In reply to a post by Suspishio:

This so-called blip affects the upstream according to my observation. Chrys has observed that it may be VM under-investment. But it happened too suddenly for that to be the case. Did they roll out a Cisco IOS update across the estate (Routers) and misapplied it - or something like that? Do these symptoms appear where the Motorola BSRs are installed?

My BT Infinity graph shows no such symptoms.

It's the silence from VM that annoys me more than the blip.