Techknow+

What is firewall ? Firewall is a software and hardware ,it is protect our system to the malware,virus, and malicious software ,which is come in to the system with the help of pen-drive or downloaded file . A firewall is a network security device that monitors incoming and outgoing network traffic and decides whether to allow or block specific traffic based on a defined set of security rules. The rule is two type outbound and inbound .It's defined by the user.firewall only protect to incoming services .  A firewall controls access to the resources of a network through a positive control model. This means that the only traffic allowed onto the network is defined in the firewall policy; all other traffic is denied. Firewalls have been a first line of defense in network security for over 25 years. They establish a barrier between secured and controlled internal networks that can be trusted and untrusted outside networks, such as the Internet.  Types of Firewall:

WHAT IS THE NETWORK SECURITY ? Network Security has the greatest of taking the necessary measures in protect different assets of the organization from various security threats within the infrastructure. Network security also ensures that there are enough security policies and procedures defined in order to safeguard various critical assets of the organization. Network Security defines various processes within the organization in order to assess, identify and remove various security threats within the organization. It is  protect the underlying  networking  infrastructure from unauthorized access, misuse, malfunction, modification, destruction, or improper disclosure, thereby creating a secure platform for computers, users and programs to perform on the system. An unauthorized user is not allowed to access the critical resources of the organisation as it is secured by defining a perimeter of a secured network. The secured perimeter of the network is called as De-Militarized

                  Open Systems Interconnection (OSI) Model in this modal we learn about 7 layer:-  APPLICATION LAYER  PRESENTATION  LAYER  SESSION LAYER TRANSPORT LAYER NETWORK LAYER  DATA LINK LAYER  PHYSICAL LAYER Some people says that 1 to 7 and some are says 7 to 1 ,i means that application layer to physical layer and physical layer to application layer .We are describe physical layer to application layer   but before this we defined osi modal. what is osi modal ? The Open System Interconnection model is a seven-layer structure which outlines how communications should happen between computers with both the generalities (language and medium) and specifics of networks. This model was defined by the International Organization for Standardization and is officially referred as ISO OSI. The OSI model is also called as Reference model because it relates to connecting systems that are open for communication with other systems. It ensures compatibility with differe

Nano tubes have a nanometer-scale tube-like structure. Nanotubes are a type of nanoparticle, and it can be large enough to work as a pipe through which other nanoparticles can be done on a channel or material basis, as an electrical conductor or electrical insulator. Can be used. Carbon nanotubes discovered in the first nanotube were found in 1952 by L. V. Radkekevich and V. M. Lukanovich published clear images of 50 nanometer diameter tubes made of carbon in the Soviet Journal of Physical Chemistry. This search was largely unnoticed because the article was published in Russian. And the reach of Western scientists was limited to the Soviet press during the Cold War. Before being known as the carbon nanotube in 1976, Moranobu Endo of CNRS opened the hollow tubes of graphite sheets aligned with chemical vapor-growth techniques. The first sample seen was later known as the Single Wall Carbon Nanotube (SWNT). Three scientists first show images of nanotube with a single graphen

More than 90% of the heat from global warming is stored in the ocean, which means oceans are key players in global climate. Heat causes ocean water to expand, adding to sea level rise. Measuring both long-term sea level trends and the shape of the ocean surface related to currents, Topex-Poseidon and the Jason series provide two basic ingredients for understanding the ocean's role in global climate variations. "As human-caused global warming drives sea levels higher and higher, we are literally contributing to the reshaping of the surface of our planet," said Josh Willis, NASA project scientist for Jason-3 at NASA's Jet Propulsion Laboratory in Pasadena, California. "The precision altimetr satellite missions tell us how much and how fast."