Network Security Protocols: The Complete Guide for IT Teams

Network security protocols are formally defined rules governing secure communication, spanning encryption protocols like TLS and IPsec, authentication protocols like RADIUS and Kerberos, and integrity protocols like DNSSEC, each defined by a standards body and operating at a specific layer of the network.

If you’ve heard IPsec, TLS, and SSH mentioned together and couldn’t confidently explain how each one actually works, this guide fixes that.

What Does Network Security Protocols Cover and How Is This Organised?

A network security protocol is a formally defined set of rules governing how devices communicate securely. That covers how connections get authenticated, how data gets encrypted in transit, and how the integrity of that communication gets verified along the way.

This guide is organized by function rather than as a flat, alphabetical list. Grouping protocols by what they actually do, encryption, authentication, name resolution, device management, wireless, gives you a genuine mental model to work from, rather than a random sequence of acronyms you have to memorize independently.

Three honest boundaries worth naming upfront. Authentication protocols get real, practical coverage here, but the complete Authentication, Authorization, and Accounting framework these protocols sit within deserves its own dedicated treatment elsewhere. Cryptographic concepts get used in context, TLS’s handshake, IPsec’s encryption modes, but symmetric versus asymmetric encryption as standalone theory belongs elsewhere. And compliance frameworks like NIST, ISO 27001, or PCI DSS aren’t developed here at all, since that’s a genuinely different topic focused on audits, not protocol mechanics.

Encryption and Transport Security Protocols — TLS, IPsec, SSH and HTTPS

TLS, or Transport Layer Security, has come up already in this pillar’s discussion of inspection and filtering, but here’s what it actually is as a protocol in its own right. TLS works through a handshake process: the client and server negotiate a cipher suite, agree on how they’ll encrypt data, and establish a shared session key together. Certificate-based authentication confirms the server is genuinely who it claims to be before any sensitive data gets exchanged. TLS 1.2 and TLS 1.3 remain the current, secure versions in active use. TLS 1.0 and 1.1 are deprecated and shouldn’t be permitted anywhere on a modern network.

IPsec is genuinely new territory worth understanding properly. It’s a protocol suite securing IP communications through two core components. Authentication Header, or AH, provides integrity and authentication without encryption, confirming data hasn’t been tampered with but not hiding its content. Encapsulating Security Payload, or ESP, provides encryption alongside authentication, actually hiding the data’s content from anyone intercepting it. IPsec also operates in two distinct modes: tunnel mode encrypts the entire original packet, the standard approach for site-to-site VPNs connecting two office locations, while transport mode encrypts only the payload, more common for direct host-to-host communication. Before AH or ESP can protect anything, Internet Key Exchange, or IKE, establishes the secure connection itself, negotiating the shared keys both sides will use.

SSH, Secure Shell, is the standard protocol for secure remote administrative access to network devices and servers. It replaced legacy, unencrypted protocols like Telnet, which transmitted credentials and commands in plain text, meaning anyone intercepting that traffic could read an administrator’s password directly.

HTTPS is worth naming directly as the most commonly encountered example of all of this working together. It’s simply HTTP running over a TLS-secured connection, the practical, everyday combination nearly every internet user interacts with constantly, whether they realize it or not.

Network Security Protocols by Function and OSI Layer

Protocol	Function	OSI Layer	Defining Standards Body
TLS	Encrypts traffic, authenticates server	Above Transport (Layer 4)	IETF (RFC)
IPsec	Encrypts/authenticates IP communications	Network (Layer 3)	IETF (RFC)
SSH	Secure remote administrative access	Application (Layer 7)	IETF (RFC)
HTTPS	HTTP secured via TLS	Application (Layer 7)	IETF (RFC)
RADIUS	Centralized network access authentication	Application (Layer 7)	IETF (RFC)
TACACS+	Administrative device access authentication	Application (Layer 7)	IETF (RFC)
Kerberos	Ticket-based authentication	Application (Layer 7)	IETF (RFC)
DNSSEC	Cryptographically verifies DNS responses	Application (Layer 7)	IETF (RFC)
SNMPv3	Secure device monitoring/management	Application (Layer 7)	IETF (RFC)

Authentication Protocols — RADIUS, TACACS+ and Kerberos

RADIUS, Remote Authentication Dial-In User Service, is a widely deployed protocol centralizing authentication, authorization, and accounting for network access. It shows up everywhere from VPN access to WiFi authentication, giving you one central place to manage who’s allowed onto your network.

TACACS+ is a related but genuinely distinct protocol. It’s more commonly associated specifically with authenticating administrative access to network devices themselves, your routers, switches, and firewalls, rather than general end-user network access. TACACS+ also separates authentication, authorization, and accounting into more distinct, granular processes than RADIUS handles them.

Kerberos works differently again. It’s a ticket-based authentication protocol, foundational to how Windows Active Directory environments authenticate users. Instead of repeatedly transmitting credentials across the network every time access is needed, Kerberos uses a trusted third party, the Key Distribution Centre, to issue time-limited tickets. That means a user’s actual password travels across the network far less often, reducing the window an attacker has to intercept it.

These three protocols are the specific technical mechanisms that actually implement authentication. The full Authentication, Authorization, and Accounting framework these protocols exist within, as a unified concept, deserves its own complete, dedicated treatment beyond what fits here.

RADIUS vs TACACS+

Criteria	RADIUS	TACACS+
Primary use case	Network access (VPN, WiFi)	Administrative device access
AAA separation	Combined authentication and authorization	Separates authentication, authorization, accounting distinctly
Typical deployment	End-user network access	Router, switch, firewall admin access

DNSSEC — Closing the DNS Blind Spot This Pillar Already Named

Here’s a direct payoff worth delivering on. DNS has already been flagged as an underappreciated security blind spot, and DNS spoofing named as a real, concrete risk, without ever naming its actual solution. DNSSEC is that solution.

DNSSEC, Domain Name System Security Extensions, adds cryptographic signatures to DNS records. That lets a resolver verify that a DNS response genuinely came from the authoritative source and wasn’t altered anywhere in transit. Without DNSSEC, a DNS response is essentially taken on faith; there’s no built-in way to confirm it hasn’t been tampered with along the way. An attacker capable of intercepting or spoofing that response could redirect an employee toward a malicious site while every other indicator looked completely normal.

Here’s a practical detail worth understanding before assuming DNSSEC just works once enabled. Validation depends on an unbroken chain of digital signatures running from the root zone all the way down to the specific domain being queried. That’s called the chain of trust, and it means partial or misconfigured deployment anywhere along that chain can break validation entirely, even if your own domain’s DNSSEC configuration looks perfectly correct in isolation. A business that enables DNSSEC on its own domain but never verifies the signature chain actually resolves cleanly, end to end, can end up with a false sense of protection. This is exactly the kind of gap Cyber Security Solutions Ltd checks for directly during a DNSSEC review, confirming the chain genuinely validates rather than just confirming a checkbox got ticked in a control panel somewhere.

SNMP and Secure Device Management

SNMP, Simple Network Management Protocol, is the standard protocol for monitoring and managing network devices remotely. It’s how many IT teams check device health, pull performance data, and push configuration changes without physically touching each piece of hardware.

Here’s a genuine, well-documented security distinction worth stating plainly. SNMPv1 and SNMPv2c transmit their “community string” credentials, essentially a shared password, in plain text. That’s a long-established, serious vulnerability; anyone intercepting that traffic reads the credential directly. SNMPv3 fixes this by adding genuine authentication and encryption, and it should be the only version permitted on any network handling sensitive traffic.

Here’s why this matters practically, beyond a theoretical checklist item. SNMP is frequently left running with default or legacy configuration on network devices, precisely because it operates quietly in the background, doing its job without anyone actively thinking about it. A device replacement or firmware update can silently reintroduce an older SNMP version even after you’ve already standardized on SNMPv3 elsewhere, making this a genuinely common, easily overlooked gap worth checking directly rather than assuming it’s fine because it was fine last time someone looked.

Wireless Security Protocols, Briefly

WPA2 and WPA3 are the encryption protocols actually securing wireless network traffic, protecting the data traveling between a device and its access point from being read or tampered with by anyone nearby.

Full wireless-specific security practice, including the technical differences between WPA2 and WPA3 and genuine deployment guidance, deserves its own complete, dedicated treatment beyond what a brief mention here can cover properly.

Where Do These Protocols Sit in the OSI Model?

Mapping these protocols back onto their OSI layer clarifies exactly what each one can and cannot protect.

IPsec operates primarily at the network layer, Layer 3, meaning it secures IP communication itself, regardless of what’s actually running on top of it. TLS sits above the transport layer, meaning it secures a specific connection between an application and its destination. SSH and HTTPS both operate at the application layer, Layer 7, working at the level of the actual application making the request.

Understanding which layer a protocol operates at genuinely matters in practice. A protocol securing traffic at Layer 3 protects the underlying connection itself, but says nothing about what’s happening inside the application traffic riding on top of it. A protocol working at Layer 7 sees and protects the application-level interaction directly, but depends on the lower layers already being reasonably secure. Knowing this distinction helps you understand exactly what gap a given protocol closes, rather than assuming any one protocol covers everything.

Network Security Standards — Clarification Before You Go Further

Here’s a genuinely honest disambiguation worth making directly, since “standards” gets used loosely and inconsistently across cybersecurity content generally.

Every protocol covered in this guide is formally defined by a specific standards body. The IETF, through published RFCs, defines TLS, IPsec, and SSH specifically. IEEE defines standards like 802.1X. NIST’s own FIPS validation programme certifies approved cryptographic implementations for use in regulated environments.

This is a genuinely different sense of “standards” from the regulatory, audit-focused meaning you’ll encounter elsewhere, things like NIST CSF, ISO 27001, or PCI DSS. Those are frameworks organizations get audited against to demonstrate compliance. The protocols covered here are technical specifications defining exactly how something works. Related concepts, worth understanding as genuinely distinct things rather than interchangeable terms.

How Do You Audit and Harden Your Actual Protocol Usage?

1. Inventory which protocol versions are actually running across your network, not which ones you assume are configured based on documentation that may be outdated.
2. Disable deprecated, insecure versions explicitly: TLS 1.0 and 1.1, SSLv3, SNMPv1 and v2c, and unencrypted Telnet in favor of SSH.
3. Verify cipher suite strength on every TLS-terminating device, rather than accepting default, potentially outdated configurations left over from initial setup.
4. Confirm DNSSEC is not just configured but actually validating correctly along the full chain of trust.
5. Review which authentication protocol, RADIUS, TACACS+, or Kerberos, is appropriate for each specific access scenario, rather than defaulting to whichever was configured first.
6. Move any devices still running SNMPv1 or v2c to SNMPv3 specifically.
7. Review protocol configuration on a recurring schedule, since deprecated versions are sometimes silently re-enabled during device replacement or firmware updates.

Conclusion

These protocols are the actual, working foundation underneath nearly everything else this pillar has covered, and knowing which one does what makes every other security decision easier to reason about. Audit what’s actually running, retire what’s deprecated, and verify DNSSEC genuinely validates rather than just appearing configured. If you want a real, working inventory of what’s currently protecting your network, Cyber Security Solutions Ltd can walk through it with you.