Application Layer
1] Introduction to DNS, SMTP, SNMP, FTP, HTTP & WWW
DNS (Domain Name System) is a protocol that translates human-readable domain names into IP addresses. This is important because the Internet relies on IP addresses to identify and communicate with devices, but domain names are easier for humans to remember and use.SMTP (Simple Mail Transfer Protocol) is a protocol used for sending and receiving email messages between servers. It allows emails to be sent from one server to another, even if the servers are located in different parts of the world.
SNMP (Simple Network Management Protocol) is a protocol used for managing and monitoring network devices. It allows administrators to monitor the performance and status of devices such as routers, switches, and servers.
FTP (File Transfer Protocol) is a protocol used for transferring files between computers on a network. It allows users to upload and download files to and from a remote server, and is often used for publishing websites or sharing large files.
HTTP (Hypertext Transfer Protocol) is a protocol used for transferring data over the World Wide Web. It is used by web browsers and servers to communicate with each other and transfer data such as web pages, images, and videos.
WWW (World Wide Web) is an information system on the Internet that allows users to access and share information using web pages and hyperlinks. It is a collection of interconnected documents and resources, and is often accessed using a web browser such as Google Chrome or Mozilla Firefox.
2] Security: Cryptography (Public, Private Key based)
Cryptography is the practice of securing communication from adversaries. It involves using mathematical algorithms to encrypt messages so that only the intended recipient can decipher them. There are two main types of cryptography: symmetric and asymmetric.Symmetric cryptography involves using the same key for both encryption and decryption. This means that both the sender and the recipient must have access to the same secret key. Examples of symmetric cryptography algorithms include Advanced Encryption Standard (AES) and Data Encryption Standard (DES).
Asymmetric cryptography, also known as public key cryptography, involves using two different keys for encryption and decryption. One key is kept private by the owner and the other key is made public. The public key can be freely distributed and is used by others to encrypt messages sent to the owner. Only the owner, who possesses the private key, can decrypt the messages. Examples of asymmetric cryptography algorithms include RSA and Elliptic Curve Cryptography (ECC).
Public key cryptography is commonly used in digital signatures, secure email communication, and secure web browsing. It provides a more secure method of communication compared to symmetric cryptography because it eliminates the need for a secret key to be shared between parties, which can be difficult to manage securely.
3] Firewalls
Firewalls are security devices or software that monitor and control incoming and outgoing network traffic based on predetermined security rules. Their main goal is to prevent unauthorized access to or from a private network while allowing authorized traffic to pass through.Firewalls can be hardware-based, such as routers or switches, or software-based, such as a standalone software application or a feature integrated into an operating system. They can operate at different layers of the network stack, including network, transport, and application layers.
Firewalls can be configured to block traffic based on various criteria, such as source and destination IP addresses, ports, protocols, and specific keywords or patterns in the packet payload. They can also be set up to perform various security functions, such as intrusion detection, antivirus scanning, content filtering, and VPN connectivity.
4] Architecture & Operation in brief Wireless LAN: IEEE 802.11
IEEE 802.11 is a standard for wireless local area networks (WLANs) that operates in the 2.4 GHz and 5 GHz frequency bands. It specifies the physical layer (PHY) and medium access control (MAC) layer protocols for wireless communication.The architecture of IEEE 802.11 WLAN typically consists of two main components: wireless stations (STA) and access points (AP). The STA can be a wireless-enabled device such as a laptop, smartphone, or tablet, while the AP acts as a bridge between the STA and a wired network infrastructure such as a router or a switch.
The operation of IEEE 802.11 WLAN is based on a shared medium concept, which means that all STAs and APs within the network share the same wireless channel for communication. The medium access control (MAC) layer protocol of IEEE 802.11 uses the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) algorithm to control access to the wireless channel.
When a STA wants to transmit data, it first listens to the wireless channel to detect whether it is busy or not. If the channel is idle, the STA can start transmitting its data. However, if the channel is busy, the STA has to wait for a random amount of time before trying again to avoid collisions with other STAs.
The physical layer (PHY) of IEEE 802.11 specifies several modulation techniques such as frequency shift keying (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM) to transmit data over the wireless channel. The PHY layer also includes features such as channel bonding, spatial streams, and beamforming to improve the throughput and range of the WLAN.
Overall, IEEE 802.11 WLAN provides a flexible and reliable wireless communication solution for various applications such as home, enterprise, and public Wi-Fi networks.
5] Introduction to blue-tooth
Bluetooth is a wireless communication technology that allows devices to connect and communicate with each other over short distances. It was first introduced in 1994 by Ericsson, a Swedish telecommunications company, and has since become a widely adopted standard for wireless connectivity.
Bluetooth technology uses radio waves to transmit data between devices, such as smartphones, headphones, speakers, and smartwatches. It operates on the 2.4 GHz frequency band and uses low power to conserve battery life.
One of the advantages of Bluetooth technology is its ease of use. Devices can be paired with each other quickly and easily, without the need for cables or complex configuration settings. Bluetooth also provides secure communication, as data is encrypted during transmission to prevent unauthorized access.
Bluetooth technology has evolved over the years, with newer versions offering faster data transfer speeds and longer range. The latest version, Bluetooth 5.2, provides a range of up to 800 feet (240 meters) and a maximum data transfer rate of 2 Mbps.
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