Open Source software may be a good option for Internet Service Providers (ISP).   As with most Open Source software there is a wide range of software available to achieve a specific goal and choosing which software to use for a specific application depends largely on what the end user requirements are.

Typically an ISP choosing to use open software would start with the Operating System (OS) and work from there. The choice of the OS would be one of the various distributions of Linux such as Red Hat or Debian.

Once the OS has been chosen it is then a matter of what services the ISP wants to provide to its customers. The following list is an example of what services could be provided together with possible software options:-

• Email - Postfix ( http://www.postifx.org/ ) as an email server and Squirrelmail Mail (http://www.squirrelmail.org) as a web based email client

• Email Discussion Groups and Newsletter lists -Mailman (http://www.gnu.org/software/mailman/index.html)

• Spam  - Spamassasssn ( http://spamassassin.apache.org ) and Greylist ( http://www.greylisting.org/ )

• Anti-virus – Clamav (http://www.clamav.net/lang/en)

• Web Servers and Domain hosting – Apache (http://www.apache.org) and Cpanel (http://www.cpanel.net) to give an option for those wishing to use Frontpage extensions

• Firewalls – Iptables (http://www.netfilter.org) – this comes with Linux and can be used to monitor bandwidth

• Proxy Servers – Squid (http://www.squid-cache.org) and you may wish to use anti-virus scanning by using Havp (www.server-side.de)

• ISP in-house monitoring – Cacti (http://www.cacti.net) – this software can be used to monitor hardware and bandwidth as examples

Once the software is selected it then becomes a matter of installation and configuration to deliver the required services. And as with any software there are updates released at various intervals which should be applied as required.

Author is Jeff Crawford. 
I've been  in the IT/IS arena for 15 years and worked for various organisations over that time and latterly for iGrin Internet.

For a reasonable portion of those years I supported, and still currently support, Microsoft Server, Workstation and various Microsoft applications such as Microsoft Office.

However in the last few years have tended to focus on Linux and the Open Source software and this is where my current focus is.

Coupled with the above I've done some programming in C and C++, Visual Basic, Microsoft .Net, Jade, Perl, Python and PHP