> You work with a bonded connection, don't you?
Indeed, three IP-bonded lines. (Not ML-PPP)
> Where does the L2TP connection terminate?
It goes from the BTW BRAS to a server at Andrews & Arnold.
> In the modems? Or in a separate piece of equipment?
Misunderstanding. See previous reply. the modems speak PPP and don't know anything about L2TP or IP.
> or 3 graphs that show the components
There are always three graphs, one per line. I just picked the one of interest. (When all is well, of course their output is very similar.) One pic shows red streaks coming down from the top of the graph, which represents loss of PPP LCP 'pings'.
In the second pic, the purple section shows that line is down. There was a fault in the Broadford exchange and the modem was just being made to cycle, gaining sync, then going down and round again.
* It seems the link I gave out was wrong, it points to an image folder in the Dropbox website, not to an individual image, and the second image is intended for discussion in another thread. Very confusing! It just shows I don't know how to use uploaded images properly.