FTTC/VDSL dropouts correlated with VPN use?

A few weeks ago I migrated to FTTC. It worked fine for the first couple of weeks, but since then I have suffered from frequent drop-outs. The tbb monitor will typically show 100% packet loss for a few minutes, then service resumes, to be interrupted again a few minutes later - rinse and repeat for several hours.
Sometime I also get longer lasting outages - a big block of red on the tbb monitor for a few hours.

My ISP have referred it to BT Wholesale, who have sent assorted engineers out, but without much improvement.

I have a router-to-router VPN to another ADSL (from the same ISP) site. The VPN is used for the other site to access a NAS on my LAN. I noticed yesterday a correlation between activity on the site at the other end of the VPN and the dropouts I got yesterday.

Is it possible that activity on the VPN could be pulling down the VDSL line? It seems unlikely to me, but I don't know enough about how these things work.

Is the FTTC itself resyncing? Or is the public IP that your router has simply not being pingable?

The packet loss may be a side effect of your Ethernet router processing the VPN and responding to pings at a lower priority, rather than any actual problem with the VDSL itself.

The base line PPPoE session can push some routers harder than a simple DHCP WAN connection, and add the processing of a VPN and it is feasible you are pushing what your router is capable of.

Then there is the additional factor that you might be saturating your upstream side, in which case a router that supports QoS and limiting how much traffic the NAS can through out across the connection may help.

Thanks, Andrew, and apologies for the radio silence. I thought I had already replied.

I think I've now satisfied myself that this isn't correlated with the VPN use. In fact, I think there have been two problems - one on the line, and one in the router.

I think the line problem manifested as long dropouts, during which the modem lost the connection (on the occasions I could be there to observe, the DSL light on the modem started flashing). After a lot of BT fiddling, those seem (touch wood) to have gone away.

The other problem continues. Occasionally, the router will lose its Internet connection, briefly. The DSL slight stays on on the modem, but for a minute or two there's no Internet access via the router. Because these outages are short it's hard to be sure, but I *think* that miniport dial-up from a PC connected directly to the modem works when the router doesn't.

A firmware upgrade (applied by my ISP) seems to have reduced the number of the short outages so that it's almost bearbale now

Nick