Computer Network Security PDF

**LESSON 3 -- COMPUTER NETWORK SECURITY** - - - **Twisted pair cable:** It is a high-speed cable that transmits the data over **1Gbps** or more. - **Coaxial cable:** Coaxial cable resembles like a TV installation cable. Coaxial cable is more expensive than twisted pair cable, but...

**LESSON 3 -- COMPUTER NETWORK SECURITY** - - - **Twisted pair cable:** It is a high-speed cable that transmits the data over **1Gbps** or more. - **Coaxial cable:** Coaxial cable resembles like a TV installation cable. Coaxial cable is more expensive than twisted pair cable, but it provides the high data transmission speed. - **Fiber optic cable:** Fiber optic cable is a high-speed cable that transmits the data using light beams. It provides high data transmission speed as compared to other cables. It is more expensive as compared to other cables, so it is installed at the government level - **Resource sharing:** Resource sharing is the sharing of resources such as programs, printers, and data among the users on the network without the requirement of the physical location of the resource and user. - **Server-Client model:** Computer networking is used in the **server-client model**. A server is a central computer used to store the information and maintained by the system administrator. Clients are the machines used to access the information stored in the server remotely. - **Communication medium:** Computer network behaves as a communication medium among the users. For example, a company contains more than one computer has an email system which the employees use for daily communication. - **E-commerce:** Computer network is also important in businesses. We can do the business over the internet. For example, amazon.com is doing their business over the internet, i.e., they are doing their business over the internet. - - - - - - - - - - - - - - - - - - - - **Wired NIC:** The Wired NIC is present inside - - - - - - - - - - - Local Area Network is a group of computers connected to each other in a small area such as building, office. - LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc. - It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and Ethernet cables. - The data is transferred at an extremely faster rate in Local Area Network. - Local Area Network provides higher security. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - **Intranet advantages:** - - - - - - The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable. - Each node is either connected to the backbone cable by drop cable or directly connected to the backbone cable. - When a node wants to send a message over the network, it puts a message over the network. All the stations available in the network will receive the message whether it has been addressed or not. - The bus topology is mainly used in 802.3 (Ethernet) and 802.4 standard networks. - The configuration of a bus topology is quite simpler as compared to other topologies. - The backbone cable is considered as a **\"single lane\"** through which the message is broadcast to all the stations. - The most common access method of the bus topologies is **CSMA** (Carrier Sense Multiple Access). - - - - - - - - -  - Ring topology is like a bus topology, but with connected ends. - The node that receives the message from the previous computer will retransmit to the next node. - The data flows in one direction, i.e., it is unidirectional. - The data flows in a single loop continuously known as an endless loop. - It has no terminated ends, i.e., each node is - connected to other node and having no termination point. - The data in a ring topology flow in a clockwise direction. - The most common access method of the ring topology is **token passing**. - **Token passing:** It is a network access method in which token is passed from - one node to another node. - **Token:** It is a frame that circulates around the network. **Working of Token passing** - A token move around the network, and it is passed from computer to computer until it reaches the destination. - The sender modifies the token by putting the address along with the data. - The data is passed from one device to another device until the destination address matches. Once the token received by the destination device, then it sends the acknowledgment to the sender. In a ring topology, a token is used as a carrier. - - - - - - - - - Star topology is an arrangement of the network in which every node is connected to the central hub, switch or a central computer. - The central computer is known as a **server**, and the peripheral devices attached to the server are known as **clients**. - Coaxial cable or RJ-45 cables are used to connect the computers. - Hubs or Switches are mainly used as connection devices in a **physical star topology**. - Star topology is the most popular topology in network implementation. - **Efficient troubleshooting:** Troubleshooting is quite efficient in a star topology as compared to bus topology. In a bus topology, the manager has to inspect the kilometers of cable. In a star topology, all the stations are connected to the centralized network. Therefore, the network administrator has to go to the single station to troubleshoot the problem. - **Network control:** Complex network control features can be easily implemented in the star topology. Any changes made in the star topology are automatically accommodated. - **Limited failure:** As each station is connected to the central hub with its own cable, therefore failure in one cable will not affect the entire network. - **Familiar technology:** Star topology is a familiar technology as its tools are cost-effective. - **Easily expandable:** It is easily expandable as new stations can be added to the open ports on the hub. - **Cost effective:** Star topology networks are cost-effective as it uses inexpensive coaxial cable. - **High data speeds:** It supports a bandwidth of approx. 100Mbps. Ethernet 100BaseT is one of the most popular Star topology networks. - - **Tree topology** - Tree topology combines the characteristics of bus topology and star topology. - - - - - - - - - - - - - - - - - - - - - **Reliable:** The mesh topology networks are very reliable as if any link breakdown will not affect the communication between connected computers. - **Fast Communication:** Communication is very fast between the nodes. - **Easier Reconfiguration:** Adding new devices would not disrupt the communication between other devices. - - - - - - When two or more different topologies are combined together is termed as Hybrid topology and if similar topologies are connected with each other will not result in Hybrid topology - - - - **Effective:** Hybrid topology is very effective as it can be designed in such a way that the strength of the network is maximized and weakness of the network is minimized - - -