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Information Technology Services

Why can't I see shared devices on the wireless network?

mDNS Information

Beginning Tuesday, February 21, 2012, Information Technology Services will begin filtering mDNS (Multicast Domain Name Service) traffic on the wireless network. We have found that mDNS degrades the performance of the wireless network and is not necessary for the services supported.

What is mDNS?

mDNS (Multicast Domain Name Service) is a name service feature that allows network devices to connect through the use of common names. For example, mDNS allows "Max's Computer" to find "Max's Printer" if they are connected to the same home wireless network. On large networks, however, these features do not work. That is because devices are grouped into subnets, and the devices in each subnet can only find each other. The odds of "Max's Computer" and "Max's Printer" being located in the same subnet is very low.

Why this change?

You may have noticed a decline in the speed of the BC wireless network in recent weeks. The problem has been traced back to the increased use of devices that support mDNS. Although you cannot take advantage of the benefits of mDNS due to the size of the BC network, mDNS still generates a large amount of traffic that has a significant impact on the speed of the network. Like many other universities, BC has decided to block mDNS in order to increase the speed of the wireless network.

What does this mean to you?

In short, you will no longer be able to use services that rely on mDNS, such as:

  • Sharing iTunes music between computers on the wireless network.
  • Applications using Bonjour.
  • Some iPhone/iPod applications that depend on mDNS services, such as Remote, Rowmote, and others.
  • Wireless personal printers used in residence halls that are not connected via a USB cable or configured using the MAC address.
  • “Browsing” to locate printers and files servers on the wireless network. Note: You will now be required to specify the network share name.

Most people will hardly notice the change, as the network's subnets make it nearly impossible to use these services to begin with. For the few who do notice the change, please understand that benefits of a faster wireless network far outweigh the benefits of mDNS services.