An issue with VPN usage over our Comcast Business Internet service has FINALLY been resolved. I'm sorry to say that it appears the issue was the Netgear gateway device, of which we went through 3 units, before the tech installed an SMC device.
Of course all the blame was pointed at our local LAN, my PC, the wiring, the VPN solution. So we checked and replaced EVERYTHING. I reimaged my PC, then got a new one, ran new wiring, and, of course, had the Netgear unit replaced twice.
Still the problem continued. The symptom was that even though I could establish a VPN connection, any activity that caused more than a few thousand bytes of traffic to flow over the VPN circuit would throttle the VPN to ZERO b/s for a minute or two.
I finally became convinced that the Comcast circuit HERE was at fault because I took my PC home and used my Comcast internet there to establish the same VPN connection without any issues at all.
So I called Comcast tech support yet again and laid out all my evidence. The tech said, "Oh, we know all about that issue. It's with the Netgear router. Let me have a tech bring out and install an SMC gateway, that will resolve it."
Doh! I can't belive all the time and effort I wasted "fixing" my stuff when Comcast knew all about this. I also can't believe the braniacs at Netgear can't make a router that works with a VPN, and from what I can tell, our STATIC IP.
Comcast - PLEASE get with the problem and either FIX the Netgear or SCRAP IT and switch to another vendor that can do VPN traffic with static IPs.