Topic: PPTP VPN Packet Loss

[Paul Isaacs]

Hi all,
I was hoping someone could explain a VPN packet loss issue to me.

Basically, I am loosing twice as many packets through a VPN ping as I am through pinging the same host, but not through VPN.

My host (millison.com.au) suffers up to 20% packet loss due to the current Testra ADSL problems, however when I connect through VPN and ping 192.168.0.1, I get a packet loss of up to 40%.

The actual packet loss percentage varies based on the time of day and network usage, but it is always roughly double through the VPN connection.

Can any one explain?
Is there a timeout or something I can change to improve this?

regards

Paul
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Paul Isaacs - Managing Director  Email  : paul.isaacs@millison.com.au
Millison Technology Pty Ltd      Phone  : +61 3 9798-7333
Electronic Manufacturing Service Fax    : +61 3 9798-7633
www.millison.com.au              Mobile : 041 936 4804
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[Charlie Brady]

Paul Isaacs wrote:

> I was hoping someone could explain a VPN packet loss issue to
> me.
>
> Basically, I am loosing twice as many packets through a VPN
> ping as I am through pinging the same host, but not through
> VPN.
...
> The actual packet loss percentage varies based on the time of
> day and network usage, but it is always roughly double
> through the VPN connection.
>
> Can any one explain?

The encryption used in PPTP needs to resynchronise encryption keys if there is packet loss. This means some packets are discarded.

> Is there a timeout or something I can change to improve this?

No.

Charlie