Low LAN speed (max 200-400KB/s)?!

Hello group!

I am having the following configuration:

- Lynksys WRT-54GL: WLAN-Router (54MBit/s) with 4x 100MBit LAN Hub
- Ubuntu 6.02 box LAN 100MBit (with apache and proftpd)
- OpenSuSE 10.2 Laptop WLAN 11MBit
- Vista Business Laptop WLAN 54MBit

Now my problem is, that I have a very slow network connection.
I try to transfer data from the ubuntu box to the two laptops. I have tried
this via HTTP and FTP. In all cases I am reaching only speeds between
200-400 KB/s (= 1.5 - 3.2 MBit/s).
And even more strange: I am reaching this speed not as a total, but PER
TRANSFER. that means: if I start more transfers, i will get EACH time a
speed of 200kb for EACH transfer!
I have checked proftpd but it has unlimited transferspeeds set up!

Any idea what I could check?

Thank you for any advice
tom

In news:5lff3fF7mjopU1@mid.dfncis.de,
Tom <null@void.void> wrote:

> I am having the following configuration:
>
> - Lynksys WRT-54GL: WLAN-Router (54MBit/s) with 4x 100MBit LAN Hub
> - Ubuntu 6.02 box LAN 100MBit (with apache and proftpd)
> - OpenSuSE 10.2 Laptop WLAN 11MBit
> - Vista Business Laptop WLAN 54MBit
>
> Now my problem is, that I have a very slow network connection.
> I try to transfer data from the ubuntu box to the two laptops. I have
> tried this via HTTP and FTP. In all cases I am reaching only speeds
> between 200-400 KB/s (= 1.5 - 3.2 MBit/s).
> And even more strange: I am reaching this speed not as a total, but
> PER TRANSFER. that means: if I start more transfers, i will get EACH
> time a speed of 200kb for EACH transfer!
> I have checked proftpd but it has unlimited transferspeeds set up!
>
> Any idea what I could check?

First thing would be to direct-connect one of the laptops with the server
using a crossover cable and see if the slow transfer rate persists. If it
doesn't, then that would indicate that the problem lies in the wireless
configuration.

Hello Gretch,

> First thing would be to direct-connect one of the laptops with the server
> using a crossover cable and see if the slow transfer rate persists. If it
> doesn't, then that would indicate that the problem lies in the wireless
> configuration.

That's a good advice!
I connected the ubuntu box and a laptop via a 100 MBit Switch (only these
both machines attached).
The transfer via the cable was approx. 5 MB/s, that equals to 40MBit/s. As
far as my researches in the internet found out, this is a pretty normal
speed for 100BaseT (due to overhead).

So as it seems my WLAN is not working correctly, isn't it?
I just retested it: I am downloading now from the ubuntu box via the Linksys
WLAN-router to the 54MBit vista business laptop a single file of 700MB via
FTP. The speed is 340 KB/s- that equals to 2.6 MBit/s.
I have WEP-PSK with TKIP encryption enabled. I know, that encryption is a
bit slower, but 2.6 MBit instead of 54?? There must something be wrong,
isn't it??

What could i check?

Thanx for any hint
tom

Tom <null@void.void> wrote:
> Hello group!

> I am having the following configuration:

> - Lynksys WRT-54GL: WLAN-Router (54MBit/s) with 4x 100MBit LAN Hub
> - Ubuntu 6.02 box LAN 100MBit (with apache and proftpd)
> - OpenSuSE 10.2 Laptop WLAN 11MBit
> - Vista Business Laptop WLAN 54MBit

> Now my problem is, that I have a very slow network connection.
> I try to transfer data from the ubuntu box to the two laptops. I have tried
> this via HTTP and FTP. In all cases I am reaching only speeds between
> 200-400 KB/s (= 1.5 - 3.2 MBit/s).
> And even more strange: I am reaching this speed not as a total, but PER
> TRANSFER. that means: if I start more transfers, i will get EACH time a
> speed of 200kb for EACH transfer!
> I have checked proftpd but it has unlimited transferspeeds set up!

> Any idea what I could check?

First, check netstat -s -t statistics on each of the Linux systems,
and use whatever Vista has for reporting TCP statistics. You want to
look for things like retransmissions.

If you see any, then you want to look at ethtool -S <interface> stats
on each of the Linux systems, and whatever Vista has for link-level
statistics. You are looking for things that are errors or drops and
the like.

If you have any of those, they could be limiting your throughput by
either having the stacks sitting there waiting to retransmit, or by
keeping the "congestion window" (aka cwnd - feel free to web search
for details) small.

One of the limits to the performance of a TCP connection is:

Tput <= Weff/RTT

Where Weff is the "effective" window size which will be the lesser of:

*) the receiver's advertised window
*) the sender's "SO_SNDBUF"
*) the sender's computed cwnd

For the RTT, you could try the results of a ping between the systems
as a decent first approximation.

It wouldn't be a bad thing to minimize the variables. While the
transfer rates are quite probably well within the limits of the
filesystems on each end, doing some "just networking" transfers would
still be a good idea. For that I would, naturally, suggest netperf :)

With netperf you can try increasing the socket buffer and hence TCP
window size to see if it makes the transfers any faster.

rick jones
--
denial, anger, bargaining, depression, acceptance, rebirth...
where do you want to be today?
these opinions are mine, all mine; HP might not want them anyway... :)
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

Tom wrote:
> Hello Gretch,
>
>> First thing would be to direct-connect one of the laptops with the server
>> using a crossover cable and see if the slow transfer rate persists. If it
>> doesn't, then that would indicate that the problem lies in the wireless
>> configuration.
>
> That's a good advice!
> I connected the ubuntu box and a laptop via a 100 MBit Switch (only
> these both machines attached).
> The transfer via the cable was approx. 5 MB/s, that equals to 40MBit/s.
> As far as my researches in the internet found out, this is a pretty
> normal speed for 100BaseT (due to overhead).
>
> So as it seems my WLAN is not working correctly, isn't it?
> I just retested it: I am downloading now from the ubuntu box via the
> Linksys WLAN-router to the 54MBit vista business laptop a single file of
> 700MB via FTP. The speed is 340 KB/s- that equals to 2.6 MBit/s.
> I have WEP-PSK with TKIP encryption enabled. I know, that encryption is
> a bit slower, but 2.6 MBit instead of 54?? There must something be
> wrong, isn't it??

You should be able to get roughly 20-25 Mbit/sec over a 54M line, at least I do when the laptop is
close to the AP (2 m, or so). The 802.11b interface in the may be slowing you down.

Things to try: (1) Turn the 802.11b (11M) laptop off, configure your AP for 802.11g only, and retest
the Vista machine. Installing iperf on both machines and using the Ubuntu box as a server will let
you see the transfer rates very easily.

(2) Try changing the channel on the AP. You should test channels 1, 6, and 11. If they all have the
bad performance, you may have interference over all the channels.

Once you have the 54M link working the best it can, then allow both -b and -g mode. It may degrade
the 54M link, but you will do the best you can.

Larry