Grade-XII (Computer Network)
1. What do you mean by computer network? Explain its advantages and roles of hardware.
Computer Network
The dictionary defines a network as a “group of computers and associated devices that are connected by communications facilities.” Thus, a network can be anything from two computers connected by a serial cable to thousands of computers connected by high-speed data communication links dispersed throughout the world. In other words, computer network is a group of computers and associated peripherals connected by a communications channel capable of sharing files and other resources between several users.
Benefits of Networking:
A network provides three principle benefits: the ability to communicate, the ability to share hardware and software, and administrative support.
a). Information sharing and communicating:
The ability to communicate and share of information, inexpensively is one of the popular benefits of networking technology. A network supports communication among users in ways that other media cannot. E-mail, the most popular form of network communication, provides low-cost, printable correspondence with the capability for forwarding, acknowledgment, storage, retrieval, and attachments.
b). Sharing of hardware and software:
Sharing involves not only information (database records, e-mail, graphics, etc.), but also resources (applications, printers, modems, disk space, scanners, etc.) Through its ability to share, a network promotes collaboration. This is the main attraction of popular software called “groupware” that is designed to allow multiple users to hold electronic meetings and work concurrently on projects
c). Centralized administration and support:
Networking simplifies administration and support tasks. The network administrator can perform administrative tasks on any computer on the network from just a single location. Also, it is more efficient for personnel to support one version of OS or application than to oversee a number of individual and unique systems and setups.
Roles of computers in a network:
The computers in a network functions as either clients or servers. The roles of computers in a network are;
a). Clients:
A client is a computer that uses the resources made available by a server. The client must have sufficient processing power on its own to run applications that interact with the resources on the server.
b). Server:
A server is a computer that makes its resources available to the network and responds to the commands of a client. The server in a network performs a variety of complex tasks. The following are some examples of different types of server included on many large networks:
i). File and Print Servers:
File and print servers provides file and printer resources from a centralized location. When a client sends a request for data to the file and print server, the entire database or file is downloaded to the computer making the request. Once the document is saved back on the server, anyone on the network who has the proper access, or permission, may look at the file. In other word, file and print servers are used to store and retrieve centralized file and data records.
ii). Database Servers:
Database servers can store large amount of data in a centralized location and make this data available to users so that they do not need to download the entire database. With a database server, the entire database stays on the server and only the results of a request are downloaded to the computer making the request.
iii). Mail Server:
Mail server operates like database servers. Mail servers manage the e-mail services for the network.
2. Explain the different types of Network:
Network models classify the network on the basis of services and geographical area.
I). Network based on services:
Based on how the computers in a network are configured and how they access information, networks are classified into two types;
a). Peer-to-Peer Network:
In a peer-to-peer network, all computers have an equal relation to one another. There is not any computer, which can be regarded, as superior to another computer. All computers are equal and therefore are known as peers. Any computer in peer-to-peer network can functions as both client and a server simultaneously. Any computer in the network is capable of accessing data, software and other resources directly without any central controlling mechanism. Peer-to-peer network are also called as workgroups.
Advantages of using peer-to-peer network:
• Peer-to-peer networks are easy to build and operate
• Peer-to-peer networks are inexpensive to operate
• The network software used to operate peer-to-peer networks are simple and easy to operate.
• If any computer in a peer-to-peer network fails, then the resources on only that computer becomes unavailable without hampering the availability of resources on other computers.
Disadvantages of using peer-to-peer network:
• The required resources are difficult to find quickly because it could be in any one of the computers.
• Peer-to-peer networks are not very secure.
• A peer-to-peer network becomes very difficult to manage and operate when the number of computer involved exceeds 15 to 20.
b). Client-Server Network:
Client server networks have become standard models for networking. In client-server network, there is a clear distinction between the computers depending upon their functionality; clients and servers. Servers are powerful computers dedicated to managing files or documents (file server), printers (print servers), web pages (web servers) etc. Client are less powerful computer on which users do their job. Client depends upon server computers to access required resources.
Advantages of using client-server network:
• Since the resources are usually located in servers, the resources are easy to find.
• Client-server network can be made very secure. The resources on the server can be controlled very tightly by identifying, who can access the resources and who cannot.
• Client-server network are very scalable. i.e. the number of clients that can be connected in a client-server network is not limited.
Disadvantages of using client-server network:
• It cost more to implement and operate than the peer-to-peer network.
• If the server in a client-server network fails, then the clients cannot access any resources.
• Specialized software is needed to implement a client-server network.
II. Network based on Geographical Area:
1). Network based on Geographical area:
Based on size and distance coverage of networks, the computer network is divided into three types:
a). Local Area Network:
A local area network (LAN) refers to a combination of computer hardware and transmission media that is relatively small. Normally, LAN is entirely contained within a school, college, building etc. LANs is typically comprised of only one transmission media type such as coaxial cable or twisted pair cable but never both. The features of LAN are;
• It covers short geographical area.
• LANs are characterized by comparatively high speed communication.
• LAN uses only one kinds of cable.
• Complete ownership by single organization.
b). Metropolitan Area Network:
A Metropolitan Area Network (MAN) is a network that is larger than a LAN. It is called metropolitan since it normally covers the area of city. Different hardware and transmission media are often used in MAN because they don’t require complete access to locations between the network sites. The features of the MAN are;
• It covers large geographical area with respect to LAN.
• MANs typically used when you need to connect dissimilar system within a single metropolitan.
• It is owned by single or multiple organizations.
• It uses private or public connection mediums.
c). Wide Area Network (WAN):
A Wide Area Network is a network of connecting two or more computers generally across a wide geographical area such as cities, districts and countries. WANs interconnect LANs which may be at the opposite side of a country or located around the world. It uses telephone lines, communication satellite and other long range communication links to connect the computers and network. Internet is an example of WAN. The characteristics of WAN are:
• It covers a large geographical area.
• Transmission cost is high
• Transmission error is higher than LAN
• It is owned by multiple organizations.
• It uses public connections mediums such as telephone lines, wireless technology etc.
• Owned by multiple organization.
3. What is Network Topology/LAN topology/Topology? Explain different types of topologies with merits and demerits.
A network topology is the physical arrangement of computers, cables and other components on a network. The type of topology you use affect the speed and performance of the computer network. The common used physical network typologies are; Bus Topology, Ring Topology, Star Topology, Mesh Topology, Tree Topology, Hybrid Topology
a). Bus Topology:
Advantages:
• Bus topology is simple, reliable (in very small network), easy to use and easy to understand.
• It is less expensive.
• It is easy to add a new node in the network.
Disadvantages:
• Heavy network traffic can slow a bus considerably.
• It is difficult to troubleshoot.
• If problems occurs on the backbone, the entire network will go down.
b). Star Topology:
In a star network, each node (file server, workstations, and peripherals) is connected to a central device called a hub. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. Data on a star network passes through the hub or switch, before continuing to its destination. The hub or switch manages and controls all functions of the network. The star topology reduces the chance of network failure by connecting all of the systems to a central node.
Advantages:
• It is easy to set up and configure.
• It is easy to modify and add new computers to a start topology without disturbing the rest of the network.
• Single computer failure does not necessarily bring down the whole start network.
• It is easy to detect the errors in star topology
Disadvantages:
• It the central device fails, the whole network stops.
• It costs more to cable a start topology because all network cable must be pulled to central point (hub).
c). Ring Topology:
Advantages:
• Ring topology is easy to setup and reconfigure.
• Each computer is given equal opportunity to access the network resources.
• Single cable connects between the nodes.
Disadvantages:
• Failure of one computer on the ring can affect the entire network.
• Adding or removing computers disturbs the networks.
• It is difficult to troubleshoot in a ring topology.
d). Mesh Topology:
• The mesh topology is fault tolerance.
• It is easy to troubleshoot.
Disadvantages:
• Difficult to installation and reconfigure
• It is costlier.
1. What do you mean by computer network? Explain its advantages and roles of hardware.
Computer Network
The dictionary defines a network as a “group of computers and associated devices that are connected by communications facilities.” Thus, a network can be anything from two computers connected by a serial cable to thousands of computers connected by high-speed data communication links dispersed throughout the world. In other words, computer network is a group of computers and associated peripherals connected by a communications channel capable of sharing files and other resources between several users.
Benefits of Networking:
A network provides three principle benefits: the ability to communicate, the ability to share hardware and software, and administrative support.
a). Information sharing and communicating:
The ability to communicate and share of information, inexpensively is one of the popular benefits of networking technology. A network supports communication among users in ways that other media cannot. E-mail, the most popular form of network communication, provides low-cost, printable correspondence with the capability for forwarding, acknowledgment, storage, retrieval, and attachments.
b). Sharing of hardware and software:
Sharing involves not only information (database records, e-mail, graphics, etc.), but also resources (applications, printers, modems, disk space, scanners, etc.) Through its ability to share, a network promotes collaboration. This is the main attraction of popular software called “groupware” that is designed to allow multiple users to hold electronic meetings and work concurrently on projects
c). Centralized administration and support:
Networking simplifies administration and support tasks. The network administrator can perform administrative tasks on any computer on the network from just a single location. Also, it is more efficient for personnel to support one version of OS or application than to oversee a number of individual and unique systems and setups.
Roles of computers in a network:
The computers in a network functions as either clients or servers. The roles of computers in a network are;
a). Clients:
A client is a computer that uses the resources made available by a server. The client must have sufficient processing power on its own to run applications that interact with the resources on the server.
b). Server:
A server is a computer that makes its resources available to the network and responds to the commands of a client. The server in a network performs a variety of complex tasks. The following are some examples of different types of server included on many large networks:
i). File and Print Servers:
File and print servers provides file and printer resources from a centralized location. When a client sends a request for data to the file and print server, the entire database or file is downloaded to the computer making the request. Once the document is saved back on the server, anyone on the network who has the proper access, or permission, may look at the file. In other word, file and print servers are used to store and retrieve centralized file and data records.
ii). Database Servers:
Database servers can store large amount of data in a centralized location and make this data available to users so that they do not need to download the entire database. With a database server, the entire database stays on the server and only the results of a request are downloaded to the computer making the request.
iii). Mail Server:
Mail server operates like database servers. Mail servers manage the e-mail services for the network.
2. Explain the different types of Network:
Network models classify the network on the basis of services and geographical area.
I). Network based on services:
Based on how the computers in a network are configured and how they access information, networks are classified into two types;
a). Peer-to-Peer Network:
In a peer-to-peer network, all computers have an equal relation to one another. There is not any computer, which can be regarded, as superior to another computer. All computers are equal and therefore are known as peers. Any computer in peer-to-peer network can functions as both client and a server simultaneously. Any computer in the network is capable of accessing data, software and other resources directly without any central controlling mechanism. Peer-to-peer network are also called as workgroups.
Advantages of using peer-to-peer network:
• Peer-to-peer networks are easy to build and operate
• Peer-to-peer networks are inexpensive to operate
• The network software used to operate peer-to-peer networks are simple and easy to operate.
• If any computer in a peer-to-peer network fails, then the resources on only that computer becomes unavailable without hampering the availability of resources on other computers.
Disadvantages of using peer-to-peer network:
• The required resources are difficult to find quickly because it could be in any one of the computers.
• Peer-to-peer networks are not very secure.
• A peer-to-peer network becomes very difficult to manage and operate when the number of computer involved exceeds 15 to 20.
b). Client-Server Network:
Client server networks have become standard models for networking. In client-server network, there is a clear distinction between the computers depending upon their functionality; clients and servers. Servers are powerful computers dedicated to managing files or documents (file server), printers (print servers), web pages (web servers) etc. Client are less powerful computer on which users do their job. Client depends upon server computers to access required resources.
Advantages of using client-server network:
• Since the resources are usually located in servers, the resources are easy to find.
• Client-server network can be made very secure. The resources on the server can be controlled very tightly by identifying, who can access the resources and who cannot.
• Client-server network are very scalable. i.e. the number of clients that can be connected in a client-server network is not limited.
Disadvantages of using client-server network:
• It cost more to implement and operate than the peer-to-peer network.
• If the server in a client-server network fails, then the clients cannot access any resources.
• Specialized software is needed to implement a client-server network.
II. Network based on Geographical Area:
1). Network based on Geographical area:
Based on size and distance coverage of networks, the computer network is divided into three types:
a). Local Area Network:
A local area network (LAN) refers to a combination of computer hardware and transmission media that is relatively small. Normally, LAN is entirely contained within a school, college, building etc. LANs is typically comprised of only one transmission media type such as coaxial cable or twisted pair cable but never both. The features of LAN are;
• It covers short geographical area.
• LANs are characterized by comparatively high speed communication.
• LAN uses only one kinds of cable.
• Complete ownership by single organization.
b). Metropolitan Area Network:
A Metropolitan Area Network (MAN) is a network that is larger than a LAN. It is called metropolitan since it normally covers the area of city. Different hardware and transmission media are often used in MAN because they don’t require complete access to locations between the network sites. The features of the MAN are;
• It covers large geographical area with respect to LAN.
• MANs typically used when you need to connect dissimilar system within a single metropolitan.
• It is owned by single or multiple organizations.
• It uses private or public connection mediums.
c). Wide Area Network (WAN):
A Wide Area Network is a network of connecting two or more computers generally across a wide geographical area such as cities, districts and countries. WANs interconnect LANs which may be at the opposite side of a country or located around the world. It uses telephone lines, communication satellite and other long range communication links to connect the computers and network. Internet is an example of WAN. The characteristics of WAN are:
• It covers a large geographical area.
• Transmission cost is high
• Transmission error is higher than LAN
• It is owned by multiple organizations.
• It uses public connections mediums such as telephone lines, wireless technology etc.
• Owned by multiple organization.
3. What is Network Topology/LAN topology/Topology? Explain different types of topologies with merits and demerits.
A network topology is the physical arrangement of computers, cables and other components on a network. The type of topology you use affect the speed and performance of the computer network. The common used physical network typologies are; Bus Topology, Ring Topology, Star Topology, Mesh Topology, Tree Topology, Hybrid Topology
a). Bus Topology:
In a Bus topology, all
devices attach to the same transmission medium. The medium has a physical
beginning and end. All buses are implemented using electrical cable, usually
coax, and the ends of the cable must be terminated with a terminating resistor
that matches the impedance of the cable. The terminating resistor prevents data
reflections from coming across as data corruption. The bus is considered a
multi-point system because all devices tap into the same backbone cable.
• Bus topology is simple, reliable (in very small network), easy to use and easy to understand.
• It is less expensive.
• It is easy to add a new node in the network.
Disadvantages:
• Heavy network traffic can slow a bus considerably.
• It is difficult to troubleshoot.
• If problems occurs on the backbone, the entire network will go down.
b). Star Topology:
In a star network, each node (file server, workstations, and peripherals) is connected to a central device called a hub. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. Data on a star network passes through the hub or switch, before continuing to its destination. The hub or switch manages and controls all functions of the network. The star topology reduces the chance of network failure by connecting all of the systems to a central node.
Advantages:
• It is easy to set up and configure.
• It is easy to modify and add new computers to a start topology without disturbing the rest of the network.
• Single computer failure does not necessarily bring down the whole start network.
• It is easy to detect the errors in star topology
Disadvantages:
• It the central device fails, the whole network stops.
• It costs more to cable a start topology because all network cable must be pulled to central point (hub).
c). Ring Topology:
In a ring network,
every device has exactly two neighbors for communication purposes. All messages
travel through a ring in the same direction. A failure in any cable or
device breaks the loop and can take down the entire network. To implement a ring
network it could use the Token Ring technology. A token, or small data packet,
is continuously passed around the network. When a device needs to transmit, it
reserves the token for the next trip around, then attaches its data packet to
it.
• Ring topology is easy to setup and reconfigure.
• Each computer is given equal opportunity to access the network resources.
• Single cable connects between the nodes.
Disadvantages:
• Failure of one computer on the ring can affect the entire network.
• Adding or removing computers disturbs the networks.
• It is difficult to troubleshoot in a ring topology.
d). Mesh Topology:
In this topology, each
node is connected to every other node in the network. Implementing the mesh
topology is expensive and difficult. In this type of network, each node may
send message to destination through multiple paths. While the data is travelling
on the Mesh Network it is automatically configured to reach the destination by
taking the shortest route.
Advantages:
• The mesh topology is fault tolerance.
• It is easy to troubleshoot.
Disadvantages:
• Difficult to installation and reconfigure
• It is costlier.
4. What
are the components of Components of Computer Network? Explain.
The communication between two computers is possible by interacting between hardware and software Components.
1). Hardware Components:
All the physical component of network that is used to connect or communicate is hardware components. The different hardware components are:
1 Server:
A server is a computer that makes its resources available to the network and responds to the commands of a client. The server in a network performs a variety of complex tasks. It is the main computer in network which has high storage capacity and high processing speed. The following are some examples of different types of server included on many large networks:
i). File and Print Servers
ii). Database Servers
iii). Mail Server
2. Client / Workstation:
A client is a computer that uses the resources made available by a server. The client must have sufficient processing power on its own to run applications that interact with the resources on the server. It is also called as work station
• Cables:
Cables are the pathway or channel along which the signals or data can be transmitted from one point to another. The most commonly used cables are coaxial, twisted pair and fiber optics.
• Network Interface Card:
Network Interface Card is the computer circuit board or card that is installed in a computer so that it can be connected to a network by using physical channel. Each NIC is assigned a unique MAC (Media Access Control) address by the manufacturer through which data is sent to the destination. The main function of NIC is to convert data into electrical signals and transfer them through cable and vice versa.
• Hub:
Hubs are centrally connectivity devices that connect computers in a star topology. Hub contains multiple ports for connecting to network components. It amplifies (increase) the signals and sends them to all connected devices. Use of hub has become very common in most of the computer networking as it cost lower and easier to install.
• Connectors:
It is an interface between NIC of the computer and the cable that passes data from one computer to another. It depends on type of cable and devices used in the network. The different types of connectors are; BNC connector, RJ 45, ST, RJ 12 etc.
• Repeater:
A repeater is a physical layer device used to interconnect the media segments of an extended network. It amplifies the incoming signals, creates a new copy of it and transmits the signals on the network. A repeater essentially enables a series of cable segment to be treated as a single cable.
• Bridge:
A bridge is a device that passes data packets between multiple network segments that use the same communication protocol. A bridge passes one signal at a time. It filters the data or inspects incoming signals and decides whether to forward the signals or discard them.
• Switch:
Switches are similar to bridge but offer a more direct network connection between the source and destination computers. The main difference between bridge and switch is the way that filtering happens. With a switc0h, filtering and performance better than bridge.
• Router:
Router is a device that acts like a bridge or switch but provides more functionality. It uses addresses for filtering and forwarding the data. Router enable all user in a network to share a single connection to the Internet or a WAN.
• Gateway:
A gateway is a device that enables communication between different network architecture. A gateway takes the data from one network and repackages it, so that each network can understand the other network’s data.
• Modem: (Modulation-Demodulation)
A modem is a communication device that enables a computer to transmit information over a standard telephone line. A modem is required when connecting to the Internet using telephone line. It is an essential link between the computer running browser and dial up service providers. A modem is needed to convert digital signal to analog signal and vice versa.
Analog Signal:
An analog signal is a constantly changing electrical wave signal that changes in a rounded or smooth pattern.
Digital Signal:
A digital signal uses a square waveform, which is reliably used to transmit electronic data.
5. What is transmission media? Explain guided media
Transmission Media / Communication Media / Network Media:
Communication media is the pathway or channel along which the signals or data can be transmitted from one point to another. The signal transmitted from one device to another is through electromagnetic signals. It includes voice, radio waves, infrared light etc. The transmission media is divided into two types:
1) Guided Media:
In guided media is a media that uses a transmission carrier to send data signals through a contained conductor. This conductor can be a metal wire through which electricity flows or a glass strand through which pulses of light flows. The different types of guided media are:
a). Twisted Pair:
Twisted pair cable is the oldest and common medium of transmission. Twisted pair cable consists of two insulated strands of copper wire twisted around each other. There are two types of twisted pair cable. There are:
i). Unshielded Twisted Pair (UTP):
UTP cable consists of a number of twisted pairs of wires with a simple plastic casing. UTP is commonly used in telephone system. It is suitable for both data and voice transmission. It comes in different categories (cat 1 to cat 7). The bandwidth of the cables depends upon the category of the cable. UTP is good for noise rejection and it covers a maximum distance of 100m.
ii). Shielded Twisted Pair (STP)
The STP cable is similar in construction to UTP except that the twisted pairs are enclosed in a woven copper and foil wrap shield for providing extra protection from external interference. STP is more difficult to install than UTP and Coaxial cable. It covers shorter distance than UTP, but it has better noise rejection capacity. The STP is more costlier than UTP cables.
b). Coaxial cable:
Coaxial cable is made of two conductors that share a common axis. The center of the cable is a relatively stiff solid copper wire insulating by plastic foam. The foam is surrounded by the second conductor, a wire mesh tube, which serves as a shield from electromagnetic interference (EMI). The coaxial cables are used in communication networks with single ended single reference where the central conductor carries the data signals. The Connectors used in Coaxial cable are BNC, T-connector and terminals.
c). Fiber Optics:
Fiber-optic cable is made of a light conducting glass or plastic core surrounded by more glass called cladding and a tough (hard) outer cover. A fiber optic consists of a bundle of glass threads, each of which is capable of transmitting message modulated onto light waves. Fiber optics uses light signals rather than electricity, so it offers high bandwidth and greatest distance of any transmission system. The main disadvantage of fiber optics are; it is costlier to produce, maintain and install. The connectors used in fiber optics are Screw Mounted Adaptors (SMA), Spring-loaded Twist (ST), SC and FC.
The communication between two computers is possible by interacting between hardware and software Components.
1). Hardware Components:
All the physical component of network that is used to connect or communicate is hardware components. The different hardware components are:
1 Server:
A server is a computer that makes its resources available to the network and responds to the commands of a client. The server in a network performs a variety of complex tasks. It is the main computer in network which has high storage capacity and high processing speed. The following are some examples of different types of server included on many large networks:
i). File and Print Servers
ii). Database Servers
iii). Mail Server
2. Client / Workstation:
A client is a computer that uses the resources made available by a server. The client must have sufficient processing power on its own to run applications that interact with the resources on the server. It is also called as work station
• Cables:
Cables are the pathway or channel along which the signals or data can be transmitted from one point to another. The most commonly used cables are coaxial, twisted pair and fiber optics.
• Network Interface Card:
Network Interface Card is the computer circuit board or card that is installed in a computer so that it can be connected to a network by using physical channel. Each NIC is assigned a unique MAC (Media Access Control) address by the manufacturer through which data is sent to the destination. The main function of NIC is to convert data into electrical signals and transfer them through cable and vice versa.
• Hub:
Hubs are centrally connectivity devices that connect computers in a star topology. Hub contains multiple ports for connecting to network components. It amplifies (increase) the signals and sends them to all connected devices. Use of hub has become very common in most of the computer networking as it cost lower and easier to install.
• Connectors:
It is an interface between NIC of the computer and the cable that passes data from one computer to another. It depends on type of cable and devices used in the network. The different types of connectors are; BNC connector, RJ 45, ST, RJ 12 etc.
• Repeater:
A repeater is a physical layer device used to interconnect the media segments of an extended network. It amplifies the incoming signals, creates a new copy of it and transmits the signals on the network. A repeater essentially enables a series of cable segment to be treated as a single cable.
• Bridge:
A bridge is a device that passes data packets between multiple network segments that use the same communication protocol. A bridge passes one signal at a time. It filters the data or inspects incoming signals and decides whether to forward the signals or discard them.
• Switch:
Switches are similar to bridge but offer a more direct network connection between the source and destination computers. The main difference between bridge and switch is the way that filtering happens. With a switc0h, filtering and performance better than bridge.
• Router:
Router is a device that acts like a bridge or switch but provides more functionality. It uses addresses for filtering and forwarding the data. Router enable all user in a network to share a single connection to the Internet or a WAN.
• Gateway:
A gateway is a device that enables communication between different network architecture. A gateway takes the data from one network and repackages it, so that each network can understand the other network’s data.
• Modem: (Modulation-Demodulation)
A modem is a communication device that enables a computer to transmit information over a standard telephone line. A modem is required when connecting to the Internet using telephone line. It is an essential link between the computer running browser and dial up service providers. A modem is needed to convert digital signal to analog signal and vice versa.
Analog Signal:
An analog signal is a constantly changing electrical wave signal that changes in a rounded or smooth pattern.
Digital Signal:
A digital signal uses a square waveform, which is reliably used to transmit electronic data.
5. What is transmission media? Explain guided media
Transmission Media / Communication Media / Network Media:
Communication media is the pathway or channel along which the signals or data can be transmitted from one point to another. The signal transmitted from one device to another is through electromagnetic signals. It includes voice, radio waves, infrared light etc. The transmission media is divided into two types:
1) Guided Media:
In guided media is a media that uses a transmission carrier to send data signals through a contained conductor. This conductor can be a metal wire through which electricity flows or a glass strand through which pulses of light flows. The different types of guided media are:
a). Twisted Pair:
Twisted pair cable is the oldest and common medium of transmission. Twisted pair cable consists of two insulated strands of copper wire twisted around each other. There are two types of twisted pair cable. There are:
i). Unshielded Twisted Pair (UTP):
UTP cable consists of a number of twisted pairs of wires with a simple plastic casing. UTP is commonly used in telephone system. It is suitable for both data and voice transmission. It comes in different categories (cat 1 to cat 7). The bandwidth of the cables depends upon the category of the cable. UTP is good for noise rejection and it covers a maximum distance of 100m.
ii). Shielded Twisted Pair (STP)
The STP cable is similar in construction to UTP except that the twisted pairs are enclosed in a woven copper and foil wrap shield for providing extra protection from external interference. STP is more difficult to install than UTP and Coaxial cable. It covers shorter distance than UTP, but it has better noise rejection capacity. The STP is more costlier than UTP cables.
b). Coaxial cable:
Coaxial cable is made of two conductors that share a common axis. The center of the cable is a relatively stiff solid copper wire insulating by plastic foam. The foam is surrounded by the second conductor, a wire mesh tube, which serves as a shield from electromagnetic interference (EMI). The coaxial cables are used in communication networks with single ended single reference where the central conductor carries the data signals. The Connectors used in Coaxial cable are BNC, T-connector and terminals.
c). Fiber Optics:
Fiber-optic cable is made of a light conducting glass or plastic core surrounded by more glass called cladding and a tough (hard) outer cover. A fiber optic consists of a bundle of glass threads, each of which is capable of transmitting message modulated onto light waves. Fiber optics uses light signals rather than electricity, so it offers high bandwidth and greatest distance of any transmission system. The main disadvantage of fiber optics are; it is costlier to produce, maintain and install. The connectors used in fiber optics are Screw Mounted Adaptors (SMA), Spring-loaded Twist (ST), SC and FC.
Q. What is ISO reference model?
Explain its different layer.
It is based on a proposal developed by the international organization for standardization (ISO). The model is called ISO reference model, because it deals with connecting open system i.e. the system that are open for communication with other system.
a. Physical Layer: This layer concerned with transmission of bit it determines voltage level for 0 & 1. It also determines the data rate of the system. This layer involves standardized protocol dealing with electrical & signaling interface.
b. Data Link Layer: It handles error in physical layer. This layer ensures the correct delivery of frame to the destination address. It consists of 2 parts or 2 sub-layers. i.e.
i. Logic Link Control & ii. Media Access Control
c. Network Layer: This layer is concerned with transmission of packet. Network layer protocol chooses the best path to send a package called routing. Two protocols are widely used in n/w layer.
i. X.25 Protocol & ii) Internet Protocol
d. Transport Layer: It provides the mechanism for the exchange of data between end systems. It ensures that the data received is in fact in order. Following jobs are performed by this layer.
i. Port Addressing ii) Segmentation & Reassemble & iii) Connection Control
e. Session Layer: It is responsible for requesting logical connection to be established for communication process. This logical connection is termed as session. It also provides data synchronization (organization) between two communication terminals.
f. Presentation layer: This layer translates format data to adapt to the needs of the application layer & nodes at both receiving & sending end of communication process. It handles data communication, formatting, encryption, decryption, etc.
g. Application Layer: It is the top-most layer of OSI model & provides user access to the n/w. It provides services that support user application, such as database access, email & file transfer, etc.
It is based on a proposal developed by the international organization for standardization (ISO). The model is called ISO reference model, because it deals with connecting open system i.e. the system that are open for communication with other system.
a. Physical Layer: This layer concerned with transmission of bit it determines voltage level for 0 & 1. It also determines the data rate of the system. This layer involves standardized protocol dealing with electrical & signaling interface.
b. Data Link Layer: It handles error in physical layer. This layer ensures the correct delivery of frame to the destination address. It consists of 2 parts or 2 sub-layers. i.e.
i. Logic Link Control & ii. Media Access Control
c. Network Layer: This layer is concerned with transmission of packet. Network layer protocol chooses the best path to send a package called routing. Two protocols are widely used in n/w layer.
i. X.25 Protocol & ii) Internet Protocol
d. Transport Layer: It provides the mechanism for the exchange of data between end systems. It ensures that the data received is in fact in order. Following jobs are performed by this layer.
i. Port Addressing ii) Segmentation & Reassemble & iii) Connection Control
e. Session Layer: It is responsible for requesting logical connection to be established for communication process. This logical connection is termed as session. It also provides data synchronization (organization) between two communication terminals.
f. Presentation layer: This layer translates format data to adapt to the needs of the application layer & nodes at both receiving & sending end of communication process. It handles data communication, formatting, encryption, decryption, etc.
g. Application Layer: It is the top-most layer of OSI model & provides user access to the n/w. It provides services that support user application, such as database access, email & file transfer, etc.
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