Hi Adrian,
1gbps is the throughput declared on the datasheet, using "recommended" policy and test traffic.
You can connect 2 gigabit ports but then you need to be sure that the amount of traffic is not overloading the device.
In IDP 4.x you can check with the 'top' linux utility, from IDP5.0 we have an option "scio idp-cpu-utilization"
Ciao 🙂
Daniele