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1. What is Computer Network and write characteristics of it?
•A computer network is a system in which multiple computers are connected to each other to share information and resources.
•The physical connection between networked computing devices is established using either cable media or wireless media.
•The best-known computer network is the Internet.
A list Of Computer network characteristics is given below.
Communication speed File sharing Back up and Roll back is easy Software and Hardware sharing Security Scalability Reliability
Communication speed Network provides us to communicate over the network in a fast and efficient manner. For example, we can do video conferencing, email messaging, etc. over the internet. Therefore, the computer network is a great way to share our knowledge and ideas.
File sharing File sharing is one of the major advantage of the computer network. Computer network provides us to share the files with each other. Back up and Roll back is easy Since the files are stored in the main server which is centrally located. Therefore, it is easy to take the back up from the main server.
Software and Hardware sharing We can install the applications on the main server, therefore, the user can access the applications centrally. So, we do not need to install the software on every machine. Similarly, hardware can also be shared.
Security Network allows the security by ensuring that the user has the right to access the certain files and applications.
Scalability Scalability means that we can add the new components on the network. Network must be scalable so that we can extend the network by adding new devices. But, it decreases the speed of the connection and data of the transmission speed also decreases, this increases the chances of error occurring. This problem can be overcome by using the routing or switching devices.
Reliability Computer network can use the alternative source for the data communication in case of any hardware failure.
2. Write advantages and disadvantages of Computer Network?
Advantages:
File sharing o The major advantage of a computer network is that is allows file sharing and remote file access. A person sitting at one workstation that is connected to a network can easily see files present on another workstation, provided he is authorized to do so.
Disadvantages :
Lack of data security and privacy o Because there would be a huge number of people who would be using a computer network to get and share some of their files and resources, a certain user’s security would be always at risk. There might even be illegal activities that would occur, which you need to be careful about and aware of.
Presence of computer viruses and malwares o If even one computer on a network gets affected by a virus, there is a possible threat for the other systems getting affected too. Viruses can spread on a network easily, because of the inter-connectivity of workstations. Moreover, multiple systems with common resources are the perfect breeding ground for viruses that multiply.
Lack of Independence o Since most networks have a centralized server and dependent clients, the client users lack any freedom whatsoever. Centralized decision making can sometimes hinder how a client user wants to use his own computer.
Lack of Robustness o As previously stated, if a computer network’s main server breaks down, the entire system would become useless. Also, if it has a bridging device or a central linking server that fails, the entire network would also come to a standstill.
Need an efficient handler o For a computer network to work efficiently and optimally, it requires high technical skills and know-how of its operations and administration. A person just having basic skills cannot do this job. Take note that the responsibility to handle such a system is high, as allotting permissions and passwords can be daunting. Similarly, network configuration and connection is very tedious and cannot be done by an average technician who does not have advanced knowledge.
3.Write applications OR uses of Computer Network?
Financial services Nowadays, almost all the financial services depend on the computer network. You can access the financial services across the world. For example, a user can transfer money from one place to another by using the electronic fund transfer feature. You can use networking in various financial areas such as ATM, foreign exchange and credit history search.
Business Nowadays, most of the works of businesses are done over the computers. To exchange the data and ideas, you need an effective data and resources sharing features. To do this, you need to connect the computer with each other through a network. For example, a person of one department of an organization can share or access the electronic data of other department through network. Email services A computer network provides you the facility to send or receive mails across the globe in few seconds. Mobile applications By using the mobile applications, such as cellular or wireless phones, you can communicate (exchange your views and ideas) with one other. Directory services It provides you the facility to store files on a centralized location to increase the speed of search operation worldwide. Teleconferencing It contains voice conferencing and video conferencing which are based in networking. In teleconferencing the participants need not to be presented at the same location.
- Define Topology? Explain different types of topology?
Network Topology is the schematic description of a network arrangement, connecting various nodes (sender and receiver) through lines of connection. A Network Topology is the arrangement with which computer systems or network devices are connected to each other.
Ring Topology
It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbors for each device.
Features :
A number of repeaters are used and the transmission is unidirectional. Date is transferred in a sequential manner that is bit by bit. Advantages : Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data. Cheap to install and expand. Troubleshooting is difficult in ring topology. Adding or deleting the computers disturbs the network activity. Failure of one computer disturbs the whole network.
Star Topology
In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.
Features :
Every node has its own dedicated connection to the hub. Acts as a repeater for data flow. Can be used with twisted pair, Optical Fibre or coaxial cable.
Advantages : Fast performance with few nodes and low network traffic. Hub can be upgraded easily. Easy to troubleshoot. Easy to setup and modify. Only that node is affected which has failed rest of the nodes can work smoothly. Disadvantages : Cost of installation is high. Expensive to use. If the hub is affected then the whole network is stopped because all the nodes depend on the hub.
Mesh Topology
It is a point-to-point connection to other nodes or devices. Traffic is carried only between two devices or nodes to which it is connected.
Features :
Ideal if workstations are located in groups. Used in Wide Area Network. Extension of bus and star topologies. Expansion of nodes is possible and easy. Easily managed and maintained. Error detection is easily done. Advantages:
Extension of bus and star topologies. Expansion of nodes is possible and easy. Easily managed and maintained. Error detection is easily done. Disadvantages : Heavily cabled. Costly. If more nodes are added maintenance is difficult. Central hub fails then network fails.
Hybrid Topology
A network structure whose design contains more than one topology is said to be hybrid topology. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).
Features :
It is a combination of two or more topologies Inherits the advantages and disadvantages of the topologies included Advantages :
Reliable as error detecting and trouble shooting is easy. Scalable as size can be increased easily. Flexible.
Disadvantages :
Complex in design. Costly.
Some protocols also support message acknowledgement and data compression designed for reliable and/or high-performance network communication. Example: HTTP, IP, FTP etc…
- Define OSI model and explain function of each layer?
OSI model is based on a proposal developed by the International Standards Organization (ISO) as a first step toward international standardization of the protocols used in the various layers. It was revised in 1995. The model is called the OSI (Open Systems Interconnection) Reference Model because it deals with connecting open systems—that is, systems that are open for communication with other systems.
The OSI model has seven layers:
- Physical Layer
- Data Link Layer
- Network Layer
- Transport Layer
- Session Layer
- Presentation Layer
- Application Layer
Fig : OSI reference model
Session (Layer 5):
This layer establishes, manages and terminates connections between applications.
The session layer sets up, coordinates, and terminates conversations, exchanges,
and dialogues between the applications at each end. It deals with session and
connection coordination.
Layer 5 Session examples include NFS, NetBios names, RPC, SQL.
Presentation (Layer 6):
This layer provides independence from differences in data representation
(e.g., encryption) by translating from application to network format, and vice
versa. The presentation layer works to transform data into the form that the
application layer can accept. This layer formats and encrypts data to be sent across
a network, providing freedom from compatibility problems. It is sometimes called
the syntax layer.
Layer 6 Presentation examples include encryption, ASCII, EBCDIC, TIFF, GIF,
PICT, JPEG, MPEG, MIDI.
Application (Layer 7):
OSI Model, Layer 7, supports application and end-user processes. Communication
partners are identified, quality of service is identified, user authentication and
privacy are considered, and any constraints on data syntax are identified.
Everything at this layer is application-specific. This layer provides application
services for file transfers, e-mail, and
other network software services. Telnet and FTP are applications that exist entirely
in the application level. Tiered application architectures are part of this layer.
Layer 7 Application examples include WWW browsers, NFS, SNMP, Telnet, HTTP, FTP
8. TCP/IP (Internet Protocol Stack layers)Reference Model and explain function of each layer?
Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite is the engine for the Internet and networks worldwide. TCP/IP either combines several OSI layers into a single layer, or does not use
certain layers at all
TCP/IP is a set of protocols developed to allow cooperating computers to share resources across the network.
The TCP/IP model has five layers.
- Application Layer
- Transport Layer
- Internet Layer
- Data Link Layer
- Physical Network
Fig: TCP/IP Reference Model
TCP/IP model combines the functions of Data link Layer and Physical Layer.
Application layer is the top most layer of four layer TCP/IP model. Application layer is present on the top of the Transport layer. Application layer defines TCP/IP application protocols and how host programs interface with Transport layer services to use the network. Application layer includes all the higher-level protocols like DNS (Domain Naming System), HTTP (Hypertext Transfer Protocol), Telnet, SSH, FTP (File Transfer Protocol), TFTP (Trivial File Transfer Protocol), SNMP (Simple Network Management Protocol), SMTP (Simple Mail Transfer Protocol), DHCP (Dynamic Host Configuration Protocol), X Windows, RDP (Remote Desktop Protocol) etc.
Network Interface Layer (Network Access Layer)
Network Access Layer defines details of how data is physically sent through the network, including how bits are electrically or optically signalled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted pair copper wire. The protocols included in Network Access Layer are Ethernet, Token Ring, FDDI, X.25, Frame Relay etc.
9. Difference between OSI and TCP/IP model?
BASIS FOR
COMPARISON
TCP/IP MODEL OSI MODEL
Expands To TCP/IP- Transmission Control OSI- Open system
BASIS FOR
COMPARISON
TCP/IP MODEL OSI MODEL
Protocol/ Internet Protocol Interconnect
Meaning It is a client server model used
for transmission of data over
the internet.
It is a theoretical model
which is used for
computing system.
No. Of Layers 4 Layers 7 Layers
Developed by Department of Defense (DoD) ISO (International Standard
Organization)
Tangible Yes No
Usage Mostly used Never used
