monline

Four popular solutions:

1. Mac OS X (starting with Tiger) provides bandwidth throttling capabilities through the built-in ipfw firewall. It's well described in this macosxhints.com article. You'll need a bit of commandline knowledge though.
2. WaterRoof is a GUI frontend to ipfw and somebody posted a nice tutorial on how to use it to throttle network bandwidth.
3. There's an even easier way and it's called Entonnoir. It's a small GUI app that requires almost no networking knowledge. However it's not open-source so you can never know what you get your hands on.
4. If you're just in need to limit your browsing bandwidth (eg. for web development and testing), you can always use one of the many HTTP proxies that support bandwidth throttling. One of them is the excellent Charles Web Debugging Proxy (but it's only a 30-day shareware so you either buy it or look for an open-source alternative).

The two most popular solutions:

• trickle, a userspace bandwidth shaper. It's just this easy:
  
  trickle -d 200 -u 30 firefox
• Wonder Shaper, a kernelspace bandwidth shaper. More efficient for interface-level bandwidth shaping (but does not support per application control at all).

It's not a big deal, really. However the MAC address is only available since Java6 and to create a Java5 compatible class for working with network interfaces, you've to use the Java reflection API. My demo class might be of help to those who have not yet used reflection. See the attachment for the source of my ListNetworkInterfaces class which will print MAC and IP addresses of all available network interfaces. It'll print MAC addresses only if invoked in a JRE6 (or later). Compilation and invocation is as usually:

I've found the info at Draytek's LAN FAQ page.

There's a nice intro on the topic in one of the Linksys knowledgebase articles. I copy the info here so it won't vanish once their knowledgebase goes offline. The original article used the Windows ping command in its examples, but I've added linux and Mac specific examples too.

"PRTG Network Monitor is the powerful network monitoring solution from Paessler AG. It ensures the availability of network components while also measuring traffic and usage. It saves costs by avoiding outages, optimizing connections, saving time and controlling service level agreements (SLAs)."

I was looking for a free solution to monitor the uptime of an internet connection (using a Windows PC) and stumbled on this one. I admit it's a bit more than I was looking for, but there're not that many free utilities for network monitoring so grab it while you can. The freeware edition handles at most 10 "sensors" (ie. you can setup monitoring of 10 network resources). For monitoring the uptime of your network connection you need only one, so it's more than enough.

I've googled quite a bit and did not find an answer to the problem. You'll get a lot of hits on the subject though and most people tell it cannot be done. In Tiger the following one liner worked like a charm:
But in Leopard not anymore. Or at least not for the wired (Ethernet) network adapter. The above method still works for the Wi-Fi interface though, but that's not much of a solace to most of us.
The solution is quite easy to guess and pretty easy to do: simply replace the network driver of Leopard with the one of Tiger.

To cut it short, use the nethogs utility. You'll see an output like this:
Nethogs is not the perfect tool despite of its ease of use. Read more for some further tips.

Quoting from A Half-Dozen or So Essential Open Source Network Administraton Tools:
"The Unix applications listed in the lefthand sidebar make a powerful suite for network monitoring, management, and troubleshooting.
Mac OS X, with its Unix core, is a great platform to use them."
Check out the site if you're working in network administration, monitoring, etc.

[The Korea Times/The Economist/HWSW] Dél-koreai kutatók egy csoportja olyan technológiát dolgozott ki, amely vezetékek vagy rádió helyett az emberi bőrt használja különféle elektronikus eszközök -- például az MP3-lejátszó és a fejhallgató, vagy a mobiltelefon és a headset -- közötti kommunikáció csatornájaként. A mérnökök szerint az ötlet egyáltalán nem vad, és gőzerővel dolgoznak azon, hogy egy éven belül tömegesen és rendkívül olcsón termelhető állapotba kerüljenek a szükséges chipek.

Nem tudom ki hogy van vele, de engem nem villanyozott fel az ötlet, hogy bitek szaladgáljanak a testemen ... :->