Data Communication and Networking

Video Presentation

OSI Layer model and Network Component

    The Open Systems Interconnection (OSI) model was first introduced in the late 1970s by International Standards Organization (ISO), it is a standard that covers all aspects of network communications. The OSI model is a reference model that describes how information from a software application in one computer moves through a physical medium to the software application in the other computer.

    The OSI model consists of seven separated but related layers, each of which defines a part of the process of moving information across a network. The seven layers from top-down are:

1. Application Layer

2. Presentation Layer

3. Session Layer

4. Transport Layer

5. Network Layer

6. Data Link Layer

7. Physical Layer

    Based on the scenario, the data will travels from student's computer using their home network to reach the Online Learning system located in OUM network facilities. We will explain the details on how the data flow based on the OSI model and the network components involve throughout the data communication.

Application Layer

    In this layer, the interfaces directly interacts with the application and provides common web application services. After this, it also makes a request to send to the presentation layer. Application layer is the highest layer of the open systems, providing services directly for the application process. Duties provided by this layer is mail services, file transfer and access, remote log in and accessing WWW. Example of protocols in this layer are  Domain Name System (DNS), Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP) and etc. It works as the figure provided below:

    From the student's computer (sender) side, it is communicating to the communication service provided by the OnlineLearning System in OUM network facilities and encapsulate the protocol of the application with data send to the presentation layer. At the OnlineLearning System server's (receiver) side, it will determine weather the protocol provide from the sender is same as its protocol and if true decapsulation of the data will occur, the sender will have permission to access the OnlineLearning System. 

Presentation Layer

    The primary goal of this layer is to take care of the syntax and semantics of the information exchanged between two communicating systems. It plays the role of a translator so that the two systems come on the same platform for communication and will easily understand each other. The presentation layer performs data compression for multimedia data before transmitting, as the length of the multimedia data is very big and much bandwidth will be required to transmit it over media, the data is compressed into small packets and at the receiver's end, it will be decompressed to get the original length of data in its original format.

    From the student's computer (sender) side, it receives data from the application layer and performs encode the data, data encryption and compressed the data then send to the session layer. At the OnlineLearning System server's (receiver) side, it receives the data from session layer and decode it performing data translation, decryption, and decompresses data from the sender.

Session Layer

    Session Layer allows users on different machines to establish active communication sessions between them by initiating the opening and closing of sessions between end-user application processes. The session layer supports full-duplex and half-duplex operations and creates procedures for checkpointing, restart and termination. If the devices are communicating over an encrypted connection, this layer will add the encryption on the sender’s end and decoding the encryption on the receiver's end so that it can present as readable data. 

    This layer supports a variety of connections and is also in charge of authentication and reconnection in the case of a network outage. After the session is established the data then passes to or from the Transport layer.

        From the student's computer (sender) side, this layer will initialize the communication session by sending request and response in between application layer and transport layer to determine whether the requested session is legitimate or not. It will proceed to the next layer if it is yes. At the OnlineLearning System server's (receiver) side, it will show request by the sender to access the platform. 

Transport Layer

    Transport Layer provides transparent transfer of data between end users to ensure complete data transfers. It provides logical communication between application processes running on different hosts within a layered architecture of protocols and other network components. Transport-layer protocols such as TCP, UDP, DCCP, and SCTP are used to control the volume of data, where it is sent, and at what rate.

    The transport layer is also responsible to manage error correction, providing quality and reliability to the end user. This layer enables the host to send and receive error-free data, packets or messages over a network and is the network component that allows multiplexing.

       At the student's computer (sender) side, the transport layer receives the data from the upper layer and performs segmentation. The source and destination port numbers are also included in the header file of the data before forwarding it to the network layer. At the OnlineLearning System server's (receiver) side, the transport layer performs the reassembly and sequencing of data. It reads the port number of the data from the header file and then directs it towards the proper application. 

Network Layer

    Network Layer controls the operation of the subnet. It gives the best path to move data from source to the destination based on the priority of service, network conditions and other factors. The main purpose of this layer is to deliver packets from source to destination across multiple networks. If two systems are connected on the same link, then there is no need for a network layer. It routes the signal through different channels to the other end acting as a network controller.

    It also breaks the outgoing messages into few packets and assemble incoming packets into messages for higher levels. In broadcast network, the routing problem is simple. Thus, the network layer is often thin or even non-existent. 

    At the student's computer (sender) side, the network layer breaks the data segments received from the upper layer into smaller units, called data packets. Similarly, at the OnlineLearning System server's (receiver) side, it reassembles the data packets into segments for the upper layer, i.e., the transport layer. Routers are mainly used in the network layer for routing purposes. Some of the protocols that are mostly used in this layer are OSPF(Open Shortest Path First), BGP(Border Gateway Protocol), IS-IS(Intermediate System to Intermediate System), etc.

Data Link Layer

    Data link layer performs the most reliable node to node delivery of data. This layer is often divided into sublayers called Media Access Control (MAC) which is a link between the Logical Link Control layer and the network's physical layer. and Logical Link Control (LLC) which is responsible for transferring the packets to the Network layer of the receiver that is receiving.

    The main aim of the data link layer is to transform a raw transmission facility into a line that appears error-free to the network layer. It runs this task by breaking up the input data by sender into data frames (typically a few hundred or few thousand bytes) and transmit the frames one after another. If the service is reliable, the receiver confirms correct receipt of each frame by sending back an acknowledgement frame. Error detection bits are used by the data link layer and it corrects the errors.

    At the Data Link layer, the data passes to or from the final layer in the OSI model which is the Physical layer. At the student's computer (sender) side, it receives the data in the form of packets from the network layer and converts it into smaller forms, called the data frame. At the OnlineLearning System server's (receiver) side, it converts the data frame into packets for the network layer.

Physical Layer

    Physical Layer is the lowest layer of the OSI reference model. It deals with the synchronization of the sender and the receiver. The sender and receiver are synchronized at bit level. Data in this layer consists of stream of bits. The bits must be encoded into signals for transmission. It defines the type of encoding (e.g how 0's and 1's are changed to signal). This layer also defines the rate of transmission which is the number of bits per second.

    This layer involves with most of the network’s physical connection such as wireless transmission, cabling standards and types, connectors and types, network interface cards, and more as per network requirements but does not deal with the actual physical medium like copper and fiber. 

    At the student's side, the physical layer will get the data from the upper layer and convert it into bitstreams(0's and 1's) and send it through a physical channel. At the OnlineLearning System server's side, it will convert the bitstreams into frames to be passed to the data-link layer.

Network Components

Presentation Layer - Encryption devices (used to encrypt data so that the receiver device can decipher the data)

Network Layer - Router (used to send packets which are formed during Network Layer to different                                devices based on their IP address)

Data Link Layer - Switch (used to determine the MAC address of all devices)

                           - Bridge (used to forward frames to their destination)

                           - Network Interface Card (used to associated with the use of MAC address)

Physical Layer - Hub (used to regenerate signal for connecting various devices together as a single                               network) 

                         -Cable (used to connect two devices; merely a device to establish a connection)

Subnetting Calculation

The scenario of this project can be referred to Figure 1. Figure 1 shows the logical network flow from a home network to OUM facilities. In this figure, a OUM’s student is trying to access the OnlineLearning system located in the OUM network facilities. The student is using her modem to connect to the public network before able to connect to the OUM facilities. From the OUM network, the data then was forwarded to IT Center where the OnlineLearning System server is located.

The OUM network is using class C for the private addressing scheme which is 203.18.0.0/28. In OUM facilities, there are 13 different faculty together with 1 IT Center building. Hence, the network address was segregated by using the subnetting concept. Each faculty is given their network address. In this case,  IT Center building is another subnet with their own network address. From this network address, the address of the OnlineLearning System Server is assigned as the 4th available address.

Subnet 13 faculties and 1 IT center

To calculate the subnet we have to know how many faculties or departments that we want to subnet. In this case we have 13 different faculty in OUM and also 1 IT Center and the total for the subnet is 14. To calculate the subnet we have to find the nearest number of subnets, which is not too large or less than the requirement of this case. Since we have 13 faculties and 1 IT Center, the most suitable number of subnets is 16. Thus we will use number of subnet, 16 to calculate the subnetting

figure1 class c subnetting

Based on figure1, we could see that 16 is the most suitable number of subnets. It is because 16 is the nearest number with 14 (13 faculties and 1 IT center). While 8 is not suitable because it does not fulfill the requirement of subnet in this case. Then, for this subnetting we only have to use 14 subnets, the rest of 2 can be used in the future.

So, 14~16=2^4

4 bits need to be borrowed from the host.

Our new subnet will be 203.18.0.0/32 and for the new subnet mask is 255.255.255.240

We get .240 from adding, 

128+64+32+16=240   ;  since we borrow 4 bits

In this case, IT Building Center is assigned as the 12th available subnet as the server assigned as 4th available address. Based on the table above we can be sure that the Online Learning System server IP address is 203.18.0.181/28 and it does not start from 203.18.0.177/28 as it will be set up as a router IP address. So, it should start from 203.18.0.178/28 and so on. The scenario given for OUM is that the Online Learning System is assigned as the 4th available address and the assigned IP address is 203.18.0.181/28. 

TCP/IP SETTING MANUAL

In the previous section, we have assigned IP address for Online Learning System which are 203.18.0.181/28. Thus, in this section we will provide a manual on how to configure the IP address on the server. The operating system use in the manual are Windows 10. The explanation will be supported with the screenshots and appropriate explanation.

Step 1: 

Go to Search Button on the taskbar and search for Control Panel. Click to open it.

Figure 1 : open Control Panel

Step 2:

In the Control Panel, list of options on the menu are shown. Click on the Network And Internet to open it.

Figure 2 : Control Panel's Menu page

Step 3:

After opened the Network And Internet, two options available on the screen. Click on the Network And Sharing Center to open it.

figure 3 : Network and Internet's Menu Page

Step 4:

After opened the Network And Sharing Center, it will show the type of network connection that you use. Either it is Wi-Fi or ethernet.

In this example, we use the home Wi-Fi connection. Then, click on the Wifi name that connected by you device for example mine is Wi-Fi Kamaludin Dollah_5G@Unifi to open the status window.

Figure 4 : Network and Sharing Center's page

Step 5:

When the status bar opened, choose and click on the Internet Protocol Version 4 (TCP/IPv4). Then, click on the Properties. 

Figure 5 : Wi-Fi Properties

Step 6: 

• After opened the Properties, it shows a windows like Figure 6a.

Figure 6a : IPv4 Properties

• Click on the 'Use the following IP address' button. After click it, it will automatically click on the 'Use the following DNS server addresses'.  

Figure 6b : Static IP address option

• Insert the IP address that we obtain in previous section. [203.18.0.181]

Figure 6c : IP address

• Next, input the Subnet mask. It will automatically generate if you have insert the IP address. [255.255.255.0]

Figure 6d : Subnet Mask

• Next, insert Default gateway. It will acts as an intermediary between the local network and world wide web (WWW). The host address are usually the same as IP address but different in the 4th octet where it is always 1.

          Thus, the Default gateway will be 203.18.0.1 .

FIgure 6e : Default Gateway

• Insert Preferred DNS server. Generally, we will use the same IP address as Default gateway.

          Thus, Preferred DNS server is 203.18.0.1 .

• For Alternate DNS server, we will use the Google DNS server, 8.8.8.8 .
• Tick the 'Validate settings upon exit' box. Then, click OK.

Figure 6f : IP address configuration

Step 7:

Click 'Close' on the Wi-Fi Properties pop-up box.

Figure 7 : Wi-Fi Properties

Step 8:

After closing the Wi-Fi Properties pop-up box, Windows Network Diagnosis will automatically pop-up and check if there is any problems with the new configuration of IP address. If there is no problem, click 'Cancel'.

Figure 8 : Windows Network Diagnosis

Step 9:

Check the internet connection. If the internet can be connected, then the configuration of IP address is successful.