[nzlug] TelstraClear cable usage fetcher

[Tony Wills]

At 12:37 29/05/2006, Volker wrote:
>On Mon 29 May 2006 11:54:07 NZST +1200, yuri wrote:
> > 3) TelstraClear does not promise that their usage meter is anything
> > more than an indication, and their billing system has the final say.
> > It's in the Ts & Cs.
>
>Ouch. So they say they have a billing system which they claim to be
>reliable, but they're feeling too stupid to tell me how much I owe them
>when I ask. Does that even pass legal scrutiny?

Presumably the same Telstra logs are used for billing.
The data in the CSV logs may or may not represent reality, but old entries 
aren't changed (ie if they missed something out of the last quarter it is 
put into the next one, they don't amend a previous entry (well, as far as 
I've noticed ;-)).  So while the CSV file is keeping up and is no more than 
15 minutes old, its data should give you an accurate total less whatever 
you've used since that last entry (plus a bit for any data which didn't 
quite get logged into that previous entry).  So it should be accurate to 
within (15mins * 60 secs * (2000000/8 bytes/sec) = 225MB) * 2 (because you 
can send & recieve at upto 2Mbits) = 450MB !! :-)

>...
>Given the huge background noise of random packets which aren't being
>charged for, it seems rather difficult to implement a reliable
>accounting scheme on some *ix box.

I've got a dedicated firewall (the linux connection, just so that people 
don't think this is too far off topic ;-) box connected directly to the 
cable modem.  The first time I looked at the traffic coming in, I got a bit 
of a shock and immediately looked at the Telstra logs to see how it 
compared.  It is continuous chatter being received by the firewall, that 
the firewall is neither replying to, nor passing through.  It amounts to a 
background noise of 10kbytes per second which equates to about 26GB per 
month (30.5 day average month).  I haven't analysed the traffic, but assume 
it is broadcast messages (windows machines looking for shares, probes, 
pings etc ???) from other machines on my local segment (otherwise it would 
make my bill look rather sick).

Comparing the traffic actually passing through the firewall (both 
directions) with the Telstra logs finds  a reasonable match. So looking at 
the traffic that has passed through your router in the last x minutes 
(usually no more than 15) since the last update to the Telstra logs should 
give you a very good guide.

Probably just looking at the data passing through your firewall should be 
sufficient, unless you're subject to some DOS attack (which could add some 
900MB/hour,on a 2Mbit line, of traffic charged to you but not counted by 
you as it didn't pass through your firewall -- of course you might notice 
the slow response times even if you didn't notice the traffic ;-)

Tony