What Are Network Protocols and How Do They Work?

As our world becomes more connected through the internet and networking, it’s important to understand how devices communicate with each other via network protocols. So what are network protocols?

In essence, network protocols are established sets of rules that determine how data is transmitted between different devices on a network. They provide common languages that allow devices to exchange information reliably, regardless of differences in their internal structures, processes, or standards. 

Network protocols are essential—without them, networked devices would be unable to interoperate and the modern internet as we know it simply could not function. When you send an email, view a web page, stream a video, or transfer a file across a network, you are relying on network protocols.

In this post, we will explore what network protocols are, how they work based on the OSI communication model, the types of protocols, who uses them, and more. By the end, you will have a solid understanding of the backbone of network connectivity.

What are network protocols? 

A network protocol specifies rules and procedures for communication between two or more network devices, enabling them to exchange information as sender and receiver reliably. Network protocols define conventions including:

• Syntax for formatting messages 
• Semantics for interpreting meaning
• Synchronization for coordinating transmission
• Error handling for fault tolerance

Protocols formalize the details of how messages and data packets should be structured, addressed, transmitted, routed, and received at the destination successfully. This allows different devices with various hardware and software to communicate across heterogeneous networks.

It’s a bit like two companies from different countries deciding on a third-party common language to conduct all their business transactions. More often than not, that language is English, even if both companies are from non-English-speaking countries.

In a similar manner, network devices with completely different hardware and software rely on common protocols to communicate reliably, just like international companies adopt English as a universal language to do business together successfully. 

The protocols provide a standardized language that allows these devices to exchange information in formats they both understand, just as English grammar and vocabulary bridge comprehension gaps between parties. 

How do network protocols work?

Understanding network protocols requires first understanding how devices communicate over networks. The OSI (Open Systems Interconnection) model is a framework that conceptualizes how network communication works across seven distinct layers. Each layer handles specific functions required for devices to communicate over networks.

To send data from one device to another, the data passes vertically down through each OSI layer on the sending device, where the protocols at each layer add more information and prepare the data for transmission. 

The data then actually gets transmitted as raw bits across the physical medium (like Ethernet cables) to the receiving device. Then on the receiving end, the data passes back up vertically through each OSI layer where protocols peel information off and process the data until it reaches the target application intact.

So in essence, each OSI layer adds more context to make raw data transmittable, kind of like putting a letter in an envelope, adding postage and an address before mailing.

Here is a simplified explanation of each layer:

1. Physical layer: This base layer handles the physical transmission of the raw data bits onto network hardware like cables and network cards. Protocols define the electrical/optical signaling and interfaces.
2. Data link layer: Takes the raw bitstream and divides it into data frames by adding physical addresses. Protocols detect transmission errors and handle retransmissions.
3. Network layer: Handles the logical transmission of data packets by adding logical addresses and routing so data hops across network paths to reach the destination. Common protocols here include IP and ICMP.
4. Transport layer: Establishes end-to-end connections, and ensures reliable delivery by checking for errors and retransmitting dropped packets if needed. This is where you’ll find TCP and UDP.
5. Session layer: Coordinates communication sessions by establishing session connections between devices, verifying access permissions, managing data exchange during sessions, and cleanly closing sessions afterward through specialized protocols.
6. Presentation layer: Handles preparing the data for the application layer through data formatting, encryption, compression, etc. through translation protocols to standardize data exchange.
7. Application layer: Contains protocols allowing software processes and applications to exchange data, including file transfers, emails, and media streaming through common application protocols like HTTP and FTP.

In other words, network communication relies on protocols embedded in each OSI layer to reliably get data from applications on one device to another device’s applications.

How network protocols function at the OSI layers

Now that you know the OSI model’s layers, here are some examples of how specific network protocols function at each layer:

Physical layer network protocols

Common physical layer protocols specify standards for transmitting raw bit streams between two network nodes connected physically.

Physical protocols include:

• Ethernet Physical Layer: Handles electrical signaling, cabling like Cat 5 and fiber optic connections.
• Wi-Fi Physical Layer Standards: Institute of Electrical and Electronics Engineers (IEEE) 802.11 protocol standards encompass wireless transmission over radio frequencies along with modulation schemes.

Data link layer network protocols

The data link layer manages node-to-node communication, turning raw physical transmissions into orderly, addressed frames via protocols handling synchronization, error checking, flow control, and more.

Examples include: 

• Ethernet Data Link Protocols: IEEE 802.2 Logical Link Control (LLC) and IEEE 802.3 Medium Access Control (MAC) jointly handle physical addressing, frame synchronization, and error detection.
• Point-to-Point Protocol (PPP): Enables direct serial data links between nodes by formally encapsulating datagrams with error detection and optional compression. 

Network layer protocols 

Network layer protocols route and forward packets through intermediary network devices over one or more physical links toward their destinations.

Key examples include:

• Internet Protocol (IP): IP defines packet structuring with source and destination addressing for transmission over the internet along with handling fragmentation and reassembly.
• Address Resolution Protocol (ARP): Discovers physical machine address tied to a known IP address for transmitting over the local network segment.
• Internet Control Message Protocol (ICMP): Reports issues in network connectivity, performance, or errors through alert messages like echo replies or destination unreachable messages. 

Transport layer protocols

End-to-end transport protocols ensure reliable, ordered delivery of application data between two hosts through layered services: 

• Transmission Control Protocol (TCP): Verifies sequenced, complete arrival of data and requests retransmission when issues are detected using acknowledgements and checksums. TCP congestion control mechanisms regulate transmission rates.
• User Datagram Protocol (UDP): Offers simpler connectionless transport of encapsulated packets without strict delivery guarantees, useful for broadcasting messages or time-sensitive purposes like games and streaming media.

Session layer protocols 

The session layer allows hosts to establish shared states for reliable, orderly exchanges through protocols handling elements like:

• Session establishment, keep alive, and termination
• Authentication and reconnection procedures
• Communication zones for full or half duplex data flows 

Common protocols include Network Basic Input/Output System (NetBIOS) or Remote Desktop Protocol (RDP).

Presentation layer protocols

The presentation layer handles data formatting, encryption, and compression through protocols enabling uniform data exchange: 

• Encryption protocols like Secure Socket Layer (SSL) and Transport Layer Security (TLS) cipher application data into encrypted payloads using certificates and digital signatures along with key exchange mechanisms.
• Video compression protocols like H.264 standardize video encoding optimized for streaming bandwidth constraints.
• Graphical image formats ranging from GIF and JPEG to PNG render digital image data uniformly across platforms.

Application layer protocols

Top-layer application protocols allow networked software processes and users to communicate, leveraged by common network apps and services, including:

• Hypertext Transfer Protocol (HTTP) retrieves web resources like HTML files from servers over TCP connections in a client-server manner to render websites in browsers.
• File Transfer Protocol (FTP) copies files between hosts over a TCP/IP network, popular for uploading web content. 
• Simple Mail Transfer Protocol (SMTP) handles sending and forwarding email reliably over IP networks between mail servers until arriving at the destination mail server. 
• Session Initiation Protocol (SIP) sets up and tears down voice-over IP or video call sessions through encoded audio data packet transmissions enabling real-time communications.

Who uses network protocols?

While network technicians and IT professionals work the closest with network protocols for their management, design, and troubleshooting purposes, practically everyone who uses any form of tech will touch networked applications.

In other words, we all depend on network protocol functionality for essential daily connectivity, including:

• Running as fundamental data transmission conduits across the internet 
• Underlying email, websites, and apps transmitting information between servers and clients like browsers, mobile devices, and computers used by billions every day
• Enabling real-time voice and video calls via mobile and conferencing apps by reliable transport of multimedia communication streams
• Allowing file downloads and transfers essential to data exchange and storage solutions like the cloud

So while the average user might not be familiar with the nitty gritty of what is a network protocol or how it works, anyone exchanging data over a network fundamentally relies on smooth protocol communication under the hood.

Types of network protocols

Given the vast range of communication responsibilities handled, network protocols come in different classifications tailored for specialized functions. The most common network protocols are categorized as follows.

Communication protocols

Communication protocols establish fundamentals for reliable data transmission between network nodes, governing how data gets formatted, addressed, routed, ordered, verified, and interpreted between sender and receiver. Examples include TCP/IP, FTP, UDP, and more.

Network management protocols 

Specialized network management protocols allow centralized configuration, monitoring, and troubleshooting so network administrators can track performance, discover issues proactively, and maintain optimal network operation. Protocols like SNMP and ICMP provide insights through status data polling, notifications, and operational messaging.

Network security protocols

Security protocols safeguard network communication and infrastructure through encryption, access restrictions, and activity monitoring to provide data protection in transit and at rest, along with guarding network resources. Common examples include IPsec, SSH, TLS, SSL, and firewall protocols.

What are the vulnerabilities of network protocols?

While network protocols enable universal connectivity, they can also open networks to risks if not properly protected. Since protocols focus chiefly on availability and performance rather than security, they carry inherent vulnerabilities that malicious actors exploit through attacks. These include:

• Protocol exploits: Discovery of specification or implementation weaknesses violating secure data exchange. For example, flaws like Heartbleed abused gaps in the TLS protocol encryption implementations.
• Eavesdropping: Intercepting insecure protocols exposing unencrypted communication, like plain text transmitted between client and server over Telnet’s TCP connection.
• Spoofing: Impersonating a trusted source by manipulating address data in protocol messages enables infiltration past network security layers and unapproved access. 
• Denial-of-service (DoS): Bombarding systems with protocol messages like pings overloads computing capacity, causing unavailability by exhausting resources. 
• Protocol tunneling: Malware and command-and-control communication sneak past firewalls camouflaged inside permitted protocol traffic, thereby evading detection through deception. 

To defend networks on an ongoing basis, protocols need regular hardening and patching to address vulnerabilities as they emerge. Additionally, monitoring protocol traffic patterns acts as a safeguard by detecting abnormal usage behaviors that reveal the fingerprints of threats seeking to exploit communication protocols for malicious ends. 

Network protocols: Enabling smooth communication through common language

Network protocols basically make modern digital connectivity possible. They allow billions of devices to exchange data every day across the internet by establishing standardized rules for communicating reliably. Whether you’re browsing a website, sending an email, or transferring files, you can do it because network protocols are working in the background to make it possible. 

While people mostly experience user-facing applications, the protocols operate the machinery that coordinates successful data delivery between devices over complex global networks. Just like standardized shipping procedures ensure mail arrives at its intended destination regardless of geography or language barriers, network protocols manage universal machine-to-machine comprehension.

Network engineers leverage protocols as building blocks configuring how networks operate, while cybersecurity analysts scrutinize them looking to mitigate vulnerabilities. Optimizing network infrastructure requires a sound grasp of the strength of these protocols to use them effectively.