[nzlug] puzzling network prob between two linux boxes on homenetwork

[Mark Foster]

I'm late into this thread, but frankly, Homeplug scares me anyway.

In terms of performance testing, you need to do similar to Nick Cliford
suggests.  I reccomend 'iperf':

http://dast.nlanr.net/Projects/Iperf/

CLI app for either 'nix or Windows.

This should give you a fairly accurate point of comparison to analyse the
different hops in your ethernet environment.

Mark.


> It may pay to check out stats in "netstat -s" and "ifconfig". You should
> have no errors in the ifconfig stats.
>
> In "netstat -s" the most important bits are "segments retransmitted" in
> the Tcp stats. It this is high compared to the number of sengments
> sent/received then you have some packet loss which will cause your
> connections to 'burp' until a timer expires and the packet is
> retransmitted.
>
> Here is an example of reasonable well connected system for reference:
>
> Tcp:
>     9110 active connections openings
>     5678 passive connection openings
>     196 failed connection attempts
>     2355 connection resets received
>     121 connections established
>     20493911 segments received
>     10752815 segments send out
>     1492 segments retransmited
>     0 bad segments received.
>     3686 resets sent
>
> Attempts to connect to 'down' sites and other things will cause a low
> level of segments to be retransmitted, so don't expect it to be 0!
>
> If you want to watch this in action, use the ftp command line client and
> use the "hash" command so you can see if the connection 'burps' due to
> packet loss.
>
> Mike
>
> -----Original Message-----
> From: nzlug-bounces at linux.net.nz [mailto:nzlug-bounces at linux.net.nz] On
> Behalf Of stephen
> Sent: Tuesday, 26 June 2007 9:53 p.m.
> To: NZLUG Mailing List
> Subject: [nzlug] puzzling network prob between two linux boxes on
> homenetwork
>
> I have a little networking mystery which is driving me nuts.
>
> Box A is connected directly via ethernet to my (cheap Belkin) router.
> The router and Box A both think they have a 100Mbps full duplex link (as
> reported by ethtool eth0 on Box A, status lights on the router).
>
> Box B is connected via ethernet to a cheap Dlink switch, which in turn
> is connected to a LAN over power (you know, Homeplug) dongle, with the
> remote dongle going to the router. Box B and the switch both think they
> have a 100Mbps full duplex link. Homeplug is supposed to be 85 Mbps in
> theory, and anecdotally I hear it should be good for 10 anyway.
>
> Box B, despite the suboptimal adhoc set of links, can max out my 4 Mbps
> cable connection, as reported by various DSL speed test sites. So can
> Box A.
>
> However, I can not get better that about 1.5 Mbps from box A to box B
> (measured with a very large file served by Apache on box B, and wget on
> box A). Sometimes it is as low as 0.9 Mbps.
>
> I have swapped cables. I have tried wireless on Box A (the router is
> also 801.11g capable). I have restarted the router, restarted the switch
> and jiggled the Homeplug dongles. No change.
>
> So, to recap, both these boxes can do at least 4 Mbps to the internet,
> but they can't manage even half that to each other.
>
> I had intended that Box B, which is in a nice quiet room upstairs,
> become a server for media files and for backups, but I want much better
> bandwidth for that.
>
> Suggestions for poking around?
>
> Stephen
>
>
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