How fast?

[drjohn999]

I am connecting a 1.8 GHz laptop running XP SP2 through a WiFi coffeshop connection (which is running some kind of NAT system that looks a lot like Wingate) that reports 54Mbps. The other end runs into the host PC via cable modem (Comcast in the Western US) that routinely runs at around 2+ Mbps. The Host PC is a 450 MHz P-II running Win2K SP4 with a 10 base-T wired connection to the cable modem. The host is also connected to two internal 10/100 NICs; one wired and one for wireless. During this test there was no other significant activity on the internal LAN.

I see from 200 to 500 Kbps reported on the Gatekeeper monitor while transferring files in the 500k to 2 mByte range, i.e. up to 25% of what appears to be the slowest part of the chain, the cable modem connection.

Given the nature of the connections, the encrypt/decrypt process on both ends, and the fact that its an older somehwat slow PC, is this what I can expect to see; or is there a throttle point that I'm not aware of that could be addressed for higher speeds?

Thanks,

DJ

[drjohn999]

Also, what can I expect to happen if 2 or 3 users are connected thru the VPN simultaneously?

-- DJ

[Pascal]

It's difficult to give you exact numbers or to comment on that. Too many different factors could be influencing it, and a lot of them might be beyond your control.

The encryption / decryption is the biggest processing overhead and you would see gains there if the machine had a bit more grunt. That is alleviated a bit by tweaking the MTU (As described in the non-fragmentable ping tests) as that ensures that you are only doing the required en/decryption.

With protocol version 2 (WinGate 6 and VPN 2 onwards) you do have the option of running the VPN without any encryption. This is not something you would want to do for average, everyday operation - but when you want to run a quick speed test it could be the most accurate reflection of the network speed. That still does the network wrapping but without the en/decryption overhead.

[genie]

Well, VPN is quite complex thing. Not only does it do encryption/decryption, which takes quite a while because of the complexity of the cyphering method used, but also generates additional traffic, because every packet is to be wrapped into a UDP packet with additional VPN header in it - and if the sending system opts for maximum packet size allowed, those big packets would be "fragmented" because of the additional headers, thus generating even more traffic. Therefore, network performance degrades.