The latest documentation can be found here: VMware HCX Components
It states: 'The VMware HCX Network Extension service provides a late Performance (4–6 Gbps) Layer 2 extension capability. The extension service permits keeping the same IP and MAC addresses during a Virtual Machine migration. Network Extension with Proximity Routing enabled ensures that forwarding between virtual machines connected to extended and routed networks, both on-premises and in the cloud, is symmetrical.'
Regarding your specific question.
- The maximum throughput the layer 2 interconnects can reach is 4-6Gbps per second. Remember that you can deploy multiple layer 2 interconnects if you wish.
- The 1Gbps limit would be (best guess) VM on site A to VM site B OR VLAN on site A to VXLAN on site B. I would presume the VM to VM statement is more accurate as it mentions (UDP/TCP) flows rather than per extension.
- The parameter is not configurable at the moment as you are unable to adjust the appliance/service-mesh size when installing. However, they are making constant improvements and upgrades to the product almost weekly, so I dare say you may have the ability to pick t-shirt sizes (small, medium or large) soon which could give you that increase/decrease.
- Typically these connections are run over a WAN or Internet connection and the bottleneck isn't the HCX appliances but more the breakout speed. Unless you have a 5Gbps+ breakout at both ends?
Hope this helps