Slow VPN data speeds between Red 15w and UTM SG230

Hi all,

Apologies if this has already been covered, but I could not find a definitive answer.

We have an SG230 at the Corporate Head Office and a number of RED 15w in staff member's homes.

Our SG230's primary WAN link is a 100Mbit/sec in both directions fibre connection. Its average utilisation is around 10-15%

We have just configured one RED 15W device in particular and it is connected to a newly installed home cable internet service with 100Mbit/sec down and 2Mbit/sec up

The RED 15w connects successfully using Standard/Unified operation.

The internet connection (supplied by Telstra Bigpond) modem has had the firewall/port scanning functions disabled. It has not been configured in Bridge mode, as there are other home multimedia systems that connect to this modem directly. The modem is configured with 4 x Gigabit LAN ports. The RED 15w WAN port is connected to LAN port 4. I have tested the cable modem by itself and have successfully downloaded at anywhere between 60 & 80Mbit per second.

I then tested the VPN connection speed by downloading large single files from the Corporate network servers to the homesite and on average get between 6 and 7 Mbit/sec.

I would have thought that this would be higher given that both the corporate SG230 can serve out at 100 Mbit/sec and the homesite can download between 60 & 80Mbit per second and the RED can (in theory) transfer at 90Mbit/Sec.

I've changed the MTU from 1500 to 9000 on both the WAN and RED interfaces on the SG230 without any difference.

Is this the expected speed or should this be higher?

Is there any other setting that I can review to help improve this?

Thanks Nathan