ITN 101: Module 01 Live Virtual Machine Lab 1.1 Introduction to the OSI Model
Data encapsulation
Data encapsulation is the process of adding additional information to the data that is being sent to another device. This process adds additional features to the data. Data that is sent across the network is encapsulated and decapsulated on every level of the OSI model. This is to ensure that each layer can communicate with each other.
What is the functionality of data encapsulation? [Choose all that apply] Assigns a MAC address to a host Converts electrical pulses to binary data Ensures security and reliability of data transmission Adds headers to the data that is sent across the network
Ensures security and reliability of data transmission Adds headers to the data that is sent across the network
Physical
Ensures the physical communication between the devices and converts an electrical pulse to binary. It defines the specific standard to which the physical components must comply to. The most commonly used protocols include the following, IEEE.802.11, IEEE.802.3 and several others.
Which of the following is a function of the Presentation layer of the OSI model? Ensures physical communication between devices Manages the flow of data across the network Handles the processing and converting of data Delivers data across network connections
Handles the processing and converting of data
Data encapsulation - Step Five
In the final step, the Physical layer receives the data frames from the Data-link layer and encapsulates them by converting them to the correct transport media associated with the physical connections, for example, Ethernet or fiber mediums.
Data encapsulation - Step Three
In the next step for the data encapsulation process, the Network layer receives the data from the Transport layer and encapsulates it further by adding an additional header to each segment. These data headers contain all the routing information to ensure delivery. The data pieces are now referred to as a data packet or datagram.
Task 1 - Identify the Network Components Associated with the Physical layer
In this task, the components associated with the Physical layer of the OSI Model will be identified. From the Network Adapter's properties, it can be seen that it is connected to a network. The Physical Layer of the OSI Model will be used to initiate communication to other devices.
The Physical Layer of the OSI Model
Is responsible for the communication between devices and deals with the physical connection to a network.
Data Decapsulation
Is the process of converting data that was sent from another device by reversing the steps of data encapsulation. In other words, the process of data decapsulation will start at the Physical layer of the OSI model and end at the Application layer.
At which layer of the OSI model does a router function? Layer 1 Layer 3 Layer 4 Layer 2
Layer 3 (Network)
TCP/IP Model Layers
Link, Internet, Transport, Application.
Which layer of the OSI model is used to forward packets on the network? Transport Network Physical Session Data Link
Network
Which layer of the OSI model maps to the Internet layer of the TCP/IP model? Data Link Transport Application Network
Network
OSI Model Layers 1-7
Physical, Data Link, Network, Transport, Session, Presentation, Application.
Network
Routers function on the Network layer. This layer is responsible for forwarding packets to specific routes on the network. This layer analyses the packets received and determines if it has reached its destination and then passes it to the Transport layer. If it is not the final destination, it will pass it to the Data link layer until it reaches its final destination. The Network layer is also responsible for updating routing tables.
Data link
The Data link layer provides communication between directly connected devices. It also provides error handling for the OSI model's physical layer. It consists of two sub-layers, Media Access Control (MAC) and the Logical Link Control (LLC) layers. Most switches operate on the Data link layer or Layer 2 for communication, but there are exceptions where switches can also work on Layer 3 and are referred to as a Layer 3 switch where routing capabilities are required.
Transport
The Transport layer's function is to deliver data across network connections. The most commonly used protocols are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). Different protocols will have different functionalities when transporting data across the network. For example, error checking is done using the TCP protocol.
Data encapsulation - Step One
The combined Application, Presentation, and Session layers of the OSI model utilizes the data from the application in the form of data streams and sends it to the Transport layer. Depending on the specific application, a header will be added to the data.
Data Decapsulation - Step Three:
The data frames from the Data link layer are passed to the OSI Model Network Layer, which is de-encapsulated. The packet header is checked to verify if the packet has been routed to the correct destination. If an incorrect destination is stipulated, the packet will be discarded; else, the packet is forwarded to the Transport Layer.
Application
The final layer in the OSI model, the Application layer, provides network services to the application. These services include protocols that integrate into the application; for example, the HTTP protocol is used to deliver data to a web browser to display a user's web page.
First 3 Layers of the OSI Model
The first three layers of the OSI Model consist of the Physical, Data-Link and Network layers.
The Network Layer of the OSI Model
The frames received from the Data-Link layer are then sent to the Network Layer, which determines where the frames need to be sent to using the headers, which contain the routing information for these frames. The Network layer allows to move traffic to networks not directly attached.
OSI model layers 4 to 7
Comprise the Transport, Session, Presentation and Application layers.
The Data-Link Layer of the OSI Model
After a connection has been established by the Physical layer, the Data-Link decapsulates the packets to form frames, which are passed to the Network layer.
Data encapsulation - Step Four
After receiving the Network layer's data packet, the Data-link layer adds additional headers and footers to the datagram. These headers and footers contain switching information and data relating to the appropriate hardware components. The footer contains information about error detection and control.
Original TCP/IP Model and how it compares to the OSI Model
Application (Layers 5-7): Session, Presentation, Application Transport (Layers 4): Transport Internet (Layers 3): Network Link (Layers 1-2): Physical, Data Link
Updated TCP/IP Model and how it compares to the OSI Model
Application (Layers 5-7): Session, Presentation, Application Transport (Layers 4): Transport Internet (Layers 3): Network Link (Layers 2): Data Link Physical (Layers 1): Physical
Task 1 - Identify Components of the Transport Layer of the OSI Model
Several different protocols operate on the Transport Layer of the OSI Model. These include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). From the output of the command (netstat -ps tcp), the different TCP connections to the PLABWIN10 device are displayed, including the connections' statistics. The statics may vary from the screenshot. The different ports that these TCP connections use are also displayed. This information can be used for troubleshooting and determining which remote devices are connected to the local device. TCP connections are connection-oriented, which means that it includes error checking. After opening the Microsoft Edge browser, a new TCP connection was established, as shown from the output after the command was executed. Notice that a connection to the Intranet was established using the TCP protocol on port 80. The Transport Layer uses the TCP protocol to establish a connection. From the command's output (netstat -ps udp), it can be seen that there are not any current UDP connections to the local device. The DHCP service uses the UDP protocol to connect to other devices utilizing ports 67 and 68.
Data Decapsulation - Step Five:
The Application, Presentation and Session Layers receive the encapsulated data from the Transport Layer and de-encapsulates it. The application-specific data is then forwarded to the correct application, for example, a web browser.
Data Decapsulation - Step Two:
The Data Link Layer receives the data from the Physical layer, de-encapsulates the data frames, and verifies if it has been sent to the correct destination. If an incorrect destination has been stipulated, the data frame will be discarded; otherwise, the footer of the data frame will be checked. If an error in the data is detected, it will request resubmission of the data frame. The de-encapsulated data frame is then sent to the Network layer.
Task 2 - Identify the Data-Link Components of the OSI Model
The Data-Link layer of the OSI Model consists of two components, the Logic Link Control (LLC) sub-layer and the Media Access Control sub-layer. Networking components that are associated with this layer are MAC Addresses and network drivers. In the Driver File Details dialog box, the specific software driver is displayed for the network adapter. On a physical machine, these details will differ and display the Network Interface card's manufacturer's driver. The network software driver facilitates the interaction between the hardware component and the Operating System and forms part of the Data-Link layer of the OSI Model. By executing the command (ipconfig /all), the network configuration of the device is displayed. The device's IP address is displayed as 192.168.0.5, and the physical address is also displayed. A device's physical address is referred to as the MAC address. This is associated with the specific Network Interface Card (NIC). A MAC address is a unique hexadecimal combination that is used to identify the NIC. Different hardware vendors have different combinations on how these MAC addresses are compiled. The MAC address displayed might differ from the screenshot. By executing the command (arp -a) the Address Resolution Protocol (ARP) is displayed, it resolves IP addresses to MAC addresses. To facilitate network communication, an IP address needs to be assigned to the network adapter. The IP address is then allocated to the MAC address, ensuring communication to other network devices. A MAC Address functions on the Data-Link layer of the OSI model.
Task 2 - Identify the Components Associated with the Application Layer of the OSI Model
The OSI Model's application layer receives the packets from the Session layer and de-encapsulates them, thus ensuring the application can display the output to the end-user, for example, a web browser displaying a webpage. Through the Task Manager you can see the different background processes running on the device are displayed. These processes ensure that the end-user can successfully launch applications and forms part of the OSI Model's Application layer. The applications running on the device can be seen in Task Manager. Note that the Microsoft Edge Browser is displayed.
Session
The OSI model's Session layer manages the flow and sequence of different network connections. This ensures the possibility for dynamic concurrent connections.
Data encapsulation - Step Two
The OSI model's Transport layer receives the data from the top layers and divides it into smaller pieces referred to as data segments. The data is encapsulated by adding the correct header to each segment of the data. Each data header contains sequencing information to ensure that it can be assembled at the receiver.
Data Decapsulation - Step One
The Physical Layer in the OSI model receives the encapsulated data from the sender and de-encapsulates it to the form of a data frame, which will be forwarded to the Data Link Layer.
Data Decapsulation - Step Four:
The Transport Layer receives the data frames from the Network Layer and de-encapsulates them. The first segment header is checked and verified, and then the data frames are assembled, which are then passed to the Application Layer.
Task 3 - Identify the Components Associated with the Network Layer of the OSI Model
The network components that are associated with the Network Layer of the OSI Model consists of the following: IP address Subnet mask Default Gateway Routing information The Network layer inspects the headers of the packet received from the Data-Link layer to determine if it has reached its final destination. If not, it will forward the packet to the correct destination. From the output of the command (ipconfig /all), the IP address, Subnet mask and Default Gateway is displayed. These are core components of the Network layer. The route add command (route -p add) creates a persistent route to the different subnets enabling communication across different subnets through the router. The route print command (route print) displays the routing table of the device. After configuring the network adapter with an IP address, the Network layer will facilitate the communication to the newly allocated subnet by inspecting the packets' headers to ensure it is routed to the correct destination. The ping command (ping) is used to verify that the newly assigned IP address can communicate with another device on a different subnet.
Presentation
The simplest part of the OSI model is the Presentation layer, as it handles the processing and converting of the data, for example, encryption and decryption, to facilitate the support for the Application layer.
