what are the 3 functions of presentation layer

  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.

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Home » Computer Network

Presentation Layer: What It Is, Design Issues, Functionalities

Description and Functions of Presentation Layer in the OSI model: In this tutorial, we are going to learn what the Presentation layer is and the Functions of the Presentation Layer in the OSI model in Computer Networking. We will also discuss the Design issues with the Presentation Layer and the working of the Presentation Layer with the help of its diagram. By Monika Jha Last updated : May 05, 2023

What is Presentation Layer?

The Presentation Layer is concerned with the syntax and semantics of the information exchanged between two communicating devices.

• The presentation layer takes care that the data is sent in that way the receiver of the data will understand the information (data) and will be able to use the data.
• Languages that are syntax can be different from the two communicating machines. In this condition, the presentation layer plays the role of translator between them.
• It is possible for two machines to communicate with different data representations, data structures to be exchanged can be defined in an abstract way.
• These abstract data structures will be managed by the presentation layer and this layer allows higher-level data structures (For example banking records), to be defined and exchanged.

This figure shows the relationship of the presentation layer to the session layer and application layer.

Design Issues with Presentation Layer

The following are the design issues with presentation layer:

• To manage and maintain the Syntax and Semantics of the information transmitted.
• Encoding data in a standard agreed-upon way just like a string, double, date, etc.
• It Performs Standard Encoding scheme on the wire.

Functionalities of the Presentation Layer

Specific functionalities of the presentation layer are as follows:

1. Translation

• The processes or running programs in two machines are usually exchanging the information in the form of numbers, character strings and so on before being transmitted. The information should be changed to bitstreams because different computers use different encoding schemes.
• The Presentation layer is responsible for compatibility between these encoding methods.
• The Presentation layer at the sender's side changes the information from its sender dependent format.
• The Presentation layer at the receiving machine changes the common format into its receivers dependent format.

Example: Convert ASCII code to EBCDIC code.

2. Encryption

• The system must be able to assure privacy regarding the message or information as it also carries sensitive information.
• Encryption means that the sender transforms the original information or message to another form, this data after encryption is known as the ciphertext and this ciphertext sends the resulting message out over the network.
• Decryption concerned with the transform of the message back to its original form. This decrypted data is known as plain text.

3. Compression

• Data Compression means reduces the number of bits to be transmitted by this reduce the bandwidth of the data.
• Data Compression becomes particularly important in the transmission of multimedia such as audio, video, text, etc.

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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.

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Presentation Layer: Protocols, Examples, Services | Functions of Presentation Layer

Presentation Layer is the 6th layer in the Open System Interconnection (OSI) model where all application programmer consider data structure and presentation, beyond of simply sending the data into form of datagram otherwise packets in between the hosts. Now, we will explain about what is presentation layer with its protocols, example, service ; involving with major functions of presentation Layer with ease. At the end of this article, you will completely educate about What is Presentation Layer in OSI Model without any hassle.

• What is Presentation Layer?

Definition : Presentation layer is 6th layer in the OSI model , and its main objective is to present all messages to upper layer as a standardized format. It is also known as the “ Translation layer “.  This layer takes care of syntax and semantics of messages exchanged in between two communication systems. Presentation layer has responsible that receiver can understand all data, and it will be to implement all data languages can be dissimilar of two communication system.

Presentation layer is capable to handle abstract data structures, and further it helps to defined and exchange of higher-level data structures.

Presentation Layer Tutorial Headlines:

In this section, we will show you all headlines about this entire article; you can check them as your choice; below shown all:

• Functions of Presentation Layer

Protocols of Presentation Layer

• Example of Presentation Layer Protocols

Presentation Layer Services

Design issues with presentation layer, faqs (frequently asked questions), what is meant by presentation layer in osi model, what protocols are used in the presentation layer, can you explain some presentation layer examples, what are the main functions of the presentation layer, what are services of presentation layer in osi, let’s get started,   functions of presentation layer.

Presentation layer performs various functions in the OSI model ; below explain each one – 

• Presentation layer helps to translate from American standard code for information interchange (ASCII) to the extended binary code decimal interchange code (EBCDIC).
• It deals with user interface as well as supporting for several services such as email and file transfer.
• It provides encoding mechanism for translating all messages from user dependent format with common format and vice – versa.
• It’s main goal for data encryption and decryption of entire data before they are getting transmission over all common platforms.
• It provides data compression mechanism for source point to decrease the all bits which are transmitted. Due to this data compression system, user are able to transmit enlarge multimedia file at fastest file transfer rate.
• Due to use of Data Encryption and Decryption algorithm, presentation layer provides more network protection and confidentiality while transmission data over the entire network.
• This layer offers best flexibility for data translation for making connections with various kinds of servers , computers, and mainframes over the similar network.
• Presentation layer has responsible to fix all translations in between all network systems .

Presentation layer is used various protocols; below list is available –

• Multipurpose Internet Mail Extensions
• File Transfer Protocol
• Network News Transfer Protocol
• Apple Filing Protocol (AFP)
• Independent Computing Architecture (ICA), the Citrix system core protocol
• Lightweight Presentation Protocol (LPP)
• NetWare Core Protocol (NCP)
• Network Data Representation (NDR)
• Telnet (a remote terminal access protocol)
• Tox Protocol
• eXternal Data Representation (XDR)
• 25 Packet Assembler/Disassembler Protocol (PAD)

Example of Presentation Layer Protocols:

Here, we will discuss all examples of presentation layer protocols; below explain each one –  

Multipurpose Internet Mail Extensions (MIME) : MIME protocol was introduced by Bell Communications in 1991, and it is an internet standard that provides scalable capable of email for attaching of images, sounds and text in a message.

File Transfer Protocol (FTP) : FTP is a internet protocol, and its main goal is to transmit all files in between one host to other hosts over the internet on TCP/IP connections.

Network News Transfer Protocol (NNTP) : This protocol is used to make connection with Usenet server and transmit all newsgroup articles in between system over internet.

Apple Filing Protocol (AFP ) : AFP protocol is designed by Apple company for sharing all files over the entire network .

Lightweight Presentation Protocol (LPP) : This protocol is used to offer ISO presentation services on top of TCP/IP based protocol stacks.

NetWare Core Protocol (NCP) : NCP is a Novell client server model protocol that is designed especially for Local Area Network (LAN). It is capable to perform several functions like as file/print-sharing, clock synchronization, remote processing and messaging.

Network Data Representation (NDR) : NDR is an data encoding standard, and it is implement in the Distributed Computing Environment (DCE).

Telnet (Telecommunication Network) : Telnet protocol was introduced in 1969, and it offers the command line interface for making communication along with remote device or server .

Tox : The Tox protocol is sometimes regarded as part of both the presentation and application layer , and it is used for sending peer-to-peer instant-messaging as well as video calling.

eXternal Data Representation (XDR) : This protocol provides the description and encoding of entire data, and  it’s main goal is to transfer data in between dissimilar computer architecture.

25 Packet Assembler/Disassembler Protocol (PAD) : Main objective of this protocol is to obtain all data from group of terminal and allots the data into X. 25 packets.

Presentation layer provides several services like as –

• Data conversion
• Character code translation
• Compression
• Encryption and Decryption
• It helps to handle and maintain Syntax and Semantics of the message transmitted.
• Encoding data can be done as standard agreed like as String, double, date, and more.
• Standard Encoding can be done on wire.

Presentation Layer is the 6th layer in the Open System Interconnection (OSI) model that is the lowest layer, where all application programmer consider data structure and presentation, beyond of simply sending the data into form of datagram otherwise packets in between the hosts.

Presentation layer is used various protocols like as:

Yes! In this article, already we have been explained many examples of presentation layer; you can check them.

Presentation layer has a responsibility for formatting, translation, and delivery of the information for getting to process otherwise display .

Now, i hope that you have completely learnt about what is presentation layer with its protocols, example, service ; involving with major functions of presentation Layer with ease. If this post is useful for you, then please share it along with your friends, family members or relatives over social media platforms like as Facebook, Instagram, Linked In, Twitter, and more.

Also Read: Data Link Layer: Protocols, Examples | Functions of Data Link Layer

If you have any experience, tips, tricks, or query regarding this issue? You can drop a comment!

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OSI Seven Layers Model Explained with Examples

This tutorial explains the OSI reference model. Learn the seven layers of the OSI model and the functions of each layer in detail through examples.

The OSI (Open System Interconnection) reference model is a comprehensive set of standards and rules for hardware manufacturers and software developers. By following these standards, they can build networking components and software applications that work in any environment. It was published in 1984 by ISO (International Organization for Standardization).

It provides a framework for creating and implementing networking standards, devices, and internetworking schemes. It explains the networking from a modular perspective, making it easier to understand and troubleshoot.

Seven layers of the OSI Model

The OSI model has seven different layers, which are divided into two groups. The following table lists all the layers with their names and numbers.

Let’s understand each layer in detail.

This tutorial is the second part of the article " Networking reference models explained in detail with examples. ". Other parts of this article are the following.

This tutorial is the first part of the article. It summarizes why the OSI model was created and what advantages it has.

This tutorial is the third part of the article. It compares the OSI reference model with the TCP/IP model and lists the similarities and differences between both.

This tutorial is the fourth part of the article. It explains the five layers of the TCP/IP model in detail.

This tutorial is the fifth part of the article. It explains how data is encapsulated and de-encapsulated when it passes through the layers.

The Application Layer

This is the last and topmost layer of the OSI model. This layer provides an interface between the local system and the application program running on the network. If an application wants to use the resources available on the remote system, it interacts with this layer. Then, this layer provides the protocols and services that the application needs to access those resources.

There are two types of application programs: Network-aware and Network-unaware . An application program is considered a Network-aware application if it can make any type of network request. If an application program cannot make any type of network request, it is considered a Network-unaware program.

Network-aware programs are further divided into two types.

Programs that are mainly built to work on a local system. This type of program occasionally accesses the network for particular reasons such as updates, documentation, and troubleshooting. MS-Word, Adobe-Photoshop, and VLC Player are examples of this type of program.

Programs that are mainly built to work with a remote system. This type of program provides a platform to access resources available on a remote system. This type of program only works if the system is connected to the network. SSH, FTP, and TFTP are examples of this type of program.

The Application layer describes only the programs which fall in the second type. But it doesn’t mean that the first type of programs can’t take the advantage of the Application layer. It simply means that they are not documented in the Application layer. But if required, they can also connect to the network through the Application layer.

The Top layer of the OSI model is the application layer. It provides the protocols and services that are required by the network-aware applications to connect to the network. FTP, TFTP, POP3, SMTP, and HTTP are examples of standards and protocols used in this layer.

The Presentation Layer

The sixth layer of the OSI model is the Presentation layer. Applications running on the local system may or may not understand the format that is used to transmit the data over the network. The presentation layer works as a translator. When receiving data from the Application layer, it converts that data in such a format that can be sent over the network. When receiving data from the Session layer, it reconverts the data in such a format that the application, which will use it, can understand.

Conversion, compression, and encryption are the main functions that the Presentation layer performs on the sending computer while on the receiving computer these functions are reconversion, decompression, and decryption. ASCII, BMP, GIF, JPEG, WAV, AVI, and MPEG are examples of standards and protocols that work in this layer.

The Session Layer

The session layer is the fifth layer of the OSI model. It is responsible for setting up, managing, and dismantling sessions between presentation layer entities and providing dialogs between computers.

When an application makes a network request, this layer checks whether the requested resource is available on the local system or on a remote system. If the requested resource is available on a remote system, it tests whether a network connection to access that resource is available or not. If a network connection is not available, it sends an error message back to the application informing that the connection is not available.

If a network connection is available, it establishes a session with the remote system. For each request, it uses a separate session. This allows multiple applications to send or receive data simultaneously. When data transmission is completed, it terminates the session.

The session layer is responsible for establishing, managing, and terminating communications between two computers. RPCs and NFS are examples of the session layer.

The Transport Layer

The transport layer is the fourth layer of the OSI model. It provides the following functionalities: -

Segmentation

On the sending computer, it breaks the data stream into smaller pieces. Each piece is known as a segment and the process of breaking the data stream into smaller pieces is known as the segmentation . On the receiving computer, it joins all segments to recreate the original data stream.

Data transportation

This layer establishes a logical connection between the sending system and receiving system and uses that connection to provide end-to-end data transportation. This process uses two protocols: TCP and UDP.

The TCP protocol is used for reliable data transportation. TCP is a connection-oriented protocol. UDP protocol is used for unreliable data transportation. UDP is a connection-less protocol.

The main difference between a connection-less and connection-oriented protocol is that a connection-oriented protocol provides reliable data delivery. For reliable data delivery, it uses several mechanisms such as the three-way handshake process, acknowledgments, sequencing, and flow control.

Multiplexing

Through the use of port numbers, this layer also provides connection multiplexing. Connection multiplexing allows multiple applications to send and receive data simultaneously.

The main functionalities of the Transport layer are segmentation, data transportation, and connection multiplexing. For data transportation, it uses TCP and UDP protocols. TCP is a connection-oriented protocol. It provides reliable data delivery.

The Network Layer

The third layer of the OSI model is the Network Layer. This layer takes the data segment from the Transport layer and adds a logical address to it. A logical address has two components; network partition and host partition. The Network partition is used to group networking components while the host partition is used to uniquely identify a system on the network. A logical address is known as the IP address. Once the logical address and other related information are added to the segment , it becomes the packet .

This layer decides whether the packet is intended for the local system or a remote system. It also specifies the standards and protocols which are used to move data packets over networks.

To move data packets between two different networks, a device known as the router is used. Routers use the logical address to make the routing decision. Routing is the process of forwarding data packets to their destination.

Defining logical addresses and finding the best path to reach the destination address are the main functions of this layer. Routers work in this layer. Routing also takes place in this layer. IP, IPX, and AppleTalk are examples of this layer.

The Data Link Layer

The Data Link Layer is the second layer of the OSI model. This layer defines how networking components access the media and what transmission methods they use. This layer has two sub-layers: MAC and LLC.

MAC (Media Access Control)

This sub-layer defines how the data packets are placed in media. It also provides physical addressing. The physical address is known as the MAC address. Unlike logical addresses that need to be configured, physical addresses are pre-configured in NIC. The MAC address is used to uniquely identify a host in the local network.

LLC (Logical Link Control)

This sub-layer identifies the network layer protocol. On the sending computer, it encapsulates the information of the Network Layer protocol in the LLC header from which the Data Link layer receives the data packet. On the receiving computer, it checks the LLC header to get the information about the network layer protocol. This way, a data packet is always delivered to the same network layer protocol from which it was sent.

Defining physical addresses, finding hosts in the local network, specifying standards and methods to access the media are the primary functions of this layer. Switching takes place in this layer. Switches and Bridges work in this layer. HDLC, PPP, and Frame Relay are examples of this layer.

The Physical Layer

The Physical Layer is the first layer of the OSI model. This layer specifies the standards for devices, media, and technologies that are used in moving the data across the network such as:-

• Type of cable used in connecting the devices
• Patterns of pins used in both sides of the cable
• Type of interface-card used in the networking device
• Type of connector used to connect the cable with the network interface
• Encoding of digital signals received from the Data Link layer based on the attached media type such as electrical for copper, light for fiber, or a radio wave for wireless.

On the sending computer, it converts digital signals received from the Data Link layer, into analog signals and loads them on the physical media. On the receiving computer, it picks analog signals from the media and converts them into digital signals, and transfers them to the Data Link layer for further processing.

The Physical Layer mainly defines standards for media and devices that are used to move data across the network. 10BaseT, 10Base100, CSU/DSU, DCE, and DTE are examples of the standards used in this layer.

That’s all for this tutorial. In the next part of this article, we will compare the OSI model with the TCP/IP model and explains the similarities and differences between both models. If you like this tutorial, please don’t forget to share it with friends.

By ComputerNetworkingNotes Updated on 2024-01-25 05:30:01 IST

ComputerNetworkingNotes CCNA Study Guide OSI Seven Layers Model Explained with Examples

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Understanding the Role of the Presentation Layer in Data Format Translation and Security

1. introduction.

According to a recent study conducted by the Institute of Electrical and Electronics Engineers (IEEE), the presentation layer is responsible for ensuring that the data is in a format that is acceptable to the application layer. This includes data compression and decompression, encryption and decryption, and character set conversion. In today’s data-driven world, the ability to effectively manage and secure data is becoming increasingly important, and understanding the role of the presentation layer in this process is crucial.

This article will explore the techniques and technologies used in the presentation layer to perform data format translation, compression and decompression, and encryption and decryption. This will include a discussion of the benefits and limitations of these techniques, as well as real-life examples and case studies of their implementation. By the end of this article, readers will have a solid understanding of the role and functions of the presentation layer in the OSI model and how it contributes to secure and efficient data transmission.

2. The role of the presentation layer

The presentation layer, also known as the syntax layer, is the sixth layer in the OSI model. It ensures that the data is in a format acceptable to the application layer. This includes data format translation, compression and decompression, encryption and decryption, and character set conversion. It acts as an interface between the application layer and the rest of the layers in the OSI model.

Data Format Translation:

The presentation layer is responsible for translating data between different formats so the application layer can understand it. For example, it may convert a file from one format, such as TIFF, to another format, such as JPEG. This ensures that the data is in a form that is compatible with the application layer and can be processed accordingly.

Compression and Decompression:

Another essential function of the presentation layer is data compression and decompression. The layer compresses the data before sending it to the next layer, the network layer. This reduces the amount of data that needs to be transmitted, reducing the time required for the data to be shared. Once the data reaches the destination, the decompression process takes place, and the data is restored to its original form. There are various compression and decompression techniques like LZ77, LZ78, and Huffman coding that are used to compress and decompress data.

3. Data compression and decompression techniques

Data compression and decompression are essential functions of the presentation layer in the OSI model. Compression refers to reducing the amount of data that needs to be transmitted. At the same time, decompression restores the data to its original form once it reaches the destination. The use of compression techniques can significantly reduce the amount of time required for data to be transmitted, as well as reduce the bandwidth needed for transmission.

The presentation layer’s most commonly used compression techniques include LZ77, LZ78, and Huffman coding.

LZ77 is a lossless data compression algorithm that Abraham Lempel and Jacob Ziv first introduced in 1977. It replaces repeated instances of a data string concerning the original series. LZ77 is a dictionary-based algorithm that uses a sliding window to identify and replace repeated data instances. This technique is effective at compressing data that contains many repeated patterns, but it can be less effective on highly random data.

LZ78 is another lossless data compression algorithm that Lempel and Ziv introduced in 1978. It is similar to LZ77 but uses a different data compression approach. Instead of using a sliding window, LZ78 uses a dictionary of previously encountered data strings. This approach allows LZ78 to achieve higher compression ratios than LZ77 but also requires more memory and processing power.

Huffman coding:

Huffman coding is a lossless data compression algorithm introduced by David Huffman in 1952. Huffman coding is a variable-length coding algorithm that assigns shorter codes to more frequently occurring symbols in the data. This technique is especially effective for compressing data that contains many repeating characters, such as text or DNA sequences.

Each technique has its advantages and disadvantages; LZ77 and LZ78 are simpler than Huffman coding and can be implemented quickly. With a limited amount of memory, on the other hand, Huffman coding is more efficient in terms of compression ratio, but it is more complex and memory-intensive.

In real-life examples, all three algorithms have been used in various applications. For instance, LZ77 has been used to compress data in the telecommunications industry, and LZ78 has been used in data storage devices like hard drives and flash drives. In contrast, Huffman coding compresses text, images, audio and video files.

4. Encryption and decryption in the presentation layer

Encryption and decryption are essential security measures that are used to protect sensitive information as it is transmitted over a network. In the OSI model, encryption and decryption occur at the presentation layer. The presentation layer is responsible for ensuring that the data is in a format acceptable to the application layer, and it also ensures that the information is protected during transmission.

Encryption refers to converting plain text into an unreadable form, known as ciphertext. The ciphertext can only be read and understood by someone with the correct decryption key. Decryption, on the other hand, is the process of converting ciphertext back into plain text using the right decryption key.

The importance of encryption and decryption in the presentation layer is clear, especially with the rise of cyber threats. It ensures that only authorised parties can access and understand the sensitive information being transmitted. Without encryption and decryption, sensitive data would be vulnerable to eavesdropping and tampering.

There are two main types of encryption and decryption methods that are commonly used in the presentation layer: symmetric key encryption and asymmetric key encryption.

Symmetric key encryption:

Symmetric key encryption is a method of encryption where the same key is used for both encryption and decryption. This method is fast and efficient, but it also has some drawbacks. The main disadvantage is that the key must be securely exchanged between the sender and the receiver before any encryption can occur.

Asymmetric key encryption:

Asymmetric key encryption, also known as public key encryption, is a method of encryption where a pair of keys is used. One key is used for encryption, and the other is used for decryption. This method is more secure than symmetric key encryption because the key used for encryption can be made public, while the key used for decryption is kept private.

In real life, symmetric key encryption is used for bulk encryption, for example, in the transportation of email, instant messaging and other types of data where the speed of encryption is more important than key exchange. On the other hand, Asymmetric key encryption is often used for digital signatures, online transactions and handshaking in secure connections.

5. Common Attacks on the Presentation Layer

The Presentation Layer in the OSI model ensures data security during transmission. However, like any other layer in the OSI model, it is also vulnerable to various attacks, vulnerabilities, and threats. These can have severe consequences, such as unauthorised access or manipulation of sensitive information.

One standard attack on the presentation layer is a “format string attack”. This occurs when an attacker can insert random formatting characters into a string, which can then be used to disrupt the normal execution of a program. This can lead to various consequences, including buffer overflows, which can be used to execute arbitrary code or crash the system.

Another attack that targets the presentation layer is “malicious code injection”. This occurs when an attacker can insert malicious code into a seemingly benign file or message. This can be done by exploiting vulnerabilities in data format translation or compression/decompression mechanisms. Once the malicious code is executed, it can cause various types of damage, such as data loss, unauthorised access to sensitive information, or even complete system compromise.

In addition to these specific attacks, the presentation layer is vulnerable to more general threats, such as “man-in-the-middle” or “replay” attacks. These are attacks in which an attacker intercepts and alters communications between two parties to gain unauthorised access to sensitive information. Such attacks can occur on any OSI model layer, but they are particularly dangerous when they target the presentation layer, as the attacker can manipulate or intercept data in transit.

6. How to Secure the Presentation Layer

Securing the Presentation Layer in the OSI model is crucial for protecting sensitive information during transmission. There are various security best practices that organisations can implement to protect against attacks, vulnerabilities, and threats on this layer.

One critical best practice is to keep software and systems up-to-date with the latest security patches and updates. This ensures that known vulnerabilities are fixed, making it harder for attackers to exploit them. It’s also important to regularly monitor systems and networks for signs of suspicious activity, such as unusual traffic patterns or login attempts.

Another best practice is to use secure protocols for data transmission and storage. Examples of secure protocols used at the Presentation Layer are Transport Layer Security (TLS) and Secure Sockets Layer (SSL), which encrypt communications between parties. Additionally, the use of robust encryption and decryption mechanisms, such as symmetric and asymmetric key encryption, can help protect against man-in-the-middle and replay attacks.

Enforcing strict access controls and implementing a solid data classification system can also secure the presentation layer. This includes access controls to limit who can view, modify or delete sensitive data and a data classification system which can help determine how data is handled, processed and protected.

Implementing a robust incident response plan that includes detailed procedures for identifying, containing and reporting security incidents can also be a valuable asset in case of a security breach. It’s also important to regularly train employees on security best practices and to make them aware of the importance of security in the presentation layer.

In addition, performing regular penetration testing, Vulnerability Assessments, and security audits can also help to identify and address security vulnerabilities. This can include testing the effectiveness of encryption and decryption mechanisms, evaluating the robustness of access controls, and identifying potential vulnerabilities in data format translation and compression/decompression mechanisms.

7. Conclusion

In conclusion, the presentation layer in the OSI model is a critical component in the data transmission process. Its functions include data format translation, data compression and decompression, and encryption and decryption. These functions are vital to ensure that the data is in a format compatible with the application layer and to protect the data during transmission.

We have discussed how the presentation layer plays a vital role in the OSI model. The techniques and technologies used in the presentation layer to perform data format translation, compression and decompression, encryption and decryption. The article also includes the advantages and disadvantages of each technique, real-life examples and case studies, if applicable, that illustrate the concepts and makes them more relatable.

The topic of the presentation layer in the OSI model is essential for anyone working in the network security and communications field, as it provides an understanding of how data is protected and formatted during transmission. We hope this article has provided a comprehensive understanding of the role and functions of the presentation layer in the OSI model.

However, it’s important to note that the Presentation Layer, like any other layer in the OSI model, is also vulnerable to various attacks, vulnerabilities, and threats. Therefore, it is crucial to implement security best practices to protect against these threats, such as keeping software and systems up-to-date with the latest security patches and updates, using secure protocols, and robust encryption and decryption mechanisms. Strict access controls, incident response plans, and regular security assessments can also help secure the Presentation Layer.

8. FAQs on the Presentation Layer

• How does the presentation layer ensure data format compatibility?

The presentation layer ensures data format compatibility by providing a set of protocols and standards for data representation and encoding. These protocols, such as ASCII or Unicode, define a standard format for data so that it can be easily understood and processed by different systems. This helps to ensure that data can be exchanged between other systems without loss of meaning or integrity.

• How does the presentation layer protect data during transmission?

The presentation layer protects data during transmission by using various encryption techniques to ensure that the data is secure as it is transmitted over a network. Encryption is the process of converting plaintext data into a coded format (ciphertext) unreadable by unauthorised parties. Standard encryption methods used at the presentation layer include SSL (Secure Sockets Layer) and TLS (Transport Layer Security).

• What are some standard encryption algorithms used in the presentation layer?

Some standard encryption algorithms used in the presentation layer include:

• RSA (Rivest-Shamir-Adleman)
• AES (Advanced Encryption Standard)
• DES (Data Encryption Standard)
• 3DES (Triple Data Encryption Standard)
• What is the difference between symmetric and asymmetric encryption in the presentation layer?

Symmetric key encryption and asymmetric key encryption are both encryption methods that are used to protect data during transmission, but they use different techniques to secure the data.

Symmetric key encryption uses a single shared key for encryption and decryption, meaning that the sender and receiver both have to use the same key to encrypt and decrypt the data.

Asymmetric key encryption, also called public-key encryption, uses a pair of keys, one for encryption (the public key) and one for decryption (the private key). So the sender uses the recipient’s public key to encrypt the data, and the recipient uses their private key to decrypt the data.

• How does the presentation layer handle data format translation for different data types?

The presentation layer handles data format translation for different data types using a set of protocols and standards for data representation and encoding. These protocols, such as ASCII or Unicode, define a standard format for data so that it can be easily understood and processed by different systems. The presentation layer can also use data conversion algorithms to convert data between other formats, such as a Word document to a PDF.

• How does the presentation layer interact with other layers in the OSI model?

The presentation layer, the sixth layer in the OSI model, acts as an intermediary between the application layer (layer 7) and the session layer (layer 5). It is responsible for translating data between different formats and encoding schemes, and it is also responsible for compressing and decompressing data. The presentation layer communicates with the application layer to convert the data it receives into a format the application can understand. It also communicates with the session layer to establish, manage, and terminate sessions between networked devices.

• How do changes in data formats affect the presentation layer?

Changes in data formats can have a significant impact on the presentation layer, as the presentation layer is responsible for converting data between different formats. The presentation layer must be updated when data formats change to support the new design. If this is done, the presentation layer can convert the data, which may be unreadable or lost. Additionally, there are changes in the protocol or standard used in the presentation layer. In that case, it will affect the compatibility with other systems, so the sending and receiving ends have to use the same protocol. Otherwise, they would not be able to understand each other.

• How does the presentation layer handle data compression and decompression in real-time communications?

The presentation layer is responsible for compressing and decompressing data in real-time communications. Compression reduces data size to improve transmission efficiency, while decompression restores the data to its original format. The presentation layer uses various compression algorithms to compress data and the same algorithms to decompress the data when it is received.

In real-time communications, the presentation layer might use lossless compression algorithms to compress the data in order not to lose any information but at the same time still be able to compress the data to a smaller size.

• How can data integrity be maintained in the presentation layer?

Data integrity in the presentation layer can be maintained using encryption, secure hash algorithms, and error-detection codes.

Encryption is the process of converting plaintext data into a coded format (ciphertext) that is unreadable by unauthorised parties. This helps to protect data from unauthorised access and modification during transmission.

Secure hash algorithms are used to create a unique digital signature for each piece of data, which can be used to verify the integrity of the data upon receipt. This helps to detect any changes or modifications that may have occurred during transmission.

Error-detection codes are used to detect errors in the data during transmission and can help to correct these errors.

Additionally, the presentation layer can also use a digital signature or digital certificate to ensure the authenticity of data, which is the process of using a digital signature to ensure that the data is not tampered with during transmission.

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Explain the functions of Presentation Layer.

The functions of the presentation layer are as follows:

• It provides the users with a way to execute the session service primitives. For that, it uses the contexts, each consisting of some data types and their transfer syntaxes. When a session is established, the peer entities negotiate for one or more contexts. It can change these contexts as the session progresses.
• Once the negotiations have been agreed upon, each machine is free to represent the data structures internally in the most convenient form. It is known that it should express that it can be transmitted and understood by the remote peer entity even if a different internal representation is used there.
• It provides a way to specify complex data structures. The presentation layer provides services dealing with the representation of data. It accepts data types from the application layer and then negotiates for the syntax representation like ASCII, Videotex, teletype etc.
• The layer also contains Abstract syntax negotiation as a language (ASN.I), which describes data structure and syntax. The layer manages the set of data structures currently required. It also converts data between internal and external forms. It uses data representations and data compression to perform this function.
• It provides an establishment and release of the presentation connection. A particular functional unit, 'kernel', is used to establish and release the presentation connection. It is a unit that is always required. The negotiation of the defined ontext set and default context is done during the connection establishment phase. These negotiated contexts are used throughout the life of the connection
• The presentation entities can modify the defined context set. This can be done only if the context management functional unit is chosen to establish the connection. During the connection, the user application entities inform the new abstract syntax to be added, deleted or changed, and the presentation entities negotiate the common transfer syntax. Such needs are in various situations. For example, if a file is required to be accessed which has a different syntax etc.
• If a resynchronization occurs at the session layer, it must restore the defined context, and the presentation layer can do it. It chooses the context restoration functional unit for this function.
• The presentation layer also encodes the defined abstract syntax into common transfer syntax. It uses various encoding and decoding rules/methods for that. The set of encoding and decoding rules are defined in ISO 8825, Specification of Basic Encoding Rules for ASN.1. They use a Type-Length-value form of encoding.
• The presentation layer also provides privacy and network security by using end to end encryption. The encryption makes the data unintelligible to all but their intended recipient.
• Using encryption can protect the data from being read by unauthorized persons. It also prevents them from inserting or deleting messages. It verifies each message’s sender and also makes it possible for users to send signed documents electronically.

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6 Important Functions of Presentation layer in OSI model

Do you know about the presentation layer in OSI model? What is the functions of Presentation Layer? All these things have been told in this article. If you want complete information about Presentation Layer, then you have come to the right place. After reading this article completely, you will have complete knowledge about the presentation layer & its responsibility of the OSI model. So without delay let’s start.

What is Presentation layer in OSI model?

The presentation layer resides between the session layer and the application layer. The presentation layer is the sixth layer in the Open Systems Interconnection (OSI) model . This layer is also called the translation layer because it receives the data from the session layer or application layer and then translates that data and sends it to the language of the receiver layer.

The presentation layer is also called the syntax layer as it is responsible for maintaining the proper syntax of data that it either receives or transmits to another layer. The primary responsibility of this layer is to provide or define data format and encryption.

Simply put, different machines connected to the network may use different languages or syntax, so when one machine sends information to another machine, the presentation layer takes care of this. So that the machine receiving the information can understand the information and can also use that information. This means the presentation layer acts as a translator for the OSI model.

6 important functions of Presentation layer

The presentation layer in OSI model has 4 functions and responsibilities. Some of them we have mentioned below.

Code conversion

The presentation layer translates data from the format used by the application layer into a common format that can be understood by both the sender and the receiver. It converts data from different character encoding schemes, such as ASCII, EBCDIC and Unicode to ensure compatibility between computer systems with different encoding standards. That’s why code conversion plays a major role in the presentation layer.

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Data Encryption / Decryption

The Presentation layer can provide encryption and decryption services to ensure the confidentiality and integrity of data during transmission. Nowadays all multinational companies and all small and big companies have started paying attention to cyber security. Hence its need has increased.

When transferring data over a network , data encryption is needed to secure that information from hackers. When the data reaches its destination only then it is decrypted.

When we send information to one or many users without encrypting it, there is a possibility of threat detection in it. So the data is kept encrypted. Thereby it prevents any other user from reading that data.

Data Compression

When we send data packets to other users through the internet, only some gaps and some repeated data remain in those data packets. To remove that gap and redundancy, we have to compress the data packets.

You must have used software named WinRAR on your computer. Just like any files and folders are compressed through this software, in the same way, data packets are also compressed. So that the size of the data decreases.

Both advantages and disadvantages occur through this compression. The advantage is that the size of the data packet decreases and sending it via the internet is easy. The disadvantage is that some data in the data packet gets lost at some times.

Data Formatting and Syntax

The presentation layer handles the formatting and syntax of the data to ensure that it is properly structured for interpretation by the receiving device. This includes converting data into a standard format or applying specific formatting rules, such as XML or JSON, to enable interoperability between different systems.

Data Protocol Conversion

This layer can convert data from one protocol to another. It is useful when devices or systems using different communication protocols need to exchange data. The presentation layer translates data from one protocol format to another, enabling seamless communication between different systems.

Data Integrity Checks

The presentation layer may include mechanisms for data integrity checking, such as error detection codes or checksums. These checks ensure that the received data is free from errors or corruption that occurred during transmission. If the error is detected then only that data is re-transmitted from the sender.

Features of Presentation layer in OSI model

The presentation layer is one of the most important layers of the OSI model. This OSI model is the 6th layer. This layer is helpful in making uninterrupted communication between two devices by becoming a translator. Some features of presentation layer is given below.

• The most important feature of the presentation layer is that it converts the language of one device into the language understood by the other device. So that communication between different devices can be established in OSI model.
• Whenever data is transmitted from presentation layer to session layer or from presentation layer to application layer, that data remains encrypted. Due to which the unauthorized user could not be able to read that data.
• This layer encrypts the data at the send end and decrypts the data at the receiver end. So that the data remains confidential between the sender and the receiver.
• In the presentation layer, the data is compressed in such a way that very little internet is used by sending that data packet. Compressing the data packet removes that unuse space in the data packet and removes the multiple value if it is written. Due to which the size of the data packet is also reduced.

Presentation layer Protocols

In the presentation layer, the data packet is translated, encrypted and compressed. For all these protocols of different types are used in the presentation layer. A list of some important protocols is given below.

Apple Filing Protocol (AFP)

This protocol is a network protocol, which helps in the exchange of data on Apple’s laptop or computer device. This protocol is specifically designed for Apple devices.

Independent Computing Architecture (ICA)

Independent Computing Architecture is a protocol designed for application server systems.

Lightweight Presentation Protocol (LPA)

Lightweight Presentation Protocol is that protocol that is used to provide ISO presentation services on top of TCP/IP-based protocol stacks.

Netware Core Protocol (NCP)

NetWare Core Protocol is a protocol using which print, clock synchronization, directory, message, remote comment, etc. can be accessed.

Network Data Representation (NDR)

The Network Data Representation Protocol is basically an implementation of the presentation layer in the OSI model, which is providing or defining various primitive data types, constructed data types, and many types of data representations.

External Data Representation (XDR)

This protocol is used for data distribution and encoding. It transfers data within the computer architecture. It helps in encoding and decoding of data.

In conclusion, the presentation layer is the sixth layer of the OSI model, which presents the information exchanged through the network in a simple and understandable form to the machines.

It also encrypts and decrypts information to protect it from hackers and unauthorized access. Along with this, the Presentation Layer also compresses and shrinks the information to transfer it easily.

In today’s article, complete information about the presentation layer in OSI model & functions of presentation layer has been given. I hope that you must have understood the presentation layer by reading this article Presentation Layer in OSI model.

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Functions of Session Layer

The Session layer is the fifth layer of the OSI (Open System Interconnection) model. The session layer is responsible for maintaining, establishing, synchronizing, and terminating sessions between them. A connection is being established among the session entities by the session layer. The data received from the presentation layer is handled by the session layer. Various protocols such as PPTP , PAP , RTCP , ADSP, and SDP are used by the session layer. The below article covers the functions of the session layer in detail.

The session layer is responsible for various tasks that are mentioned below:

1. Session Establishment

The basic and most important function of the session layer is to establish a connection between the communicating parties known as sessions. This connection helps to transfer the data such as files, remote login, and communication over these sessions in a more ordered and reliable way. The session layer can establish connection-oriented as well as connectionless sessions. Whenever any session is released, the transport connection is also released. Sessions can be mapped onto transport connections in three ways. They are:

• One-to-one mapping: In one-to-one mapping, one transport connection is being used by one session.
• Many-to-one mapping: In many-to-one mapping, the same transport connection is being used by the consecutive sessions.
• One-to-many mapping: In one-to-many mapping, multiple transport connections are used by one session.

2. Communication Synchronization

The session layer provides proper connectivity among the systems, during this if any occurs, a recovery option known as the state is provided. For using the known state session layer adds synchronization bits in every state of the error and these bits are then used as checkpoints. For longer and complex communications the checkpoints are added to the data stream. It makes sure that data streams are received successfully and acknowledged up to the checkpoints. If any failure occurs then only the stream is retransmitted after the checkpoints. The functionality is being provided by the session layer because transport layer can mask only the communication errors, not the upper layer errors.

3. Activity Management

The session layer provides with the feature for users to differentiate among the activities that are performed during the session. The message stream can split into logical units and these logical units are known as an activities. Activity management is defined as a process of splitting of message stream into activities.

4. Dialog Management

Dialog management is defined as a process of keeping log data for the connections established for transmitting and receiving data. It is required for establishing, synchronization, preserving and ending of the conversation between the communicating parties namely sender and the receiver. For this a mechanism known as token mechanism is being used in which a user that is sharing the data is given a token if it is in half duplex mode and after the exchange it is transferred to the the another device. If the operation is in full duplex mode then no token is used for transmission of data. The efficiency of the connection is maintained if token mechanism is used.

5. Data Transfer

Data transfer is also one of the basic and important function of session layer. Session layer handles the exchange of data between the communicating systems. This exchange of data between the users can be in two modes of transmission. They are:

• Half-duplex mode: In half duplex mode of transmission of data only one user has right for initiating the data transfer.
• Full- duplex mode: In full duplex mode of transmission data can be transmitted in both the directions simultaneously.

6. Resynchronization

Resynchronisation is also known as backward synchronization. Resynchronisation is defined as a process in which the state of dialog is being restored to its previously defined state. After the resynchronization all the tokens are restored to the positions that were set during synchronization. There are various options of resynchronisation. They are:

• Set: Set option is being used for setting the synchronization point serial number to any value that is being chosen by the user.
• Abandon: Abandon option is being used for setting the synchronization point serial number to an unused value.
• Restart: Restart option is being used for setting the synchronization point serial number o any of the used value that is grater than the synchronization point serial number which identifies the last acknowledged major synchronization point.

Frequently Asked Questions

Q.1: which layer lies above the session layer of osi model.

Presentation layer lies above the session layer of OSI model. Presentation layer prepares the data for its upper layer. It states about how the devices should encode, encrypt and compress the data.

Q.2: Which layers of OSI model are known as software layers or upper layers?

The session layer, presentation layer and application layer are known as the software or upper layers of OSI model.

Q.3: What is meant by session termination?

Session termination is defined as a process of ending the session communication. This process of session termination is important because it releases the resources and makes sure that both the communicating devices know that session has been ended.

Q.4: Can applications interact directly with session layer?

No, applications cannot directly interact with the session layer. They interacts with other higher layers namely presentation layer and application layer.

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