\subsection*{Practice Week 4: Understanding the TCP/IP Model}

\begin{objetivopractica}
The student will create a functional network in GNS3 and use both GNS3 and Wireshark to examine how the TCP/IP model organizes network communication into four practical layers. This practice will demonstrate how the simplified TCP/IP model relates to real network implementation and internet communication.
\end{objetivopractica}

The practice begins with the student creating a new GNS3 project named "TCP/IP Model Demo." They build a simple network with two PCs connected through a router, creating a multi-segment network that demonstrates TCP/IP routing functionality.

\definicion{TCP/IP model}{A four-layer protocol suite that provides the foundation for internet communication}

The student configures IP addresses on both PCs using simple addressing schemes. The first PC receives address 192.168.1.10 and the second PC receives 192.168.2.10, placing them on different network segments that require routing for communication.

% \includegraphics[width=\textwidth]{figuras/captura04_tcpip_network.png}

The student configures the router with appropriate IP addresses on both interfaces: 192.168.1.1 on the interface connecting to the first PC and 192.168.2.1 on the interface connecting to the second PC. This configuration enables the router to forward packets between the two network segments.

To observe TCP/IP communication, the student starts packet capture on one of the network links using GNS3's built-in Wireshark integration. They right-click on a cable and select "Start capture" to monitor traffic flowing through that network segment.

\definicion{link layer}{The TCP/IP layer that handles local network communication and physical addressing}

The student examines the link layer by observing Ethernet frame information in captured packets. This layer handles local communication within each network segment and includes physical addressing using MAC addresses. The student notices how frames change as they pass through router interfaces.

% \href{https://www.youtube.com/watch?v=XXXXXXX}{TCP/IP layers in practice}

The internet layer analysis focuses on IP packet headers that enable communication across network boundaries. The student performs ping tests between the PCs and observes how IP addresses provide logical addressing that remains constant while MAC addresses change at each network segment.

\definicion{internet layer}{The TCP/IP layer responsible for logical addressing and routing between networks}

During ping testing, the student observes how routers modify link layer information while preserving internet layer addressing. This demonstrates how the TCP/IP model separates local communication concerns from end-to-end addressing requirements.

% \includegraphics[width=\textwidth]{figuras/captura04_ping_routing.png}

The transport layer examination involves observing ICMP protocol operation during ping tests. While ping uses ICMP rather than TCP or UDP, the student can observe transport layer concepts such as port addressing and protocol identification in the IP headers.

\definicion{transport layer}{The TCP/IP layer that provides end-to-end communication services between applications}

The application layer becomes visible when the student configures simple services on the virtual PCs. Basic connectivity testing represents application layer communication that uses the services provided by lower TCP/IP layers.

The student documents the relationship between TCP/IP layers and actual packet structure by examining how each layer adds headers to outgoing data and removes headers from incoming data. This encapsulation process shows how the layered model works in practice.

\definicion{encapsulation}{The process of adding layer-specific headers to data as it moves down the protocol stack}

The practice includes comparing the four-layer TCP/IP model with the seven-layer OSI model. The student observes how TCP/IP combines certain OSI functions into fewer layers while maintaining the same essential communication capabilities.

% \includegraphics[width=\textwidth]{figuras/captura04_model_comparison.png}

The student tests network functionality by introducing routing problems and observing how different TCP/IP layers respond. They temporarily misconfigure router addresses and observe how this affects packet delivery, demonstrating the interdependence of protocol layers.

The practice concludes with the student creating a summary that explains how the TCP/IP model provides a practical framework for internet communication. They understand that this model reflects how networks actually implement communication services rather than theoretical organization.

\begin{rubrica}
The student must submit a report containing clear evidence of completing the practice. The document should include screenshots, explanations of observations, and reflection on the learning achieved. The submission must demonstrate that the student understood the concept and was able to apply it with the indicated software.
\end{rubrica}

\subsection*{Suggested Report Format}

\textbf{Title:} Practice Week 4 - Understanding the TCP/IP Model \\
\textbf{Objective:} Written by the student according to what they understood. \\
\textbf{Development:} Clear narration of actions performed. \\
\textbf{Evidence:} Screenshots or other data obtained. \\
\textbf{Conclusions:} Technical reflection on what was learned. \\
\textbf{Personal Opinion:} Student's free opinion about the usefulness or difficulty of the practice.