Understanding the Presentation Layer: A Beginner’s Guide

Key takeaways

The presentation layer is a key part of a functioning OSI system, which gives structure to data moving through networks. 

• The median total pay for a network technician in the US is $83,000 [1].

• The presentation layer is the sixth layer within the open systems interconnection (OSI) model, located next to the application layer, and translates data by converting, compressing, encrypting, and serializing data into different forms. 

• You can explore both modern and historical presentation layer protocols, such as the independent computing architecture, network data representation, and Apple filing protocol, to gain a deeper understanding of how the presentation layer functions.

Learn more about the basic function of each layer in the OSI, how the presentation layer works to translate data for transmission, and the various protocols it uses in this process. Or, start learning network fundamentals with the IBM IT Support Professional Certificate. You'll have the opportunity to master the most up-to-date practical skills and tools used by IT support professionals and how to apply them in an everyday professional setting. By the end, you’ll have had the opportunity to gain the skills required to succeed in an entry-level IT job. 

Layers in network models

The open systems interconnection (OSI) model is a framework for the structure of data transmission through networks. The OSI model has seven layers, but not each is necessarily implemented as the model suggests for a functioning network. The layers are an abstract view of how a network functions, so that network administrators or technicians can more easily identify where issues in the work occur. The seven layers that make up the OSI are:

• Layer 7: The application layer, where users interact with applications connected to the internet

• Layer 6: The presentation layer, where data is partially encrypted and translated into a transmittable format

• Layer 5: The session layer, which controls ports and sessions and maintains connections between devices

• Layer 4: The transport layer, which uses TCP and other protocols to assemble and sequence packets in the order they are to be sent out 

• Layer 3: The network layer, which routes packets by telling them which physical path to take between routers and switches 

• Layer 2: The data link layer, which works with layer 2 switches, hubs, and other devices, and splits into the MAC layer 

• Layer 1: The physical layer, which transmits the data over the hardware components of the network, such as cables and the network architecture 

Read more: Network Certification: 5 Options for Your IT Career

What does the presentation layer do in the OSI model?

The presentation layer translates data from the application layer for transmission to the application layer for use by the intended device. It makes the data readable to and from the application layer. This layer is where encryption occurs when data is sent from the application layer, and when decryptions occur, it is sent back to the application layer. It identifies the receiving data to know it and decrypts data to the proper receiving device in a process known as authentication. 

When sending data to layer 5, the session layer compresses data to save storage space and speed transmission. Serializing complex structures also helps translate data structures into different formats that are easier to transmit. This process converts complex data structures into easily transmittable bytes in a format that all networks can read. The presentation layer uses abstract syntax notation (ASN.1). 

Abstract syntax notation (ASN.1)

ASN.1 is the international standard for representing, encoding, and transmitting data structures across networks. It uses abstract syntax to indicate data structures universally and transfer syntax to describe the bit encoding of the ASN.1 object. It also provides a standardized set of rules for device encoding processes, making it non-ambiguous and readable by programmers and network engineers. 

When an application sends data, the presentation layer converts the data object into ASN.1 for transmission across the network. Upon reception of the intended device, the presentation layer converts the data out of ASN.1 and back into the original data object on the intended device. This process is useful because it follows the structure of other programming languages, like C. 

External data representation (XDR)

External data representation (XDR) is a less complex but less powerful alternative to ASN.1. For XDR to function, network peers must know the defined types involved in transmission instead of the universal method of ASN.1. XDR only uses data streams of 4 bytes, in the order in which the network receives them. All of these simpler processes give XDR a speed advantage over ASN.1. 

Additional presentation layer protocols

The presentation layer may use a series of additional protocols depending on the needs of the application layer. Several historical (and contemporary) examples can help illustrate how the presentation layer functions. These protocols include:

• Independent computing architecture (ICA—active): Developed by Citrix, this protocol allows users from different locations to house data in one central virtual server.

• Network data representation (NDR—active): This protocol encodes data in a distributed computing environment (DCE) by placing an architecture tag before each message and using a compiler to generate stubs.

• Apple filing protocol (AFP—legacy): Developed by Apple, this protocol allowed users of multiple Mac computers to share files over a network easily.

• Lightweight presentation protocol (LPP—legacy): This smaller, simpler non-ISO presentation protocol allowed ISO presentation services over UDP and TCP networks.

• NetWare core protocol (NCP—legacy): Developed by Novell, this protocol described routines and primitives allowing client-server communication on Novell NetWare operating systems and others, such as Linux, UNIX, and Windows NT.

Who uses OSI and the presentation layer?

The OSI model is a framework that IT professionals, such as network administrators and cybersecurity analysts, use to diagnose network or security problems. The OSI layers give network admins a working structure to diagnose whether network issues occur on the application end, host device, or network. Since the presentation layer works with encryption and decryption, it is vulnerable to attacks, making it an important networking aspect for cybersecurity analysts to understand. 

Understanding the OSI and presentation layer is also useful for software designers, as it allows them to understand how their software interacts with the network when it makes network requests or sends data. 

How to get started in networking

Understanding the OSI model is important for anyone needing to troubleshoot a network. It provides a framework for understanding how the bitstream flows through various networking aspects.

Network technicians are an entry-level position that must diagnose and analyze network issues and work with computer problems that may arise from a network or device issue. To become a network technician, you typically need at least an associate degree, and some employers may require you to have specific IT certifications that validate your skills. In this role, you'll often work under network administrators who also often start as network technicians. Employers typically require a bachelor’s degree in IT or computer engineering to advance to a network administrator. The median total pay for a network technician in the US is $83,000 [1]. This figure includes base salary and additional pay, which may represent profit-sharing, commissions, bonuses, or other compensation.

Understanding and having various methods to troubleshoot networking issues is an essential skill for network technicians to develop to be effective in their work. You might also consider developing technical support skills and gaining experience with LINUX, VPN, and other networking hardware systems.

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