Try PingPlotter for Mac OS X Free
Everything required to "See the Network, Pinpoint the Problem" is included in the new PingPlotter Mac Preview. Anyone interested in peeking at the future of the OS X platform is free to trial for thirty days or run free mode as long as they like. License owners can upgrade this, and future, releases (even the imminent official release) as long as their maintenance is active. Check out the announcement page for downloads and more information about Preview #3.