OSI LAYER MODEL

A UTeM’s student tries to access the Ulearn system located in the UTeM network facilities using her modem to connect to the public network before being able to connect to the UTeM facilities. It will then forward the data from UTeM network to IT Center where the Ulearn System server is located.

In term of private addressing scheme, UTeM network is using Class C private addressing scheme which is 192.168.0.0/16. In UTeM facilities, there are 30 different departments. Hence, the network address was segregated by using subnetting concept. Each department is given their network address. In this case, IT Center is being assigned as the 11^th available subnet as their network address. From this network address, the ULearn System server is assigned as the 3^rd available address. Use this information to identify the address of the ULearn System server.

 LAYER 7 : APPLICATION LAYER

Based on the OSI Model, Application Layer is the top layer which is responsible for syntax and semantics of the information exchanged between two systems. According to the project scenario, the student’s computer needs to connect to the public network using her modem before able to connect with the Ulearn system server located at IT Center in the UTeM network facilities. The student is able to direct interact with the Ulearn system by typing the website URL (http://ulearn.utem.edu.my/) using any supported browsers such as Google Chrome, Safari, Mozilla Firefox and etc. In this case, we can clearly say that the application layer is known as software provided for the end-user to interact with.

LAYER 6 : PRESENTATION LAYER

As for presentation layer, the student’s computer receives the data from application layer and performs data translation, encryption and compression to the data before transmitting to the session layer. It translates the data of the running program received from application layer to bit streams, encrypt sensitive info on the system to ensure privacy and also compress the data which will help improve the speed and efficiency of the data uploaded in any way before being pass to session layer. While at the receiver’s side, the Ulearn System server, it receives data from transport layer and perform data translation, decryption and uncompressed the data.

LAYER 5 : SESSION LAYER

The session layer is in charge of maintaining, establishing, and synchronizing communication between systems. According to the scenario, the session layer from the student's home network is in charge of choosing appropriate protocols to fulfil the application layer's request for services. It will check to see if the required resource is available in Ulearn System server then, it will attempt to connect to the requested resource if it is available. If the connection is successful, this layer will begin and continue the session for as long as it is required. However, if the connection fails, it will send an error message to the application layer informing it of the failure.

This layer request for a logical connection which should be established on end user’s requirements. Thus, when a student attempts to access the Ulearn System through the UTeM campus network, the system server will attempt to authenticate the user and establish a session. This layer manages and authorizes any files that the student wants to access, as well as all necessary log-on and password validation. This session will end once the student has finished using the Ulearn System.

LAYER 4 : TRANSPORT LAYER

The fourth layer in OSI Model which is Transport Layer are responsible for delivery of a message from one process to another. Meaning that this layer is establishing a temporary communication session between two applications and delivering data between them. Transport Layer provides for addressing port, the segmentation of data, and the control necessary such as connection control, flow control and error control to reassemble these segments into the various communication streams. There are two common transport layer protocols which is Transmission Control Protocol (TCP) and the User datagram Protocol (UDP). The protocols that were being used for this project scenario when the data is delivered is TCP (Transmission Control Protocol). 

The student’s computer needs to establish with a connection with the Ulearn system server first using a three-way handshake when she wants to send data over TCP. It will be ready to receive packets containing actual data once the handshake is done. When a packet of data is sent over TCP, the server must always acknowledge what they received. The computer sends a packet with the data and a sequence number. The server acknowledges it by setting the ACK bit and increasing the acknowledgement number by the length of the received data. Finally, the connection will be closed when they finished sending and receiving data. TCP connections can also detect lost packets.

LAYER 3 : NETWORK LAYER

Network layer will be functionally from transport layer to data link layer for the delivery of packets from the original source to the final destination. On the receiving end, the network layer will disassemble the segments into network packets and reassemble the packets. This layer also can route packets by discovering the best path across a physical network.

LAYER 2 : DATA LINK LAYER

From the physical addressing and media access processes, data link layer can transmit frames got from packets  from one node to the next. The data frame then converted into bits to reach Physical Layer.

LAYER 1 : PHYSICAL LAYER

Physical layer is the lowest layer in OSI Model which is concerned with electrically and optically transmitting raw unstructured data bit across the network from the sending device to the receiving device.

Based on project scenario given, 4 devices are used for this project. One (1) PC which is student’s computer, one (1) router, one (1) switch and one (1) server which is Ulearn System Server. Physical layer that is used copper straight through cable from student’s PC to switch and from switch to router. From computer to router , physical layer that is used is rollover cable. Router to server connected by crossover cable. The physical components transmit and carry the signals to transmit and carry the signals to represent the bits to layer 2 which is Data Link Layer.