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What is Networking?
What is Networking?
Network is a collection of computers or other hardware devices that connect to each other (physically or logically) using special hardware and software to allow them to share resources - information, hardware (printers, scanners, storage, compute power, etc), or software.
Networking is the process of designing, implementing, upgrading, managing, and troubleshooting networks and network technologies.
Network Advantages
Network Advantages
Connectivity & Communication - transmission of information is easier, cheaper, and more efficient that it would be without a network.
Data Sharing - allows millions of people (and applications) to share data quicker and much more easily.
Hardware Sharing - organizations can share a single expensive hardware asset (printers, network storage, or computing power - cloud computing) with several individuals reducing cost and improving ease of access.
Internet Access & Sharing - individuals (and applications) are granted internet access via a single internet connection that can be managed and secured.
Data Security & Management - IT administrators can more easily and effectively manage access and security of an organization's data.
Performance Enhancement & Balancing - application performance and processing can be enhanced via distributing the computation tasks to various computers on the network.
Entertainment - games, audio/video streaming, etc.
Network Disadvantages
Network Disadvantages
Network Hardware, Software, & Setup Costs - initial capital expenditure required to design, plan, purchase, implement, configure, and maintain increases greatly as the size of the network increases.
Hardware & Software Management & Administration Costs - ongoing maintenance and management requires skilled IT professionals especially for large corporate networks.
Data Security Concerns - poorly designed, configured, and secured networks increases the risk of exposing critical data - threat actors, unauthorized access, and even sabotage.
OSI and TCP/IP Model
OSI and TCP/IP Model
TLDR;
Open System Interconnection (OSI) Model
This is a theoretical framework with 7 detailed layers that explain network fundamentals and communication.
Physical
Data Link
Network
Transport
Session
Presentation
Application
TCP/IP Model
This practical model was developed to standardize communication protocols for the Internet and real-world networks. It merges OSI layers into 4 layers for simplicity.
Link/Network Access
Internet/Network
Transport
Application
OSI Model Layers
OSI Model Layers
Layer 7 - Application
This is the highest layer in the OSI model, allowing users to access network resources and services. It is the only layer seen by end users - it provides an interface that is the base of all other activities.
Layer 6 - Presentation
This layer transforms the data it receives into a format the Application layer can read.
The data encoding and decoding depend on the application protocol sending or receiving the data.
This layer also handles encryption and decryption used for securing data.
Layer 5 - Session
This layer establishes, manages, and terminates connections between communicating devices and services.
It is also responsible for establishing whether a connection is duplex or half-duplex and for gracefully closing a connection between hosts.
Layer 4 - Transport
The primary purpose of this layer is to provide reliable data transmission to lower layers.
Its features include flow control, segmentation, desegmentation, and error control; it ensures that data moves error-free from point to point.
The transport layer provides services to connection-oriented (TCP) and connectionless (UDP) protocols.
Firewalls and proxies operate at this layer.
Layer 3 - Network
It is responsible for routing data between physical networks.
It is also responsible for logically addressing network hosts (IP address), packet segmentation, protocol identification, and, in some cases, error detection.
Routers operate at this level.
Layer 2 - Data Link
Provides the means of transporting data across a physical network (LAN).
Its primary purpose is to provide an addressing scheme that can be used to identify physical devices (MAC) and provide error-checking features to ensure data integrity.
Network switches operate at this layer.
Layer 1 - Physical
The lowest layer of the OSI model is the physical medium through which network data is transferred.
It defines the physical and electrical nature of all hardware used - voltages, hubs, network adaptors, repeaters, & cabling specifications.
It establishes and terminates connections, provides a means for sharing communication resources, and converts signals from digital to analog and vice versa.
TCP/IP Model Layers
TCP/IP Model Layers
Application Layer
It is the highest layer of the TCP/IP model and merges the OSI Application, Presentation, and Session layers.
It groups the following functionality:
Provides an interface via applications for uses to access and manage network resources.
Establishes, maintains, and terminates connections between network applications and services.
Handles data encoding, decoding, encryption, and description.
Transport Layer
Similar to the OSI model, it establishes, maintains, and terminates connections between network devices.
It divides data from the application layer into packets for transmission via sequences, flow control, and error control.
The protocols used in this layer are:
TCP: Transmission Control Protocol is responsible for the proper transmission of segments over the communication channel. It also establishes a network connection between the source and destination system.
UDP: User Datagram Protocol is responsible for identifying errors, and other tasks during the transmission of information. UDP maintains various fields for data transmission such as:
Source Port Address: This port is responsible for designing the application that makes up the message to be transmitted.
Destination Port Address: This port receives the message sent from the sender side.
Total Length: The total number of bytes of the user datagram.
Checksum: Used for error detection of the message at the destination side.
Network/Internet Layer
Similar to the OSI Network layer, it controls the transmission of data over the network by:
Specifying the path the data packets will use during transmission.
Providing logical addresses (IP addresses) to identify devices on the network.
Link/Network Access Layer
It is the lowest layer of the TCP/IP model and merges the OSI Physical and Data Link layers.
It is responsible for sending and receiving data in raw bits, i.e., in binary format, over the physical communication modes in the network channel.
It uses the device's physical address (MAC) to map the transmission path over a LAN.
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