[wellylug] Broadcast flood?

[JP]

 --- Cameron Hart wrote: 
> I just happened to notice the light flashing on my
> ethernet card thats
> connected to my cable modem, and wondered why seeing
> as noone was
> actually using the net at the time. So I started up
> IPTraf to see how
> much bandwidth was going through. IPTraf is
> reporting that there is a
> constant 3 to 15 k/sec of broadcast packets going
> through... is this
> normal? I don't seem to remember this happening last
> time I looked at
> IPtraf...
> 
> I have attached a tcpdump of the last 200 packets to
> go through in case
> someone can work out what is causing this.
> 
The way I understand it (and I could be talking
through my arse) you are physically on a sub-net with
a bunch of other people when you are on cable (and
somehow separated when on dial-up).

Because of that, you will get arp requests, which
match IP addresses to the MAC address on your network
card.  I guess the arp table on everybody's machine is
refreshed periodically.  With a point-to-point
protocol, there's only one IP->MAC mapping to do, but
on a subnet of many machines there could be a lot of
such mappings.

As to whether or not you are charged for the traffic
-- dunno.  I understood that any traffic to/from
paradise servers (and not beyond) was free.  No sure
if that also applies to people on your subnet.

</speculate>

Anyone care to elucidate?

Cheers
Tony

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