Networking Devices
Modem: Modem stands for Modulator-Demodulator. It is used to connect computers for communication via telephone lines.
Hub: It works at the Physical layer. It just acts like a connector of several computers i.e. simply connects all the devices on its ports together. It broadcasts all the data packets arriving at it with no filtering capacity.
Switch: It works at the Data Link Layer. It is used for dividing a network into segments called
subnets. It provides filtering of data packets and prevents network traffic also.
Repeater: It operates at thePhysical Layer. It is used to amplify a signal that has lost its original strength so as to enable them to travel long distances. It can only join the networks that transmit similar data packets. It does not have filtering capacity i.e. all data including noise is amplified and passed on in the network so don’t help in reducing network traffic.
Router: It works at the Network Layer and is used to connect different networks that have different architectures and protocols. It sends the data packets to desired destination by choosing the best path available thus reducing network traffic. It routes the data packets using the routing table that contains all the Information regarding all known network addresses, possible paths and cost of transmission over them. Availability of path and cost of transmission decide sending of data over that path. It is of 2 types: static (manual configuration of routing table is needed) and dynamic (automatically discovers paths).
Gateway: It operates in all the layers of the network architecture. It can be used to connect two different networks having different architectures, environment and even models. It converts the data packets in form that is suitable to the destination application. The two different networks may differ in types of communication protocols they use, language, data formats etc.
Bridge: They are used two connect two LANs with the same standard but using different types of cables. It provides an intelligent connection by allowing only desired messages to cross the bridge thus improving performance. It uses physical addresses of the packets for this decision. It works on Data Link Layer of the OSI model. A bridge uses Spanning tree Algorithm for data transmission so as to avoid loops in the network.
IPv4 - 32 bits
IPv6 - 128 bits
A Computer Virus is a computer program or code that can replicate itself and spread from one computer system to another system. A computer virus has the capacity to corrupt or to delete data on your computer and it can utilize an e-mail program to spread the virus to other computer systems. In the worst case scenario, it can even delete everything on your hard disk. The purpose of it is to disrupt the operation of the computer or the program.
Some examples of Computer Virus are Trojan viruses. stealth viruses, worms, malware (malicious software), Disk Killer, Stone virus, Sunday, Cascade, Nuclear, Word Concept, etc.
Malware, short for malicious software, is any software used to disrupt computer operation, gather sensitive information, or gain access to private computer systems. It can appear in the form of executable code, scripts, active content, and other software.
Antivirus Software is used to scan the hard disk to remove the virus from them. Some of the famous anti – viruses available are Avast!, Norton, Avira, Kaspersky, AVG, etc.
A person who uses his or her expertise to gain access to other people’s computers to get information illegally or do damage is a Hacker.
Authorization is the function of specifying access rights to resources related to information security and computer security in general and to access control in particular. More formally, "to authorize" is to define an access policy.
Authentication is the act of confirming the truth of an attribute of a single piece of data or entity. It might involve confirming the identity of a person by validating their identity documents, verifying the validity of a website with a digital certificate, tracing the age of an artifact by carbon dating, or ensuring that a product is what its packaging and labelling claim to be. In other words, Authentication often involves verifying the validity of at least one form of identification.
Phishing is the attempt to acquire sensitive information such as usernames, passwords, and credit card details (and sometimes, indirectly, money) by masquerading as a trustworthy entity in an electronic communication.
A Spoofing attack is a situation in which one person or program successfully represents oneself as another by falsifying data and thereby gaining an illegitimate advantage.
The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO).
Seven layers of OSI Model are:
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data link Layer
Physical Layer
Network topology is the arrangement of the various elements (links, nodes, etc.) of a computer network.There are two basic categories of network topologies:
Physical topologies and logical topologies.
Physical topology is the placement of the various components of a network, including device location and cable installation, while logical topology illustrates how data flows within a network, regardless of its physical design. Various types of topologies are:
Bus Topology
Star Topology
Ring Topology
Mesh Topology
Tree Topology
Hybrid Topology
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