presentation layer systems

Layer 6 Presentation Layer

De/Encryption, Encoding, String representation

The presentation layer (data presentation layer, data provision level) sets the system-dependent representation of the data (for example, ASCII, EBCDIC) into an independent form, enabling the syntactically correct data exchange between different systems. Also, functions such as data compression and encryption are guaranteed that data to be sent by the application layer of a system that can be read by the application layer of another system to the layer 6. The presentation layer. If necessary, the presentation layer acts as a translator between different data formats, by making an understandable for both systems data format, the ASN.1 (Abstract Syntax Notation One) used.

OSI Layer 6 - Presentation Layer

The presentation layer is responsible for the delivery and formatting of information to the application layer for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems. An example of a presentation service would be the conversion of an EBCDIC-coded text computer file to an ASCII-coded file. The presentation layer is the lowest layer at which application programmers consider data structure and presentation, instead of simply sending data in the form of datagrams or packets between hosts. This layer deals with issues of string representation - whether they use the Pascal method (an integer length field followed by the specified amount of bytes) or the C/C++ method (null-terminated strings, e.g. "thisisastring\0"). The idea is that the application layer should be able to point at the data to be moved, and the presentation layer will deal with the rest. Serialization of complex data structures into flat byte-strings (using mechanisms such as TLV or XML) can be thought of as the key functionality of the presentation layer. Encryption is typically done at this level too, although it can be done on the application, session, transport, or network layers, each having its own advantages and disadvantages. Decryption is also handled at the presentation layer. For example, when logging on to bank account sites the presentation layer will decrypt the data as it is received.[1] Another example is representing structure, which is normally standardized at this level, often by using XML. As well as simple pieces of data, like strings, more complicated things are standardized in this layer. Two common examples are 'objects' in object-oriented programming, and the exact way that streaming video is transmitted. In many widely used applications and protocols, no distinction is made between the presentation and application layers. For example, HyperText Transfer Protocol (HTTP), generally regarded as an application-layer protocol, has presentation-layer aspects such as the ability to identify character encoding for proper conversion, which is then done in the application layer. Within the service layering semantics of the OSI network architecture, the presentation layer responds to service requests from the application layer and issues service requests to the session layer. In the OSI model: the presentation layer ensures the information that the application layer of one system sends out is readable by the application layer of another system. For example, a PC program communicates with another computer, one using extended binary coded decimal interchange code (EBCDIC) and the other using ASCII to represent the same characters. If necessary, the presentation layer might be able to translate between multiple data formats by using a common format. Wikipedia

Data conversion
Character code translation
Compression
Encryption and Decryption

The Presentation OSI Layer is usually composed of 2 sublayers that are:

CASE common application service element

Sase specific application service element, layer 7 application layer, layer 6 presentation layer, layer 5 session layer, layer 4 transport layer, layer 3 network layer, layer 2 data link layer, layer 1 physical layer.

The OSI Model – The 7 Layers of Networking Explained in Plain English

This article explains the Open Systems Interconnection (OSI) model and the 7 layers of networking, in plain English.

The OSI model is a conceptual framework that is used to describe how a network functions. In plain English, the OSI model helped standardize the way computer systems send information to each other.

Learning networking is a bit like learning a language - there are lots of standards and then some exceptions. Therefore, it’s important to really understand that the OSI model is not a set of rules. It is a tool for understanding how networks function.

Once you learn the OSI model, you will be able to further understand and appreciate this glorious entity we call the Internet, as well as be able to troubleshoot networking issues with greater fluency and ease.

All hail the Internet!

Prerequisites

You don’t need any prior programming or networking experience to understand this article. However, you will need:

Basic familiarity with common networking terms (explained below)
A curiosity about how things work :)

Learning Objectives

Over the course of this article, you will learn:

What the OSI model is
The purpose of each of the 7 layers
The problems that can happen at each of the 7 layers
The difference between TCP/IP model and the OSI model

Common Networking Terms

Here are some common networking terms that you should be familiar with to get the most out of this article. I’ll use these terms when I talk about OSI layers next.

A node is a physical electronic device hooked up to a network, for example a computer, printer, router, and so on. If set up properly, a node is capable of sending and/or receiving information over a network.

Nodes may be set up adjacent to one other, wherein Node A can connect directly to Node B, or there may be an intermediate node, like a switch or a router, set up between Node A and Node B.

Typically, routers connect networks to the Internet and switches operate within a network to facilitate intra-network communication. Learn more about hub vs. switch vs. router.

Here's an example:

For the nitpicky among us (yep, I see you), host is another term that you will encounter in networking. I will define a host as a type of node that requires an IP address. All hosts are nodes, but not all nodes are hosts. Please Tweet angrily at me if you disagree.

Links connect nodes on a network. Links can be wired, like Ethernet, or cable-free, like WiFi.

Links to can either be point-to-point, where Node A is connected to Node B, or multipoint, where Node A is connected to Node B and Node C.

When we’re talking about information being transmitted, this may also be described as a one-to-one vs. a one-to-many relationship.

A protocol is a mutually agreed upon set of rules that allows two nodes on a network to exchange data.

“A protocol defines the rules governing the syntax (what can be communicated), semantics (how it can be communicated), and synchronization (when and at what speed it can be communicated) of the communications procedure. Protocols can be implemented on hardware, software, or a combination of both. Protocols can be created by anyone, but the most widely adopted protocols are based on standards.” - The Illustrated Network.

Both wired and cable-free links can have protocols.

While anyone can create a protocol, the most widely adopted protocols are often based on standards published by Internet organizations such as the Internet Engineering Task Force (IETF).

A network is a general term for a group of computers, printers, or any other device that wants to share data.

Network types include LAN, HAN, CAN, MAN, WAN, BAN, or VPN. Think I’m just randomly rhyming things with the word can ? I can ’t say I am - these are all real network types. Learn more here .

Topology describes how nodes and links fit together in a network configuration, often depicted in a diagram. Here are some common network topology types:

What is Network Topology? Best Guides to Types & Diagrams - DNSstuff

A network consists of nodes, links between nodes, and protocols that govern data transmission between nodes.

At whatever scale and complexity networks get to, you will understand what’s happening in all computer networks by learning the OSI model and 7 layers of networking.

What is the OSI Model?

The OSI model consists of 7 layers of networking.

First, what’s a layer?

No, a layer - not a lair . Here there are no dragons.

A layer is a way of categorizing and grouping functionality and behavior on and of a network.

In the OSI model, layers are organized from the most tangible and most physical, to less tangible and less physical but closer to the end user.

Each layer abstracts lower level functionality away until by the time you get to the highest layer. All the details and inner workings of all the other layers are hidden from the end user.

How to remember all the names of the layers? Easy.

Please | Physical Layer
Do | Data Link Layer
Not | Network Layer
Tell (the) | Transport Layer
Secret | Session Layer
Password (to) | Presentation Layer
Anyone | Application Layer

Keep in mind that while certain technologies, like protocols, may logically “belong to” one layer more than another, not all technologies fit neatly into a single layer in the OSI model. For example, Ethernet, 802.11 (Wifi) and the Address Resolution Protocol (ARP) procedure operate on >1 layer.

The OSI is a model and a tool, not a set of rules.

OSI Layer 1

Layer 1 is the physical layer . There’s a lot of technology in Layer 1 - everything from physical network devices, cabling, to how the cables hook up to the devices. Plus if we don’t need cables, what the signal type and transmission methods are (for example, wireless broadband).

Instead of listing every type of technology in Layer 1, I’ve created broader categories for these technologies. I encourage readers to learn more about each of these categories:

Nodes (devices) and networking hardware components. Devices include hubs, repeaters, routers, computers, printers, and so on. Hardware components that live inside of these devices include antennas, amplifiers, Network Interface Cards (NICs), and more.
Device interface mechanics. How and where does a cable connect to a device (cable connector and device socket)? What is the size and shape of the connector, and how many pins does it have? What dictates when a pin is active or inactive?
Functional and procedural logic. What is the function of each pin in the connector - send or receive? What procedural logic dictates the sequence of events so a node can start to communicate with another node on Layer 2?
Cabling protocols and specifications. Ethernet (CAT), USB, Digital Subscriber Line (DSL) , and more. Specifications include maximum cable length, modulation techniques, radio specifications, line coding, and bits synchronization (more on that below).
Cable types. Options include shielded or unshielded twisted pair, untwisted pair, coaxial and so on. Learn more about cable types here .
Signal type. Baseband is a single bit stream at a time, like a railway track - one-way only. Broadband consists of multiple bit streams at the same time, like a bi-directional highway.
Signal transmission method (may be wired or cable-free). Options include electrical (Ethernet), light (optical networks, fiber optics), radio waves (802.11 WiFi, a/b/g/n/ac/ax variants or Bluetooth). If cable-free, then also consider frequency: 2.5 GHz vs. 5 GHz. If it’s cabled, consider voltage. If cabled and Ethernet, also consider networking standards like 100BASE-T and related standards.

The data unit on Layer 1 is the bit.

A bit the smallest unit of transmittable digital information. Bits are binary, so either a 0 or a 1. Bytes, consisting of 8 bits, are used to represent single characters, like a letter, numeral, or symbol.

Bits are sent to and from hardware devices in accordance with the supported data rate (transmission rate, in number of bits per second or millisecond) and are synchronized so the number of bits sent and received per unit of time remains consistent (this is called bit synchronization). The way bits are transmitted depends on the signal transmission method.

Nodes can send, receive, or send and receive bits. If they can only do one, then the node uses a simplex mode. If they can do both, then the node uses a duplex mode. If a node can send and receive at the same time, it’s full-duplex – if not, it’s just half-duplex.

The original Ethernet was half-duplex. Full-duplex Ethernet is an option now, given the right equipment.

How to Troubleshoot OSI Layer 1 Problems

Here are some Layer 1 problems to watch out for:

Defunct cables, for example damaged wires or broken connectors
Broken hardware network devices, for example damaged circuits
Stuff being unplugged (...we’ve all been there)

If there are issues in Layer 1, anything beyond Layer 1 will not function properly.

Layer 1 contains the infrastructure that makes communication on networks possible.

It defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating physical links between network devices. - Source

Fun fact: deep-sea communications cables transmit data around the world. This map will blow your mind: https://www.submarinecablemap.com/

And because you made it this far, here’s a koala:

OSI Layer 2

Layer 2 is the data link layer . Layer 2 defines how data is formatted for transmission, how much data can flow between nodes, for how long, and what to do when errors are detected in this flow.

In more official tech terms:

Line discipline. Who should talk for how long? How long should nodes be able to transit information for?
Flow control. How much data should be transmitted?
Error control - detection and correction . All data transmission methods have potential for errors, from electrical spikes to dirty connectors. Once Layer 2 technologies tell network administrators about an issue on Layer 2 or Layer 1, the system administrator can correct for those errors on subsequent layers. Layer 2 is mostly concerned with error detection, not error correction. ( Source )

There are two distinct sublayers within Layer 2:

Media Access Control (MAC): the MAC sublayer handles the assignment of a hardware identification number, called a MAC address, that uniquely identifies each device on a network. No two devices should have the same MAC address. The MAC address is assigned at the point of manufacturing. It is automatically recognized by most networks. MAC addresses live on Network Interface Cards (NICs). Switches keep track of all MAC addresses on a network. Learn more about MAC addresses on PC Mag and in this article . Learn more about network switches here .
Logical Link Control (LLC): the LLC sublayer handles framing addressing and flow control. The speed depends on the link between nodes, for example Ethernet or Wifi.

The data unit on Layer 2 is a frame .

Each frame contains a frame header, body, and a frame trailer:

Header: typically includes MAC addresses for the source and destination nodes.
Body: consists of the bits being transmitted.
Trailer: includes error detection information. When errors are detected, and depending on the implementation or configuration of a network or protocol, frames may be discarded or the error may be reported up to higher layers for further error correction. Examples of error detection mechanisms: Cyclic Redundancy Check (CRC) and Frame Check Sequence (FCS). Learn more about error detection techniques here .

Example of frames, the network layer, and the physical layer

Typically there is a maximum frame size limit, called an Maximum Transmission Unit, MTU. Jumbo frames exceed the standard MTU, learn more about jumbo frames here .

How to Troubleshoot OSI Layer 2 Problems

Here are some Layer 2 problems to watch out for:

All the problems that can occur on Layer 1
Unsuccessful connections (sessions) between two nodes
Sessions that are successfully established but intermittently fail
Frame collisions

The Data Link Layer allows nodes to communicate with each other within a local area network. The foundations of line discipline, flow control, and error control are established in this layer.

OSI Layer 3

Layer 3 is the network layer . This is where we send information between and across networks through the use of routers. Instead of just node-to-node communication, we can now do network-to-network communication.

Routers are the workhorse of Layer 3 - we couldn’t have Layer 3 without them. They move data packets across multiple networks.

Not only do they connect to Internet Service Providers (ISPs) to provide access to the Internet, they also keep track of what’s on its network (remember that switches keep track of all MAC addresses on a network), what other networks it’s connected to, and the different paths for routing data packets across these networks.

Routers store all of this addressing and routing information in routing tables.

Here’s a simple example of a routing table:

A routing table showing the destination, subnet mask, and interface

The data unit on Layer 3 is the data packet . Typically, each data packet contains a frame plus an IP address information wrapper. In other words, frames are encapsulated by Layer 3 addressing information.

The data being transmitted in a packet is also sometimes called the payload . While each packet has everything it needs to get to its destination, whether or not it makes it there is another story.

Layer 3 transmissions are connectionless, or best effort - they don't do anything but send the traffic where it’s supposed to go. More on data transport protocols on Layer 4.

Once a node is connected to the Internet, it is assigned an Internet Protocol (IP) address, which looks either like 172.16. 254.1 (IPv4 address convention) or like 2001:0db8:85a3:0000:0000:8a2e:0370:7334 (IPv6 address convention). Routers use IP addresses in their routing tables.

IP addresses are associated with the physical node’s MAC address via the Address Resolution Protocol (ARP), which resolves MAC addresses with the node’s corresponding IP address.

ARP is conventionally considered part of Layer 2, but since IP addresses don’t exist until Layer 3, it’s also part of Layer 3.

How to Troubleshoot OSI Layer 3 Problems

Here are some Layer 3 problems to watch out for:

All the problems that can crop up on previous layers :)
Faulty or non-functional router or other node
IP address is incorrectly configured

Many answers to Layer 3 questions will require the use of command-line tools like ping , trace , show ip route , or show ip protocols . Learn more about troubleshooting on layer 1-3 here .

The Network Layer allows nodes to connect to the Internet and send information across different networks.

OSI Layer 4

Layer 4 is the transport layer . This where we dive into the nitty gritty specifics of the connection between two nodes and how information is transmitted between them. It builds on the functions of Layer 2 - line discipline, flow control, and error control.

This layer is also responsible for data packet segmentation, or how data packets are broken up and sent over the network.

Unlike the previous layer, Layer 4 also has an understanding of the whole message, not just the contents of each individual data packet. With this understanding, Layer 4 is able to manage network congestion by not sending all the packets at once.

The data units of Layer 4 go by a few names. For TCP, the data unit is a packet. For UDP, a packet is referred to as a datagram. I’ll just use the term data packet here for the sake of simplicity.

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) are two of the most well-known protocols in Layer 4.

TCP, a connection-oriented protocol, prioritizes data quality over speed.

TCP explicitly establishes a connection with the destination node and requires a handshake between the source and destination nodes when data is transmitted. The handshake confirms that data was received. If the destination node does not receive all of the data, TCP will ask for a retry.

TCP also ensures that packets are delivered or reassembled in the correct order. Learn more about TCP here .

UDP, a connectionless protocol, prioritizes speed over data quality. UDP does not require a handshake, which is why it’s called connectionless.

Because UDP doesn’t have to wait for this acknowledgement, it can send data at a faster rate, but not all of the data may be successfully transmitted and we’d never know.

If information is split up into multiple datagrams, unless those datagrams contain a sequence number, UDP does not ensure that packets are reassembled in the correct order. Learn more about UDP here .

TCP and UDP both send data to specific ports on a network device, which has an IP address. The combination of the IP address and the port number is called a socket.

Learn more about sockets here .

Learn more about the differences and similarities between these two protocols here .

How to Troubleshoot OSI Layer 4 Problems

Here are some Layer 4 problems to watch out for:

Blocked ports - check your Access Control Lists (ACL) & firewalls
Quality of Service (QoS) settings. QoS is a feature of routers/switches that can prioritize traffic, and they can really muck things up. Learn more about QoS here .

The Transport Layer provides end-to-end transmission of a message by segmenting a message into multiple data packets; the layer supports connection-oriented and connectionless communication.

OSI Layer 5

Layer 5 is the session layer . This layer establishes, maintains, and terminates sessions.

A session is a mutually agreed upon connection that is established between two network applications. Not two nodes! Nope, we’ve moved on from nodes. They were so Layer 4.

Just kidding, we still have nodes, but Layer 5 doesn’t need to retain the concept of a node because that’s been abstracted out (taken care of) by previous layers.

So a session is a connection that is established between two specific end-user applications. There are two important concepts to consider here:

Client and server model: the application requesting the information is called the client, and the application that has the requested information is called the server.
Request and response model: while a session is being established and during a session, there is a constant back-and-forth of requests for information and responses containing that information or “hey, I don’t have what you’re requesting.”

Sessions may be open for a very short amount of time or a long amount of time. They may fail sometimes, too.

Depending on the protocol in question, various failure resolution processes may kick in. Depending on the applications/protocols/hardware in use, sessions may support simplex, half-duplex, or full-duplex modes.

Examples of protocols on Layer 5 include Network Basic Input Output System (NetBIOS) and Remote Procedure Call Protocol (RPC), and many others.

From here on out (layer 5 and up), networks are focused on ways of making connections to end-user applications and displaying data to the user.

How to Troubleshoot OSI Layer 5 Problems

Here are some Layer 5 problems to watch out for:

Servers are unavailable
Servers are incorrectly configured, for example Apache or PHP configs
Session failure - disconnect, timeout, and so on.

The Session Layer initiates, maintains, and terminates connections between two end-user applications. It responds to requests from the presentation layer and issues requests to the transport layer.

OSI Layer 6

Layer 6 is the presentation layer . This layer is responsible for data formatting, such as character encoding and conversions, and data encryption.

The operating system that hosts the end-user application is typically involved in Layer 6 processes. This functionality is not always implemented in a network protocol.

Layer 6 makes sure that end-user applications operating on Layer 7 can successfully consume data and, of course, eventually display it.

There are three data formatting methods to be aware of:

American Standard Code for Information Interchange (ASCII): this 7-bit encoding technique is the most widely used standard for character encoding. One superset is ISO-8859-1, which provides most of the characters necessary for languages spoken in Western Europe.
Extended Binary-Coded Decimal Interchange Code (EBDCIC): designed by IBM for mainframe usage. This encoding is incompatible with other character encoding methods.
Unicode: character encodings can be done with 32-, 16-, or 8-bit characters and attempts to accommodate every known, written alphabet.

Learn more about character encoding methods in this article , and also here .

Encryption: SSL or TLS encryption protocols live on Layer 6. These encryption protocols help ensure that transmitted data is less vulnerable to malicious actors by providing authentication and data encryption for nodes operating on a network. TLS is the successor to SSL.

How to Troubleshoot OSI Layer 6 Problems

Here are some Layer 6 problems to watch out for:

Non-existent or corrupted drivers
Incorrect OS user access level

The Presentation Layer formats and encrypts data.

OSI Layer 7

Layer 7 is the application layer .

True to its name, this is the layer that is ultimately responsible for supporting services used by end-user applications. Applications include software programs that are installed on the operating system, like Internet browsers (for example, Firefox) or word processing programs (for example, Microsoft Word).

Applications can perform specialized network functions under the hood and require specialized services that fall under the umbrella of Layer 7.

Electronic mail programs, for example, are specifically created to run over a network and utilize networking functionality, such as email protocols, which fall under Layer 7.

Applications will also control end-user interaction, such as security checks (for example, MFA), identification of two participants, initiation of an exchange of information, and so on.

Protocols that operate on this level include File Transfer Protocol (FTP), Secure Shell (SSH), Simple Mail Transfer Protocol (SMTP), Internet Message Access Protocol (IMAP), Domain Name Service (DNS), and Hypertext Transfer Protocol (HTTP).

While each of these protocols serve different functions and operate differently, on a high level they all facilitate the communication of information. ( Source )

How to Troubleshoot OSI Layer 7 Problems

Here are some Layer 7 problems to watch out for:

All issues on previous layers
Incorrectly configured software applications
User error (... we’ve all been there)

The Application Layer owns the services and functions that end-user applications need to work. It does not include the applications themselves.

Our Layer 1 koala is all grown up.

Learning check - can you apply makeup to a koala?

Don’t have a koala?

Well - answer these questions instead. It’s the next best thing, I promise.

What is the OSI model?
What are each of the layers?
How could I use this information to troubleshoot networking issues?

Congratulations - you’ve taken one step farther to understanding the glorious entity we call the Internet.

Learning Resources

Many, very smart people have written entire books about the OSI model or entire books about specific layers. I encourage readers to check out any O’Reilly-published books about the subject or about network engineering in general.

Here are some resources I used when writing this article:

The Illustrated Network, 2nd Edition
Protocol Data Unit (PDU): https://www.geeksforgeeks.org/difference-between-segments-packets-and-frames/
Troubleshooting Along the OSI Model: https://www.pearsonitcertification.com/articles/article.aspx?p=1730891
The OSI Model Demystified: https://www.youtube.com/watch?v=HEEnLZV2wGI
OSI Model for Dummies: https://www.dummies.com/programming/networking/layers-in-the-osi-model-of-a-computer-network/

Chloe Tucker is an artist and computer science enthusiast based in Portland, Oregon. As a former educator, she's continuously searching for the intersection of learning and teaching, or technology and art. Reach out to her on Twitter @_chloetucker and check out her website at chloe.dev .

The OSI Model’s 7 Layers, Explained

The seven layers in the Open Systems Interconnection (OSI) model each serve a specific function and work together to create an efficient network communication system.

The Open Systems Interconnection (OSI) model is a framework in network communication that simplifies complex network interactions into a structured format.

What Is the OSI Model?

The Open Systems Interconnection model is a framework in network communication designed to simplify complex network interactions into a structured format. This architecture has seven layers, each of which serves a specific function. All seven layers work together to create a robust and efficient network communication system.

Each of its seven layers has a distinct role, ensuring efficient data transfer from one device to another . The OSI model is essential for understanding how data is transmitted in a network and is also a practical guide for network protocol design and problem solving.

learn more about cybersecurity An Introduction to Microsegmentation in Network Security

The OSI model, developed by the International Organization for Standardization , outlines the essential functions of networking and telecommunications systems for practical application. It plays a crucial role in telecommunications, where vendors use it to define the features and capabilities of their products and services.

This approach allows for a detailed explanation of different aspects of network communication, including transport protocols, addressing schemes and data packaging methods. As a result, the OSI model resolves the complexities of network communication and fosters a more integrated and coherent digital world .

The 7 Layers of the OSI Model

Each layer of the OSI model serves a specific function, yet they work in harmony to create a robust and efficient network communication system. Understanding these layers provides valuable insights into the complexities of network design and operation, showcasing the intricate nature of modern digital communication.

Layer 7: Application Layer

Functionality: The Application Layer is the closest to the end user. It facilitates user interaction with networked systems, providing interfaces and protocols for web browsers, email clients and other applications.

Key protocols: Protocols like HTTP, FTP and SMTP operate at this layer, enabling services such as web browsing, file transfers and email communications.

Layer 6: Presentation Layer

Role: The Presentation Layer acts as a translator, converting data formats from the application layer into a network-compatible format and vice versa. It ensures that data sent from one system is readable by another.

Data formatting: This layer is responsible for data encryption and compression, playing a significant role in maintaining data privacy and efficient transmission.

Layer 5: Session Layer

Managing sessions: It establishes, manages and terminates sessions between applications. This layer ensures that sessions are maintained for the duration of the communication.

Coordination: The Session Layer coordinates communication between systems, managing dialogues and synchronizing data exchange.

Layer 4: Transport Layer

Data segmentation and control: The Transport Layer is crucial for segmenting data into smaller packets. It ensures end-to-end data integrity and delivery, managing flow control, error correction and sequencing.

Protocols: TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are key protocols in this layer, differing in their approach to data transmission.

Layer 3: Network Layer

Routing and addressing: This layer is responsible for logical addressing and routing data packets across different networks. It determines the best path for data to travel from source to destination.

Internet protocol: The Internet Protocol (IP), fundamental for internet data exchange, operates at this layer.

Layer 2: Data Link Layer

Framing and MAC addressing: The Data Link Layer frames data into packets. It handles physical addressing through MAC addresses, ensuring that data is directed to the correct hardware.

Error detection: This layer is also involved in error detection and handling, improving overall data transmission reliability.

Layer 1: Physical Layer

Physical transmission: The Physical Layer deals with the physical aspects of data transmission, including cable types, electrical signals and data rates.

Hardware components: It involves hardware components like cables, switches and network interface cards, forming the foundation of network communication.

How Data Flows in the OSI Model

Understanding this data flow process is crucial for professionals, as it aids in diagnosing and troubleshooting network issues, designing efficient network solutions and ensuring robust data security and management.

Encapsulation Process

When data is sent, it begins at the Application Layer and moves down through the layers. At each stage, it is encapsulated with the necessary headers, trailers, and other control information relevant to that layer. For instance, at the Transport Layer, data is segmented and encapsulated with port numbers, while at the Network Layer, IP addresses are added.

Each layer plays a role in preparing the data for transmission. The Presentation Layer may encrypt the data for security, while the Data Link Layer ensures it is formatted into frames suitable for physical transmission.

Data Transmission Across the Network

The Physical Layer transmits the raw bits over a physical medium, such as a cable or wireless network. This transmission is the actual movement of data across the network. In cases where data must move across different networks, the Network Layer’s routing functionalities become crucial. It ensures that data packets find the most efficient path to their destination.

Decapsulation Process

Upon reaching the destination, the data moves up the OSI model, with each layer removing its respective encapsulation. The Data Link Layer, for instance, removes framing, and the Transport Layer checks for transmission errors and reassembles the data segments. Once the data reaches the Application Layer, it is in its original format and ready to be used by the receiving application, whether it’s an email client, a web browser or any other networked software.

Seamless Data Flow

The OSI model ensures that each layer only communicates with its immediate upper and lower layers, creating a seamless flow. This layered approach means changes in one layer’s protocols or functionalities can occur without disrupting the entire network.

OSI Model Advantages

The OSI model is a cornerstone in network architecture for several reasons:

Simplification of network design

The OSI model’s layered approach breaks down complex network processes, making design and operation more manageable. Each layer focuses on a specific aspect of communication, allowing for independent development and easier troubleshooting.

Standardization and interoperability

It establishes universal standards for network communication, enabling different technologies to interact seamlessly. This interoperability is crucial for the efficient functioning of diverse network devices and applications.

Flexibility and Scalability

Adaptable to technological advancements, the OSI model allows individual layers to evolve without overhauling the entire system. This scalability makes it suitable for various network sizes and types.

Enhanced Security

Security measures are integrated at multiple layers, providing a robust defense against threats. Each layer can address specific security concerns, leading to comprehensive network protection.

Real-World Applications of the OSI Model

The OSI model’s influence extends well beyond theoretical concepts, playing a crucial role in various practical aspects of networking:

Network Design and Protocol Development

Network professionals use the OSI model as a blueprint for structuring and developing robust networks. It guides the creation of new protocols, ensuring seamless integration and functionality across different network layers.

Efficient Troubleshooting and Management

In troubleshooting, the OSI model provides a systematic approach for identifying issues, from physical connectivity to application-level errors. It also aids in network maintenance and performance optimization, addressing each layer to enhance overall efficiency.

Cybersecurity Strategy

The model is foundational in crafting layered security strategies . By implementing security measures at different layers, it offers comprehensive protection against various cyber threats. Understanding the OSI layers is key in detecting and mitigating attacks targeting specific network segments.

Educational and Training Tool

It serves as an essential framework in networking education, helping students and professionals alike understand complex network operations. The OSI model is a cornerstone in training programs , emphasizing the intricacies of network architecture and security.

safety first When and How to Run a Phishing Simulation

OSI Model vs. TCP/IP Model

While the OSI model offers a detailed conceptual framework, the TCP/IP model is recognized for its practical application in today’s internet-driven world.

Structural Differences

OSI model : Introduced as a comprehensive, protocol-independent framework, the OSI model details seven distinct layers, offering a more granular approach to network communication.

TCP/IP model : Developed earlier by the U.S. Department of Defense, the TCP/IP model consists of four layers (Application, Transport, Internet and Network Access), combining certain OSI layers.

Theoretical vs. Practical Approach

OSI model : Developed as a theoretical and universal networking model, it’s used more for educational purposes to explain how networks operate.

TCP/IP model : This model is designed around specific standard protocols, focusing on solving practical communication issues. It leaves sequencing and acknowledgment functions to the transport layer, differing from the OSI approach.

Adoption and Use

OSI model: While not widely implemented in its entirety, the OSI model’s clear layer separation is influential in protocol design and network education; simpler applications in the OSI framework may not utilize all seven layers, with only the first three layers (Physical, Data Link, and Network) being mandatory for basic data communication.

TCP/IP model : The dominant model used in most network architectures today, especially in internet-related communications. In TCP/IP, most applications engage all layers for communication.

Frequently Asked Questions

Why is the osi model important.

The OSI model is crucial for standardizing network communication and ensuring interoperability between various devices and systems. It simplifies network design and troubleshooting and serves as a fundamental educational tool in networking.

What are the 7 layers of the OSI model?

Layer 1: Physical Layer — Transmits raw data.

Layer 2: Data Link Layer — Manages direct links and framing.

Layer 3: Network Layer — Handles addressing and routing.

Layer 4: Transport Layer — Ensures reliable data transfer.

Layer 5: Session Layer — Manages connections.

Layer 6: Presentation Layer — Translates data formats.

Layer 7: Application Layer — Interfaces with applications.

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Presentation layer in osi model.

Last Updated on March 7, 2024 by Abhishek Sharma

The OSI (Open Systems Interconnection) model is a conceptual framework used to understand the functions of a telecommunication or computing system. It consists of seven layers, each responsible for specific tasks. The sixth layer, known as the Presentation Layer, plays a crucial role in ensuring that data exchanged between systems is readable and usable. Let’s explore the functions and importance of the Presentation Layer in the OSI model.

What is Presentation Layer in OSI Model?

The Presentation Layer, the sixth layer of the OSI (Open Systems Interconnection) model, is responsible for ensuring that data exchanged between systems is in a format that can be interpreted and used by the receiving system. It performs various functions, including data translation, encryption, compression, and formatting, to facilitate efficient and secure communication between networked devices.

Functions of the Presentation Layer

Below are some of the functions of the Presentation Layer in OSI Model:

Data Translation: The Presentation Layer translates data from the format used by the application layer into a format that can be transmitted over the network. This includes encoding, compression, and encryption.
Data Formatting: It ensures that data is formatted according to the specifications of the application layer. This includes converting between different character sets, such as ASCII and Unicode.
Data Compression: The Presentation Layer compresses data to reduce the amount of bandwidth required for transmission, improving network efficiency.
Data Encryption: It encrypts data to ensure that it remains secure during transmission, protecting it from unauthorized access.
Data Syntax: The Presentation Layer defines the syntax for data representation, ensuring that both the sender and receiver understand the structure of the data being exchanged.

Importance of the Presentation Layer

Importance of Presentation Layer are:

Data Integrity: By ensuring that data is formatted correctly and encrypted, the Presentation Layer helps maintain the integrity of data during transmission.
Interoperability: The Presentation Layer enables different systems to communicate with each other by ensuring that data is translated into a common format that both systems understand.
Efficiency: Data compression reduces the amount of data that needs to be transmitted, improving network efficiency and reducing bandwidth requirements.
Security: Encryption provided by the Presentation Layer ensures that data remains secure and protected from unauthorized access.

Conclusion The Presentation Layer is a crucial component of the OSI model, responsible for ensuring that data exchanged between systems is in a format that can be understood and used. By performing functions such as data translation, formatting, compression, and encryption, the Presentation Layer plays a vital role in maintaining data integrity, facilitating interoperability, and ensuring the security of data during transmission.

FAQs related to Presentation Layer in OSI Model

Here are some of the FAQs related to Presentation Layer in OSI Model:

Q1: What is the role of the Presentation Layer in the OSI model? The Presentation Layer ensures that data exchanged between systems is in a usable format, performing functions such as data translation, encryption, compression, and formatting.

Q2: How does the Presentation Layer ensure data security? The Presentation Layer encrypts data before transmission, making it unreadable to unauthorized parties, thus ensuring data security.

Q3: Why is data compression important in the Presentation Layer? Data compression reduces the size of data packets, leading to faster transmission speeds and optimized bandwidth usage, which is crucial in high-traffic networks.

Q4: How does the Presentation Layer facilitate interoperability between systems? By translating data into a common format that both sender and receiver understand, the Presentation Layer enables different systems to communicate with each other seamlessly.

Q5: Can the Presentation Layer be bypassed in data transmission? While it is possible to bypass the Presentation Layer in some cases, doing so can lead to compatibility issues between systems and is not recommended.

Presentation Layer

Last Edited

What is the Presentation Layer?

Presentation Layer is the Layer 6 of the seven-layer Open Systems Interconnection (OSI) reference model . The presentation layer structures data that is passed down from the application layer into a format suitable for network transmission. This layer is responsible for data encryption, data compression, character set conversion, interpretation of graphics commands, and so on. The network redirector also functions at this layer.

Presentation Layer functions

Translation: Before being transmitted, information in the form of characters and numbers should be changed to bit streams. Layer 6 is responsible for interoperability between encoding methods as different computers use different encoding methods. It translates data between the formats the network requires and the format the computer.
Encryption: Encryption at the transmitter and decryption at the receiver
Compression: Data compression to reduce the bandwidth of the data to be transmitted. The primary role of data compression is to reduce the number of bits to be transmitted. Multimedia files, such as audio and video, are bigger than text files and compression is more important.

Role of Presentation Layer in the OSI Model

This layer is not always used in network communications because its functions are not always necessary. Translation is only needed if different types of machines need to talk with each other. Encryption is optional in communication. If the information is public there is no need to encrypt and decrypt info. Compression is also optional. If files are small there is no need for compression.

Explaining Layer 6 in video

Most real-world protocol suites, such as TCP/IP , do not use separate presentation layer protocols. This layer is mostly an abstraction in real-world networking.

An example of a program that loosely adheres to layer 6 of OSI is the tool that manages the Hypertext Transfer Protocol (HTTP) — although it’s technically considered an application-layer protocol per the TCP/IP model.

However, HTTP includes presentation layer services within it. HTTP works when the requesting device forwards user requests passed to the web browser onto a web server elsewhere in the network.

It receives a return message from the web server that includes a multipurpose internet mail extensions (MIME) header. The MIME header indicates the type of file – text, video, or audio – that has been received so that an appropriate player utility can be used to present the file to the user.

In short, the presentation layer

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.

ensures proper formatting and delivery to and from the application layer;
performs data encryption; and
manages serialization of data objects.

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The OSI model explained and how to easily remember its 7 layers

A tutorial on the open systems interconnection networking reference model and tips on and how to memorize the seven layers.

The Open Systems Interconnect (OSI) model is a conceptual framework that describes networking or telecommunications systems as seven layers, each with its own function.

The layers help network pros visualize what is going on within their networks and can help network managers narrow down problems (is it a physical issue or something with the application?), as well as computer programmers (when developing an application, which other layers does it need to work with?). Tech vendors selling new products will often refer to the OSI model to help customers understand which layer their products work with or whether it works “across the stack”.

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.

It wasn’t always this way. Conceived in the 1970s when computer networking was taking off, two separate models were merged in 1983 and published in 1984 to create the OSI model that most people are familiar with today. Most descriptions of the OSI model go from top to bottom, with the numbers going from Layer 7 down to Layer 1. The layers, and what they represent, are as follows:

Layer 7 – Application

The Application Layer in the OSI model is the layer that is the “closest to the end user”. It receives information directly from users and displays incoming data to the user. Oddly enough, applications themselves do not reside at the application layer. Instead the layer facilitates communication through lower layers in order to establish connections with applications at the other end. Web browsers (Google Chrome, Firefox, Safari, etc.) TelNet, and FTP, are examples of communications that rely on Layer 7.

Layer 6 – Presentation

The Presentation Layer represents the area that is independent of data representation at the application layer. In general, it represents the preparation or translation of application format to network format, or from network formatting to application format. In other words, the layer “presents” data for the application or the network. A good example of this is encryption and decryption of data for secure transmission; this happens at Layer 6.

Layer 5 – Session

When two computers or other networked devices need to speak with one another, a session needs to be created, and this is done at the Session Layer . Functions at this layer involve setup, coordination (how long should a system wait for a response, for example) and termination between the applications at each end of the session.

Layer 4 – Transport

The Transport Layer deals with the coordination of the data transfer between end systems and hosts. How much data to send, at what rate, where it goes, etc. The best known example of the Transport Layer is the Transmission Control Protocol (TCP), which is built on top of the Internet Protocol (IP), commonly known as TCP/IP. TCP and UDP port numbers work at Layer 4, while IP addresses work at Layer 3, the Network Layer.

Layer 3 – Network

Here at the Network Layer is where you’ll find most of the router functionality that most networking professionals care about and love. In its most basic sense, this layer is responsible for packet forwarding, including routing through different routers . You might know that your Boston computer wants to connect to a server in California, but there are millions of different paths to take. Routers at this layer help do this efficiently.

Layer 2 – Data Link

The Data Link Layer provides node-to-node data transfer (between two directly connected nodes), and also handles error correction from the physical layer. Two sublayers exist here as well–the Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. In the networking world, most switches operate at Layer 2. But it’s not that simple. Some switches also operate at Layer 3 in order to support virtual LANs that may span more than one switch subnet, which requires routing capabilities.

Layer 1 – Physical

At the bottom of our OSI model we have the Physical Layer, which represents the electrical and physical representation of the system. This can include everything from the cable type, radio frequency link (as in a Wi-Fi network), as well as the layout of pins, voltages, and other physical requirements. When a networking problem occurs, many networking pros go right to the physical layer to check that all of the cables are properly connected and that the power plug hasn’t been pulled from the router, switch or computer, for example.

Why you need to know the 7 OSI layers

Most people in IT will likely need to know about the different layers when they’re going for their certifications, much like a civics student needs to learn about the three branches of the US government. After that, you hear about the OSI model when vendors are making pitches about which layers their products work with.

In a Quora post asking about the purpose of the OSI model, Vikram Kumar answered this way:

“The purpose of the OSI reference model is to guide vendors and developers so the digital communication products and software programs they create will interoperate, and to facilitate clear comparisons among communications tools.”

While some people may argue that the OSI model is obsolete (due to its conceptual nature) and less important than the four layers of the TCP/IP model, Kumar says that “it is difficult to read about networking technology today without seeing references to the OSI model and its layers, because the model’s structure helps to frame discussions of protocols and contrast various technologies.”

If you can understand the OSI model and its layers, you can also then understand which protocols and devices can interoperate with each other when new technologies are developed and explained.

The OSI model remains relevant

In a post on GeeksforGeeks, contributor Vabhav Bilotia argues several reasons why the OSI model remains relevant, especially when it comes to security and determining where technical risks and vulnerabilities may exist.

For example, by understanding the different layers, enterprise security teams can identify and classify physical access, where the data is sitting, and provide an inventory of the applications that employees use to access data and resources.

“Knowing where the majority of your company’s data is held, whether on-premises or in cloud services, will help define your information security policy,” writes Bilotia. “You can invest in the correct solutions that provide you data visibility within the proper OSI layers once you have this knowledge.”

In addition, the OSI model can be used to understand cloud infrastructure migrations, particularly when it comes to securing data within the cloud.

And because the model has been around for so long and understood by so many, the uniform vocabulary and terms helps networking professionals understand quickly about the components of the networking system “While this paradigm is not directly implemented in today’s TCP/IP networks, it is a useful conceptual model for relating multiple technologies to one another and implementing the appropriate technology in the appropriate way,” Bilotia writes. We couldn’t agree more.

How to remember the OSI Model 7 layers – 8 mnemonic tricks

If you need to memorize the layers for a college or certification test, here are a few sentences to help remember them in order. The first letter of each word is the same as the first letter an OSI layer.

From Application to Physical (Layer 7 to Layer 1):

All People Seem To Need Data Processing
All Pros Search Top Notch Donut Places
A Penguin Said That Nobody Drinks Pepsi
A Priest Saw Two Nuns Doing Pushups

From Physical to Application (Layer 1 to Layer 7):

Please Do Not Throw Sausage Pizza Away
Pew! Dead Ninja Turtles Smell Particularly Awful
People Don’t Need To See Paula Abdul
Pete Doesn’t Need To Sell Pickles Anymore

Keith Shaw was a Network World editor and the writer of the Cool Tools column. He is now a freelance writer and editor from Worcester, Mass.

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OSI Presentation and Application Layers

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Paul D. Bartoli 3

Part of the book series: Applications of Communications Theory ((ACTH))

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This chapter discusses the Application and Presentation Layers of the Reference Model of Open Systems Interconnection (OSI) [1]. The Application and Presentation Layers perform functions necessary to exchange information between application processes; the Application Layer is concerned with the semantic aspects of the information exchange, while the Presentation Layer is concerned with the syntactic aspects. The ability to manage the semantic and syntactic elements of the information to be exchanged is key to ensuring that the information can be interpreted by the communicants.

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ISO 7498, “Information processing systems—Open Systems Interconnection—Basic Reference Model,” 1984. CCITT Recommendation X.200, “Reference model of open systems interconnection for CCITT applications,” 1984 (updated expected in 1988).

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ISO 8571, “Information processing systems—Open systems interconnection—File transfer, access, and management,” Parts 1–4, 1988.

ISO/DIS 9804, “Information processing systems”Open systems interconnection—Service definition for commitment, concurrency, and recovery,” 1988 (text in SC 21 N 2573, March, 1988). ISO DIS 9805, “Information processing systems—Open systems interconnection—Protocol specification for commitment, concurrency, and recovery,” 1988 (text in SC 21 N 2574, March, 1988). CCITT Recommendation X.237, “Commitment, concurrency, and recovery service definition,” Draft Text, 1988. CCITT Recommendation X.247, “Commitment, concurrency, and recovery protocol specification, Draft Text, 1988.

ISO DIS 9040, “Information processing systems—Open systems interconnection—Virtual terminal service—Basic class,” 1988 (text in SC 21 N 2615, March, 1988). ISO DIS 9041, “Information processing systems—Open systems interconnection—Virtual terminal protocol—Basic class,” 1988 (text in SC 21 N 2616, March, 1988).

ISO DIS 9066–1, “Reliable transfer service”, 1988 (text in SC 18 N 1408, March, 1988). ISO DIS 9066–2, “Reliable transfer protocol specification,” 1988 (text in SC 18 N 1409). CCITT Recommendation X.218, “Reliable transfer: Model and service definition,” 1988. CCITT Recommendation X.228, “Reliable transfer: Protocol specification,” 1988.

ISO DIS 9072–1, “Remote operations service,” 1988 (text in SC 18 N 1410, March, 1988). ISO DIS 9072–2, “Remote operations protocol specification,” 1988 (text in SC 18 N 1411, March, 1988). CCITT Recommendation X.219, “Remote operations: Model, notation, and service definition,” 1988. CCITT Recommendation X.229, “Remote operations: Protocol specification,” 1988.

ISO DIS 9594, “Information processing—Open systems interconnection—The directory,” parts 1–8, 1988 (text in SC 21 N 2751 through N 2758, April, 1988). CCITT X.500, “Series recommendations on directory,” November, 1987.

ISO DIS 10021, “Information processing—Text communication—Message oriented text interchange system,” 1988 (text in SC 18 N 1487 through N 1493, May, 1988). CCITT X.400, “Series recommendations for message handling systems,” 1988.

ISO 8613/1–8, “Office document architecture and interchange format,” 1988, awaiting publication. CCITT T.400, “Series recommendations for document architecture, transfer, and manipulation,” 1988.

ISO 8824, “Information processing systems—Open systems interconnection—Specification of abstract syntax notation one (ASN.1),” 1987; and ISO 8824/PDAD 1, “Information processing systems—Open systems interconnection—Specification for ASN.1: Proposed draft Addendum 1 on ASN.1 extensions,” 1988 (final text in SC 21 N 2341 Revised, April, 1988). CCITT Recommendation X.208, “Specification of abstract syntax notation one (ASN.1),” 1988.

ISO 8822, “Information processing systems—Open systems interconnection—Connection oriented presentation service definition,” 1988. CCITT Recommendation X.216, “Presentation service definition for open systems interconnection for CCITT applications,” 1988.

ISO 8825, “Information processing—Open systems interconnection—Specification of basic encoding rules for abstract syntax notation one (ASN.1),” 1987; and ISO 8825/ PDAD 1, “Information processing systems—Open systems interconnection—Specification of basic encoding rules for ASN.1: Proposed draft addendum 1 on ASN.1 extensions,” 1988 (text in SC 21 N 2342 Revised, April, 1988). CCITT Recommendation X.209, “Specification of basic encoding rules for abstract syntax notation one (ASN.1),” 1988.

ISO 8823, “Information processing systems—Open systems interconnection—Connection oriented presentation protocol specification,” 1988. CCITT Recommendation X.226, “Presentation protocol specification for open systems interconnection for CCITT applications,” 1988.

ISO 8326, “Information processing systems—Open systems interconnection—Basic connection oriented session service definition,” 1987; and ISO 8326/AD 2, “Information processing systems—Open systems interconnection—Basic connection oriented session service definition—Addendum 2: Incorporation of unlimited user data,” 1988. ISO 8327, “Information processing systems—Open systems interconnection—Basic connection oriented session protocol specification,” 1987; and ISO 8327/AD 2, “Information processing systems—Open systems interconnection—Basic connection oriented session protocol specification—Addendum 2: Unlimited session user data protocol specification,” 1988.

CCITT Recommendation X.215, “Session service definition for open systems interconnection for CCITT applications,” 1988. CCITT Recommendation X.225, “Session protocol specification for open systems interconnection for CCITT applications,” 1988.

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Bartoli, P.D. (1989). OSI Presentation and Application Layers. In: Sunshine, C.A. (eds) Computer Network Architectures and Protocols. Applications of Communications Theory. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-0809-6_13

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What is the OSI Model?

Explanation, layers, and data flows in the Open Systems Interconnection model.

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OSI Model Explained

The Open Systems Interconnection (OSI) model is a framework that describes the functions of a networking system. The OSI model categorizes the computing functions of the different network components, outlining the rules and requirement needed to support the interoperability of the software and hardware that make up the network.

In addition to understanding what the OSI model is, note that the OSI model layers are particularly helpful when visualizing the flow of data from the sender to the receiver. The descriptions of the various levels, as well as their interdependency, make it easier to pinpoint networking issues. Also, programmers can use the OSI model to better understand how data gets to and from their applications or to write code specific for use at certain levels.

In the following sections, you will see the OSI model explained.

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What Are the 7 Layers of the OSI Model?

There are seven abstraction layers that make up the OSI model. Communication from one person to another goes from Layer 7 to Layer 1. Each layer performs a specific job before it sends the data on to the next layer.

Layer 7 - Application layer

The application layer is the closest to the end-user. It initiates communication between the user and the applications they personally interact with. At this layer, data is translated from the syntax it was converted to into something the user can read.

Examples of Layer 7 applications include a web browser like Chrome, Safari, or Firefox, or an email application. Layer 7 can also identify communication partners, check to see which resources are available, and make sure communication is properly synced.

Layer 6 - Presentation layer

The presentation layer takes care of getting data ready for the application layer. The two devices that are communicating may use different methods of encoding their data. Layer 6 therefore turns the incoming data into something that can be read at the application layer. This includes encrypting and decrypting data.

The presentation layer also compresses data that comes from the application layer before it sends it on to Layer 5, the session layer.

Layer 5 - Session layer

The session layer handles opening and closing network communications between two interacting devices. The “session” refers to the time between the opening and closing of the interaction. The session layer makes sure the session is open for a long enough period of time for all the necessary data to be sent through. The session layer then closes the session to prevent expending unnecessary resources.

Also, it synchronizes the data transfer. If a large amount of data is being sent, the session layer can set up checkpoints. If the transmission gets interrupted before all the data is downloaded, the checkpoints allow the transmission to be resumed without it starting all over again.

Layer 4 - Transport layer

The transport layer handles end-to-end communication between the devices interacting with each other. The management of the communication involves taking the data in the session layer and dividing it into pieces referred to as segments. The transport layer on the device receiving the communication handles the reassembly of the segments into data that is consumable by the session layer.

Also, the transport layer takes care of managing the flow and any necessary error messages that need to be sent in the event something goes wrong. To manage data flow, the transport layer makes sure it is not being sent so quickly that the receiver’s device cannot handle it. To control errors, the transport layer checks to see if the data transmitted was done so completely. If it is not, this layer will request a retransmission.

Layer 4 is where Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) port numbers work. Internet Protocol (IP) addresses operate at Layer 3, the network layer. TCP, UDP, and IP are protocols that facilitate how data is sent and received.

Layer 3 - Network layer

The network layer facilitates the transfer of data when two networks are communicating with each other. If two communicating devices are using the same network, then there is no need for the network layer. The network layer divides the segments that come from the transport layer. These are referred to as packets. The division of the segments into packets happens on the sender’s device, and they are reassembled on the receiving device.

The network layer also functions as an efficiency tool. It figures out the optimal physical path needed to get the data to its destination. This function is called “routing.”

Layer 2 - Data link layer

The data link layer is like the network layer, except that the data link layer facilitates data transfer between two devices using the same network. In the data link layer, packets are broken into pieces referred to as frames. Similar to the network layer, the data link layer handles flow and error control. The transport layer is different in that it only manages the flow of data and errors when two networks are communicating with each other.

Within the data link layer, you have two sublayers, the media access control (MAC) and logical link control (LLC) layers. The majority of switches perform their duties at Layer 2. In some cases, switches work at Layer 3 because they are facilitating communication between two networks or virtual local-area networks (VLANs). This has to happen at Layer 3 because, in these situations, the data needs to be routed, which is a Layer 3 task.

Layer 1 - Physical layer

The physical layer involves the physical equipment that transfers data, like switches and cables. In this layer, the data is converted into strings of 1s and 0s. In the physical layer, the devices have to agree on a method of distinguishing the 1s from the 0s, which enables the digital data to be properly interpreted by each device.

The physical layer includes a variety of components, such as cables, the radio frequency used to transmit data, Wi-Fi, and the other physical structures for transmitting data, such as pins, necessary voltages, and types of ports.

How Data Flows through OSI Model Layers

Each of the seven OSI model layers communicates with layers below and above it. For example, the application layer interacts with software applications, while the presentation layer provides encryption and data compression. Likewise, the session layer creates communications between devices. The transport layer breaks data into chunks (called segments) to send them, then the receiving device reassembles the segments before the network layer breaks them into smaller packets to send to other networks. The data link layer facilitates data transfer between devices on the same network, and, finally, the physical layer transfers data in machine language (ones and zeros).

Frequently Asked Questions about OSI Model

What is osi model, why do we use the osi model.

OSI model layers are particularly helpful when visualizing the flow of data from the sender to the receiver. The descriptions of the various levels, as well as their interdependency, make it easier to pinpoint networking issues.

What are 7 layers of the OSI model?

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Transport Layer
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What is OSI Model? – Layers of OSI Model

OSI stands for Open Systems Interconnection , where open stands to say non-proprietary. It is a 7-layer architecture with each layer having specific functionality to perform. All these 7 layers work collaboratively to transmit the data from one person to another across the globe. The OSI reference model was developed by ISO – ‘International Organization for Standardization ‘, in the year 1984.

The OSI model provides a theoretical foundation for understanding network communication . However, it is usually not directly implemented in its entirety in real-world networking hardware or software . Instead, specific protocols and technologies are often designed based on the principles outlined in the OSI model to facilitate efficient data transmission and networking operations.

Prerequisite: Basics of Computer Networking

What is OSI Model?

What are the 7 layers of the osi model, physical layer – layer 1, data link layer (dll) – layer 2, network layer – layer 3, transport layer – layer 4, session layer – layer 5, presentation layer – layer 6, application layer – layer 7, what is the flow of data in osi model, advantages of osi model.

OSI Model in a Nutshell

OSI vs TCP/IP Model

The OSI model, created in 1984 by ISO , is a reference framework that explains the process of transmitting data between computers. It is divided into seven layers that work together to carry out specialised network functions , allowing for a more systematic approach to networking.

Table diagram of the OSI model illustrating communication between sender and receiver and the addition of headers to the transmitted data

The OSI model consists of seven abstraction layers arranged in a top-down order:

Physical Layer
Session Layer
Presentation Layer

The lowest layer of the OSI reference model is the physical layer. It is responsible for the actual physical connection between the devices. The physical layer contains information in the form of bits. It is responsible for transmitting individual bits from one node to the next. When receiving data, this layer will get the signal received and convert it into 0s and 1s and send them to the Data Link layer, which will put the frame back together.

Functions of the Physical Layer

Bit synchronization: The physical layer provides the synchronization of the bits by providing a clock. This clock controls both sender and receiver thus providing synchronization at the bit level.
Bit rate control: The Physical layer also defines the transmission rate i.e. the number of bits sent per second.
Physical topologies: Physical layer specifies how the different, devices/nodes are arranged in a network i.e. bus, star, or mesh topology.
Transmission mode: Physical layer also defines how the data flows between the two connected devices. The various transmission modes possible are Simplex, half-duplex and full-duplex.

Note: Hub, Repeater, Modem, and Cables are Physical Layer devices. Network Layer, Data Link Layer, and Physical Layer are also known as Lower Layers or Hardware Layers .

The data link layer is responsible for the node-to-node delivery of the message. The main function of this layer is to make sure data transfer is error-free from one node to another, over the physical layer. When a packet arrives in a network, it is the responsibility of the DLL to transmit it to the Host using its MAC address . The Data Link Layer is divided into two sublayers:

Logical Link Control (LLC)
Media Access Control (MAC)

The packet received from the Network layer is further divided into frames depending on the frame size of the NIC(Network Interface Card). DLL also encapsulates Sender and Receiver’s MAC address in the header.

The Receiver’s MAC address is obtained by placing an ARP(Address Resolution Protocol) request onto the wire asking “Who has that IP address?” and the destination host will reply with its MAC address.

Functions of the Data Link Layer

Framing: Framing is a function of the data link layer. It provides a way for a sender to transmit a set of bits that are meaningful to the receiver. This can be accomplished by attaching special bit patterns to the beginning and end of the frame.
Physical addressing: After creating frames, the Data link layer adds physical addresses ( MAC addresses ) of the sender and/or receiver in the header of each frame.
Error control: The data link layer provides the mechanism of error control in which it detects and retransmits damaged or lost frames.
Flow Control: The data rate must be constant on both sides else the data may get corrupted thus, flow control coordinates the amount of data that can be sent before receiving an acknowledgment.
Access control: When a single communication channel is shared by multiple devices, the MAC sub-layer of the data link layer helps to determine which device has control over the channel at a given time.

Note: Packet in the Data Link layer is referred to as Frame. Data Link layer is handled by the NIC (Network Interface Card) and device drivers of host machines. Switch & Bridge are Data Link Layer devices.

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.

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.

Note: Segment in the Network layer is referred to as Packet . Network layer is implemented by networking devices such as routers and switches.

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.

Note: The sender needs to know the port number associated with the receiver’s application. Generally, this destination port number is configured, either by default or manually. For example, when a web application requests a web server, it typically uses port number 80, because this is the default port assigned to web applications. Many applications have default ports assigned. 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.

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

1. Connection-Oriented Service: It is a three-phase process that includes

Connection Establishment
Data Transfer
Termination/disconnection

In this type of transmission, the receiving device sends an acknowledgment, back to the source after a packet or group of packets is received. This type of transmission is reliable and secure.

2. 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.

Note: Data in the Transport Layer is called Segments . Transport layer is operated by the Operating System. It is a part of the OS and communicates with the Application Layer by making system calls. The transport layer is called as Heart of the OSI model. Device or Protocol Use : TCP, UDP NetBIOS, PPTP

This layer is responsible for the establishment of connection, maintenance of sessions, and authentication, and also ensures security.

Functions of the Session Layer

Session establishment, maintenance, and termination: The layer allows the two processes to establish, use, and terminate a connection.
Synchronization: This layer allows a process to add checkpoints that are considered synchronization points in the data. These synchronization points help to identify the error so that the data is re-synchronized properly, and ends of the messages are not cut prematurely and data loss is avoided.
Dialog Controller: The session layer allows two systems to start communication with each other in half-duplex or full-duplex.

Note: All the below 3 layers(including Session Layer) are integrated as a single layer in the TCP/IP model as the “Application Layer”. Implementation of these 3 layers is done by the network application itself. These are also known as Upper Layers or Software Layers. Device or Protocol Use : NetBIOS, PPTP.

For example:-

Let us consider a scenario where a user wants to send a message through some Messenger application running in their browser. The “ Messenger ” here acts as the application layer which provides the user with an interface to create the data. This message or so-called Data is compressed, optionally encrypted (if the data is sensitive), and converted into bits (0’s and 1’s) so that it can be transmitted.

Communication in Session Layer

The 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.

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

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.

Note: 1. The application Layer is also called Desktop Layer. 2. Device or Protocol Use : SMTP

Functions of the Application Layer

The main functions of the application layer are given below.

Network Virtual Terminal(NVT) : It allows a user to log on to a remote host.
File transfer access and management(FTAM): This application allows a user to access files in a remote host, retrieve files in a remote host, and manage or control files from a remote computer.
Mail Services: Provide email service.
Directory Services: This application provides distributed database sources and access for global information about various objects and services.

Note: The OSI model acts as a reference model and is not implemented on the Internet because of its late invention. The current model being used is the TCP/IP model.

When we transfer information from one device to another, it travels through 7 layers of OSI model. First data travels down through 7 layers from the sender’s end and then climbs back 7 layers on the receiver’s end.

Let’s look at it with an Example:

Luffy sends an e-mail to his friend Zoro.

Step 1: Luffy interacts with e-mail application like Gmail , outlook , etc. Writes his email to send. (This happens in Layer 7: Application layer )

Step 2: Mail application prepares for data transmission like encrypting data and formatting it for transmission. (This happens in Layer 6: Presentation Layer )

Step 3: There is a connection established between the sender and receiver on the internet. (This happens in Layer 5: Session Layer )

Step 4: Email data is broken into smaller segments. It adds sequence number and error-checking information to maintain the reliability of the information. (This happens in Layer 4: Transport Layer )

Step 5: Addressing of packets is done in order to find the best route for transfer. (This happens in Layer 3: Network Layer )

Step 6: Data packets are encapsulated into frames, then MAC address is added for local devices and then it checks for error using error detection. (This happens in Layer 2: Data Link Layer )

Step 7: Lastly Frames are transmitted in the form of electrical/ optical signals over a physical network medium like ethernet cable or WiFi.

After the email reaches the receiver i.e. Zoro, the process will reverse and decrypt the e-mail content. At last, the email will be shown on Zoro’s email client.

The OSI Model defines the communication of a computing system into 7 different layers. Its advantages include:

It divides network communication into 7 layers which makes it easier to understand and troubleshoot.
It standardizes network communications, as each layer has fixed functions and protocols.
Diagnosing network problems is easier with the OSI model .
It is easier to improve with advancements as each layer can get updates separately.

OSI Model – Layer architecture

Some key differences between the OSI model and the TCP/IP Model are:

TCP/IP model consists of 4 layers but OSI model has 7 layers. Layers 5,6,7 of the OSI model are combined into the Application Layer of TCP/IP model and OSI layers 1 and 2 are combined into Network Access Layers of TCP/IP protocol.
The TCP/IP model is older than the OSI model, hence it is a foundational protocol that defines how should data be transferred online.
Compared to the OSI model, the TCP/IP model has less strict layer boundaries.
All layers of the TCP/IP model are needed for data transmission but in the OSI model, some applications can skip certain layers. Only layers 1,2 and 3 of the OSI model are necessary for data transmission.

Did you Know? TCP/IP protocol ( Transfer Control Protocol/Internet Protocol ) was created by U.S. Department of Defense’s Advanced Research Projects Agency (ARPA) in 1970s.

We have discussed about What is OSI model?, What are layers of OSI model, How data flows in the 7 layers of OSI model, and the differences between TCP/IP protocol and OSI protocol.

What is OSI Model? – FAQs

Is osi layer still used.

Yes, the OSI model is still used by networking professionals to understand data abstraction paths and processes better.

What is the highest layer of the OSI model?

Layer 7 or Application layer is highest layer of OSI model.

What is layer 8?

Layer 8 doesn’t actually exist in the OSI model but is often jokingly used to refer to the end user. For example: a layer 8 error would be a user error.

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What is the presentation layer in the OSI model?

The presentation layer is the sixth layer in the OSI model and is responsible for converting different file formats. This allows two systems to communicate. Other tasks carried out by the sixth layer include data compression and encryption.

What is the presentation layer?

What does the presentation layer do, which format does the presentation layer use, presentation layer protocols, skipping the presentation layer.

The presentation layer is the sixth layer of the OSI model. It is primarily used to convert different file formats between the sender and the receiver . The OSI model is a reference model that is used to define communication standards between two devices within a network . The development of this standard began in the 1970s and it was officially published at the beginning of the following decade. This standard enables seamless interaction between different technical systems.

The model is made up of a total of seven different layers, all having their own clearly defined tasks. While there are clear boundaries between the layers, the layers interact with each other, with each layer building off the one below it. The different layers are as follows:

Physical layer
Data link layer
Network layer
Transport layer
Session layer
Presentation layer
Application layer

The presentation layer interacts closely with the application layer, which is located directly above it. The presentation layer’s main task is to present data in such a way that it can be understood and interpreted from both the system sending the data and the system receiving it. After this has been accomplished, the application layer then determines how the data should be structured and what sort of data and values are permissible.

Using these entries, a command set or an abstract transfer syntax is then automatically created. The presentation layer now has the task of transferring the data in such a way that it is readable without changing the information contained within it.

The presentation layer is often also responsible for the encryption and decryption of data . The information is first encrypted on the sender’s side and then sent to the receiver in an encrypted state. Keys and encryption methods are then exchanged in the presentation layer. The recipient is then able to decrypt the unreadable data and convert it into a format that can be understood and interpreted.

If data is shown during a transfer, we often use the term transfer syntax. These are separated into the abstract transfer syntax , in which the transferred values are written, and the concrete syntax, which contains a definition of the value coding.

The receiver can only process and understand the data they receive if they receive all of the information from the presentation layer. The most common definition language is Abstract Syntax Notation One (ASN.1) , which is also recommended by the ISO. The ISO is an organisation that is responsible for developing international standards in technology, management and manufacturing.

The presentation layer has many different formats. The most common text formats are the ASCII (American Standard Code for Information Interchange) and EBCDIC (Extended Binary-Coded Decimal Interchange Code). The most common image formats are GIF, JPEG and TIFF. Widely used video formats include MIDI, MPEG and QuickTime.

There are many different presentation layer protocols as well as transfer and encryption technologies in the presentation layer. These include:

The tasks which are carried out by the presentation layer are not always necessary for communication between two systems. In instances where both systems use the same formats, data conversion is not necessary. Additionally, encryption and compression are not required for every interaction and can also be carried out in another layer of the OSI model. If this is the case, the presentation layer can be skipped and the application layer (7) can communicate directly with the session layer (5) instead .

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Three-tier architecture is a well-established software application architecture that organizes applications into three logical and physical computing tiers: the presentation tier, or user interface; the application tier, where data is processed; and the data tier, where application data is stored and managed.

The chief benefit of three-tier architecture is that because each tier runs on its own infrastructure, each tier can be developed simultaneously by a separate development team. And can be updated or scaled as needed without impacting the other tiers.

For decades three-tier architecture was the prevailing architecture for client-server applications. Today, most three-tier applications are targets for modernization that uses cloud-native technologies such as containers and microservices and for migration to the cloud.

Connect and integrate your systems to prepare your infrastructure for AI.

Presentation tier

The presentation tier is the user interface and communication layer of the application, where the end user interacts with the application. Its main purpose is to display information to and collect information from the user. This top-level tier can run on a web browser, as desktop application, or a graphical user interface (GUI), for example. Web presentation tiers are developed by using HTML, CSS, and JavaScript. Desktop applications can be written in various languages depending on the platform.

Application tier

The application tier, also known as the logic tier or middle tier, is the heart of the application. In this tier, information that is collected in the presentation tier is processed - sometimes against other information in the data tier - using business logic, a specific set of business rules. The application tier can also add, delete, or modify data in the data tier.

The application tier is typically developed by using Python, Java, Perl, PHP or Ruby, and communicates with the data tier by using API calls.

The data tier, sometimes called database tier, data access tier or back-end, is where the information that is processed by the application is stored and managed. This can be a relational database management system such as PostgreSQL , MySQL, MariaDB, Oracle, Db2, Informix or Microsoft SQL Server, or in a NoSQL Database server such as Cassandra, CouchDB , or MongoDB .

In a three-tier application, all communication goes through the application tier. The presentation tier and the data tier cannot communicate directly with one another.

Tier versus layer

In discussions of three-tier architecture, layer is often used interchangeably – and mistakenly – for tier , as in 'presentation layer' or 'business logic layer'.

They aren't the same. A 'layer' refers to a functional division of the software, but a 'tier' refers to a functional division of the software that runs on infrastructure separate from the other divisions. The Contacts app on your phone, for example, is a three - layer application, but a single-tier application, because all three layers run on your phone.

The difference is important because layers can't offer the same benefits as tiers.

Again, the chief benefit of three-tier architecture is its logical and physical separation of functionality. Each tier can run on a separate operating system and server platform - for example, web server, application server, database server - that best fits its functional requirements. And each tier runs on at least one dedicated server hardware or virtual server, so the services of each tier can be customized and optimized without impacting the other tiers.

Other benefits (compared to single- or two-tier architecture) include:

Faster development : Because each tier can be developed simultaneously by different teams, an organization can bring the application to market faster. And programmers can use the latest and best languages and tools for each tier.
Improved scalability : Any tier can be scaled independently of the others as needed.
Improved reliability : An outage in one tier is less likely to impact the availability or performance of the other tiers.
Improved security : Because the presentation tier and data tier can't communicate directly, a well-designed application tier can function as an internal firewall, preventing SQL injections and other malicious exploits.

In web development, the tiers have different names but perform similar functions:

The web server is the presentation tier and provides the user interface. This is usually a web page or website, such as an ecommerce site where the user adds products to the shopping cart, adds payment details or creates an account. The content can be static or dynamic, and is developed using HTML, CSS, and JavaScript.
The application server corresponds to the middle tier, housing the business logic that is used to process user inputs. To continue the ecommerce example, this is the tier that queries the inventory database to return product availability, or adds details to a customer's profile. This layer often developed using Python, Ruby, or PHP and runs a framework such as Django, Rails, Symphony, or ASP.NET.
The database server is the data or backend tier of a web application. It runs on database management software, such as MySQL, Oracle, DB2, or PostgreSQL.

While three-tier architecture is easily the most widely adopted multitier application architecture, there are others that you might encounter in your work or your research.

Two-tier architecture

Two-tier architecture is the original client-server architecture, consisting of a presentation tier and a data tier; the business logic lives in the presentation tier, the data tier or both. In two-tier architecture the presentation tier - and therefore the end user - has direct access to the data tier, and the business logic is often limited. A simple contact management application, where users can enter and retrieve contact data, is an example of a two-tier application.

N-tier architecture

N-tier architecture - also called or multitier architecture - refers to any application architecture with more than one tier. But applications with more than three layers are rare because extra layers offer few benefits and can make the application slower, harder to manage and more expensive to run. As a result, n-tier architecture and multitier architecture are usually synonyms for three-tier architecture.

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Presentation Layer in OSI model
Prerequisite : OSI Model Introduction : 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.
Presentation layer
The presentation layer ensures the information that the application layer of one system sends out is readable by the application layer of another system. On the sending system it is responsible for conversion to standard, transmittable formats. [7] On the receiving system it is responsible for the translation, formatting, and delivery of ...
Presentation Layer
OSI Layer 6 - Presentation Layer. The presentation layer is responsible for the delivery and formatting of information to the application layer for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems. An example of a presentation service ...
The OSI Model
Chloe Tucker. This article explains the Open Systems Interconnection (OSI) model and the 7 layers of networking, in plain English. The OSI model is a conceptual framework that is used to describe how a network functions. In plain English, the OSI model helped standardize the way computer systems send information to each other.
What is presentation layer?
What is the presentation layer? The presentation layer resides at Layer 6 of the Open Systems Interconnection communications model and ensures that communications that pass through it are in the appropriate form for the recipient application.In other words, the presentation layer presents the data in a readable format from an application layer perspective.
The OSI Model's 7 Layers Explained
The seven layers in the Open Systems Interconnection (OSI) model each serve a specific function and work together to create an efficient network communication system. Written by Andrei Neacsu. Published on Dec. 08, 2023 ... The Presentation Layer may encrypt the data for security, while the Data Link Layer ensures it is formatted into frames ...
Presentation Layer in OSI Model
The Presentation Layer is a crucial component of the OSI model, responsible for ensuring that data exchanged between systems is in a format that can be understood and used. By performing functions such as data translation, formatting, compression, and encryption, the Presentation Layer plays a vital role in maintaining data integrity ...
Presentation Layer
Presentation Layer is the Layer 6 of the seven-layer Open Systems Interconnection (OSI) reference model. The presentation layer structures data that is passed down from the application layer into a format suitable for network transmission. This layer is responsible for data encryption, data compression, character set conversion, interpretation ...
What is Presentation Layer in the OSI Model?
Key functions of the Presentation Layer in the OSI model include: Data Encryption: It securely encrypts data to prevent unauthorized access during transmission. Data Compression: It reduces data ...
OSI Model
1. Overview. The OSI model stands for Open Systems Interconnection model and is a standardized framework that describes a networking system's communication functions. It consists of 7 layers, and each layer has specific functionality to perform. In this tutorial, we'll discuss the OSI model and its layers in detail.
Presentation Layer of the OSI Model
The presentation layer is a very important layer because it handles encryption, decryption, and the conversion of complex data into flat-byte strings, a format that is easily transmittable. The ...
OSI model
1. Physical layer. v. t. e. The Open Systems Interconnection ( OSI) model is a reference model from the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." [2] In the OSI reference model, the communications between systems ...
The OSI model explained and how to easily remember its 7 layers
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. It wasn't always this way ...
PDF 13 OSI Presentation and Application Layers
II. The Application Layer This section discusses the underlying assumptions and viewpoint that led to the development of the OSI Application Layer. The general structure of the Application Layer is presented [2]. This model describes how the Application and Presentation Layers cooperate to support the exchange of
What is the OSI Model? 7 Network Layers Explained
OSI Model Explained. The Open Systems Interconnection (OSI) model is a framework that describes the functions of a networking system. The OSI model categorizes the computing functions of the different network components, outlining the rules and requirement needed to support the interoperability of the software and hardware that make up the ...
What is OSI Model
The Open Systems Interconnection (OSI) model describes seven layers that computer systems use to communicate over a network. It was the first standard model for network communications, adopted by all major computer and telecommunication companies in the early 1980s. ... Presentation Layer - Layer 6. The presentation layer is also called the ...
What is the presentation layer?
The presentation layer interacts closely with the application layer, which is located directly above it. The presentation layer's main task is to present data in such a way that it can be understood and interpreted from both the system sending the data and the system receiving it. After this has been accomplished, the application layer then determines how the data should be structured and ...
OSI model (Open Systems Interconnection)
OSI (Open Systems Interconnection) is a reference model for how applications communicate over a network. This model focuses on providing a visual design of how each communications layer is built on top of the other, starting with the physical cabling, all the way to the application that's trying to communicate with other devices on a network.
Unveiling the Interpreter: Fortifying the Presentation Layer's Role in
Welcome back to Tea with C. As we navigate deeper into the OSI model, today's spotlight shines on Layer 6: the Presentation Layer. The Presentation Layer, often likened to an adept interpreter in the digital realm, plays a pivotal role in the seamless transmission and reception of data across the network. At its essence, the Presentation ...
Lec 10: Transport layer, Session Layer, and Presentation Layer
The Transport Layer's primary functions are: - To enable efficient network transmission, the Transport Layer splits the data it receives from the applications running at the higher layers into ...
Presentation Layer in OSI Model
Independent Computing Architecture (ICA): It is a presentation layer protocol in the OSI model, which was formed by Citrix Systems. It is used for transferring data from server to client. It is a very thin protocol as it does not require much overhead in order to transmit data from the server over to the client. It is well-optimized for the WAN.
Multitier architecture
Multitier architecture. In software engineering, multitier architecture (often referred to as n-tier architecture) is a client-server architecture in which presentation, application processing and data management functions are physically separated. The most widespread use of multitier architecture is the three-tier architecture .
What Is Three-Tier Architecture?
For decades three-tier architecture was the prevailing architecture for client-server applications. Today, most three-tier applications are targets for modernization that uses cloud-native technologies such as containers and microservices and for migration to the cloud. Connect and integrate your systems to prepare your infrastructure for AI.

Layer 6 Presentation Layer

OSI Layer 6 - Presentation Layer

CASE common application service element

The OSI Model – The 7 Layers of Networking Explained in Plain English

Prerequisites

Learning Objectives

Common Networking Terms

What is the OSI Model?

OSI Layer 1

How to Troubleshoot OSI Layer 1 Problems

OSI Layer 2

How to Troubleshoot OSI Layer 2 Problems

OSI Layer 3

How to Troubleshoot OSI Layer 3 Problems

OSI Layer 4

How to Troubleshoot OSI Layer 4 Problems

OSI Layer 5

How to Troubleshoot OSI Layer 5 Problems

OSI Layer 6

How to Troubleshoot OSI Layer 6 Problems

OSI Layer 7

How to Troubleshoot OSI Layer 7 Problems

Learning Resources

The OSI Model’s 7 Layers, Explained

What Is the OSI Model?

The 7 Layers of the OSI Model

Layer 7: Application Layer

Layer 6: Presentation Layer

Layer 5: Session Layer

Layer 4: Transport Layer

Layer 3: Network Layer

Layer 2: Data Link Layer

Layer 1: Physical Layer

How Data Flows in the OSI Model

Encapsulation Process

Data Transmission Across the Network

Decapsulation Process

Seamless Data Flow

OSI Model Advantages

Simplification of network design

Standardization and interoperability

Flexibility and Scalability

Enhanced Security

Real-World Applications of the OSI Model

Network Design and Protocol Development

Efficient Troubleshooting and Management

Cybersecurity Strategy

Educational and Training Tool

OSI Model vs. TCP/IP Model

Structural Differences

Theoretical vs. Practical Approach

Adoption and Use

Frequently Asked Questions

What are the 7 layers of the OSI model?

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What is Presentation Layer in OSI Model?

Functions of the Presentation Layer

Importance of the Presentation Layer

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The OSI model explained and how to easily remember its 7 layers

The 7 layers of the OSI model

Layer 7 – Application

Layer 6 – Presentation

Layer 5 – Session

Layer 4 – Transport

Layer 3 – Network

Layer 2 – Data Link

Layer 1 – Physical