Nearly every hosting company or network administrator will rate limit traffic. This is commonly done by leaving the port speed of access switches to 10 or 100 Mbps but enforcing a policer or rate limit statement to restrict traffic flow. Generally this is done for egress (outbound or outgoing) traffic. In data centers and networks that contain servers, most of the bandwidth consumed is traffic from the servers hitting the Internet.

That being said, it may also be advantageous to put a policer statement in your switches to also rate limit ingress traffic. I have seen and experienced problems with networks that had zero restrictions on ingress traffic. If a server or group or servers suddenly requests data from outside the network, saturation quickly brings the network down or to a crawl. Unfortunately, because of the way TCP works, you must have bandwidth available (both ingress and egress) to complete connection requests.

If you ever transfer large files using your cable modem, you may notice slow web browsing while the transfer is running. Same concept applies. Now, saturation of Ingress bandwidth is usually only a problem on small networks. By small I mean networks with 100 Mbps or less of transport to the Internet.

Larger networks with 200+ Mbps usually run fine as requests in excess of 200 Mbps are rare. Speaking from experience, I had a group of Sonicwall CDP devices configured to collect backup data from remote networks. Manually activating the transfer requested over 70 Mbps of Ingress traffic. That combined with other requests from the network saturated the 100 Mbps pipe and some servers were reporting offline.

Placing a high rate limit on ingress traffic may be worth your while depending on what devices live on your network. In my case, it would have stopped the Sonicwalls from eating all the bandwidth. If you are using Juniper gear, rate limiting can be done in the ScreenOS GUI. In JunOS this is done by attaching a policer statement the interface. Cisco PIX/ASAs will also rate limit traffic. If you are using Cisco Catalysts make sure you have the "Enhanced" version of IOS. They require specific models like the 2950T. The standard 2950 will not do rate limiting. All layer 3 Cisco devices such as 3750s and 4548s will work fine right out of the box.