[mrtg] Traffic (incoming, outcoming) - what does it correspond to??

[Alia]

Hi guys,

I'm sorry but I'm not very well-versed in all things network and server 
related, so this may be a really dumb post, but I'm trying to understand 
the graphs related to traffic on my website.  What I really want to 
know, is how much traffic our server is capable of handling, but I'm 
having a hard time deciphering these graphs.  What I do know is that 
about ten days ago we sent out a mass e-mail to 800,000 people and 
experienced an onslaught of connections to the site at the same time.  
Predictably (not that we actually predicted this) the site slowed to a 
crawl and mass panic ensued at our headquarters.  Unsurprising, perhaps, 
but what IS surprising (at least to me) is that the MRTG traffic graph 
doesn't show any kind of peak whatsoever corresponding to this time 
period!  The monthly peak occurs a week afterwards, and even that peak 
is only about the same size as the almost daily peaks for the months of 
April and May!!

And even crazier, the peaks for December, November, and September are 
five times higher, with a bizarre and sudden drop-off at the end of 
September, even though our traffic (as in, clicks recorded) has been 
increasing ever since!!

So what I'd like to know is whether the "traffic" shown in these graphs 
has anything to do with the number of people connected, the activity on 
the site, or what?  Last but not least, I'm also unclear on the 
difference between "incoming" and "outcoming" traffic.  Any help would 
be most appreciated!!

Thank you!

Alia