2024 IEC L1.pptx

The OSI Model Overview  Lecture Outline The aim of this lecture is to briefly introduce each layer in the OSI reference model to students. The Physical Layer The Data Link Layer The Network Layer The Transport Layer The Session Layer The Presentatio...

The OSI Model Overview  Lecture Outline The aim of this lecture is to briefly introduce each layer in the OSI reference model to students. The Physical Layer The Data Link Layer The Network Layer The Transport Layer The Session Layer The Presentation Layer The Application Layer  AL – Application Layer Nomenclature ARP – Address Resolution Protocol DLL – Data Link Layer FTP – File Transfer Protocol IP- Internet Protocol N/W- Network Layer PrtL - Presentation Layer PL - Physical Layer SL – Session Layer TCP – Transmission Control Protocol TL - Transport Layer PDU – Protocol Data Unit DNS – Domain Naming System FTP — File Transfer Protocol HTTP/S — Hypertext transfer protocol / Security HTML – Hypertext Mark-Up Language JSON – JavaScript Object Notation SMTP — Simple Mail Transfer Protocol OSI – Open Systems Interconnections UDP – User Datagram Protocol  Electronic Communication Electronic communication is any form of communication that’s broadcast, transmitted, stored or viewed using electronic media, such as computers, phones, email and video. Examples of electronic communications : Email, text messaging, social networking, video chats, blogging, multimedia etc. Data transmitted: images, graphics, sound, pictures, maps etc. Modern communication systems are analyzed as a sequence of layers. This concept of layering in communication systems is best illustrated by the Open Systems Interconnection (OSI) model for computer communications.  Computer Networking A computer network comprises of nodes connected together by communication links. A node is defined as any device capable of sending/receiving data generated by other nodes in the N/W. E.g, computer, printer, server, bridges & switches etc. A communication link is the medium that carries data. Com links can be either a wired link or a wireless link. Wired – cabled (wires) Wireless – no physical connection (air) The function of a computer N/W is resource sharing among users. We will use the Seven Layered OSI model in this course to help us understand computer N/W.  What is OSI? Open Systems Interconnection (OSI) model is a structured conceptual framework developed by the International Organization for Standardization in the 1970s with the purpose of enabling diverse and effective communication using standard protocols. OSI was first published in 1984 as ISO 7498, with the current version being ISO/IEC 7498-1:1994. OSI divides network communication functions into seven layers: Physical, Data Link, Network, Transport, Session, Presentation and Application. Transmitting data over a network is a complex task because various hardware and software technologies must work cohesively across different terrains and boundaries. The OSI data model provides a universal language for computer networking, so diverse technologies can communicate effectively using standard protocols.  What is OSI? Technologies in a specific layer must possess certain abilities and perform specific functions to be useful in networking. Technologies at different layers must be able to rely on each other for efficient communication. For example, technologies in the higher layers benefit from abstraction as they can use lower-level technologies without concern for underlying implementation details.  Standards vs Protocols Standards provide guidelines to manufacturers, vendors, government agencies, and other service providers to ensure the kind of interconnectivity necessary in today's market place and in international communications. A protocol in computer networking is a set of rules that form standards for data communication. A protocol defines what is being communicated, how it is being communicated ,and when it is being communicated.  What is the Significance of OSI? OSI model is important because it forms the basis for the development of standards for systems interconnection while considering existing standards within the overall reference model. Due to the complexity of networking, OSI helps promote shared experience among engineers to develop and organize complex model architectures using OSI as reference model. It helps in understanding how other network models and technologies operate. It lays down a clear framework to be followed by developers so the digital communications products and software programs they create can interoperate.  What is the Significance of OSI? OSI allows each system component’s operating layer to be separated into its main functionality. Structure makes it easy for conceptualization when each system component can be easily decomposed into smaller parts. It is advantageous to engineers to use a series of repeated processes and protocols to develop complex models. Flexible standardization Integration with other models. Threat identification: enables IT experts identify threats across entire network. Security : OSI prioritizes network security. OSI is data centric/driven. Takes inventory of all the organizations assets and resources. Cloud security : Cloud users can take advantage of OSI existing infrastructure as the OSI model.  Are there Alternate Models to the OSI Model? Sequenced Packet Exchange/Internet Packet Exchange (SPX/IPX) Network Basic Input Output System (NetBIOS). Today, the main alternative to the Open Systems Interconnection (OSI) model is the TCP/IP model. 7Layer OSI Model Nodes & Intermediary Nodes End Devices : Intermediary Nodes Nodes PC Router Tablets Modem Smart Phones Internet Cloud Printer Wireless Router Servers Cell Tower What each layer represents OSI Layers OSI Layers & Protocols Each Layer Communicates with Each Corresponding Layer  Protocol Data Unit Layer Type PDU Application Layer Data Presentation Layer Data Session Layer Data Transport Layer Segments Network Layer Packets Data Link Layer Frames Physical Layer Bits  Data Exchange Using the OSI Model Sender Receiver 1.The Physical Layer  1. The Physical Layer This is the lowest layer of the OSI model. PL contains information in the form of bits (PDU). Hubs, Ethernet, Fiber, Wireless etc. are used in this layer. Functions : Responsible for transmitting individual bits Transforming bits into signals. Determines and maintains data rate (how many bits a sender can send per second). Performs synchronization of bits by a clock.  1. The Physical Layer Helps in transmission of bits over a transmission channel. Provides physical topology (Mesh, Star, Bus, Ring) decisions. Aids in providing physical medium and interface decisions. It provides two types of configuration : Point-Point and Multi-Point configuration. It provides an interface between devices (like PCs/computers) and the transmission medium. Uses different techniques of multiplexing. 2. The Data Link Layer  2. The Data Link Layer This is the layer right above the PL. Consists of two main layers: Logical Link Layer (LLL) & Medium Access Control (MAC). DLL receives data in the form of packets from the N/W layer, divides packets into frames and sends these frames to the PL. We think MAC address at this layer. The primary function of a MAC address is managing how data is transported from one network node to another on a direct, physical basis (hop to hop) or node-to-node delivery. Functions: Framing : Receives data in the form of packets from the N/W layer and creates frames (PDU). Physical Addressing : adds a physical address to these frames and passes them onto the PL. Flow control Damage control Access control  2. Data Link Layer The DLL adds a ‘trailer’ to the packet. DLL only works for the same network. Data Link Layer devices : switches & bridges. 3. The Network Layer  3. The Network Layer This is the third layer in the OSI model. Receives data in the form of segments (PDU) from the transport layer. Responsible for source-destination packet delivery across multiple networks. The network layer uses the Internet protocol (IP), the Address Resolution Protocol (ARP), and the Internet Control Message Protocol (ICMP) for error control. Functions : Packetization Routing Logical Network Addressing 4. The Transport Layer  4. Transport Layer This is the fourth layer in the OSI model. Also called the ‘heart’ of the OSI model. Is operated by the OS as it is a part of the OS and communicates with the application layer. TL takes data from the above layer, converts it into segments (PDU) and sends it to the N/W layer. (By adding the port address onto it) TL is a point-to-point OR node-to-node protocol. Provides two main service : Connection-oriented Transmission & Connectionless Transmission.  4. Transport Layer Functions : TCP and UDP: create segments Sender’s Side : TL receives message from TL, assembles them into packets and reassembles these packets again into message at the destination. Error check : checks for error control at receiver’s end and flow control at sender’s end to ensure that message is received without error. Flow control: control bit rates TL header includes a port address with each process. 5. The Session Layer  5.The Session Layer This is the fifth layer in the OSI model. Responsible for opening and closing communication between two devices. The time between when the communication is opened and closed is called the session. The session layer ensures that the session stays open long enough to transfer all the data being exchanged, and then promptly closes the session to avoid wasting resources.  5. The Session Layer Functions : This layer is also again responsible for three (3) main functions : 1. Session Management Session establishment between 2 nodes. Session Opening for dialogue control and dialogue separation. Session Closing 2. Authentication 3. Authorization 6. The Presentation Layer  6. Presentation Layer This is the sixth layer in the OSI model. The PDU in this layer is data. The PrtL receives data in textual format from the AL. Functions: It primarily conducts three operations on this data. Data Translation Data Compression Data Encryption 7. The Application Layer  7. Application Layer This layer is the topmost layer of the OSI model. The PDU is data. AL directly interacts with data from the user. Enables communication between software applications through protocols like HTTP, FTP, SMTP, and DNS. Software applications like web browsers and email clients rely on the AL to initiate communications.  Tutorial Questions 1. What is computer networking? Why is it important? 1. What does OSI stand for? 2. List five advantages of the OSI model? 3. List the seven layers of the OSI model in order with their main functions. 4. Which layer directly interacts with the user? 5. Imagine yourself as a receiver. Show your understanding of how data is moved from one layer to the other by drawing these layers out and indicating the steps.