Why is Netflix Buffering? Dispelling the Congestion Myth

After receiving the letter from a customer in Los Angeles asking why he was not getting a good experience watching Netflix on his 75 Mbps FiOS connection, claiming Verizon was “throttling” Netflix traffic, our network operations team studied the network connection for this customer for the week preceding the date that he emailed us.

They measured the utilization -- or the percentage of total capacity used -- at every link in the Verizon network -- from the customer to the edge of our network, where we receive Netflix traffic -- to determine where, if at all, congestion was occurring.

This review confirmed again what I’ve explained before: there was no congestion anywhere within the Verizon network. There was, however, congestion at the interconnection link to the edge of our network (the border router) used by the transit providers chosen by Netflix to deliver video traffic to Verizon’s network.

While the links chosen by Netflix were congested (congestion occurs when use approaches or reaches 100% capacity during peak usage periods), the links from other transit providers (carrying non-Netflix traffic) to Verizon’s network did not experience congestion and were performing fine. The maximum amount of capacity used (or peak utilization) over the links between these other networks and Verizon’s network ranged from 10% to 80% (with an average peak utilization of 44%).

One might wonder why Netflix and its transit providers were the only ones that ran into congestion issues. What it boils down to is this: these other transit and content providers took steps to ensure that there was adequate capacity for their traffic to enter our network.