[Openswan Users] File transfer speed slowing down

alet at librelogiciel.com alet at librelogiciel.com
Wed Jan 5 18:28:27 EST 2011


On Tue, Jan 04, 2011 at 09:59:27PM -0500, Paul Wouters wrote:
> On Wed, 5 Jan 2011, alet at librelogiciel.com wrote:
> >I've got a problem on a roadwarrior machine when doing file transfers,
> >not sure where the problem could come from, and not sure if the problem
> >happens elsewhere (not tried yet)
> >Both the roadwarrior and VPN gateway use openswan 2.6.28+dfsg-5 and
> >xl2tpd 1.2.7+dfsg-1 from Debian.
> >
> >VPN gateway is a vmware virtual Debian machine running kernel
> >2.6.26-2-686
> >When connected (ipsec+l2tp) I transfer a big file either from or to the
> >roadwarrior from another machine, not connected to the VPN but which
> >uses the VPN gateway precisely as the gateway to connect to the
> >roadwarriors, and now the problem begins : the file transfer works but
> >is slower and slower and slower. On the roadwarrior side, xl2tpd eats
> >all CPU. On the VPN gateway side, xl2tpd eats almost no CPU.
> Odd. Can you see if the xl2tpd process is getting bigger?

No, the xl2tpd process doesn't grow over time, it simply eats CPU.

> Are you getting retransmitted packets?

Yes there are some retransmissions, segments losts and so on.

> Is this using netkey or klips?


After more testing this seems it was due to my environment, the
roadwarrior machine is being prepared for shipment on the local net and
then connects to the VPN gateway from the inside through several
hops and through a NAT box (OpenBSD).

If for testing I put the roadwarrior machine on the same network as the
VPN gateway then there's no slowdown.

ASAP I'll try to put the roadwarrior machine really on the outside
(where it will be when ready), and I'll see what happens.


Jerome Alet

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