Re: PPTPD upload speed bottleneck

[ re-sent ]

Gustavo Homem wrote...

> Command line scp transfer performance between end points WITHOUT
> using the VPN is:
> 
> up  ~ 700KB/s
> down ~ 1100MB/s

That should be "KB" I presume (but it shouldn't matter).

(...)

> So, either the PPPD client or PPTPD is limiting the traffic rate to
> something way below the connection rate and, therefore, queuing
> happens. Which one would it be and why?

Wild guessing: Some rate limiting is still in effect. Either on the
client, hidden deeply in an ip-up script, or in the network, applied
to ecapsulated (i.e. GRE) traffic and in client->server direction
only.

To find out, I'd run tcpdump on both sides and compare the latency for
encapsulated and other packets under load. If there's no significant
difference, it might be local. Then comparing the timestamps on client
side's dumps (when did a packet leave ppp0, when the related one
eth1?) should give an indication.

FWIW, I was not able to reproduce your scenario. I am however quite
sure that pppd, pptpd and pptp-client are innocent. Blaming the
network instead is always a good start :->

    Christoph
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