much network traffic: is there a problem here?

[Kevin O'Gorman]

I've been trying to debug a problem with local connections, and turned
to tcpdump(8) for help.

I'm quite surprised at the amount of traffic even when I think of the
system as idle.
I expected ARP,  NTP, and web spider/crawler traffic, but not much.
I'm signing in with xfce these days, but have bits of both gnome and
KDE installed.

I know enough to struggle through and start identifying things, but
I'm not experienced in doing this and I wonder if there are guides,
shortcuts or advice about figuring out if there's something bad
happening.

-- 
Kevin O'Gorman, PhD