On our network at work we have a squid proxy between us and the internet. It's main function is to cache windows updates. However, at times, there are overwhelming amounts of traffic coming in on our squid proxy's external interface, but it isn't being read by any of the client machines. This traffic always originates from llnw.com or msecn.net. It lasts for varying amounts of time, and uses up nearly all of our bandwidth. Netstat -p confirms that squid is the program with the connection open.
What is causing this?