ISP : which Service on which OS

Hi,

We're Planning for an Enterprise ISP and reached to point to decide about "which service on which OS".

I've talked with many people ; some bashed Linux, some bashed Windows 2000.

What I need is first of all, do you suggest a full-linux-based or full-windows2000-based or an integrated solution?

The services that I need to have on these OSs are :

AAA (Authentication, Authorization, Accounting) (+Centralized Authentication)
DNS (internal and external)
DHCP
Web Server
Mail Server
Firewall
Cache

The factors that are important for me are Availabality, Reliability and Security. as you know, Uptime for an ISP is very important.

If you suggest an integrated solution using some services on linux and some services on windows, would you please tell me which-on-which and why?

The only reasonalbe difference that I know is Linux does not need restart on most new patches. (Uptime)

Also I need "Switch Fault Tolerance" (NIC Teaming) which as far as I know, Intel NICs only support this on Windows.


Regards,
Joe.