2️⃣Web Connectivity
Introduction to Web Connectivity
TCP/IP Stack
The TCP/IP (Transmission Control Protocol/Internet Protocol) stack is a suite of networking protocols that enables communication between devices over the internet or any network that uses the Internet Protocol. It's essentially a set of rules that govern how data is transmitted and received over networks.
The TCP/IP stack consists of four layers:
Application Layer: This layer includes protocols used for specific applications or services, such as HTTP for web browsing, FTP for file transfer, SMTP for email, etc.
Transport Layer: TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) reside in this layer. TCP provides reliable, connection-oriented communication by establishing a connection, ensuring data delivery, and handling retransmissions if data is lost. UDP, on the other hand, offers faster but less reliable communication, without the features for ensuring delivery.
Internet Layer: This layer handles addressing, routing, and packaging of data packets. The Internet Protocol (IP) is the main protocol in this layer, responsible for assigning unique IP addresses to devices, ensuring packets are routed correctly across networks, and handling fragmentation and reassembly of data packets.
Link Layer: This layer deals with the physical connection between devices and the network. It includes protocols specific to the hardware used for transmitting data, like Ethernet or Wi-Fi.
The TCP/IP stack is the foundation of modern internet communication, allowing devices from different manufacturers and running different operating systems to communicate and exchange data seamlessly across networks.
The TCP/IP stack works by managing the flow of data between devices over a network, ensuring reliable communication and proper routing of information. Here's an overview of how it operates:
Data Packaging: When data needs to be transmitted, it's broken down into smaller units called packets. Each packet contains a portion of the data, along with addressing information (source and destination IP addresses) and control information.
Transmission at the Link Layer: At the bottom of the stack is the Link Layer, responsible for transmitting these packets over the physical network medium, whether it's Ethernet cables, Wi-Fi signals, or other physical connections. It handles tasks like framing data into frames suitable for the medium and addressing within the local network.
Routing and Addressing: The Internet Layer (IP) adds logical addressing to the packets, assigning unique IP addresses to devices and determining how packets should be routed through the network. It defines how data moves from one network to another, across routers and switches, to reach its destination.
Transport Layer: The Transport Layer provides communication services to the Application Layer and manages the transmission of data between devices. TCP ensures reliable, ordered, and error-checked delivery of packets. It establishes connections, breaks down data into smaller segments, and handles retransmission of lost packets. UDP, on the other hand, provides a simpler, connectionless communication service without the reliability mechanisms of TCP.
Application Layer: This top layer contains various protocols that enable specific applications to interact with the network. HTTP, FTP, SMTP, and many others reside here, utilizing the services provided by lower layers to transmit data appropriately.
Data Reassembly: Upon reaching the destination, the packets are reassembled into the original data by the recipient device based on sequence numbers, acknowledgments, and other control information provided by the Transport Layer.
Throughout this process, each layer of the TCP/IP stack adds its own set of information (header data) to the original data, encapsulating it before passing it down to the lower layer. When the data reaches its destination, each layer of the receiving device's TCP/IP stack interprets and strips away the corresponding header information, ultimately delivering the original data to the intended application.
By dividing the tasks into separate layers, the TCP/IP stack ensures modular and efficient communication between devices while allowing for interoperability and scalability in network design and implementation.
Let's consider an example of how the TCP/IP stack works when you access a website, say "www.example.com", using a web browser:
Address Resolution (DNS): Your browser initiates the process by converting the human-readable domain name "www.example.com" into an IP address. It sends a Domain Name System (DNS) query to a DNS server.
Packet Creation (Application Layer): Once the IP address is obtained, your browser generates an HTTP request. This request contains information about what page you want to access on the website.
Data Packaging (Transport and Internet Layers): The HTTP request is then handed over to the Transport Layer, where TCP may establish a connection to the server hosting "www.example.com". The data is then divided into smaller chunks called packets and each packet is given an IP header that includes the source and destination IP addresses. These packets are sent over the Internet Layer, which determines the best route for them to reach the server.
Transmission (Link Layer): At the Link Layer, these packets are transmitted over the physical medium, such as Ethernet cables or Wi-Fi signals. This layer handles the physical addressing within your local network.
Routing and Delivery: The packets travel through various routers and switches across the internet, following the best available paths based on routing algorithms and the destination IP address until they reach the server hosting "www.example.com".
Server Response: The server receives these packets and, using the TCP/IP stack on its end, interprets the packets. It then assembles the packets back into the original HTTP request, processes it, and generates an HTTP response containing the requested webpage.
Data Reassembly (Transport and Application Layers): The response data is divided into packets, which are sent back through the layers of the TCP/IP stack. At the Transport Layer, TCP ensures that all packets are received correctly and in order. The application, in this case, your web browser, then reassembles these packets into the complete webpage.
Displaying the Webpage: Finally, your browser interprets the HTML, CSS, and other resources received in the HTTP response and renders the webpage for you to view and interact with.
Throughout this entire process, the TCP/IP stack manages the flow of data, ensures proper addressing and delivery, and handles errors or lost data packets to facilitate seamless communication between your device and the web server.
Last updated