Nothing runs well without good software
Well, on the firmware of Ascend / Lucent and Cisco and others, you have very little influence. You need to take what you can get. And then you must live with what you have. So you need to complete your checklist before you decide to buy or rent product "x" or "y".
But the key software is the application software on your gatekeeper server in conjunction with your accounting software. because we are running all our production servers with Linux (currently SUSE 9.2), we have very good experience with Compaq dual cpu DL380 and balanced loading of both cpu´s.
So in the past and now we are looking for free and public software only. When we have the sources, we can (we believe, that we could) help ourselfs in case of trouble. Look to this page you are on. It is stored in a TYPO3 content management system from a Danish company under GNU/GPL. It is free and it is nearly perfect. Of course, we need to publish our own developments for free too and we need to report problems as soon as possible.
In the reality, you are dealing with two large applications. The gatekeeper software is hardware dependent and the accountig software is user and customer (humans) dependent.
Both must (absolutely) work hand in hand and transparently to you, your support employees, the government and the ministry of finance. Dont ignore the influence and power of the last two institutions. In case of problems, they will close your company within minutes.
Now we have experience with GNUGK gatekeeper software.
more shortly