Analysis of the Art of Communication between Computers

Network Basics

First, let's talk about networking basics, that is, how computers communicate with each other.

At the core of this communication is the IP address, which is a unique identifier for each device on the network. IPv4 addresses are 32 bits, allowing for approximately 4 billion unique addresses. However, as the number of devices increases, we are moving to IPv6, which uses 128-bit addresses, significantly increasing the number of available unique addresses.

When two computers communicate over a network, they send and receive packets of data. Each packet contains an IP header that contains important information such as the sender and receiver's IP addresses, ensuring that the data reaches the correct destination.

This process is governed by the Internet Protocol (IP), a set of rules that defines how data is sent and received.

Besides the IP layer, we also have the application layer, where data specific to the application protocol is stored.

The data in these packets is formatted according to a specific application protocol data format, such as HTTP for Web browsing, so that the receiving device can interpret the data correctly.

TCP and protocol layers

Once we understand the basics of IP addresses and packets, we can delve deeper into the transport layer, where TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) come into play.

TCP operates at the transport layer and ensures reliable communication. It is like a courier making sure your package arrives and checking that nothing is missing.

Each packet also contains a TCP header that carries important information such as port numbers and control flags that are necessary to manage the connection and data flow.

TCP is known for its reliability; it ensures the integrity and correct delivery of data packets. It keeps track of the order of packets through features such as sequence numbers, and establishes a stable connection between two devices through a process called a three-way handshake.

In contrast, UDP is faster but less reliable than TCP. It does not establish a connection before sending data, and does not guarantee the delivery or order of packets.

But this makes UDP better suited for time-sensitive communications, like video calls or live streaming, where speed is critical and some data loss is acceptable.

DNS

To tie all of these concepts together, let's talk about DNS (Domain Name System).

DNS is like a phone book for the Internet, translating human-friendly domain names into IP addresses. When you enter a URL into your browser, the browser sends a DNS query to find the corresponding IP address, thereby establishing a connection with the server and retrieving the web page.

The functioning of the DNS is overseen by ICANN (Internet Corporation for Assigned Names and Numbers), which coordinates the global IP address space and the Domain Name System.

Domain registrars like Namecheap or Godaddy are accredited by ICANN to sell domain names to the public.

DNS uses different types of records, like A records, which map a domain name to its corresponding IPv4 address, ensuring your request reaches the right server, or AAAA records, which map a domain name to its IPv6 address.

Network Infrastructure

Finally, let's talk about the infrastructure that supports all of this communication.

Devices on a network have either public or private IP addresses. Public IP addresses are unique across the internet, while private IP addresses are unique within a local network.

IP addresses can be static, permanently assigned to a device, or dynamic, changing over time. Dynamic IP addresses are commonly used for home Internet connections.

Devices connected on a local area network (LAN) can communicate directly. To protect these networks, firewalls are used to monitor and control inbound and outbound network traffic based on security policies.

Inside a device, a specific process or service is identified by a port, which, combined with the IP address, creates a unique identifier for the network service. Some ports are reserved for specific protocols, like port 80 for HTTP or port 22 for SSH, and so on.

Simplified Hierarchy Diagram

So this is a simplified diagram representing the different layers of the Internet Protocol Suite, from the application layer down to the physical hardware.

• Application layer: This is where application-specific protocols (such as HTTP for web browsing, FTP for file transfers, and SMTP for email) operate. Data is formatted according to these protocols and sent to the transport layer. Ports are used to transfer the data to the correct application. DNS belongs to the application layer because it is a network service that converts human-readable domain names (such as www.example.com[1]) into network-understandable IP addresses.
• Transport layer: At the transport layer, we have TCP and UDP. TCP provides reliable and ordered delivery of data, while UDP provides faster but unreliable delivery. TCP uses sequence numbers and acknowledgments to ensure that all data is received and in the correct order.
• Internet Layer: Here are IP addresses and IP headers, which route packets across the network. IP addresses are used to identify devices on the network and can be public/private and static/dynamic.
• Link Layer: This layer is responsible for physical network connections, using MAC addresses to identify devices on the local network and using switches to transfer traffic.
• Physical hardware: This includes computers, routers, firewalls, and the local area network they form.