Group Project Data Communication by Group 9

WHAT IS OSI MODEL

The OSI open network reference model or the OSI Reference Model for open networks is a network architecture model developed by the International Organization for Standardization (ISO) in Europe in 1977. Open systems interconnection or OSI created in the form of a conceptual framework. Even now it has become a standard connection for a computer. Moreover, it was created to fulfil a specific purpose.

The goal is that the OSI model becomes a reference for each vendor or developer so that the software and products they make have interpolated properties. This means that users do not need to make special efforts and they can collaborate with the system or product.

In OSI itself, there are 7 layers and each of them has its own function namely physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer.

SEVEN LAYERS OF OSI MODEL

source: https://insights.profitap.com/osi-7-layers-explained-the-easy-way

1. LAYER 1: PHYSICAL LAYER

The physical layer is responsible for the physical cable or wireless connection between network nodes. It defines the connector, the electrical cable or wireless technology connecting the devices, and is responsible for transmission of the raw data, which is simply a series of 0s and 1s, while taking care of bit rate control.

It can include specifications such as voltages, pin layout, cabling, and radio frequencies. At the physical layer, one might find “physical” resources such as network hubs, cabling, repeaters, network adapters or modems. For example, the Ethernet standard for 100BaseT cable specifies the electrical characteristics of the twisted-pair cables, the size and shape of the connectors, the maximum length of the cables.

The OSI model upper layers will assign meanings to the bits transmitted at the Physical Layer. One very important type of Physical Layer device used in networks is a Network TAP. A Network TAP is a hardware device that is used to copy the traffic on a network link and redirect the copy to troubleshooting and analysis tools without interrupting traffic flow or introducing a point of failure even if the TAP loses power.

2. LAYER 2: DATA LINK LAYER

At the data link layer, directly connected nodes are used to perform node-to-node data transfer where data is packaged into frames. The data link layer also corrects errors that may have occurred at the physical layer. The data link layer encompasses two sub-layers of its own. The first, media access control (MAC), which uses MAC addresses to connect devices and define permissions to transmit and receive data. The second, the logical link control (LLC), which identifies network protocols, performs error checking and synchronizes frames.

3. LAYER 3: NETWORK LAYER

The network layer is responsible for receiving frames from the data link layer and delivering them to their intended destinations among based on the addresses contained inside the frame. The network layer finds the destination by using logical addresses, such as IP (internet protocol). At this layer, routers are a crucial component used to quite literally route information where it needs to go between networks.

The network layer has two main functions. One is breaking up segments into network packets, and reassembling the packets on the receiving end. The other is routing packets by discovering the best path across a physical network. The network layer uses network addresses (typically Internet Protocol addresses) to route packets to a destination node.

5. LAYER 5: SESSION LAYER

The session layer controls the conversations between different computers. A session or connection between machines is set up, managed, and terminated at layer 5. It is responsible for opening sessions, ensuring they remain open and functional while data is being transferred, and closing them when communication ends. The session layer can also set checkpoints during a data transfer—if the session is interrupted, devices can resume data transfer from the last checkpoint.

6. LAYER 6: PRESENTATION LAYER

The presentation layer formats or translates data for the application layer based on the syntax or semantics that the application accepts. Because of this, it at times also called the syntax layer. It defines how two devices should encode, encrypt, and compress data so it is received correctly on the other end. The presentation layer takes any data transmitted by the application layer and prepares it for transmission over the session layer.

7. LAYER 7: APPLICATION LAYER

At this layer, both the end user and the application layer interact directly with the software application. It provides protocols that allow software to send and receive information and present meaningful data to users. The application layer identifies communication partners, resource availability, and synchronizes communication. A few examples of application layer protocols are the Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), and Domain Name System (DNS).

WHY DOES OSI MODEL MATTER?

The open system interconnection model (OSI model) is a conceptual model that simplify the communication between two end points through layers or functions. The OSI model defines the network functions that occur at each layer. More essential, the OSI model enables an understanding of how data flows throughout a network.

source: https://hackonology.com/courses/computer-networking/lesson/osi-model/

The OSI reference model supplies a number of benefits in understanding how network function by doing the following:

Decreasing problems: the OSI model breaks network communications into sections, simpler parts.

Assisting modular engineering: the OSI model allows different types of network hardware and software to communicate with one another.

Accelerating development: the OSI model supplies for successful updates and improvements to individual parts without affecting other parts or having to rewrite the entire protocol.

Easier teaching and learning: the OSI model breaks network communications into smaller components to make learning easier.

Using communication: the OSI model helps us to send a data through layers, starting from application layer and end the physical layer.

HOW DATA FLOWS THROUGH THE OSI MODEL

A data to be sent must travel to the seven layers of the OSI model on the sending device and then up to the seven layers on the receiving side through a network.

An example of this is when we want to send an email to someone. The email that will be sent will be forwarded by the email sending application to the application layer which will choose a protocol and forward the data to the presentation layer. Then the presentation layer will compress the data and pass it to the session layer which will initialize the communication session.

After initializing the data communication session, the data will be forwarded to the transport layer of the sender to be segmented. The data will be broken down into packets at the network layer which will be further split into frames at the data link layer. Then the frame will be sent by the link layer to the physical layer which will convert the data into a bit stream of numbers 1 and 0 and send it through the physical media, for example, a cable.

Once a stream of bits enters the receiving device via a physical medium such as a WIFI, the data flows through the same set of layers on the device, but in the opposite order.

First of all, the bit stream data will be converted by the physical layer into frames and will be passed to the data link layer. Then the data link layer will reattach the frame into a packet for the network layer. Then the packet will be converted into data by rearranging the segments generated by the network layer.

Then the data will flow to the session layer and pass it to the presentation layer and end the communication session. The presentation layer will uncompressing that data and pass it to the application layer. The application layer converts this data so that it can be read by humans and displays it on the screen of the receiving device.

SUBNETTING CALCULATION

FSLM

192.168.10.0/26

128	64	32	16	8	4	2	1
1	2	3	4	5	6	7	8
9	10	11	12	13	14	15	16
17	18	19	20	21	22	23	24
25	26

Class

4 Faculties

Subnet Mask

Host

Subnet Block

4 subnets

256/4 = 64 IP address each faculty

64 + 128 = 192

255.255.255.192

64 - 2 = 62 Hosts

256 - 192 = 64

it will be 0, 64, 128, 192

CALCULATION for 4 SUBNETS

	Subnet Address	Host Address Range	Broadcast Range
1	192.168.10.0	192.168.10.1 – 192.168.10.62	192.168.10.63
2	192.168.10.64	192.168.10.65 – 192.168.10.126	192.168.10.127
3	192.168.10.128	192.168.10.129 – 192.168.10.190	192.168.10.191
4	192.168.10.192	192.168.10.193 – 192.168.10.254	192.168.10.225

TCP/IP CONFIGURATION

The screenshots of how to assign static IP address (TCP/IP)

The first step we need to do is to open the network adapter settings.

Then right click on my network adapter (Ethernet) and after that I’m going to click properties.

Then inside properties I want to select (internet protocol) version 4 TCP/IP version and I’m going to click properties.

This step you have to click (use the following IP address) and you need to use IP address, subnet mask, default and DNS sever.

If we want to use IP address, we have to press the windows key and the letter R and then we are going to type CMD and press ENTER.

When terminal opened, we are going to do IP configuration box (first picture) and then press ENTER and this is going to give me quite a few information (second picture).