Is the GRE protocol restricted in speed?

We have internet from NOS with download speed of 200 Mbps and upload of 20 Mbps. This speed is tested using the IP protocol and is ok.

For job reasons, we have set up a router on Port 4 in bridge mode. Here, the IP traffic has also been successfully tested to 200/20 Mbps, using the router to the router speed test functionality. However, we need to use the GRE (47) protocol instead of the IP protocol in a peer to peer tunnel to an offsite router. Through this protocol, the upload speed is still 20 Mbps, but the download speed is only 12 Mbps! It should be 200. Here we test the speed using the same routers in a peer-to-peer setup as when we tested the IP speed. So it looks like NOS is limiting the download speed for the GRE protocol. Our subscription tells 200 Mbps, and we can not see why this should not also include GRE.

We have contacted NOS technical support and told them that the download speed of the GRE protocol appears to be limited. But NOS support says "they are not authorized" and asks us to call "PC Medic" instead. We do not need support for our equipment, we need NOS to remove the restriction. NOS support cannot even tell if the GRE protocol is restricted in speed or not. It sounds more like they have no idea what we're asking about.

Who can give a clear answer to this, and how can we get the same speed for the GRE protocol as for the IP protocol?

JO