1.1 Application layer
Provides a means for the user to access information on the network through an application. This layer is the main interface for the user to interact with the application and therefore the network.
The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer.
Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).
1.2 Presentation layer
Manages the presentation of the information in an ordered and meaningful manner. This layer's primary function is the syntax and semantics of the data transmission. It converts local host computer data representations into a standard network format for transmission on the network. On the receiving side, it changes the network format into the appropriate host computer's format so that data can be utilized independent of the host computer. ASCII and EBCDIC conversions, cryptography, and the like are handled here.
The presentation layer provides a variety of coding and conversion functions that are applied to application layer data. These functions ensure that information sent from the application layer of one system would be readable by the application layer of another system. Some examples of presentation layer coding and conversion schemes include common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes.
Common data representation formats, or the use of standard image, sound, and video formats, enable the interchange of application data between different types of computer systems. Using different text and data representations, such as EBCDIC and ASCII, uses conversion schemes to exchange information with systems. Standard data compression schemes enable data that is compressed. or encrypted at the source device to be properly decompressed, or deciphered at the destination.
Presentation layer implementations are not typically associated with a particular protocol stack. Some well-known standards for video include QuickTime and Motion Picture Experts Group (MPEG). QuickTime is an Apple Computer specification for video and audio, and MPEG is a standard for video compression and coding.
Among the well-known graphic image formats are Graphics Interchange Format (GIF), Joint Photographic Experts Group (JPEG), and Tagged Image File Format (TIFF). GIF is a standard for compressing and coding graphic images. JPEG is another compression and coding standard for graphic images, and TIFF is a standard coding format for graphic images.
1.3 Session layer
Coordinates dialogue/session/connection between devices over the network. This layer manages communications between connected sessions. Examples of this layer are token management (the session layer manages who has the token) and network time synchronization.
The session layer establishes, manages, and terminates communication sessions. Communication sessions consist of service requests and service responses that occur between applications located in different network devices. These requests and responses are coordinated by protocols implemented at the session layer. Some examples of session-layer implementations include Zone Information Protocol (ZIP), the AppleTalk protocol that coordinates the name binding process; and Session Control Protocol (SCP), the Decent Phase IV session layer protocol.
1.4 Transport layer
Responsible for reliable transmission of data and service specification between hosts. The major responsibility of this layer is data integrity--that data transmitted between hosts is reliable and timely. Upper layer data grams are broken down into network-sized data grams if needed and then implemented using appropriate transmission control. The transport layer creates one or more than one network connection, depending on conditions. This layer also handles what type of connection will be created. Two major transport protocols are the TCP (Transmission Control Protocol) and the UDP (User Data gram Protocol).
Important features of Transport layer:
- Transport layer ensures reliable service.
- Breaks the message (from sessions layer) into smaller packets, assigns sequence number and sends them.
- Reliable transport connections are built on top of X.25 or IP.
- In case IP, lost packets arriving out of order must be reordered.
Important features of TCP/UDP:
- TCP/IP Widely used for network/transport layer (UNIX).
- TCP (Transport Control Protocol): This is a connection oriented protocol.
- UDP (Universal Data gram Protocol): This is a connectionless transport layer protocol.
- Application programs that do not need connection-oriented protocol generally use UDP.
1.5 Network layer
Responsible for the routing of data (packets) through the network; handles the addressing and delivery of data. This layer provides for congestion control, accounting information for the network, routing, addressing, and several other functions. IP (Internet Protocol) is a good example of a network layer protocol. Network layer does not deal with lost messages.
Important features of Network layer protocols:
- Concerned with the transmission of packets.
- Choose the best path to send a packet (routing).
- The routing may be complex in a large network (e.g. Internet).
- Routing packets through a network may be accomplished by using simple static routes or by using complex dynamic routing algorithms.
1.6 Data link layer
Provides for the reliable delivery of data across a physical network. This layer deals with issues such as flow regulation, error detection and control, and frames. This layer has the important task of creating and managing what frames are sent out on the network. The network data frame, or packet, is made up of checksum, source address, destination address, and the data itself. The largest packet size that can be sent defines the maximum transmission Unit (MTU).
Important features of Data link layer:
- Handles errors in the physical layer.
- Groups bits into frames and ensures their correct delivery.
- Adds some bits at the beginning and end of each frame plus the checksum.
- Receiver verifies the checksum.
- If the checksum is not correct, it asks for retransmission. (Send a control message).
- Consists of two sub layers:
Logical Link Control (LLC) defines how data is transferred over the cable and provides data link service to the higher layers.
Medium Access Control (MAC) defines who can use the network when multiple computers are trying to access it simultaneously (i.e. Token passing, Ethernet [CSMA/CD]).
The data link layer provides reliable transit of data across a physical network link. Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control. Physical addressing (as opposed to network addressing) defines how devices are addressed at the data link layer. Network topology consists of the data link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Error notification alerts upper-layer protocols that a transmission error has occurred, and the sequencing of data frames reorders frames that are transmitted out of sequence. Finally, flow control moderates the transmission of data so that the receiving device is not overwhelmed with more traffic than it can handle at one time.
The protocols used in Data link layer are SLIP, PPP, MTU, and CSLP.
1.7 Physical layer
Handles the bit-level electrical/light communication across the network channel. The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Physical layer specifications define characteristics such as media, voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors.
Basically, this layer ensures that a bit sent on one side of the Network is received correctly on the other side.
Data travels from the application layer of the sender, down through the levels, across the nodes of the network service, and up through the levels of the receiver
To keep track of the transmission, each layer "wraps" the preceding layer's data and header with its own header. A small chunk of data will be transmitted with multiple layer headers attached to it. On the receiving end, each layer strips off the header that corresponds to its respective level.
Physical layer is concerned with the following:
- Physical interface characteristics like electrical, and mechanical specifications,
- Number of bits of second to be transmitted,
- Transmission type like duplex or half-duplex etc.
Frequently used Physical layer protocols:
Some of the important standards that deal with physical layer specifications are:
RS-232(for serial communication lines), X.21, EIA 232, and G730.
Physical layer and Data link layer implementations can be categorized as either LAN or WAN specifications.
In the OSI reference model, the communications between a computing system are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
Which are the 7 layers of OSI model explain the function of each layer What is the TCP IP model write the difference between OSI and TCP IP model? ›
TCP/IP vs OSI: What are the different layers? The TCP/IP Model comprises four layers: Network Interface, Internet, Transport and Application. The OSI Model comprises seven layers: Physical, Data Link, Network, Transport, Session, Presentation and Application.
The 7 layers of the OSI model. The layers are: Layer 1—Physical; Layer 2—Data Link; Layer 3—Network; Layer 4—Transport; Layer 5—Session; Layer 6—Presentation; Layer 7—Application.
The OSI Model or the Open Systems Interconnection Model is a conceptual framework which describes the functions of a networking system. It is used for the transfer of data over a network which moves through different layers.
Layer 7 is responsible for the data manipulation and protocols that software needs to present data so it is meaningful to humans. For example, layer 7 protocols include HTTP which enables internet communication and SMTP which enables email communications.
- Layer 1: Physical = Please.
- Layer 2: Data Link = Do.
- Layer 3: Network = Not.
- Layer 4: Transport = Touch.
- Layer 5: Session = Steve's.
- Layer 6: Presentation = Pet.
- Layer 7: Application = Alligator.
Characteristics of OSI Model
The upper layer deals with application issues using the software. Application layers are nearest to the users. The layer above another one refers to the upper layer. The lower layer deals with data transport using hardware and software.
OSI stands for Open System Interconnection is a reference model that describes how information from a software application in one computer moves through a physical medium to the software application in another computer. OSI consists of seven layers, and each layer performs a particular network function.
A layer-1 network is another name for a base blockchain. BNB Smart Chain (BNB), Ethereum (ETH), Bitcoin (BTC), and Solana are all layer-1 protocols. We refer to them as layer-1 because these are the main networks within their ecosystem.
The main concept of OSI is that the process of communication between two endpoints in a network can be divided into seven distinct groups of related functions, or layers. Each communicating user or program is on a device that can provide those seven layers of function.
The Open Systems Interconnection (OSI) model is a conceptual framework for the streamlined transfer of information from one logical address in the network to another logical address in the network.
The OSI allows you to identify threats across your entire tech stack. The OSI model has been used for decades to help IT experts understand networking and troubleshoot issues that may arise at any stage in the networking process.
The main reason the OSI model was created was so that different networks could communicate. The primary goal for developing the OSI model (Open System Interconnections model) is to provide the functionality of interoperating the software programs and communication of products.
Examples of network layer protocols include: Internet Protocol. Internet Control Message Protocol (ICMP or "ping") Internet Gateway Management Protocol (IGMP)
The transport layer controls the reliability of communications through flow control, segmentation, and error control. Two great examples of transport protocols are TCP (as in TCP/IP) and UDP.
The Transmission Control Protocol (TCP) is a transport layer protocol, and the Internet Protocol (IP) is a network layer protocol.
Using the OSI model, the communications between computing systems are done through seven abstraction layers; it's easy to remember the sequence of OSI Model 7 Layers using this simple sentence: "All people seem to need data processing."
Layer 3, the Network Layer
This is the most important layer of the OSI model, which performs real time processing and transfers data from nodes to nodes.
Layers are used in digital image editing to separate different elements of an image. A layer can be compared to a transparency on which imaging effects or images are applied and placed over or under an image.
The most significant protocol at layer 3 (also called the network layer) is the Internet Protocol, or IP.
Two major examples of layer 2 solutions are the Bitcoin Lightning Network and the Ethereum Plasma. Despite having their own working mechanisms and particularities, both solutions are striving to provide increased throughput to blockchain systems.
Popular examples of Ethereum layer 2 solutions include Immutable X, Polygon, and Polkadot.
3. Network layer: Handles the routing and sending of data between different networks. The most important protocols at this layer are IP and ICMP.
- List the Layers of OSI Model? ...
- What are the Functions of Transport, Network and Data Link Layer? ...
- Which Layer is responsible for Reliable connection? ...
- What are the different protocols works at each of the layers in OSI Model? ...
- What is a port number and give some examples?
That the OSI Model is a reference model on how two systems talk to each other over a network. We don't use this model in real life. Instead, we use another similar model called the TCP/IP model.
The Open Systems Interconnection (OSI) model describes how information moves from one device to another. This model was developed by International Organization for Standardization (ISO) in 1984.
The OSI model was developed by the International Organization for Standardization (ISO), so some sources confusingly call it the ISO model, or even the ISO OSI model. The model is formally called “X. 200: Information technology—Open Systems Interconnection—Basic Reference Model.”
The OSI model was first defined in raw form in Washington, DC, in February 1978 by Hubert Zimmermann of France and the refined but still draft standard was published by the ISO in 1980.
OSI model is a generic model that is based upon functionalities of each layer. TCP/IP model is a protocol-oriented standard. OSI model distinguishes the three concepts, namely, services, interfaces, and protocols. TCP/IP does not have a clear distinction between these three.
The network access layer is equivalent to OSI layers 1 and 2. The Internet Protocol layer is comparable to layer 3 in the OSI model. The host-to-host layer is equivalent to OSI layer 4. These are the TCP and UDP (user datagram protocol) functions.
Layer 4 of the OSI Model Handles Transport Protocols Like TCP and UDP. Layer 4 of the OSI model, also known as the transport layer, manages network traffic between hosts and end systems to ensure complete data transfers.
Layer 7 refers to the top layer in the 7-layer OSI Model of the Internet. It is also known as the "application layer." It's the top layer of the data processing that occurs just below the surface or behind the scenes of the software applications that users interact with.
The purpose of the OSI reference model is to guide technology vendors and developers so the digital communications products and software programs they create can interoperate and to promote a clear framework that describes the functions of a networking or telecommunications system that's in use.
In theoretical discussions, the OSI Reference Model helps you understand how networks and network protocols function. In the “real world”, it also helps you figure out which protocols and devices can interact with each other.
How Data Flows Through the OSI Model. Data flows from layer 7 down to layer 1 from the sender, and then flows from layer 1 to layer 7 on the recipient device. The simplest example of communication flow through the OSI Model is an email application.
The basic function of the Transport layer is to accept data from the session layer, split it up into smaller units if need be, pass these to the Network layer, and ensure that all the pieces arrive correctly at the other end.
TCP and IP are two separate computer network protocols. IP is the part that obtains the address to which data is sent. TCP is responsible for data delivery once that IP address has been found. It's possible to separate them, but there isn't really a point in making a difference between TCP and IP.
Transmission Control Protocol (TCP)
The OSI Model. The OSI model has seven layers, as shown in Table 4.1. The layers may be listed in a top-to-bottom or bottom to top order. Using the latter, they are Physical, Data Link, Network, Transport, Session, Presentation, and Application.
The transport layer controls the reliability of communications through flow control, segmentation, and error control. Two great examples of transport protocols are TCP (as in TCP/IP) and UDP.
However, the OSI 7-layer model is still widely used, as it helps visualize and communicate how networks operate, and helps isolate and troubleshoot networking problems. OSI was introduced in 1983 by representatives of the major computer and telecom companies, and was adopted by ISO as an international standard in 1984.
Layer 7 load balancing allows the load balancer to route a request based on information in the request itself, such as what kind of content is being requested. So now a request for an image or video can be routed to the servers that store it and are highly optimized to serve up multimedia content.
Layer 1 of The OSI Model: Physical Layer defines electrical and physical specifications for devices. The physical layer defines the relationship between a device and a transmission medium, such as a copper or optical cable.