network throughput over a wireless access point is bad for LAN traffic, yet good for internet traffic

[David Bandel]

On 6/19/06, Net Llama! <netllama at linux-sxs.org> wrote:
> On Mon, 19 Jun 2006, David Bandel wrote:
> > On 6/19/06, Net Llama! <netllama at linux-sxs.org> wrote:
> > > I've got an bunch of 802.11b hardware (wireless access point WAP, pcmcia
> > > cards) setup at home, connected to a wired network via a 100Mb Netgear
> > > switch.  The same switch is also connected to the border
> > > router/NAT/firewall box which goes out to the DSL modem/internet.  I've
> > > had this setup for years, and haven't made any changes to it since setting
> > > it up originally.
> > >
> > > Over the past few weeks, I've noticed that all network traffic over the
> > > WAP that is local (just on my home LAN) is horribly slow (like 1KB/s
> > > slow), yet all traffic over the WAP to/from the internet is fine (about
> > > 1.5Mb/s).  I've tried scp/http/nfs and all of them are slow as can be
> > > possibly imagined when between LAN systems (both between wireless systems,
> > > and between wireless & wired systems). The problem does not exist between
> > > wired systems.  There are no errors in dmesg/messages, its just like
> > > something is swallowing 99% of the packets.
> > >
> > > All the systems (wireless and wired) are running FC5-x86, however there
> > > are no firewalls or traffic shaping on the LAN,  just on the border
> > > router/firewall/NAT box, which is never in the equation except for traffic
> > > going to/from the internet (where this problem never appears).
> > >
> > > Anyone have any troubleshooting suggestions/ideas?
> >
> > Scan for your neighbors' new AP.  Move at least 4 channels away.
>
> Already did that.  I've been using channel 11 for over 3 years, and all my
> neighbors are (sharing) channel 6.
>
> > Better- go to 802.11a (5GHz).
>
> ugh, that costs $$$ that i was hoping not to spend.

OK, then don't.

>
> >
> > And welcome to the wonderful world of wireless.  It will only get worse.
>
> ok, but if i'm already 5 channels away from my neighbors, then isn't the
> problem elsewhere?  and would a channel/frequency conflict really exhibit
> itself like this?

Obviously, one of your neighbors changed channels.  Yes, many will be
on channel 6 because that's 802.11g's channel.

Scan again.  And yes, this is how interference manifests itself.
OTOH, you could just have a bad card in your AP.

Little secret.  You can buy 802.11a/b/g miniPCI cards based on the
Atheros chipset for $38.00/ea in the US (I get them shipped down here
and they're still less than $50).  I have one in my laptop.  Newer
laptops have 2.4 and 5.0 antennas.  Older ones have 2.4 antennas only
(at least that's true of Dells).

There are also PCMCIA cards based on them for laptops without built-in antennas.

But scan first.  Damaged card or interference -- I'm betting on the latter.

OTOH, you could just buy an amplifier and start the amplifier wars
(careful not to burn yourself).

Ciao,

David A. Bandel
-- 
Focus on the dream, not the competition.
            - Nemesis Air Racing Team motto