Network diagnostic software wanted

[Douglas Floer]

I'm looking for network diagnostic software that can be used to accumulate
statistics on network load, capacity, peak usage, etc.  It would be nice
if the software could be used to examine individual packets.  Sun's
"traffic" is useful but only displays current statistics and doesn't
accumulate.  An extended, ASCII form of traffic (and netstat and
etherfind) would fill the bill.  It would be nice to get the stuff for
nothing but I'll take whatever suggestions/recommendations you net gurus
may have.