Is there a method or tool(s) to prove network outages?

[Notify Me <notify.sina () gmail com>]

Hi Everyone

Please I have a very problematic radio link which goes out and back on
again every few hours.
The only way I know this is happening is from my gateway device: a Sophos
UTM that sends email anytime there's been an outage.

The ISP refuses to accept this as outage/instability proof, and I'm
wondering if there's something I can run behind the gateway UTM that can
provide output information over time.
They seem to be a primarily Windows+Cisco shop (as is common here in the
4th world). We are primarily Linux.
 Is there some set of command incantations I can run who's output I can
collect and send to them (besides some sort of sustained ping)?

Thanks in advance!

Sina