OSI all seven layers REFERENCE MODEL.pptx

ISO

1. Network Layer – Layer 3 The network layer works for the transmission of data from one host to the other located in different networks. It also takes care of packet routing i.e. selection of the shortest path to transmit the packet, from the number of routes available. The sender & receiver’s IP address es are placed in the header by the network layer.

2. Functions of the Network Layer Routing : The network layer protocols determine which route is suitable from source to destination. This function of the network layer is known as routing. Logical Addressing : To identify each device inter-network uniquely, the network layer defines an addressing scheme. The sender & receiver’s IP addresses are placed in the header by the network layer. Such an address distinguishes each device uniquely and universally. It is a layer 3 that manages device addressing, tracks the location of devices on the network. It determines the best path to move data from source to the destination based on the network conditions, the priority of service, and other factors. The Data link layer is responsible for routing and forwarding the packets. Routers are the layer 3 devices, they are specified in this layer and used to provide the routing services within an internetwork. The protocols used to route the network traffic are known as Network layer protocols. Examples of protocols are IP and Ipv6. Internetworking: An internetworking is the main responsibility of the network layer. It provides a logical connection between different devices. Packetizing: A Network Layer receives the packets from the upper layer and converts them into packets. This process is known as Packetizing. It is achieved by internet protocol (IP).

3. Transport Layer – Layer 4 The transport layer provides services to the application layer and takes services from the network layer. The data in the transport layer is referred to as Segments . It is responsible for the end-to-end delivery of the complete message. The transport layer also provides the acknowledgment of the successful data transmission and re-transmits the data if an error is found. At the sender’s side: The transport layer receives the formatted data from the upper layers, performs Segmentation , and also implements Flow and error control to ensure proper data transmission. It also adds Source and Destination port number s in its header and forwards the segmented data to the Network Layer. At the receiver’s side: Transport Layer reads the port number from its header and forwards the Data which it has received to the respective application. It also performs sequencing and reassembling of the segmented data.

4. Functions of the Transport Layer Segmentation and Reassembly: This layer accepts the message from the (session) layer, and breaks the message into smaller units. Each of the segments produced has a header associated with it. The transport layer at the destination station reassembles the message. Service Point Addressing: To deliver the message to the correct process, the transport layer header includes a type of address called service point address or port address. Thus by specifying this address, the transport layer makes sure that the message is delivered to the correct process. Services Provided by Transport Layer Connection-Oriented Service Connectionless Service

5. 1. Connection-Oriented Service: It is a three-phase process that includes: Connection Establishment Data Transfer Termination/disconnection Connection-Oriented Service is basically a technique that is typically used to transport and send data at session layer. The data streams or packets are transferred or delivered to receiver in a similar order in which they have seen transferred by sender. It is actually a data transfer method among two devices or computers in a different network, that is designed and developed after telephone system. Whenever a network implements this service, it sends or transfers data or message from sender or source to receiver or destination in correct order and manner. This connection service is generally provided by protocols of both network layer (signifies different path for various data packets that belongs to same message) as well as transport layer (use to exhibits independence among packets rather than different paths that various packets belong to same message will follow).

6. Operations : There is a sequence of operations that are needed to b followed by users. These operations are given below : Establishing Connection – It generally requires a session connection to be established just before any data is transported or sent with a direct physical connection among sessions. Transferring Data or Message – When this session connection is established, then we transfer or send message or data. Releasing the Connection – After sending or transferring data, we release connection.

7. Different Ways : There are two ways in which connection-oriented services can be done. These ways are given below : Circuit-Switched Connection – Circuit-switching networks or connections are generally known as connection-oriented networks. In this connection, a dedicated route is being established among sender and receiver, and whole data or message is sent through it. A dedicated physical route or a path or a circuit is established among all communication nodes, and after that, data stream or message is sent or transferred. Virtual Circuit-Switched Connection – Virtual Circuit-Switched Connection or Virtual Circuit Switching is also known as Connection-Oriented Switching. In this connection, a preplanned route or path is established before data or messages are transferred or sent. The message Is transferred over this network is such a way that it seems to user that there is a dedicated route or path from source or sender to destination or receiver.

8. Connectionless service: It is a one-phase process and includes Data Transfer. In this type of transmission, the receiver does not acknowledge receipt of a packet. This approach allows for much faster communication between devices. Connection-oriented service is more reliable than connectionless Service A Connectionless Service is technique that is used in data communications to send or transfer data or message at Layer 4 i.e., Transport Layer of Open System Interconnection model. This service does not require session connection among sender or source and receiver or destination. Sender starts transferring or sending data or messages to destination. In other words, we can say that connectionless service simply means that node can transfer or send data packets or messages to its receiver even without session connection to receiver. Message is sent or transferred without prior arrangement. This usually works due to error handling protocols that allow and give permission for correction of errors just like requesting retransmission. In this service, network sends each packet of data to sender one at a time, independently of other packets. But network does not have any state information to determine or identify whether packet is part of stream of other packets. Even the network doesn’t have any knowledge and information about amount of traffic that will be transferred by user. In this, each of data packets has source or destination address and is routed independently from source to destination. Therefore, data packets or messages might follow different paths to reach destination. Data packets are also called datagrams. It is also similar to that of postal services, as it also carries full address of destination where message is to send. Data is also sent in one direction from source to destination without checking that destination is still present there or not or if receiver or destination is prepared to accept message.

9. Connectionless Protocols : These protocols simply allow data to be transferred without any link among processes. Some Of data packets may also be lost during transmission. Some of protocols for connectionless services are given below: Internet Protocol (IP) – This protocol is connectionless. In this protocol, all packets in IP network are routed independently. They might not go through same route. User Datagram Protocol (UDP) – This protocol does not establish any connection before transferring data. It just sends data that’s why UDP is known as connectionless. Internet Control Message Protocol (ICMP) – ICMP is called connectionless simply because it does not need any hosts to handshake before establishing any connection. Internetwork Packet Exchange (IPX) – IPX is called connectionless as it doesn’t need any consistent connection that is required to be maintained while data packets or messages are being transferred from one system to another.

10. Session Layer – Layer 5 his layer is responsible for the establishment of connection, maintenance of sessions, and authentication, and also ensures security. Working of Session Layer : Session Layer, which is the 5th layer in the OSI model, uses the services provided by The transport layer, enables applications to establish and maintain sessions and to synchronize the sessions. Now, in order to establish a session connection, several things should be followed. First thing is we should map the session address to the shipping address. The second thing is that we need to select the required transport quality of service (also referred as QoS) parameters. Next thing is we need to take care of the negotiations which should happen between session parameters. Then we further need to transmit limited transparent user data. Then at last, we need to monitor Data Transfer phase properly. The ability to send larger amount of data files is extremely important and a necessary thing too.

11. Functions of Session Layer : The session layer being the fifth layer in the OSI model performs several different as well as important functions which are need for establishing as well as maintaining a safe and secure connection. Following are some of the functions which are performed by Session Layer – Session Layer works as a dialog controller through which it allows systems to communicate in either half-duplex mode or full duplex mode of communication. This layer is also responsible for token management, through which it prevents two users to simultaneously access or attempting the same critical operation. This layer allows synchronization by allowing the process of adding checkpoints, which are considered as synchronization points to the streams of data. This layer is also responsible for session checkpointing and recovery. This layer basically provides a mechanism of opening, closing and managing a session between the end-user application processes. The services offered by Session Layer are generally implemented in application environments using remote procedure calls (RPCs). The Session Layer is also responsible for synchronizing information from different sources. This layer also controls single or multiple connections for each-end user application and directly communicates with both Presentation and transport layers. Session Layer creates procedures for checkpointing followed by adjournment, restart and termination. Session Layer uses checkpoints to enable communication sessions which are to be resumed from that particular checkpoint at which communication failure has occurred. The session Layer is responsible for fetching or receiving data information from its previous layer (transport layer) and further sends data to the layer after it (presentation layer).

12. Session Layer Protocols : Session Layer uses some protocols which are required for safe, secure and accurate communication which exists between two-ender user applications. Following are some of the protocols provided or used by the Session Layer – AppleTalk Data Stream Protocol (ADSP): ADSP is that type of protocol which was developed by Apple Inc. and it includes a number of features that allow local area networks to be connected with no prior setup. This protocol was released in 1985.  This protocol rigorously followed the OSI model of protocol layering. ADSP itself has two protocols named: AppleTalk Address Resolution Protocol (AARP) and Name Binding Protocol (NBP), both aimed at making system self-configuring. Real-time Transport Control Protocol (RTCP): RTCP is a protocol which provides out-of-band statistics and control information for an RTP (Real-time Transport Protocol) session. RTCP’s primary function is to provide feedback on the quality of service (QoS) in media distribution by periodically sending statistical information such as transmitted octet and packet counts or packet loss to the participants in the streaming multimedia session. Point-to-Point Tunneling Protocol (PPTP): PPTP is a protocol which provides a method for implementing virtual private networks. PPTP uses a TCP control channel and a Generic Routing Encapsulation tunnel to encapsulate PPP (Point-to-Point Protocol) packets This protocol provides security levels and remote access levels comparable with typical VPN (Virtual Private Network) products. Password Authentication Protocol (PAP): Password Authentication Protocol is a password-based authentication protocol used by Point to Point Protocol (PPP) to validate users. Almost all network operating systems, remote servers support PAP. PAP authentication is done at the time of the initial link establishment and verifies the identity of the client using a two-way handshake (Client-sends data and server in return sends Authentication-ACK (Acknowledgement) after the data sent by client is verified completely). Remote Procedure Call Protocol (RPCP): Remote Procedure Call Protocol (RPCP) is a protocol that is used when a computer program causes a procedure (or a sub-routine) to execute in a different address space without the programmer explicitly coding the details for the remote interaction. This is basically the form of client-server interaction, typically implemented via a request-response message-passing system. Sockets Direct Protocol (SDP): Sockets Direct Protocol (SDP) is a protocol that supports streams of sockets over Remote Direct Memory Access (RDMA) network fabrics. The purpose of SDP is to provide an RDMA-accelerated alternative to the TCP protocol. The primary goal is to perform one particular thing in such a manner which is transparent to the application.

13. Presentation Layer – Layer 6 he presentation layer is also called the Translation layer . The data from the application layer is extracted here and manipulated as per the required format to transmit over the network. Presentation Layer is the 6th layer in the Open System Interconnection (OSI) model. This layer is also known as Translation layer, as this layer serves as a data translator for the network. The data which this layer receives from the Application Layer is extracted and manipulated here as per the required format to transmit over the network. The main responsibility of this layer is to provide or define the data format and encryption. The presentation layer is also called as Syntax layer since it is responsible for maintaining the proper syntax of the data which it either receives or transmits to other layer(s).

14. The presentation layer, being the 6th layer in the OSI model, performs several types of functions, which are described below- Presentation layer format and encrypts data to be sent across the network. This layer takes care that the data is sent in such a way that the receiver will understand the information (data) and will be able to use the data efficiently and effectively. This layer manages the abstract data structures and allows high-level data structures (example- banking records), which are to be defined or exchanged. This layer carries out the encryption at the transmitter and decryption at the receiver. This layer carries out data compression to reduce the bandwidth of the data to be transmitted (the primary goal of data compression is to reduce the number of bits which is to be transmitted). This layer is responsible for interoperability (ability of computers to exchange and make use of information) between encoding methods as different computers use different encoding methods. This layer basically deals with the presentation part of the data. Presentation layer, carries out the data compression (number of bits reduction while transmission), which in return improves the data throughput. This layer also deals with the issues of string representation. The presentation layer is also responsible for integrating all the formats into a standardized format for efficient and effective communication. This layer encodes the message from the user-dependent format to the common format and vice-versa for communication between dissimilar systems.

15. Features of Presentation Layer in the OSI model: Presentation layer, being the 6th layer in the OSI model, plays a vital role while communication is taking place between two devices in a network. List of features which are provided by the presentation layer are: Presentation layer could apply certain sophisticated compression techniques, so fewer bytes of data are required to represent the information when it is sent over the network. If two or more devices are communicating over an encrypted connection, then this presentation layer is responsible for adding encryption on the sender’s end as well as the decoding the encryption on the receiver’s end so that it can represent the application layer with unencrypted, readable data. This layer formats and encrypts data to be sent over a network, providing freedom from compatibility problems. This presentation layer also negotiates the Transfer Syntax. This presentation layer is also responsible for compressing data it receives from the application layer before delivering it to the session layer (which is the 5th layer in the OSI model) and thus improves the speed as well as the efficiency of communication by minimizing the amount of the data to be transferred.

16. Presentation Layer Protocols : Presentation layer being the 6th layer, but the most important layer in the OSI model performs several types of functionalities, which makes sure that data which is being transferred or received should be accurate or clear to all the devices which are there in a closed network. Presentation Layer, for performing translations or other specified functions, needs to use certain protocols which are defined below – Apple Filing Protocol (AFP): Apple Filing Protocol is the proprietary network protocol (communications protocol) that offers services to macOS or the classic macOS. This is basically the network file control protocol specifically designed for Mac-based platforms. Lightweight Presentation Protocol (LPP ): Lightweight Presentation Protocol is that protocol which is used to provide ISO presentation services on the top of TCP/IP based protocol stacks. NetWare Core Protocol (NCP): NetWare Core Protocol is the network protocol which is used to access file, print, directory, clock synchronization, messaging, remote command execution and other network service functions.

17. NetWare Core Protocol (NCP): NetWare Core Protocol is the network protocol which is used to access file, print, directory, clock synchronization, messaging, remote command execution and other network service functions. Network Data Representation (NDR): Network Data Representation is basically the implementation of the presentation layer in the OSI model, which provides or defines various primitive data types, constructed data types and also several types of data representations. External Data Representation (XDR): External Data Representation (XDR) is the standard for the description and encoding of data. It is useful for transferring data between computer architectures and has been used to communicate data between very diverse machines. Converting from local representation to XDR is called encoding, whereas converting XDR into local representation is called decoding. Secure Socket Layer (SSL): The Secure Socket Layer protocol provides security to the data that is being transferred between the web browser and the server. SSL encrypts the link between a web server and a browser, which ensures that all data passed between them remains private and free from attacks.

18. Functions of the Presentation Layer Translation: For example, ASCII to EBCDIC . Encryption/ Decryption: Data encryption translates the data into another form or code. The encrypted data is known as the ciphertext and the decrypted data is known as plain text. A key value is used for encrypting as well as decrypting data. Compression: Reduces the number of bits that need to be transmitted on the network. Note: Device or Protocol Use: JPEG, MPEG, GIF.

19. Application Layer – Layer 7 At the very top of the OSI Reference Model stack of layers, we find the Application layer which is implemented by the network applications. These applications produce the data to be transferred over the network. This layer also serves as a window for the application services to access the network and for displaying the received information to the user. Example : Application – Browsers, Skype Messenger, etc. The Application Layer of OSI (Open System Interconnection) model, is the top layer in this model and takes care of network communication. The application layer provides the functionality to send and receive data from users. It acts as the interface between the user and the application. The application provides services like file transmission, mail service, and many more. In this article we will explore the application layer in the OSI model, application layer functions, the working of the application layer, and services provided by the application layer.

20. What is an Application Layer in OSI Model? Application Layer is the topmost layer in the Open System Interconnection (OSI) model . This layer provides several ways for manipulating the data (information) which actually enables any type of user to access network with ease. This layer also makes a request to its bottom layer, which is presentation layer for receiving various types of information from it. The Application Layer interface directly interacts with application and provides common web application services. This layer is basically highest level of open system, which provides services directly for application process. Functions of Application Layer The Application Layer, as discussed above, being topmost layer in OSI model, performs several kinds of functions which are requirement in any kind of application or communication process. Following are list of functions which are performed by Application Layer of OSI Model:

21. Application Layer Provides A Facility By Which Users Can Forward Several Emails And It Also Provides A Storage Facility. This Layer Allows Users To Access, Retrieve And Manage Files In A Remote Computer. It Allows Users To Log On As A Remote Host. This Layer Provides Access To Global Information About Various Services. This Layer Provides Services Which Include: E-mail, Transferring Files, Distributing Results To The User, Directory Services, Network Resources And So On. It Provides Protocols That Allow Software To Send And Receive Information And Present Meaningful Data To Users. It Handles Issues Such As Network Transparency, Resource Allocation And So On. This Layer Serves As A Window For Users And Application Processes To Access Network Services. Application Layer Is Basically Not A Function, But It Performs Application Layer Functions. The Application Layer Is Actually An Abstraction Layer That Specifies The Shared Protocols And Interface Methods Used By Hosts In A Communication Network. Application Layer Helps Us To Identify Communication Partners, And Synchronizing Communication. This Layer Allows Users To Interact With Other Software Applications. In This Layer, Data Is In Visual Form, Which Makes Users Truly Understand Data Rather Than Remembering Or Visualize The Data In The Binary Format (0’s Or 1’s). This Application Layer Basically Interacts With Operating System ( Os ) And Thus Further Preserves The Data In A Suitable Manner. This Layer Also Receives And Preserves Data From It’s Previous Layer, Which Is Presentation Layer (Which Carries In Itself The Syntax And Semantics Of The Information Transmitted).