21⟩ Explain me what are the layers in OSI Reference Models? Describe each layer briefly?
☛ #1) Physical Layer (Layer 1): Physical Layer converts data bits into electrical impulse or radio signals. E.g. Ethernet.
☛ #2) Data Link Layer (Layer 2): At Data Link layer, data packets are encoded and decoded into bits and it provides a node to node data transfer. Data Link Layer also detects the errors occurred at Layer 1.
☛ #3) Network Layer (Layer 3): Network Layer transfers variable length data sequence from one node to another node in the same network. This variable length data sequence is also known as “Datagrams”.
☛ #4) Transport Layer (Layer 4): It transfers data between nodes and also provides acknowledgment of successful data transmission. It keeps track of transmission and sends the segments again if the transmission fails.
OSI Reference Model
☛ #5) Session Layer (Layer 5): Session Layer manages and controls the connections between computers. It establishes, coordinates, exchange and terminates the connections between local and the remote applications.
☛ #6) Presentation Layer (Layer 6): It is also called as “Syntax Layer”. Layer 6 transforms the data into the form in which the application layer accepts.
☛ #7) Application Layer (Layer 7): This is the last layer of OSI Reference Model and is the one which is close to the end user. Both end-user and application layer interacts with the software application. This layer provides services for email, file transfer etc.
