I've heard about Radius. What does it do and how secure it is compared to other authentications? Is there a how-to on it?

You can't have a howto on radius, as radius is a protocol, and implemented in many different ways by different software. if you want to play with a particular radius server, check out freeradius.

radius stands for "Remote Authentication Dial In User Service" and is a generic way for network device to authentication with a username and password. a standard dictionary is used to allow additinoal details to be passed back for configuration, e.g. how long a person is allowed to be connected for, what firewall rules should be applied for that user etc... depends how you use it as to what attributes are of interest.

Ok. So how does Radius and PAM differ? I've heard that it Radius is difficult to configure. Can I use Radius to authenticate dial up users. I've been wanting to have my own dial up service. Wherein I will dial up on the office and gain access in the internet and local network. I've already setup my own VPN server but I want to dial in to the office so that I can also gain access to the internet. Do you have an idea on how to do it? Or if possible to use Radius as authentication? Thanks.

radius and pam are just totally different things. how do monkeys and xmas differ? pam can be used to generically hook into radius as an authentication source if you wanted, so you could just login to servers normally via a radius server authentication. i'd have thought the acronym of radius would have given away what it was intended for use with... it's certainly possile to do that, although i'm not familiar with particular ppp servers.

Who handles the authentication (radius or pam)? I am aware that PAM is also an authentication. Is it possible to use just the Radius without the PAM? Someone also told me that most of wireless authentications is controlled by radius. How can I make a good use of Radius? Can you please site to me an instance where to use Radius? Does it mean the Active Directory and Radius are the same in a way?

pam is a modular framework. it in itself does not authenticate anything, but it controls the structures and requirements to decide when an authentication criteria was passed. if i were to want to log in via radius i would use pam to connect the request from the login program through to the radius server. in the same way i could use pam to authenticate against ldap (active directory), kerberos, nis+, local files or any combination of these.