Ping flooding (fwd)

Per Gregers Bilse bilse at
Wed Jul 10 16:18:28 UTC 1996

On Jul 10, 10:44, John Hawkinson <jhawk at> wrote:
> > Is it just me, or are the ANS commandos after me?
> It's just you, really :-)

Good to hear. :-)

> This is the short-term, long-term issue.
> If you want to know who you exchange traffic with, who you need to
> consider peering with in more places or establishing additional links
> to, you need things like AS matrices. We certainly appreciate the
> modicum of data we have now, and would be happier with more of it.
> Knowing how hot each of your links is is nice, and may 
> help you see short-term spikes, but it doesn't help long-term
> engineering of your network.

Yes, but 'long-term' is one of these things ...  You can't really
project with any degree of accuracy more than 6-9 months ahead, and
our experience indicates that historical data is not all that
useful.  (Ie, that is the case for us; it may be different for other
people.)  There aren't any agreed ways of measuring the capacity of
networks, but my take on our capacity is that we have 100-150 times
more capacity than three years ago.  Ie, this is what we can extract
from historical data; but there is a limit to how far into the future
one can project, using this data, and it certainly isn't three years.

> > As noted, busy core routers are ill suited for collecting IP
> > accounting. The fact that they may be border routers in BGP terms
> > doesn't make them any less core routers from a network perspective.
> > So you just have to rig things differently, then.
> This is getting silly :-) It's relatively well-established that if you
> want to collect data somewhere, getting it right is going to be hard.
> The more you want to collect, the harder it is.

Yes, but my point is that bean-counting accuracy, "proof", hard
facts, etc isn't particularly important.  You want to look at trends
for long-term planning, and current measurements to see if you should
maybe reroute traffic over alternative connections, sort of "right
now".  Between those two extremes, a good nose and healthy gut is
likely to be more useful than even the most careful analysis of
historical data, simply because growth doesn't necessarily follow any
particular pattern.

> Invariably it's useful to have stats on boxes at the borders of your
> network where you peer with other folks, and it's also useful
> inside your network. All of these things depend on what you're trying
> to engineer for, and almost all of them are useful. Balancing usefulness
> versus forwarding path performance is a tricky thing, but one should not
> assume it's impossible, and considering the possibilities is far more
> than a waste of time.

Sure, nobody would disagree with that.

------ ___                        --- Per G. Bilse, Mgr Network Operations Ctr
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