> One frustration I have is the lack of tools (so far as I have been
> able to find) that will tell me what the instantaneous bandwidth
> consumption is through each interface,

There is no such thing - or rather, there is, but it's uninteresting,
as it's always either 0% or 100%.  At least for any interface I can
think of.  (Unless you want an aggregate figure for input and output,
in which case full-duplex interfaces have 0%, 50%, and 100%, or four
values if input and output speeds are different.)

> e.g. similar to what the Cisco "show interface" command shows.

I'm not familiar with Ciscos, but I would hazard a guess that that
shows you consumption over the last second, or tenth of a second, or
some such, even if it's documented as being the instantaneous rate.

> I know that we collect byte & packet counts per interface, so it
> should be a simple set of changes to netstat or systat to show
> bytes/sec or packets/sec measured over some interval (or since boot,
> since we do have the data...),

Well, since the interface was last created, for interfaces that can be
created and destroyed on the fly (think pcmcia, or cloning interfaces).

> plus error rates.

It might be worth doing.  For my own netlink, I long ago started
logging byte and packet counts every five minutes (and added an option
to netstat suited to doing so), and when I get curious I massage the
resulting data and see what interesting facts I can pull out of it....

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