation

4.      It is robust.

5.      Privacy between computers is maintained as message travel along dedicated path.

Disadvantages of Mesh Topology

1.      The length of cabling required is high

2.      A large number of input/output ports are required.

3.      Cost of the networking is high because of cable and ports

E. Hybrid topology: A network topology that uses two or more topologies is called hybrid topology. A network can contain two or more sub network where each sub-network may have different topologies (bus, star, ring etc.)

Communication devices:

MODEM: It is a device that allows a computer to transmit information over a telephone line. The Modem translates between the digital signal that the computer uses and analog signal that telephone line carries. The process of converting digital signal in the form of 0 and 1 to analog signal is called modulation and the process of converting analog signal to digital signal in the form of 0 and 1 is called demodulation. The speed at which modem can transfer data is measures in bits per second. Most popular modems are 28 kbps or 56 kbps.

Multiplexers: It is also called mux. It is a device that selects one of the several analog or digital input signals and forwards the selected input into a single line. It is used to increase the amount of data that can be sent over the network within certain amount of time and bandwidth. Demultiplexer (or demux) is a device taking a single input signal and selecting one of many data output line, which is connected to the single input.

Repeater: As signal travels along a cable, its strength or amplitude decreases. Repeaters can regenerate the weak signal so that they can travel additional cable length. A repeater is a physical layer device used to interconnect the media segments of an extended network.

Hub: Hubs are connecting device that connects computer in a star topology. Hubs contain multiple ports for connecting network components. Hub broadcasts data receives by any ports to all other ports on the hub except the segment from which the data was received. It is also called multiport repeater or connector. Hub is mainly used in computer lab for networking as it cost is lower and easier to install.

Switch: switch offers a direct network connection between the source and destination computer. When a switch receives a data packet, it creates a separate internal connection or segments between any two of its ports and forwards the data packet to the appropriate port of the destination computer only.

Bridge: A bridge device filters data traffic at a network boundary. Bridges reduce the amount of traffic on a local area network (LAN) by dividing it into two segments. Bridges operate at the data link layer (Layer 2) of the OSI model. Bridges inspect incoming traffic and decide whether to forward or discard it.  Example  Ethernet bridge.

Router: A router is a networking device that forwards data packets between computer networks. A router is connected to two or more data lines from different networks. When a data packet comes in, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table it directs the packet to the next network on its journey. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers are located at gateways, the places where two or more networks connect.

Amplifier: An amplifier is a device that is used to boost the power of the signal that is transmitted over. It is mainly used in analog transmission.

Network Adapters: Network Interface card is a hardware device that provides connectivity between a PC and network. Internal NICs are built in to the system motherboard. The transfer rate of NICs is in Mbps (Megabit per second). Each NIC is uniquely identified by a special MAC (Media Access Control) Address.

Transmission Media (or Communication channel or Communication media): It is the path which signal travels from one location to another location. Each transmission has its own properties like bandwidth, delay, cost, error rate, ease of transmission and maintenance.

Transmission media are groups into bound media and unbound media

Bound media: The transmission of data and information from source to destination by using physical medium like wires are called bounded transmission media or guided transmission media Example: Coaxial Cable, twisted pair cable, optical fiber.

A. Twisted-pair cable: A twisted pair wire consists of two thin copper wires, each enclosed separately in a plastic insulation, the twisted around each other to reduce electromagnetic interference by adjacent wires. There are two types of twisted pair cable.

Shielded Twisted Pair Cable (STP): If the twisted pair cable is shield by metallic cover is called STP. These metallic cover is inside p the plastic jacket is used to protect from external factors such as EMI.

Unshielded Twisted pair Cable (UTP): If the twisted pair cable is uncovered by the metallic protective cover is called UTP cable. UTP are prone to interference. These cables are ideal for short range data transmission like Ethernet networking, telephone networking.  Cat-5, Cat-5e and Cat-6 are mostly used UTP.

Advantages of Twisted Pair Cable

1.      It is thin and flexible hence it is easy to string between walls.

2.      More lines can be run through the same wiring ducts.

3.      UTP costs less per meter than any other type of LAN cable

4.      These cables can carry higher bandwidth ever in Gbps.

5.      It can support 1024 computer in network.

Disadvantages of Twisted Pair Cable

1.      It cannot transmit data for long distance. Typical range is less than 200 meters.

2.      These cables are prone to EMI. Electricity and magnetic noise.

3.      These cables are not suitable for video transmitting

B. Coaxial Cable (Commonly called coax). The central of the cable is relatively solid copper wire encased in insulating plastic foam. The foam is surrounded by second conductor, a wire mesh, which server as a shield from EMI (Electromagnetic interface), high voltage, and radiation. The inner cable is used to carry data signal to other. Coaxial cable is used for cable television. There are two type of coaxial Cable

a)     Thinnet It used thin type of coaxial cable of diameter 0.19 inch. It is also known as 10 Base2 i.e. 10Mbps Baseband connector and 200 m for data transmission. Thinnest cable segment up to 185 m and maximum 30 nodes can be attached on it.

b)     Thicknet: Uses thick type of coaxial cable. Its diameter is 0.375 inch technically known as 10Base 5 i.e.  10 Mbps data transmission and 500 meter for data transmission used as backbone of Ethernet support 100 nodes on it.

Advantages of Coaxial cable:

1.      These cables are less affective by EMI because of shield.

2.      It is easy to install, modify and maintain network.

3.      It has high bandwidth up to 10 Mbps.

4.      It has sufficient frequency range to support multiple channels.

Disadvantages of coaxial cable

1.      It is most expensive to install.

2.      It can be use only for bus topology.

3.      It is outdated technology for computer networking.

4.      It can support limited number of computer in the network.

C. Fiber optic cable: A fiber optics cable consists of a bundle of glass or plastic threads, each of which is capable of transmitting messages modulates onto light wave Optical fibers typically include a transparent core surrounded by a transparent cladding material and protective coating of plastic called jacket. It works on the principle of total internal reflection of light. It has two modes: Single mode fiber- It can carry single ray of light whereas multimode fiber can carry beam of light.

Advantages of Optical Fiber

1.      It is totally immune from radio frequency interference (RFI), electromagnetic Interference (EMI) and electricity.

2.      Tapping of data is difficult. Concentric dual core optical fiber is tap proof.

3.      It has larger bandwidth.

4.      It can travel longer distance without loss of data. Typical range is 70 to 150 KM without repeater's

5.      It is smaller, thinner, low cost material and light weight than any other bound media.

6.      It contain no electricity, hence no chance of short circuit or fire.

Disadvantages of Optical Fiber

1.      Physical vibration can generate disturbance in data transmission.

2.      It has limited physical ace of the cable, cannot bent.

3.      It is difficult to install and efficient technical manpower required.

4.      Operation cost, installation cost and maintenance cost are high.

5.      Joining two segment of optical fiber is complex.

Unguided media: If there is no physical connectors (wires) between the communicating devices is called wireless / unguided / unbound transmission. Example: Satellite transmission. Wireless media can be divided into

A. Radio Wave: Electronic magnetic waves ranging from 3 KHz to 300GHz are called radio waves. These are omnidirectional i.e. they are propagated in all direction. Radio waves are used in AM, FM, Cordless phone, paging, Wi-Fi, VHF bands.

B. Microwaves: Electronic magnetic waves ranging from 300MHz to 300GHz. These are unidirectional. The receiving and sending antennas should be aligned. It has very little penetration power and cannot pass through wall. Thus it needs LOS (Line Of Sight).

Microwaves are two types

Terrestrial Microwave: It employs earth based transmission and receiver. Parabolic antennas are used to transmit and receive signal. Terrestrial microwave typically operates at 2-6GHz and 21-23 GHZ.

Satellite Microwave: Satellite microwave system relay transmission through communication satellite that operates in geosynchronous 22,300 miles above earth surface. It is also called artificial satellite. It is used for different purpose such as communication, military, weather forecasting etc.

C. Infrared wave: Electromagnetic wave ranging from 300GHZ to 400 THz. It is used for very short distance communication. It needs LOS. It travels in straight line hence it is direction by nature. Example remote controller, wireless keyboard, mouse, Bluetooth.

Data transmission across Media

1.      Simplex Mode: Simplex communication system can transmit data in one direction only. Example radio, Television, Keyboard to CPU.

2. Half duplex Mode: Half duplex communication system can transmit data in both direction but in one direction at a time. Example: Walkie-Talkie

3. Full duplex mode: Full duplex communication system can transmit data in both directions simultaneously. Both device can transmit and receive data at same time. Examples telephone, mobile, full duplex Ethernet communication.

Speed of transmission: It is determined by two factors

A. Bandwidth:-The range of frequencies available in the communication channel. It is measured in Hertz.

B. Baud rate: - It is the number of symbols or signal that can be transmitted per sec.

For example, if the symbol rate is 4800 baud and each symbol represents two bits that translates into an overall bit rate of 9600 bits/s.

Analog and Digital Transmission:

Analog Transmission is the method of conveying voice, data, image, signal or video information using a continuous signal which varies in amplitude, phase.

A digital signal is a physical signal that is representation of a sequence of discrete values. Information transmitting in and out of the computer system is in the form of digital signals (0 and 1). Example: Pen drive to hard drive data transmission, DVD-ROM to pen drive, RAM to Microprocessor and ADSL modem to your computer.

Data transmission and Data Networking

In circuit switching   two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. Example Telephone network.

Message switching: It does not establish a dedicated path between two stations for entire conversation. Rather, conversation are divided into message and packed with its own destination address and then transmitted the message from one device to another device through the network. Intermediate device receive the message, store it briefly and then transmit the message to the next device. This type of network is also called store-and-forward network. E-mail is example of a message switching system.

Packet switching: Packet switching is a digital networking communications in which relatively small units of data called packets are routed through a network, based on the destination address contained within each packet. Breaking communication down into packets allows the same data path to be shared among many users in the network. This type of communication between sender and receiver is known as connectionless. Most traffic over the Internet uses packet switching

Wireless Networking: A wireless network is any type of computer network (homes, telecommunication, and enterprise) that uses wireless data connections for connecting network nodes. It generally implemented using radio communication. Examples of wireless networks include cell phone networks, Wi-Fi local networks and terrestrial microwave networks.

Benefits

1.  Convenience: Access the network resources from any location within wireless network coverage.

2.      Mobility: Roam without losing the connection.

3.      Productivity: It improves customer service by connecting staff to the information they need. For example, a doctor in a small medical office can access online patient files while moving between exam rooms.

4.      Easy setup: Installation is quick and cost -effective.

5.    Expandable: IT can be expanded easily with existing equipment.

6.   Security: Wireless network provide robust security protection.

7.   Cost:  Wireless networks eliminate or reduce wiring costs, so inexpensive than wired network

Wireless LAN: A wireless local area network (WLAN) is a wireless computer network that links two or more devices using a wireless distribution method (often spread-spectrum or OFDM radio) within a limited area such as a home, school, computer laboratory, or office building. This gives users the ability to move around within a local coverage area and still be connected to the network, and can provide a connection to the wider Internet.

  

Wireless WAN:  WWAN are wireless networks that cover large area, such as towns, cities. These networks can be used to connect branch office. The wireless connection between access points are usually point to point microwave link using directional antenna rather than omnidirectional antenna. GSM, CDMA and WiMAX are major wireless WAN technologies.