In 2010, Jim Gettys, a veteran computer programmer who currently works at Google, was at home uploading a large file to his work server. His kids came into his study and said, “Daddy, the Internet is slow today.” Wondering how his upload activity could be affecting downloads by his kids, he began to investigate.
Source: The hidden cause of slow Internet and how to fix it | Network World
This is actually really straight-forward and we cover this in Networking.