Computer Networks

In order for computers to communicate with each other and transfer data to each other, the whole formed by the connection established between them, usually using a cable, is called a network. The means used to connect computers usually determines the data transmission capacity in a network. Coaxial cable, telephone wires, fiber optic cables, macro waves can be given as examples to the most widely used of these tools today. All of these vehicles have varying data transmission capacities and speeds. Fiber optic cables, on the other hand, are the fastest transmission means of connection today.

Networks are basically divided into two as LAN and WAN according to their size. Networks created by connecting computers in a building or, for example, by connecting computers in adjacent buildings on a university campus are called LAN = Local Area Networks. Networks created by connecting geographically distant computers are called wide area networks (WAN = Wide Area Networks).

The biggest benefit of local networks is that they allow software and hardware resources to be shared by network users. Examples of these resources are printers, hard disks, CD drives, word processors, spreadsheets, database programs. When a local network environment is created, the printer connected to a computer becomes usable by all computers on that network. Thus, all users can print from that printer. These structures are economically very advantageous. For example, when a company establishes such a network structure, it avoids buying a separate printer for all employees and offers a printer with better printing quality and printing speed to everyone's common use. Similarly, unnecessary expense in software can be avoided. For example, a word processing program will be much cheaper if a copy is purchased and used with a network license instead of purchasing it separately for everyone. Similarly, maintenance and renewal of hardware and software will be easier and cheaper. It is also sufficient to keep a single copy of the files in the network environment. This saves the hassle of duplicating and inconsistencies as everyone will make changes to this file. With the reduction in the number of copies, backup and security operations are also performed effortlessly and carefully.

Network Types

LAN (Local Area Network): It is a local network system. In an institution or organization, in a room; It is a network system formed between one or more buildings with Ethernet cards, cable and terminator or Hub.

MAN (Metropolitan/Middle Area Network): It is a medium-sized network system. Requires auxiliary network devices for routing, reinforcement, and authentication within a campus or city; It is a network system that contains and connects multiple LAN systems. The best example of these is the Intranet system.

WAN (Wide Area Network): It is a comprehensive network system. They are systems that connect more than one MAN system to each other or that can be connected to the network by connecting directly with the help of external modems. The best example of this system is Internet.

Components of the Network System

Computer: A network system consists of at least one SERVER (Server) and accordingly CLIENT (Client).

 

Connection and Communication Elements

Ethernet Card: It is the hardware that manages and performs data exchange in the creation of local networks. Its technologies have reached the capacity to transfer 100 Megabits of data. The cable connections of these cards, which are installed in PCI or ISA slots, can be made with BNC or RJ45 connectors; that is, they can be used with two types of cables.

Cables: TwsistedPair (UTP) or Coaxial (BNC) cable is commonly used.

Hub: In network systems created with TwistedPair cables and RJ45 connectors, they are the basic distribution elements of the network.

Switch: It is a distribution element like a hub and provides data switching and reinforcement of the message.

Gatewa: It is the gateway that undertakes the communication control. All data entering and leaving the network passes through this device.

Repeaters: A repeater amplifies the signal on the cable and extends the reach. It does not need any additional software for data transfer. It outputs the input signal as amplified, without any waiting.

Modem: Dial-up networking is the device that provides access to remote network systems. A modem basically converts Analog data to Digital and Digital data to Analog, allowing it to be transmitted over telephone lines.

Modems are of two types as a way of connecting to a computer.

External Modems (External): This type of modem, which is connected to the computer using COM ports, is ideal for cases with expansion slot problems. Since the problems of growing elements that can be experienced in printed circuits are less in these, it can have features such as error verification and interference prevention; With these features, line breaks are less common in these modems.

Internal Modems: These modems, which are directly plugged into the ISA and PCI slots on the motherboard, communicate using the COM3 or COM4 communication channel opened on the bus with the software. Models that do some of the modulation with device driver software instead of chips on them are cheaper.