KNemo - the KDE Network Monitor

KNemo offers a network monitor similar to the one found in Windows.
For every network interface it displays an icon in the systray.

It also does a whole lot more:

 * Supports a variety of interface and connection types
   - ethernet, wireless, and ppp connections
   - IPv4 and IPv6 addresses
   - multiple addresses per interface

 * Supports optional traffic statistics
   - logs hourly, daily, weekly, monthly, yearly statistics
   - optional billing periods; a billing period can start on an arbitrary day
     and can span nearly any length you choose; it can also track configurable
     peak/offpeak hours
   - if running on KDE SC >= 4.4 statistics will use the calendar selected in
     System Settings

 * Provides detailed information about an interface
   - tray icon displays incoming/outgoing traffic
   - customizable dynamic tray tooltip provides quick access to info
   - left clicking the tray icon presents a status dialog
   - traffic plotter dialog modelled after the plotter in System Monitor

 * Supports notifications
   - can notify when an interface connects/disconnects from a network, becomes
     available/unavailable, or when traffic exceeds a threshold

 * Supports tray icon themes
   - themes modeled after the network status icons in the freedesktop.org icon
     naming specification

 * Allows further flexibility
   - tray icons can always be visible or can be hidden when an interface
     becomes disconnected or unavailable
   - tray icon context menu supports custom menu entries that can run arbitrary
     commands
   - automatically detects available interfaces; by default it monitors only
     the default route interface
   - supports update intervals from 0.1 to 2 seconds
   - configurable via the tray icon's context menu or System Settings