A computer network is a complex system that connects various devices like computers, servers, printers, routers, and switches. Its primary purpose is to enable these devices to communicate with one another and share resources effectively.
Networks can take the form of physical cable connections or wireless communication through radio waves and other wireless technologies.
They play a crucial role in facilitating communication, data sharing, and collaborative work among users in diverse settings, including homes, businesses, and organizations of all sizes.
Types of Networks:
Computer networks come in various types, each serving specific purposes. Here are some common types of networks:
Local Area Network (LAN):
Limited to a small geographic area, such as a home, office, or building.
Utilizes wired or wireless connections to connect devices for communication and resource sharing.
Wide Area Network (WAN):
Spans larger geographic areas, like cities, regions, or even entire countries.
Uses telecommunications links, such as leased lines or satellite connections, to connect devices across great distances.
Metropolitan Area Network (MAN):
Covers a geographic area larger than a LAN but smaller than a WAN, often a single city or metropolitan area.
Used by businesses with multiple locations within one city.
Wireless Local Area Network (WLAN):
Similar to LAN but relies on wireless connections, like Wi-Fi, eliminating the need for physical cables.
Storage Area Network (SAN):
Specialized networks for storing and accessing data, known for high-speed connections and specialized hardware.
Virtual Private Network (VPN):
Creates secure, private connections between devices using public networks like the internet.
Frequently used by remote workers to access resources on a company network from anywhere.
Network Entities:
To understand how networks operate, we must consider the components or devices that make up a network, facilitating communication between devices. Common network entities include:
Nodes: Devices connected to the network, such as computers, servers, printers, and routers.
Switches: Devices connecting multiple nodes and facilitating communication within the network.
Routers: Devices that link different networks together, like LAN and WAN, using protocols like IP.
Gateways: Devices that provide access to various networks (e.g., connecting a LAN to the internet) and may perform protocol translation.
Firewalls: Devices protecting networks by filtering incoming and outgoing traffic to prevent unauthorized access.
Servers: Devices offering resources or services to other devices on the network, such as file storage, email, or web hosting.
How Networks Work
A network operates by connecting devices and enabling communication and resource sharing. The key steps in how a network works include:
Connecting Devices: Devices like computers, servers, and routers are physically or wirelessly connected to the network.
Transmitting Data: Devices communicate using protocols (e.g., TCP/IP) to send data packets to each other.
Routing Data: Routers guide data between networks, deciding the best path based on network conditions.
Sharing Resources: Devices on the network can share resources like files, printers, and internet connections.
Implementing Security Measures: Security measures like firewalls, access controls, and encryption are implemented to protect against unauthorized access and data breaches.
The specifics of how a network operates depend on the network type, devices, protocols, and user requirements. However, the fundamental concept of connecting devices to enable communication and resource sharing applies to all networks.
The OSI Model:
The OSI (Open Systems Interconnection) model is a conceptual framework that describes network communication functions. It consists of seven layers, each with specific roles:
Physical Layer: Manages physical aspects like electrical signals and hardware.
Data Link Layer: Transfers data between devices and handles error detection and correction.
Network Layer: Routes data between networks, selecting the best path based on various factors.
Transport Layer: Ensures reliable data transfer, breaks data into packets, and manages data flow.
Session Layer: Establishes, maintains, and terminates sessions between devices.
Presentation Layer: Manages data formatting, encryption, and compression.
Application Layer: Provides services supporting user applications like web browsing, email, and file transfer.
Although not a specific standard, the OSI model serves as a reference for communication protocols and networking technologies in the industry.
Lists of Protocols:
Application Layer Protocols: HTTP, FTP, SMTP, DNS, DHCP, Telnet, SSH, POP3, IMAP, SNMP, and more.
Transport Layer Protocols:TCP, UDP, SCTP, DCCP, RSVP, SPX, NetBEUI, and ISCSI.
Network Layer Protocols: IP, ICMP, ARP, RARP, OSPF, BGP, IS-IS, EIGRP, and more.
Data Link Layer Protocols:Ethernet, Wi-Fi, PPP, HDLC, ATM, FDDI, Token Ring, SLIP, and more.
Each of these protocols serves specific functions and applications within their respective layers, contributing to the functionality of computer networks.
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