Networking Basics.pdf

COMPUTER is an electronic device that receives input, stores or processes the input as per user instructions and provides output in desired format. Characteristics of Computer  Speed − Typically, a computer can carry out 3-4 million instructions per second.  Accuracy − Computers exhi...

COMPUTER is an electronic device that receives input, stores or processes the input as per user instructions and provides output in desired format. Characteristics of Computer  Speed − Typically, a computer can carry out 3-4 million instructions per second.  Accuracy − Computers exhibit a very high degree of accuracy. Errors that may occur are usually due to inaccurate data, wrong instructions or bug in chips – all human errors.  Reliability − Computers can carry out same type of work repeatedly without throwing up errors due to tiredness or boredom, which are very common among humans.  Versatility − Computers can carry out a wide range of work from data entry and ticket booking to complex mathematical calculations and continuous astronomical observations. If you can input the necessary data with correct instructions, computer will do the processing.  Storage Capacity − Computers can store a very large amount of data at a fraction of cost of traditional storage of files. Also, data is safe from normal wear and tear associated with paper. Advantages of Using Computer  Computers can do the same task repetitively with same accuracy.  Computers do not get tired or bored.  Computers can take up routine tasks while releasing human resource for more intelligent functions. Disadvantages of Using Computer  Computers have no intelligence; they follow the instructions blindly without considering the outcome.  Regular electric supply is necessary to make computers work, which could prove difficult everywhere especially in developing nations. A computer system is a combination of hardware and software. Physical and tangible parts/components of a computer can be seen and touched which are known as hardware. Hardware consists of physical components of a computer system such as input devices( keyboards, mouse, scanners, etc.), output devices(monitors, printers, speakers, etc.), processing devices(CPU) and storage devices, compact discs, hard disks, DVDs, etc.. Software is the set of programs and instructions that control the operation of a computer system. The computer system cannot do anything on its own. The computer performs the same function as the user is instructed by it. The programs written in the computer are written in the language understood by the computer. Firmware is a software program or set of instructions programmed on a hardware device. It provides the necessary instructions for how the device communicates with the other computer hardware. Firmware is typically stored in the flash ROM of a hardware device. Types of software The system software is a collection of programs designed to operate, control, and extend the processing capabilities of the computer itself. System software is generally prepared by the computer manufacturers. Some examples of system software are Operating System, Compilers, Interpreter, Assemblers, etc. Application software products are designed to satisfy a particular need of a particular environment. Examples of Application software are Income Tax Software, Railways Reservation Software, Microsoft Word, Microsoft Excel, Microsoft PowerPoint. An OPERATING SYSTEM(OS) is a program that acts as an interface between the software and the computer hardware. The operating system performs the following functions in a device. 1. Instruction 2. Input/output Management 3. Memory Management 4. File Management 5. Processor Management 6. Job Priority 7. Special Control Program 8. Scheduling of resources and jobs 9. Security 10. Monitoring activities 11. Job accounting Kernel Vs. Shell Both of these are used in a computer system for establishing communication and operating the system. But there is a fundamental difference between shell and kernel. A shell is basically an interface present between the kernel and the user. It allows all of its users to establish communication with the kernel. A kernel is the very core of a typical OS. It functions to control all the tasks that come with a system. Let us know a bit more about each of these individually. NETWORK: A network is a collection of devices connected together, ie, a computer network is a group of computers and other hardware devices that are linked together through communication channels to facilitate communication and resource sharing among a wide range of users. Networks are used for a number of reasons, one way or another it’s usually about sharing: Information: we use networks for applications like e-mail or to reach certain websites. File sharing: we need a network so that users can reach a shared network drive with documents, pictures and/or other files. Resource sharing: we can connect a printer to the network that is used by multiple users. No need to connect a printer directly to each computer. Application sharing: we might have users that require access to the same application. For example, a finance department with five users that need access to the same bookkeeping software. A network can be as small as two computers that are directly connected to each other or as large as the Internet with millions of devices. Computer network components Hardware components: computer, NIC, media/cables, switch/hub, router, modem, firewall. Software components: NOS, protocol, firewall. NIC: Short for network interface card, the NIC is also referred to as an Ethernet card and network adapter. A NIC is a computer expansion card for connecting to a network (e.g., home network or Internet) using an Ethernet cable with an RJ-45 connector. HUB: A hub is a physical layer networking device which is used to connect multiple devices in a network. They are generally used to connect computers in a LAN.A hub has many ports in it. A computer which intends to be connected to the network is plugged in to one of these ports. When a data frame arrives at a port, it is broadcast to every other port, without considering whether it is destined for a particular destination or not. SWITCHES: A switch is a data link layer networking device which connects devices in a network and uses packet switching to send and receive data over the network. Like a hub, a switch also has many ports, to which computers are plugged in. However, when a data frame arrives at any port of a network switch, it examines the destination address and sends the frame to the corresponding device(s). Thus, it supports both unicast and multicast communications. ROUTERS: Routers are networking devices operating at layer 3 or a network layer of the OSI model. They are responsible for receiving, analysing, and forwarding data packets among the connected computer networks. When a data packet arrives, the router inspects the destination address, consults its routing tables to decide the optimal route and then transfers the packet along this route. MODEM: A modem is a hardware device that allows the computer to connect to the internet over the existing telephone line.It stands for Modulator/Demodulator. It converts the digital data into an analog signal over the telephone lines. FIREWALL: In computing firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a rusted network and an untrusted network, such as the internet Next generation firewall A next generation firewall(NGFW) is a part of the third generation of firewall technology, combining a traditional firewall with other network devices filtering functionalities, such as an application firewall using inline deep packet inspection(DPI) and an intrusion prevention system(IPS). i.e., NGFW=FW + IPS NGFW must include 1. Standard firewall capabilities like statefull inspection 2. Integrated intrusion prevention 3. Application awareness and control to see and block risky apps 4. Threat intelligent sources 5. Upgrade paths to include future information feeds 6. Techniques to address evolving security threats Some common NGFW: Firepower 1000 series, 2100 series, 4100 series, 9300 series Server and Client A server is a computer or system that provides resources, data, services, or programs to other computers, known as clients, over a network (LAN/WAN). In theory, whenever computers share resources with client machines they are considered servers. There are many types of servers, including web servers, mail servers, and virtual servers. An individual system can provide resources and use them from another system at the same time. This means that a device could be both a server and a client at the same time. Endpoints Endpoints are clients that consumes OR generates new data. Endpoints range from IP phones to web, mobile and desktop clients. In other words, we can say endpoints refers to end hosts or hosts devices such as desktops, laptops, mobile phones and servers. Network Operating System(NOS) Network Operating System is a computer operating system that facilitates to connect and communicate various autonomous computers over a network. It is self-capable to perform operations and processing for a single user. They can either run the same or different O.S. Some examples of network operating systems include Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, Novell NetWare, and BSD. Protocols  A protocol is a set of rules that governs the communications between computers on a network. In order for two computers to talk to each other, they must be speaking the same language.  Many different types of network protocols and standards are required to ensure that your computer (no matter which operating system, network card, or application you are using) can communicate with another computer located on the next desk or half-way around the world.  There are many protocols while establishing a connection in the internet. According to the type of connection need to be established, the protocols used varies.  The protocols define the characteristics of the connection. Common Protocols Used and Their Ports File Transfer Protocol (FTP) 20, 21 Secured Shell (SSH) 22 Telnet 23 Simple Mail Transfer Protocol (SMTP) 25 Domain Name System (DNS) 53 Dynamic host configuration protocol (DHCP) 67, 68 Trivial file transfer protocol (TFTP) 69 Hypertext Transfer Protocol (HTTP) 80 Kerberos 88 Post Office Protocol version 3 (POP 3) 110 Network time protocol (NTP) 123 Simple Network Management Protocol (SNMP) 161 Border gateway protocol (BGP) 179 Lightweight directory access protocol (LDAP) 389 Hypertext Transfer Protocol over SSL/TLS (HTTPS) 443 Syslog 514