You're going to get differnt answers from different people, so as they say, YMMV, but IMNSHO,
http://dev.wifidog.org/ is the best, wrt Open Source Software.
But if you're really serious, I would recommend you only use it on test beds since as you're going to find out, you'll need to do some coding no matter what anyone says. But it's been developed into a solution for about $400.00 which is a commercial product that literally blows everything else away:
http://wifigator.com/
Before you start spending money though, unless you're one of those boneheads that's looking for a turnkey system that someone else manages, cutting you in for a so-called percentage (and there are a lot of them that promise to come in and set up your clients and then you make almost nothing for a while until they get you out of the picture), you should join the forums here:
http://www.ubnt.com/forum/
WifiGator integrates wonderfully w/Open-Mesh.org style technologies and openmesh even is going to license and incorporate several features that WifiDog has developed which everyone else has been unable to perfect until last month.
I'm not a fan of mesh networks - they really suck unless you're going to be setting up a marina or something along those lines. You'll loose up to 50% of your bandwidth at every link and bridge - no matter what anyone tells you, but it really depends on what your requirements are. I'm a PtMP person myself.
Mesh networks do have their place though, in my case, as an extension of a PtMP AP for a small area you want to bring service to - like a park or business center, etc...
But if you're really seroius, and not some hobbyist bonehead like I mentioned above, instead of WifiDog, and RADIUS and ModenBill and Cisco, I would also recommend that you use Azotel for all of your billing and bandwidth management, and ImageStream for your routers.
Bottom line is, you're selling yourself right on out of the job if you don't bring in the Internet presence to the client site yourself, backhauling all authentication through your own network, and handling all the billing yourself - you own the Internet connections, you control the bandwidth, tech support, and management of the captive portal system.
Also, no matter what anyone says, even though a merchant account gateway is best, PayPal works really well.
Or let's say that it's a coffee or sandwich house - you can implement a system whereby the retailer can provide a code on the customer receipt (or even hand it to the customer if asked for one) that permits the user to access the Internet via your captive portal system for a predetermined duration, for free, as long as the customer purchases an ice cream cone or coffee, whatever.
Even if you're looking at an Intranet solution for a corporation, host the infrastructure yourself.
There's a wealth of info out there for you - these forums aren't really the place that is going to educate you on the industry, but when you get back down to the UNIX level of things this is where you're going to find the most help
But WifiDog will get you into the guts so you have an educated idea of how to implement exactly what your requirements are, and probably open up a lot of other possibilities as well that you didn't know about.
I guess you've got your homework cut out for you eh?
I hope that helps
Kindest regards,
