Computer networks have become integral to our modern digital world. From browsing the web to sending emails and transferring files, network connectivity enables countless applications and services. However, this would not be possible without network protocols, which provide a common language for devices to exchange information reliably.
This article will explore some of the most common network protocols that drive communication and connectivity in networks and the Internet. We’ll explore what network protocols are, the main types, and then dive into 30 of the most common protocols—from foundational communication protocols like TCP/IP to specialized ones for network security, management, and various applications.
What is a network protocol?
A network protocol consists of guidelines and procedures for communication between network devices. These common languages allow networked systems to understand each other, similar to human languages. For example, people who speak English can understand each other due to the common vocabulary and grammatical rules.
Protocols define rules for transmitting or exchanging data, such as syntax, semantics, synchronization, and error recovery. They enable the reliable transfer of information by formalizing details like formatting, addressing, packaging, and error checking. Like how books have specific structures, such as parts, chapters, sections, and so on, which both the author and the reader can understand.
Network hardware and software require protocol support to understand incoming data and handle tasks like routing traffic to intended destinations. Many key protocols are standardized to ensure cross-platform interoperability. However, some proprietary protocols may only work between devices from the same vendor.
Main types of network protocols
Network protocols serve different primary purposes, which allow us to categorize them into main functional types. It’s helpful to understand the role of each type within the bigger picture.
Communication protocols
Like a postal service delivering letters and packages between homes, communication protocols enable devices to exchange messages and data payloads across networks. They establish rules and conventions for reliable data transfer from senders to recipients.
Examples include TCP/IP, the core delivery protocol of the Internet, FTP for file transfers, and SMTP for email.
Communication protocols enable vital networked applications and services we use daily, such as websites, email, file sharing, media streaming, and more. They form the basic transport mechanisms for connectivity.
Network security protocols
If communication protocols are the messengers moving data between devices, network security protocols act like security guards regulating access and protecting the data flows.
Security protocols employ measures like encryption and authentication to secure communications from eavesdropping or harmful tampering—much like security personnel safeguard facilities.
Protocols like SSH, SSL/TLS, and IPsec create secure tunnels to shield data and validate identities. Just as guards check badges at facility gates, security protocols block unauthorized access.
Network management protocols
Network management protocols enable administration capabilities to monitor performance and remotely configure network equipment.
They’re like IT administrators overseeing the health of devices across networks and managing configurations. Protocols like SNMP and ICMP provide insights into network status to diagnose and troubleshoot issues. Others like DHCP and DNS dynamically assign IP addresses and map device names.
Management protocols grant networks greater robustness and control just as capable administrators keep enterprise IT infrastructure humming.
16 common network protocols
When it comes to the day-to-day functioning of modern networks, a core set of protocols handles the heavy lifting behind the scenes.
Here are some of the most common network protocols you’ll encounter, from the widespread TCP/IP that keeps the Internet humming to more specialized ones routing email, securing remote access, and much more.
Communication protocols
1. Transmission control protocol/Internet protocol (TCP/IP)
The Transmission Control Protocol/Internet Protocol (TCP/IP) suite facilitates communication by handling the encapsulation of data into packets at the sender, transmitting it reliably across networks, routing packets to the destination address via intermediary network devices like routers and switches using Internet Protocol (IP), before finally reassembling packets in the proper order at the receiving host.
Built-in error-checking capabilities automatically request the retransmission of any missing or corrupted packets. This provides reliable end-to-end connectivity crucial for virtually all modern applications to function well over LANs and the Internet alike.
However, attacks such as SYN floods and IP spoofing may attempt to undermine availability by overwhelming target systems with bogus requests or impersonating trusted devices.
2. User datagram protocol (UDP)
User Datagram Protocol (UDP) offers a lean alternative to TCP. It essentially trades reliability for speed, proving useful for time-sensitive purposes like video calling, streaming media, and online gaming. By skipping error-checking steps, UDP saves processing overhead and accelerates data transfers, delivering packets quickly but without guarantees.
Thus, packets may arrive out-of-order or go missing altogether. While acceptable for streaming audio/video applications able to tolerate such losses, UDP can be risky in transferring critical data. Security mechanisms are also lacking, making encrypted alternatives more secure for sensitive applications.
3. File transfer protocol (FTP)
The venerable File Transfer Protocol (FTP) still sees widespread use for uploading and downloading files between client and server over a TCP/IP network. Web hosting environments often employ FTP to provide multiple contributors with file access for routine website updates.
FTP options like directory listings and non-interactive transfers make batch operations convenient. However, privacy is sorely lacking as login credentials and data transfer in cleartext without encryption. The encrypted FTPS variant addresses this issue for use cases requiring tighter security.
4. Session initiation protocol (SIP)
SIP serves as the backbone for multimedia sessions over IP networks. So, while analog signals ran over telephone networks before, SIP helped “packetize” voice and media into data that can be transmitted digitally.
From modern video conferencing apps to entire cloud phone systems used by large contact centers, SIP makes all of that possible. It handles the nitty-gritty signaling, session management, and teardown details so audio, video, and other media exchange happen smoothly across the internet. SIP integrates with standardized voice and video protocols to make internet-based real-time communications possible.
Network security protocols
5. Secure shell (SSH)
Secure shell, commonly known as SSH, is one of the most prevalent network protocols used today. It enables secure remote login connections to devices like servers, switches, and firewall appliances from client software.
SSH sets up an encrypted tunnel to protect the authentication session and subsequent remote access from eavesdroppers. It prevents plainly transmitting credentials that could be intercepted. SSH replaces older insecure protocols like Telnet and rlogin, which are still sometimes used but lack encryption.
Over the years, SSH has become a Swiss-army knife network tool that administrators worldwide rely on for tasks like securely transferring files with SFTP and tunneling or port forwarding network traffic.
Commercial SSH implementations boast advanced features out of necessity focused on availability, compliance, and threat prevention. For example, granular access controls, detailed session logging, and host key management integrate SSH deeply with identity and authentication ecosystems while responding to vulnerabilities.
6. Secure sockets layer (SSL) / Transport layer security (TLS)
Transport layer security (TLS) and its older relative, the Secure sockets layer (SSL), implement cryptographic protections for data in motion across networks. Encrypting application traffic and authenticating connecting parties using certificates prevents tampering and eavesdropping.
Numerous applications transparently overlay TLS/SSL without users noticing. Examples include HTTPS web browsing, Secure shell encrypted terminal sessions (SSH), Virtual Private Network tunnels (VPN), and secure email.
However, TLS is vulnerable because, when faced with certain attacks, it devolves connections to a weaker encryption. Keeping software up-to-date and properly validating certificate chains maintains robust security foundations for applications.
7. Secure FTP (FTPS)
FTP enjoys longevity, securing crucial yet predictable file transfer needs globally across industries. FTPS supercharges FTP by adding SSL/TLS-based encryption, mitigating data theft or tampering risks over unprotected transfers.
Depending on the configuration, FTPS setup modes implicitly presume encryption versus explicitly commanding upfront. Supporting the latest cryptographic agility and enforcement practices is key, given lengthening data retention mandates.
With growing runtime exploitation and malware threats, however, content scanning before final storage brings vital assurances. Overall, while FTPS brings necessary encryption, centralized access controls and integration with funnel points like proxies and firewalls ensure governance beyond just the wire.
FTPS will continue meeting tactical secure file transfer demands while web portals and managed file-sharing services suit more dynamic requirements involving external parties.
Network management protocols
8. Simple network management protocol (SNMP)
Simple network management protocol or SNMP is widely used for monitoring and managing all sorts of network-connected devices—from routers and switches to printers, firewalls, and servers. It works by letting an SNMP manager send queries to devices being monitored, which each have a small piece of SNMP agent software installed to collect status and performance data.
SNMP can track valuable telemetry like uptime stats, link utilization, errors spotted, and plenty more. The agents gather all this and report back to monitoring tools so network administrators can get a nice centralized view instead of checking individually. SNMP even supports alerts and notifications for faults or thresholds being crossed, known as SNMP traps, namely messages sent from monitored devices to the manager to indicate an anomaly or issue.
When it comes to SNMP, there are a few different versions available. SNMPv2 and SNMPv3 are the most common currently in use. SNMPv3 is more advanced, introducing stronger security with encryption and authentication, unlike the older SNMPv2.
However, SNMPv2 remains popular still in many organizations due to legacy compatibility issues making it hard to upgrade fully to SNMPv3 across the board. The tradeoffs between SNMP v2 vs. v3 center around improved security and performance gains in the newer standard at the cost of a more complex configuration.
9. Internet control message protocol (ICMP)
The Internet Control Message Protocol (ICMP) handles basic diagnostic functions like querying whether destinations are reachable and responding with status updates. ICMP is best recognized as enabling ubiquitous “ping” connectivity verification requests emitted by network troubleshooting tools, triggering target devices to report back timing and availability data.
By default, networks usually permit ICMP packets as blocking will obstruct vital network monitoring. However, excess ICMP traffic can sometimes be exploited to flood networks in denial-of-service brinksmanship. Like UDP, ICMP eschews hard security, given it predates modern encryption.
10. Address resolution protocol (ARP)
Devices communicate via MAC addresses on local networks. But we often only know IP addresses for destinations. The address resolution protocol bridges this gap by resolving IP addresses to associated MAC addresses that network adapters use. Your computer maintains an ARP table caching these mapped addresses locally.
When you try reaching a new destination, broadcasts seek the MAC for the IP, update the table after getting a reply, and subsequently transmit. Under the hood, the process is invisible to users. Unfortunately, ARP lacks authentication natively, meaning cache entries can get overwritten by spoofing attacks. Protecting ARP behavior is thus important for robust connectivity on local network segments.
11. NetFlow
Where SNMP focuses on device-level statistics, NetFlow lets you step up to network-wide monitoring and analysis by understanding traffic patterns coursing through your infrastructure. By processing flow-based data about connections, the volume, timing, directionality, duration, endpoints, and applications involved all become transparent.
Network flow records cement visibility into network usage and dependency, empowering informed decisions about capacity, security, layout, and more. The catch lies in NetFlow compliance—next-gen firewalls and web proxies generally work, but switches and routers need capabilities enabled. Otherwise, blind spots manifest where critical flows lack visibility.
12. sFlow
sFlow is a packet sampling technology used for monitoring network devices like routers, switches, and wireless access points across vendors. Unlike NetFlow, which samples full packet flows, sFlow randomly samples 1 out of N individual packets passing through an interface. This sampling occurs at wire speed via dedicated hardware chips embedded in the network devices.
A sFlow software agent combines the sampled packet data with interface counters and forwards table info into sFlow datagrams. These datagrams are shipped off to a central sFlow collector for analysis. So, while less comprehensive than NetFlow, sFlow provides network-wide visibility with quantifiable accuracy—especially for bandwidth-heavy traffic like streaming video.
The sFlow collector can feed data to traffic analysis tools. By processing sFlow data from multiple interfaces, these tools deliver valuable capabilities like spotting traffic congestion, detecting rogue apps, and profiling historical trends for proactive performance management.
So, the sFlow vs NetFlow debate lies in whether an organization can work with packet sampling or requires full-flow analysis.
13. Border gateway protocol (BGP)
On the wild internet, BGP helps tame things by managing routing data exchange between organizations. It essentially maintains a large-scale map of network reachability between autonomous systems that agree to share access. Your ISP likely participates, enabling your traffic to traverse multiple networks when accessing websites abroad.
By distributing routing updates, BGP-enabled routers know which paths packets should traverse to reach intended destinations. Validating route announcements and preventing malicious hijacking is thus crucial for BGP security and reliability mechanisms. Within corporate networks as well, BGP is key for connecting privately managed subnets and sharing route data.
14. Domain name system (DNS)
DNS functions as a phonebook for the Internet. This protocol translates domain names that humans can easily remember, like google.com or wikipedia.org, into numerical IP addresses that computers and routers use to fetch the correct websites and content. It essentially matches names with the right numbers.
A breakdown can occur if the DNS information that maps a domain to an IP gets somehow modified or corrupted by an attack. When the DNS “records” providing this name-to-address mapping get poisoned or altered, browsers and apps can get misdirected. This unfortunately remains one of the simpler ways even massive websites go offline suddenly.
15. Dynamic host configuration protocol (DHCP)
Networks keep functioning smoothly in part thanks to DHCP performing helpful background work across all those routers, switches, servers, and devices. Whenever endpoints like laptops, phones, or tablets connect to the wireless network or plug into the wired LAN ports in office buildings, DHCP does the housekeeping work of assigning them valid IP addresses plus other critical networking information as part of the join process.
By automatically allocating IP addresses instead of manual configuration, DHCP simplifies management for devices ranging from home routers to complex enterprise networks. However, if something goes wrong, such as a rogue DHCP server appearing on the network and interfering or a denial-of-service attack flooding a DHCP server with fake requests, new devices won’t be able to obtain the settings they need to get online.
16. Telnet
Despite security shortcomings compared to newer tools, Telnet remains a useful way to remotely access devices over the network. It enables commands to be run on routers, switches, or servers from another system with network connectivity as though seated at the target device’s console, which is handy for tasks like tweaking settings or grabbing debug logs.
However, everything gets exchanged between the admin’s PC and the managed device in plain, unencrypted text, including account credentials and privileged commands. Sniffing the traffic makes stealing sensitive information extremely easy, meaning Telnet access requires additional controls like jumpboxes to limit exposure.
Tools and resources for network protocol analysis
Analyzing network protocols and traffic is vital for monitoring performance, troubleshooting issues, and identifying security threats on a network. Many tools and platforms provide network administrators visibility into protocols and data flows.
Packet analyzers like Wireshark offer deep inspection into traffic down to individual packets and bytes on a network segment. Wireshark can decode and log TCP/IP communications, ICMP error messages, application protocol exchanges, and more for advanced diagnostics. Platforms like SolarWinds also provide integrated network monitoring and analysis with capabilities like packet capturing to record traffic for examination.
Flow-based analyzers, including ManageEngine NetFlow Analyzer, give longer-term visibility into overall traffic volumes and patterns by tracking IP flows. As an alternative to packet-level data, flow analysis conserves resources for high-level bandwidth monitoring, capacity planning, and usage trends.
Vulnerability scanners like Nessus can uncover weaknesses in the implementation of various network protocols and services. By checking for open ports running outdated protocol versions or known vulnerable software, these tools can reveal services susceptible to compromise. Penetration testing also probes real-world protocol robustness.
Tools like Nmap check for ports and services exposed to networks, reporting on versions and configurations to identify unneeded connectivity that warrants closing to avoid exposure. Port scanning gives administrators network topology visibility to tighten access control and flows between network zones.
Intuitive monitoring systems like Auvik provide an integrated view of network status and performance with automation to reduce the overhead of continually gathering data manually. Auvik leverages capabilities like automated network discovery and mapping to track infrastructure, combined with machine learning for traffic analysis without extensive customization. This enables insight into bandwidth consumption and protocols without hands-on packet inspection.
The wealth of analytics data from Auvik’s TrafficInsights and related tools allows for quick drilling into details when high-level overviews expose anomalies or underperformance. Geolocation of traffic flows also facilitates tracking unauthorized or suspicious connectivity that could reflect vulnerabilities being exploited.
With its configuration change tracking and backup, along with intelligent alerting, Auvik enables administrators to maintain networks proactively. Trend data guards against emerging issues, while rapid fault isolation capabilities speed mitigation when problems do arise.
Emerging technology influencing network protocols
While entrenched protocols like TCP/IP continue to power much of today’s networks, innovative new approaches are emerging to enable the connectivity demands of cutting-edge technologies on the horizon.
As technologies like self-driving cars, artificial intelligence, Internet of Things (IoT) devices, and new cellular standards like 5G transition from buzzwords to reality, they place unprecedented demands on networks in terms of scale, speed, reliability, and adaptability.
Lightning speed 5G and AI
5G cellular networks aim to be up to 100x faster than existing 4G networks. We’re talking gigabits per second data rates, allowing HD movie downloads in seconds. Existing protocols may fall short, requiring new optimized mechanisms tailored for technologies like network slicing and software-defined mobile edge computing essential for 5G services.
Similarly, bandwidth-hungry AI and machine learning applications need to shuttle enormous training data sets from sensors and datasets to power predictive analytics, autonomous decision-making, and conversational interfaces. TCP with congestion control throttles throughput for reliability. New protocols like Quick UDP Internet Connections (QUIC) offer innovations like improved congestion handling.
Internet of things and edge computing
Connecting billions of IoT devices, such as appliances, machinery, meters, and wearables, poses scaling challenges. Low-power devices often lack resources for complex protocols, requiring compact, efficient alternatives.
New device-centric IoT protocols optimize message formats, operating with limited processing capability and intermittent connectivity typical of sensors. Data flows need management from edge gateways.
As edge computing proliferates with intelligence heading closer to local devices, protocol mechanisms customized for localized traffic domination, high-volume data aggregation, and location or context awareness help cut networking overhead. Serverless designs offload connectivity management across decentralized nodes.
Connected transport
Network protocols for autonomous vehicle systems need location-based optimizations with reliable hand-offs between cells and hardware heading up to gigabit speeds as vehicles rapidly traverse multi-access edge networks.
V2X communication protocols tailored for cloud-supported transport apps offer smart junction negotiation and collective perception for traffic management. Security is also paramount with vehicle communication vulnerabilities being extremely risky.
Crypto-agile security
With cyberattacks becoming increasingly advanced and devastating, zero-trust approaches are imperative for concealing even metadata like message headers or packet timing via encryption. Improperly implemented cryptography remains a top vulnerability, though.
Future-ready protocols increasingly support algorithm extensibility and agility to allow security upgrades. Design best practices like crypto-first methodologies promote encryption rather than bolting it on later.
In essence, new protocols optimize for specific use cases like high-performance media delivery, reliability in intermittent connections, collective communication within endpoint groups, security hardening, and decentralized operation. These are key expectations from new technology that today’s networks weren’t originally built for.
Adaptable protocols also ease the transition, like improving congestion handling during the 5G rollout. Sometimes, multiple protocols run alongside each other. For example, Wi-Fi and 5G sharing loads in hybrid access. Ultimately, the network shifts from rigid plumbing to a smart, customizable connectivity canvas suiting specialized needs.
Common network protocols form the foundation of connectivity
Network protocols work tirelessly behind the scenes to drive the connectivity most people take for granted nowadays. These common network protocols come in all shapes and sizes, from foundational communication protocols like TCP/IP that deliver data packets between devices to specialized security protocols like SSH that build encrypted tunnels to protect sensitive information in transit.
New innovative protocols are emerging to handle cutting-edge technologies like 5G and IoT that pose greater demands. But the proven workhorse protocols will continue to provide reliable heavy lifting day in and day out for the networking tasks that we count on.
However, as new connectivity paradigms like edge computing and widespread encryption reshape traffic and access patterns, network administrators need deeper visibility into protocol behavior, performance impact, and security vulnerabilities.
Integrated monitoring and analytics platforms, along with advanced capabilities like machine learning and automation, will be key enablers for next-gen network operations capable of harnessing the protocol innovations to come. By understanding what powers networks beneath the surface, we are better equipped to design, manage, and secure our connectivity infrastructure.
