DCN_Ch_01 - Network Models_Aug 31, 2023.pdf

Data Communications & Networking Introduction to Data Communications Dr. Ramakrishna Dantu College of Business Network Models Network Models Basics • All communication networks involve transferring messages from sender to receiver. • This is accomplished by breaking the entire set of communicati...

Data Communications & Networking Introduction to Data Communications Dr. Ramakrishna Dantu College of Business Network Models Network Models Basics • All communication networks involve transferring messages from sender to receiver. • This is accomplished by breaking the entire set of communications functions into a series of layers. • The two important network models are:  Open Systems Interconnection Reference (OSI) model and  The Internet model, which is the most commonly used. Open Systems Interconnection Reference Model OSI Model Open Systems Interconnection Reference model Image Source: https://www.networkworld.com/article/3239677/the-osi-model-explained-and-how-to-easily-remember-its-7-layers.html The OSI Model Overview • Open Systems Interconnection (OSI) model describes how computers communicate with each other on a network • It outlines the various protocols and activities, and tells how the protocols and activities relate to each other The OSI Model Overview The OSI Model Overview • Each layer possesses a trait known as 'successive dependence' Image Source: https://www.linkedin.com/pulse/osi-model-explained-how-easily-remember-its-7-layers-rahul-jasrotia/ The OSI Model Layer 7: Application Layer The OSI Model Layer 7: Application Layer • The Application Layer protocols form the basis for various network services such as  File transfer, Web surfing, Emails, Virtual terminals, etc.,. • For example:  File transfer relies on FTP  Web surfing relies on HTTP/HTTPS  Emails use SMTP  Virtual terminals use Telnet The OSI Model Layer 6: Presentation Layer • Essentially, the presentation layer performs three functions:  Translation  Compression  Encryption/Decryption Application Layer ADJFLKAJDLF 546616646646 Presentation Layer 100011000011 100111100010 The OSI Model Layer 5: Session Layer setting up assisting cleaning closing the party The OSI Model Layer 5: Session Layer • Session layer is responsible for  Setting up and managing all connections or sessions  Sending and receiving of data  Termination of connections or sessions • Similar to the way we have helpers in organizing the party, session layer also has its own helpers • These helpers are called Application Programming Interfaces (APIs)  E.g., NETBIOS allows applications on different computers to communicate with each other Network Basic Input/Output System The OSI Model Layer 5: Session Layer • Session Layer performs two functions – Authentication & Authorization • Authentication  Verifies the identity of the client where the user name and password are matched • Authorization  It is the process where the server checks if the user has permission to access a file or any resource The OSI Model Layer 5: Session Layer • Session Management The OSI Model Layer 5: Session Layer • Thus, the session layer performs three key functions  Authentication  Authorization  Session Management • Our web browser performs all these functions of:  Session layer  Presentation layer, and  Application layer The OSI Model Layer 4: Transport Layer • The transport layer deals with endto-end issues  That is, procedures for entering and departing from the network • Transport layer controls the reliability of communication through  Segmentation  Flow Control  Error Control The OSI Model Layer 4: Transport Layer Segmentation Thank You