When we talk about user authentication protocols, RADIUS (Remote Access Dial-In User Service) and TACACS+ (Terminal Access Controller Access-Control System Plus) are the two most commonly used protocols. In addition, they are the two most widely used security protocols for centralized network access.
While TACACS+ is most frequently used for administrator access to network equipment like routers and switches, the intention behind creating RADIUS was to authenticate and log remote enterprise network users. Both protocols offer centralized authentication, authorization, and accounting (AAA) administration for systems connecting to and using a network service.
Let’s understand each of these user authentication protocols and how they work.
What Is User Authentication Protocol?
User Authentication Protocols are used to authenticate users to access a centralized network. They are software programs that provide an interface between an authentication server and a user account database, such as a Microsoft Active Directory or Linux LDAP server.
RADIUS and TACACS+ are the two most widely used User Authentication Protocols today, with RADIUS being used by many commercial networks and TACACS+ being used by many enterprise networks.
How User Authentication Protocols Work?
User Authentication Protocols are used to authenticate users and devices. For example, one can use a RADIUS server to authenticate users trying to access a website and a TACACS+ server for the same purpose on a network switch or router.
The first component of user authentication is, you guessed it, authentication. Authentication happens when a client sends an authentication request message to the server. The second component of authentication is authorization—or determining what resources (like files) the user should have access to after being authenticated.
RADIUS vs TACACS+
RADIUS and TACACS+ are remote user authentication protocols that enable a central server to authenticate users attempting to access a network or device. Both RADIUS and TACACS+ require authentication, authorization, and the accounting (AAA) server to work. The difference lies in your method: RADIUS uses port 1812, while TACACS+ uses port 49 by default.
Difference Between RADIUS and TACACS+
RADIUS is a client-server protocol, whereas TACACS+ is a server-server protocol. It means that in RADIUS, the servers and clients communicate directly with each other over a network, which isn’t the case with TACACS+.
In addition to this, RADIUS is also a centralized authentication protocol where all of its functions are performed in one single place.
On the other hand, TACACS+ uses distributed authentication, so there will be no single point of failure for your network security system.
We’ve made a table to make it easy for you to differentiate between RADIUS and TACACS+
How to Choose Between RADIUS and TACACS+?
To choose between RADIUS and TACACS+, you should consider the following:
- RADIUS is more secure than TACACS+. It can be seen in the fact that RADIUS uses only one-way authentication, while TACACS+ uses two-way authentication.
- RADIUS is a more common protocol. So, if you are looking for a solution that everyone else has already implemented, this could be an advantage.
- TACACS+ is more flexible than RADIUS when configuring your system settings. Suppose you want to create some custom features on top of what’s already available from the library. In that case, choosing TACACS+ might be preferable to using an older version of the standard software library provided by Cisco Systems.
Which Is The Best User Authentication Protocol?
There is no such thing as a “best” user authentication protocol. Both RADIUS and TACACS+ have pros and cons, depending on your network infrastructure’s needs. It all comes down to whether you want to use a simple or complex set of protocols for secure access control. The best way to choose between the two is by consulting with an expert who will help determine which one works best for your business.