COMPUTER NETWORKING FOR CCNA OSI MODEL

 OSI  MODEL

7 A conceptual framework known as the OSI (Open Systems Interconnection) model standardizes communication system functionalities into seven different levels. To enable data interchange between devices on a network, each layer interacts with the layers below it and performs a defined set of functions.

• Application Layer: The application layer is the closest to the end-user and provides network services directly to applications. It supports application protocols such as HTTP, FTP, SMTP, and DNS, enabling users to interact with network services and access information.

• Presentation Layer: Encryption and data representation are handled by this layer. It guarantees that information given by one system's application layer can be correctly read by another system's application layer. It deals with things like data encryption, data format conversion, and data compression.

• Transport Layer: The transport layer ensures reliable and efficient end-to-end communication between devices. It provides services such as segmentation, acknowledgment, and retransmission of data. The popular protocols TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) operate at this layer.

• Network Layer: The network layer handles the routing and forwarding of data packets across multiple networks. It determines the optimal path for data transmission, performs logical addressing, and deals with congestion control and packet sequencing. Routers operate at this layer.

• Data Link Layer: The data link layer provides error-free transfer of data frames between adjacent nodes on a network. It ensures data integrity and performs functions such as framing, error detection, and flow control. Ethernet switches and wireless access points operate at this layer.

• Physical Layer: This layer deals with the physical transmission of data over the network medium. It defines specifications for cables, connectors, and other hardware components. It primarily focuses on the electrical, mechanical, and procedural aspects of communication.

DATA               L7    Application  Layer 

DATA              L6    Presentation Layer    SOFTWARE LAYER     

DATA              L5     Session Layer

SEGMENTS    L4    Transport Layer   WORKS TCP/IP,UDP IP

 PACKET         L3   Network Layer      HARDWARE LAYER

DATA              L2    Data Link Layer

DATA               L1    Physical Layer

 

SEGMENT -  L4 HEADER         DATA    SPN & DPN                                             

 

PACKET -  L3 HEADER       L4 HEADER    |   DATA    SIP & DIP SPN & DPN

FRAME -  L2 HEADER        L3 HEADER   L4 HEADER  SMAC & DMAC     SEP & DEP       SPN & DPN

 

TCP = TRANSMISSION CONTROL PROTOCOL

UDP = USER DATAGRAM PROTOCOL

SPN = SOURCE PORT NUMBER

DPN = DESTINATION PROTOCOL NUMBER

SIP = SOURCE IP

DIP = DESTINATION IP

SMAC = SOURCE MAC ADDRESS

DMAC = DESTINATION MAC ADDRESS

• IN THE APPLICATION LAYER, PRESENTATION LAYER & SESSION LAYER DATA FORM.

• IN THE TRANSPORT LAYER DATA CHANGE INTO SEGMENTS.

• IN NETWORK LAYER DATA CALLED PACKETS.

• IN THE DATA LINK LAYER DATA IS CALLED FRAME.

• AND PHYSICAL LAYER DATA CALLED BITS.

• THE APPLICATION LAYER PROVIDES UI INTERFACE OR PLATFORM.

• L5 SESSION LAYER ESTABLISH, MAINTAIN & TERMINATE.

• TCP  AND UDP HELP DATA TRANSFER FROM SOFTWARE TO HARDWARE
• 
  

TCP / IP MODEL

OSI REFERENCE MODEL             TCP IP CONCEPTUAL LAYER

APPLICATION                                                   APPLICATION

PRESENTATION

SESSION

TRANSPORT                                                       TRANSPORT

NETWORK                                                           NETWORK

DATA LINK                                                          NETWORK

PHYSICAL                                                           INTERFACE

TLS AND SSL

TRANSPORT LAYER SECURITY BETWEEN SESSION & TRANSPORT

SSL SECURE SOCKET LAYER

WORKS ON SESSION, WHEN RETURN THE HTTP CONVERT INTO HTTPS.