Computer Network Question And Answer

Explain in brief FDDI networks 

What is FDDI (Fiber Distributed Data Interface)?

FDDI (Fiber Distributed Data Interface) is a network standard that uses fiber optic connections in a local area network (LAN) that can extend in range up to 200 kilometers (124 miles). The FDDI protocol is based on the token ring protocol. A FDDI LAN can support thousands of users. While FDDI is frequently used on the backbone for a wide area network (WAN) or campus area network (CAN), it has been largely superseded by other networking technologie

Fiber Distributed Data Interface topology and design

A FDDI network contains two token rings: a primary ring and a secondary ring that is used as a redundant backup. The primary ring offers up to 100 megabits per second (Mbps) capacity, while the secondary ring can also be used to carry data, increasing capacity to 200 Mbps. One ring will operate in a clockwise direction and the other in a counterclockwise direction. The single ring can extend the maximum distance of 200 km (124 miles); a dual ring can extend 100 km (62 miles). Users can connect thousands of devices to a single FDDI network.

Although the FDDI topology is a token ring network, users may also implement it in a star topology structure. FDDI is derived from the Institute of Electrical and Electronics Engineers 802.4 token bus timed token protocol.

In a token network, only the device with the token may transmit. The use of a timed token ensures the maximum wait time for each device to be able to transmit. Depending on the network latency requirements, users can configure FDDI as synchronous with guaranteed timings for latency-sensitive networks or as asynchronous, which does not rely on strict token timings.

FDDI is a product of the American National Standards Committee X3T9 standard and operates on Open Systems Interconnection model Layer 1 (physical) and Layer 2 (media access control data link). It has a large maximum transmission unit frame size of 4,352 bytes.

Single-mode fiber optic cable is FDDI's primary interconnect medium. FDDI standards using nonfiber optic cable also exist, such as Copper Distributed Data Interface, Twisted-Pair Physical Medium-Dependent or Twisted-Pair Distributed Data Interface.

In a FDDI network, users attach the primary routers and devices to both rings of the network. These nodes are called dual attachment stations. Users can also connect other nodes via a single fiber optic connection; these are called single attachment stations. FDDI can also be interconnected to other types of networks using other protocols, thereby creating a larger WAN or interconnecting many clients

Explain two types of topologies with the help of diagram

Types of Networking Topologies
It is widely used when a network installation is small, simple, or temporary.
It is one of the passive topologies. So computers on the bus only listen for data being sent, that are not responsible for moving the data from one computer to others.
Disadvantages:
Here are the cons/drawbacks of bus topology:
In case if the common cable fails, then the entire system will crash down.
When network traffic is heavy, it develops collisions in the network.
Whenever network traffic is heavy, or nodes are too many, the performance time of the network significantly decreases.
Cables are always of a limited length.
Ring Topology
Ring Topology Diagram

In a ring network, every device has exactly two neighboring devices for communication purpose. It is called a ring topology as its formation is like a ring. In this topology, every computer is connected to another computer. Here, the last node is combined with a first one.
This topology uses token to pass the information from one computer to another. In this topology, all the messages travel through a ring in the same direction.
Advantages:
Here are pros/benefits of ring topology:
Easy to install and reconfigure.
Adding or deleting a device in-ring topology needs you to move only two connections.
The troubleshooting process is difficult in a ring topology.
Failure of one computer can disturb the whole network.
Offers equal access to all the computers of the networks
Faster error checking and acknowledgment.
Disadvantages:
Here are drawbacks/cons of ring topology:
Unidirectional traffic.
Break in a single ring can risk the breaking of the entire network
Modern days high-speed LANs made this topology less popular.
In the ring, topology signals are circulating at all times, which develops unwanted power consumption.
It is very difficult to troubleshoot the ring network.
Adding or removing the computers can disturb the network activity.
Star Topology
Star Topology Diagram

In the star topology, all the computers connect with the help of a hub. This cable is called a central node, and all other nodes are connected using this central node. It is most popular on LAN networks as they are inexpensive and easy to install.
Advantages:
Here are pros/benefits of start topology:
Easy to troubleshoot, set up, and modify.
Only those nodes are affected, that has failed. Other nodes still work.
Fast performance with few nodes and very low network traffic.
In Star topology, addition, deletion, and moving of the devices are easy.
Disadvantages:
Here are cons/drawbacks of using Star:
If the hub or concentrator fails, attached nodes are disabled.
Cost of installation of star topology is costly.
Heavy network traffic can sometimes slow the bus considerably.
Performance depends on the hub’s capacity
A damaged cable or lack of proper termination may bring the network down.
Mesh Topology
The mesh topology has a unique network design in which each computer on the network connects to every other. It is develops a P2P (point-to-point) connection between all the devices of the network. It offers a high level of redundancy, so even if one network cable fails, still data has an alternative path to reach its destination.
Types of Mesh Topology:
Partial Mesh Topology: 

In this type of topology, most of the devices are connected almost similarly as full topology. The only difference is that few devices are connected with just two or three devices.
Partially Connected Mesh Topology
Full Mesh Topology: 

In this topology, every nodes or device are directly connected with each other.
Fully Connected Mesh Topology
Advantages:
Here, are pros/benefits of Mesh topology
The network can be expanded without disrupting current users.
Need extra capable compared with other LAN topologies.
No traffic problem as nodes has dedicated links.
Dedicated links help you to eliminate the traffic problem.
A mesh topology is robust.
It has multiple links, so if any single route is blocked, then other routes should be used for data communication.
P2P links make the fault identification isolation process easy.
It helps you to avoid the chances of network failure by connecting all the systems to a central node.
Every system has its privacy and security.
Disadvantages:
Installation is complex because every node is connected to every node.
It is expensive due to the use of more cables. No proper utilization of systems.
Complicated implementation.
It requires more space for dedicated links.
Because of the amount of cabling and the number of input-outputs, it is expensive to implement.
It requires a large space to run the cables.
Tree Topology

Tree topologies have a root node, and all other nodes are connected which form a hierarchy. So it is also known as hierarchical topology. This topology integrates various star topologies together in a single bus, so it is known as a Star Bus topology. Tree topology is a very common network which is similar to a bus and star topology.
Advantages:
Here are pros/benefits of tree topology:
Failure of one node never affects the rest of the network.
Node expansion is fast and easy.
Detection of error is an easy process
It is easy to manage and maintain
Disadvantages:
Here are cons/drawback of tree topology:
It is heavily cabled topology
If more nodes are added, then its maintenance is difficult
If the hub or concentrator fails, attached nodes are also disabled.
Hybrid Topology

Hybrid topology combines two or more topologies. You can see in the above architecture in such a manner that the resulting network does not exhibit one of the standard topologies.
For example, as you can see in the above image that in an office in one department, Star and P2P topology is used. A hybrid topology is always produced when two different basic network topologies are connected.
Advantages:
Here, are advantages/pros using Hybrid topology:
Offers the easiest method for error detecting and troubleshooting
Highly effective and flexible networking topology
It is scalable so you can increase your network size
Disadvantages:
The design of hybrid topology is complex
It is one of the costliest processes

Write the difference between transmission media and communication media

The transmission medium can be defined as a pathway that can transmit information from a sender to a receiver. Transmission media are located below the physical layer and are controlled by the physical layer. Transmission media are also called communication channels.

With diagram explain any 2 layers of OSI reference model

OSI or Open System Interconnection model was developed by International Standards Organization (ISO). It gives a layered networking framework that conceptualizes how communications should be done between heterogeneous systems. It has seven interconnected layers.

The seven layers of the OSI Model are

Physical layer

Data link layer

Network layer

Transport layer

Session layer

Presentation layer

Application layer

The physical layer, data link layer and the network layer are the network support layers. The layers manage a physical transfer of data from one device to another. Session layer, presentation layer, and application layer are the user support layers. These layers allow communication among unrelated software in dissimilar environments. Transport layer links the two groups.

Physical Layer

This is the shortest layer in the model. The physical layer is vital for transmitting bits from one device to the other device. It is not involved with the bits representation, but it manages the physical relation to the structure with communication and signal acceptance.

The Physical Layer is responsible for the transmission and reception of unstructured raw data between a device, such as a network interface controller, Ethernet hub, or network switch, and a physical transmission medium. It converts the digital bits into electrical, radio, or optical signals. Layer specifications define characteristics such as voltage levels, the timing of voltage changes, physical data rates, maximum transmission distances, modulation scheme, channel access method and physical connectors. This includes the layout of pins, voltages, line impedance, cable specifications, signal timing and frequency for wireless devices. Bit rate control is done at the physical layer and may define transmission mode as simplex, half duplex, and full duplex. The components of a physical layer can be described in terms of a network topology. Physical layer specifications are included in the specifications for the ubiquitous Bluetooth, Ethernet, and USB standards. An example of a less well-known physical layer specification would be for the CAN standard.

The Physical Layer also specifies how encoding occurs over a physical signal, such as electrical voltage or a light pulse. For example, a 1 bit might be represented on a copper wire by the transition from a 0-volt to a 5-volt signal, whereas a 0 bit might be represented by the transition from a 5-volt signal to 0-volt signal. As a result, common problems occurring at the Physical Layer are often related to the incorrect media termination, EMI or noise scrambling, and NICs and hubs that are misconfigured or do not work correctly.

Data Link Layer

It takes the physical layer’s bits and detects an error. This establishes an error-free communications path between the network nodes over the physical medium. Moreover, it frames the messages for transmission and tests the integrity of received messages. It manages the access to and uses the medium and also ensures the proper sequence of the transmitted data.

Network Layer

The network layer is the makeup software that addresses the protocol data units (PDUs) and transfers them to the ultimate destination. This is done by setting up the suitable paths between the multiple nodes. The primary objective of this layer is to control the service of the subnet. It is the layer, which supports Internet Protocol (IP) to use it. It is mainly responsible for delivering routing services from source to destination across the Internet.

Transport Layer

This layer guarantees the orderly and reliable delivery of data between the end systems after accepting the data from the session layer. The session layer maps the data to the Network layer, and it provides that the packets appear correctly at the receiving side.

Session Layer

This layer is vital for establishing, controlling, and arbitrating the dialogues between the communication software. It is also answerable for the orderly recovery from failures by implementing appropriate check pointing mechanisms.

Presentation Layer

The presentation layer performs the functions related to the syntax and semantics of the information transmitted. These functions include formatting and displaying the received data by terminals and printers. This layer is responsible for rectifying those differences by resorting to mechanisms that change the local syntax to a typical data exchange.

Application Layer

This layer provides the services for user and software tasks. It determines how the user will use the data web. It enables the client to use the network. For example, it provides the network-based services to the end-user.

The application layer is the layer of the OSI model that is closest to the end user, which means both the OSI Application Layer and the user interact directly with software application that implements a component of communication between the client and server, such as File Explorer and Microsoft Word. Such application programs fall outside the scope of the OSI model unless they are directly integrated into the Application layer through the functions of communication, as is the case with applications such as Web Browsers and Email Programs. Other examples of software are Microsoft Network Software for File and Printer Sharing and Unix/Linux Network File System Client for access to shared file resources.

Application-layer functions typically include file sharing, message handling, and database access, through the most common protocols at the application layer, known as HTTP, FTP, SMB/CIFS, TFTP, and SMTP. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. The most important distinction in the application layer is the distinction between the application-entity and the application. For example, a reservation website might have two application-entities: one using HTTP to communicate with its users, and one for a remote database protocol to record reservations. Neither of these protocols have anything to do with reservations. That logic is in the application itself. The application layer has no means to determine the availability of resources in the network.

What are the functions of OSI Layers

Functions of the OSI Layers

There are various functions of OSI Layers which are as follows:

Physical Layer − Its function is to transmit individual bits from one node to another over a physical medium.

Data Link Layer − It is responsible for the reliable transfer of data frames from one node to another connected by the physical layer.

Network Layer − It manages the delivery of individual data packets from source to destination through appropriate addressing and routing.

Transport Layer −It is responsible for delivery of the entire message from the source host to destination host.

Session Layer − It establishes sessions between users and offers services like dialog control and synchronization.

Presentation Layer − It monitors syntax and semantics of transmitted information through translation, compression, and encryption.

Application Layer − It provides high-level APIs (application program interface) to the users.

Write a short note on wireless LAN

A wireless LAN (WLAN) is a wireless computer network that links two or more devices using wireless communication to form a local area network (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building. This gives users the ability to move around within the area and remain connected to the network. Through a gateway, a WLAN can also provide a connection to the wider Internet.

Wireless LANs based on the IEEE 802.11 standards are the most widely used computer networks in the world. These are commonly called Wi-Fi, which is a trademark belonging to the Wi-Fi Alliance. They are used for home and small office networks that link together laptop computers, printers, smart phones, Web TVs and gaming devices with a wireless router, which links them to the internet. Hotspots provided by routers at restaurants, coffee shops, hotels, libraries, and airports allow consumers to access the internet with portable wireless devices.

A wireless LAN (WLAN) is a wireless computer network that links two or more devices using wireless communication to form a local area network (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building. This gives users the ability to move around within the area and remain connected to the network. Through a gateway, a WLAN can also provide a connection to the wider Internet.

Wireless LANs based on the IEEE 802.11 standards are the most widely used computer networks in the world. These are commonly called Wi-Fi, which is a trademark belonging to the Wi-Fi Alliance. They are used for home and small office networks that link together laptop computers, printers, smart phones, Web TVs and gaming devices with a wireless router, which links them to the internet. Hotspots provided by routers at restaurants, coffee shops, hotels,

Libraries and airports allow consumers to access the internet with portable wireless devices.

Write advantages of WLANs

Advantages of WLANs

They provide clutter-free homes, offices and other networked places.

The LANs are scalable in nature, i.e. devices may be added or removed from the network at greater ease than wired LANs.

The system is portable within the network coverage. Access to the network is not bounded by the length of the cables.

Installation and setup are much easier than wired counterparts.

The equipment and setup costs are reduced.

Explain circuit switching in brief/What Is Circuit Switching?

Circuit switching technique is a connection-oriented network that is divided into pieces and has a dedicated path established between the sender and receiver providing a guaranteed data rate. In circuit switching network resources (bandwidth) are divided into pieces and bit delay is constant during a connection. The dedicated path/circuit established between sender and receiver provides a guaranteed data rate. Data can be transmitted without any delays once the circuit is established. 

While circuit switching is commonly used for connecting voice circuits, the concept of a dedicated path persisting between two communicating parties or nodes can be extended to signal content other than voice. The advantage of using circuit switching is that it provides for continuous transfer without the overhead associated with packets, making maximal use of available bandwidth for that communication. 

Types of Circuit Switching

TDM (Time Division Multiplexing)

FDM (Frequency Division Multiplexing) are two methods of multiplexing multiple signals into a single carrier. 

Frequency Division Multiplexing: Divides into multiple bands 
Frequency Division Multiplexing or FDM is used when multiple data signals are combined for simultaneous transmission via a shared communication medium. It is a technique by which the total bandwidth is divided into a series of non-overlapping frequency sub-bands, where each sub-band carry different signal. Practical use in radio spectrum & optical fibre to share multiple independent signals.
Time Division Multiplexing: Divides into frames 
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line. TDM is used for long-distance communication links and bears heavy data traffic loads from end user. 
Time division multiplexing (TDM) is also known as a digital circuit switched.

Circuit Switching Diagram

Circuit Switching Examples

Telephone system network

Analog telephone network

Optical mesh network

Public Switched Telephone Network (PSTN)

Characteristics of Circuit Switched Network

It is also known as the public network.

Handling digital data and traffic is easy as the signals are voice signals.

The transfer of electric current along with the voice signal is possible.

The process is known as connection-oriented.

In a circuit switching network, the establishment of the path takes place first and then the data transmission takes place.

The amount of data transferred in the circuit switching is fixed.

The termination of the path is possible only when there is a termination of the connection.

Advantages and Disadvantages of Circuit Switching

Advantages

This type of switching technique is suitable for the continuous transmission of data as the data remains in conservation.

The rate of communication is steady as a dedicated path for transmission.

With the establishment of the circuit, there are no intermediate delays that make it suitable for voice and data transmission.

Disadvantages

As there is an establishment of a dedicated connection between both ends, the transmission of any other data is challenging.

Data with low volume demand high bandwidth.

The usage of system resources becomes underutilized as the repetition of resources for other connections is not possible.

The establishment time is high.

Write the Difference between Circuit and Packet Switching

The following is the list of differences between circuit and packet switching:

Circuit Switching	Packet Switching
The transfer of data takes place after the establishment of the dedicated path.	The transfer of data takes place in the form of packets following dynamic routing.
It is mainly preferred for voice transmission.	It is mainly preferred for data transmission.
The implementation of this type of switching takes place at the physical layer.	The implementation of this type of switching takes place at the network layer.
Transmission of the data is done by the source.	Transmission of the data is done not only by the source but also by the intermediate routers.
Circuit switching is more reliable.	Packet switching is less reliable.
Wastage of resources is more in Circuit Switching	Less wastage of resources as compared to Circuit Switching
It is not a store and forward technique.	It is a store and forward technique.
In-Circuit switching, data is processed at the source system only	In Packet switching, data is processed at all intermediate nodes including the source system.
The delay between data units in circuit switching is uniform.	The delay between data units in packet switching is not uniform.
Resource reservation is the feature of circuit switching because the path is fixed for data transmission.	There is no resource reservation because bandwidth is shared among users.

Write a short note on IEEE 802.4 token bus

Token Bus (IEEE 802.4) is a popular standard for token passing LANs. In a token bus LAN, the physical media is a bus or a tree, and a logical ring is created using a coaxial cable. The token is passed from one user to another in a sequence (clockwise or anticlockwise). Each station knows the address of the station to its “left” and “right” as per the sequence in the logical ring. A station can only transmit data when it has the token. The working of a token bus is somewhat similar to Token Ring. 

The Token Bus (IEEE 802.4) is a standard for deploying token rings in LANs over a virtual ring. The physical medium uses coaxial cables and has a bus or tree architecture. The nodes/stations form a virtual ring, and the token is transmitted from one node to the next in a sequence along the virtual ring. Each node knows the address of the station before it and the station after it. When a station has the token, it can only broadcast data. The token bus works in a similar way as the Token Ring.

Advantages of token rings

Token rings reduce the chances of data collision.

Token passing performs better than bus topology under heavy traffic.

A server is not needed to control connectivity among the nodes.

In this data flows in one direction which reduces the chance of packet collisions.

In this topology additional workstations can be added after without impacting performance of the network.

Equal access to the resources.

There is no need of server to control the connectivity among the nodes in the topology.

It is cheap to install and expand.

Minimum collision.

Speed to transfer the data is very high in this type of topology.

Due to the presence of token passing the performance of ring topology becomes better than bus topology under heavy traffic.

Easy to manage.

Ring network is extremely orderly organized where every device has access to the token and therefore the opportunity to transmit.

Disadvantages of Ring topology

Due to the Uni-directional Ring, a data packet (token) must have to pass through all the nodes.

If one workstation shuts down, it affects whole network or if a node goes down entire network goes down.

It is slower in performance as compared to the bus topology

It is Expensive.

Addition and removal of any node during a network is difficult and may cause issue in network activity.

Difficult to troubleshoot the ring.

In order for the entire computer to communicate with each other, all computers must be turned on.

Total dependence in on one cable.

They were not scalable.

Explain TCP/IP model//What is TCP/IP?

TCP/IP stands for Transmission Control Protocol/Internet Protocol and is a suite of communication protocols used to interconnect network devices on the internet. TCP/IP is also used as a communications protocol in a private computer network (an intranet or extranet).

The entire IP suite -- a set of rules and procedures -- is commonly referred to as TCP/IP. TCP and IP are the two main protocols, though others are included in the suite. The TCP/IP protocol suite functions as an abstraction layer between internet applications and the routing and switching fabric

TCP/IP specifies how data is exchanged over the internet by providing end-to-end communications that identify how it should be broken into packets, addressed, transmitted, routed and received at the destination. TCP/IP requires little central management and is designed to make networks reliable with the ability to recover automatically from the failure of any device on the network.

The two main protocols in the IP suite serve specific functions. TCP defines how applications can create channels of communication across a network. It also manages how a message is assembled into smaller packets before they are then transmitted over the internet and reassembled in the right order at the destination address.

IP defines how to address and route each packet to make sure it reaches the right destination. Each gateway computer on the network checks this IP address to determine where to forward the message.

A subnet mask tells a computer, or other network device, what portion of the IP address is used to represent the network and what part is used to represent hosts, or other computers, on the network.

Network address translation (NAT) is the virtualization of IP addresses. NAT helps improve security and decrease the number of IP addresses an organization needs.

Common TCP/IP protocols include the following:

Hypertext Transfer Protocol (HTTP) handles the communication between a web server and a web browser.

HTTP Secure handles secure communication between a web server and a web browser.

File Transfer Protocol handles transmission of files between computers.

How does TCP/IP work?

TCP/IP uses the client-server model of communication in which a user or machine (a client) is provided a service, like sending a webpage, by another computer (a server) in the network.

Collectively, the TCP/IP suite of protocols is classified as stateless, which means each client request is considered new because it is unrelated to previous requests. Being stateless frees up network paths so they can be used continuously.

The transport layer itself, however, is stateful. It transmits a single message, and its connection remains in place until all the packets in a message have been received and reassembled at the destination.

The TCP/IP model differs slightly from the seven-layer Open Systems Interconnection (OSI) networking model designed after it. The OSI reference model defines how applications can communicate over a network.

Why is TCP/IP important?

TCP/IP is nonproprietary and, as a result, is not controlled by any single company. Therefore, the IP suite can be modified easily. It is compatible with all operating systems (OSes), so it can communicate with any other system. The IP suite is also compatible with all types of computer hardware and networks.

TCP/IP is highly scalable and, as a routable protocol, can determine the most efficient path through the network. It is widely used in current internet architecture.

The 4 layers of the TCP/IP model

TCP/IP functionality is divided into four layers, each of which includes specific protocols:

The application layer provides applications with standardized data exchange.

Its protocols include

HTTP

FTP

Post Office Protocol 3

Simple Mail Transfer Protocol and Simple Network Management Protocol.

Uses of TCP/IP

TCP/IP can be used to provide remote login over the network for interactive file transfer to deliver email

to deliver WebPages over the network and to remotely access a server host's file system. Most broadly

it is used to represent how information changes form as it travels over a network from the concrete physical layer to the abstract application layer.

It details the basic protocols, or methods of communication, at each layer as information passes through

TCP/IP specifies how data is exchanged over the internet by providing end-to-end communications that identify how it should be broken into packets, addressed, transmitted, routed and received at the destination.

Write a short note on telnet

TELNET stands for Teletype Network. It is a type of protocol that enables one computer to connect to local computer. It used as a standard TCP/IP protocol for virtual terminal service which is provided by ISO. The computer which starts the connection is known as the local computer. The computer which is being connected to i.e. which accepts the connection known as the remote computer. During telnet operation, whatever is being performed on the remote computer will be displayed by the local computer. Telnet operates on client/server principle. The local computer uses telnet client program and the remote computers uses telnet server program. 

The better solution is to provide a general client-server program that lets the user access any application program on a remote computer. Therefore, a program that allows a user to log on to a remote computer. A popular client-server program Telnet is used to meet such demands. Telnet is an abbreviation for Terminal Network.

Telnet provides a connection to the remote computer in such a way that a local terminal appears to be at the remote side.

Write the functions of network layers

Internetworking: This is the main duty of network layer. It provides the logical connection between different types of networks.

Addressing: Addressing is necessary to identify each device on the internet uniquely. This is similar to telephone system. The address used in the network layer should uniquely and universally define the connection of a computer.

Routing: In a network, there are multiple roots available from a source to a destination and one of them is to be chosen. The network layer decides the root to be taken. This is called as routing and it depends on various criterions.

Packetizing: The network layer encapsulates the packets received from upper layer protocol and makes new packets. This is called as packetizing. It is done by a network layer protocol called IP (Internetworking Protocol).

Error handling and diagnostics

Error handling and diagnostics are critical aspects of this layer. For example, certain protocols at this layer allow devices that connect logically, or that try to route traffic, to exchange information about the status of hosts on the devices themselves or on the network. One protocol, Internet Control Message Protocol (ICMP), handles errors and diagnostics.

Fragmentation and reassembly

Fragmentation occurs in this layer when the size of a packet, or datagram, exceeds the size of data that can be held in a frame. This layer divides the package it receives from the transport layer into fragments so that no disruption happens in data flows. The reassembly of fragments takes place at the destination because packets take independent paths and may arrive out of order.

What are the advantages and disadvantages of computer network?

The basis of comparison	Advantages of computer networks	Disadvantages of computer networks
Communication	An effective form of communication	An ineffective form of communication
Resource sharing	Convenient resource sharing	Less effective resource sharing
File sharing	Easier	Difficult
Flexibility	A higher level of flexibility	Low flexibility
Price	Inexpensive	Expensive
Operating cost efficiency	Efficient	Inefficient
Storage capacity	Boosts storage capacity	Limited storage capacity
Security	Less secure	More Secure
Independence	Lacks independence	Systems are more independent
Robustness	Lacks robustness	More robust
Viruses and malware attack prone	More prone to attacks	Less vulnerable
Requires efficient Handler	More technically sound person needed	A person with basic skills will do

 

Explain any two transmissions media

What is Transmission Media in Computer Network?

Transmission media is a communication channel that transmits information from the source/transmitter to the receiver. It is a physical path for data transfer through electromagnetic signals. Information is carried over in the form of bits through LAN. It can mediate the propagation of signals for telecommunication. Signals are imposed on a wave that is suitable for the chosen medium. These media lie underneath the physical layer that regulates them. 

Types of Transmission Media in Computer Networks

Broadly, there are two types of transmission media in computer networks including guided and unguided media. These two types of transmission medium in computer networks have further subtypes. Let us discuss these in detail.

Guided Transmission Media

Guided media are also known as wired or bounded media. These media consist of wires through which the data is transferred. Guided media is a physical link between transmitter and recipient devices. Signals are directed in a narrow pathway using physical links. These media types are used for shorter distances since physical limitation limits the signal that flows through these transmission media.

Twisted Pair Cable

In this type of transmission media, two insulated conductors of a single circuit are twisted together to improve electromagnetic compatibility. These are the most widely used transmission medium cables. These are packed together in protective sheaths. They reduce electromagnetic radiation from pairs and crosstalk between the neighboring pair. Overall, it improves the rejection of external electromagnetic interference. These are further subdivided into unshielded and shielded twisted pair cables. 

Unshielded Twisted Pair Cable (UTP): These consist of two insulated copper wires that are coiled around one another. These types of transmission media block interference without depending on any physical shield. The unshielded twisted pair is very affordable and are simple to set up. These provide a high-speed link. 

Shielded Twisted Pair (STP): This twisted cable consisted of a foil shield to block external interference. The insulation within these types of the twisted cable allow greater data transmission rate. These are used in fast-data-rate Ethernet and in data and voice channels of telephone lines.  

Optical Fibre Cable

Also known as fiber optic cable, these are thin strands of glass that guide light along their length. These contain multiple optical fibers and are very often used for long-distance communications. Compared to other materials, these cables can carry huge amounts of data and run for miles without using signal repeaters. Due to lesser requirements, they have less maintenance costs and it improves the reliability of the communication system. These can be unidirectional as well as bidirectional in nature. 

Coaxial cable

These guided transmission media contain an insulation layer that transmits information in baseband mode and broadband mode. Coaxial cables are made of PVC/Teflon and two parallel conductors that are separately insulated. Such cables carry high frequency electrical signals without any big loss. The dimension of cable and connectors are controlled to give them constant conductor spacing for efficient functioning as a transmission line.

Stripline 

This is a transverse electromagnetic (TEM) transmission media that is built on the inner layers of multi-layer printed circuit boards. These are used in high or low-level RF signals that require isolation from surrounding circuitry. It is a type of printed circuit transmission line in which a signal trace is sandwiched between the upper and lower ground place. Stripline minimizes emissions electromagnetic radiation is completely enclosed within homogeneous dielectric. Along with the reduced emissions, it also shields against incoming spurious signals. 

Microstripline

While Microstripline is simiar to stripline, it is not sandwiched and are present above the ground plane. These can be fabricated with any technology where the conductor is separated from the ground plane by a dielectric layer called subtrated. These transmission media convert microwave frequency signals.. Microstrip is also used for building microwave components such as couplers, filters, power dividers, antennas, etc. In comparison with the traditional waveguide technology, it is less expensive.

Unguided Transmission Media

Also known as unbounded or wireless media, they help in transmitting electromagnetic signals without using a physical medium. Here, air is the medium. There is no physical connectivity between transmitter and receiver. These types of transmission media are used for longer distances however they are less secure than guided media. There are three main types of wireless transmission media. 

Radio Waves

Radio waves are transmitted in every direction throughout free space. Since these are omnidirectional, sent waves can be received by any antenna. These waves are useful when the data is to multicasted from one sender to multiple receivers. Radio waves can cover large areas and even penetrate obstacles such as buildings and walls. The frequency of these waves ranges between 3 kHz to 1GHz. Due to its omnidirectional nature; issues such as interference might arise when another signal with the same bandwidth or frequency is sent.  

Infrared

These waves are useful for only very short distance communication. Unlike radio waves, they do not have the ability to penetrate barriers. Their range varies between 300GHz – 400THz. Since they have larger bandwidth, the data rate is very high for infrared waves. These have less interference and are more secure. 

Microwaves

For these waves, it is important for the transmitter and receiver antenna to be aligned. This is why it is known as line-of-sight transmission. Due to this, they are suitable for shorter distances. They comprise of electromagnetic waves with frequencies ranging between 1-400 GHz. Microwaves provide bandwidth between the range of 1 to 10 Mbps. Distance covered by the signal is proportional to the height of the antenna. For travelling to longer distances, the height of the tower should be increased. These are further sub categorized as terrestrial and satellite type microwave transmission. 

Terrestrial type microwave transmission: In this type, high directional antennas are used for line of sight propagation paths that use frequency between 4-12 GHz. These are parabolic antennas having diameters that range from 12 inches to feet depending on their spacing. 

Satellite type microwave transmission: Signals are transmitted to those spaces where satellites are positioned and they retransmit the signal to appropriate locations. Since they only receive and retransmit the signal, they act as repeaters. It is a much more flexible and reliable method of communication in comparison with cables and fiber systems. 

 

Applications of Transmission Media in Computer Networks

Type	Uses
Unshielded Twisted Pair	Telephonic applications
Shielded Twisted Pair	Fast data rate ethernet
Optical Fibre Cable	For transferring large volume of data
Coaxial Cable	Cable TVs,  Analog TV
Stripline	Solid-state microwave systems
Microstripline	Solid-state microwave systems
Radio	Cordless phones, AM/FM radios
Infrared	Wireless mouse, printers, keyboards
Microwave	Mobile phones, televisions

 

Explain the characteristics of LAN

Basic characteristics of a Computer Network

Security

Security is one of the most essential characteristics of a computer network. Most businesses nowadays rely on computers, which are accessed through networking. As a result, if computer network technology is not robust and secure, unauthorized access to the company's critical data might be possible. However, nowadays, computer networking tools primarily provide the highest level of security and prevent any unauthorized access.

Reliability

Computer networks are very reliable tools, and users can easily interconnect their devices with their help. Computer networks have alternative sources of supply to provide high reliability. Their networking experience remains consistent even if users need to print, check messages, attend a meeting, or access data from another computer.

Scalability

Scalability refers to the ability to scale up in response to changing needs while maintaining high performance. The internet is the best example of scalability; many new users connect via the internet and communicate with other devices, but our network still works properly.

Flow of Data

Users can access and transmit data such as files, documents, and other types of information with the help of computer networking. It is a crucial feature of a computer network as it allows data to flow from one device to another.

High performance

The performance is evaluated using the time required by a command. If it requires less time to transfer the data and the response is quick, it is a significant advantage for the users to transfer data and use multiple resources. The performance can be increased using multiple processors.

Fault tolerance

Fault tolerance is also a great feature offered by computer networks. Let’s suppose two devices are connected with both wired and wireless mediums. If the sender’s device sends the information, and the receiver’s device has a blockage at its wireless medium. It will find the other best alternative medium to send the information to the receiver’s device, which is a wired medium in this case. Using this, they can continue to work even if the networking is down or damaged. This is how fault tolerance works.

Quality of Service (QoS)

It means users can prioritize and customize their data transmission while also minimizing any transmission delays. It also allows for the loss of any data if it occurs regularly. As a result, another feature of a computer network is that it provides a high level of service to its users.