Note for Cryptography And Network Security - CNS by kishan chandra

Topics ( 6 )

Text from page-1

Network Security By :- Kumar Kishan Chandra Ast. Professor RD & DJ College Munger,Bihar

Text from page-2

Table of Contents 1. NETWORK SECURITY – Introduction .................................................................................................... 2. APPLICATION LAYER SECURITY............................................................................................................... 3. SECURITY IN TRANSPORT LAYER ........................................................................................................... 4. NETWORK LAYER SECURITY ................................................................................................................... 5. DATA LINK LAYER SECURITY................................................................................................................... 6. NETWORK ACCESS CONTROL .................................................................................................................. 7. FIREWALLS ...................................................................................................................................................... 8. NETWORK SECURITY – CRITICAL NECESSITY ..........................................................................................

Text from page-3

1.Introduction about Network and Network Security Network :- A network is defined as a group of two or more computer systems linked together. Why Network ? Computer networks allow the user to access remote programs and remote databases either of the same organization or from other enterprises or public sources. Computer networks provide communication possibilities faster than other facilities. Because of these optimal information and communication possibilities, computer networks may increase the organizational learning rate, which many authors declare as the only fundamental advantage in competition. Types Of Network  local-area networks (LANs): The computers are geographically close together (that is, in the same building).  wide-area networks (WANs): The computers are farther apart and are connected by telephone lines or radio waves.  campus-area networks (CANs): The computers are within a limited geographic area, such as a campus or military base.

Text from page-4

 metropolitan-area networks MANs): A data network designed for a town or city.  home-area networks (HANs): A network contained within a user's home that connects a person's digital devices. Network Characteristics In addition to these types, the following characteristics are also used to categorize different types of networks:  topology : The geometric arrangement of a computer system. Common topologies include a bus, star, and ring..  protocol : The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network .  architecture : Networks can be broadly classified as using either a peer-topeer or client/server architecture. Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers. Computer Security The meaning of the term computer security has evolved in recent years. Before the problem of data security became widely publicized in the media, most people‟s idea of computer security focused on the physical machine. Traditionally, computer facilities have been physically protected for three reasons:  To prevent theft of or damage to the hardware  To prevent theft of or damage to the information  To prevent disruption of service Strict procedures for access to the machine room are used by most organizations, and these procedures are often an organization‟s only obvious computer security measures. Today, however, with pervasive remote terminal access, communications, and networking, physical measures rarely provide meaningful protection for either the information or the service; only the hardware is secure. Nonetheless, most computer facilities continue to protect their physical machine far better than they do their data, even when the value of the data is several times greater than the value of the hardware.