How Upload Bandwidth/Latency Can Affect Download Speed

Part of what makes TCP so great is that it guarantees reliable transport for data transmissions. It does this by verifying that all of the data was received before more data is sent. This verification is accomplished by the receiver sending acknowledgments (ACKs) to the sender. In the event of a timeout, the sender will retransmit all of the missing data.

Though this process doesn’t require much upload bandwidth, it can still be slowed down if there is high latency on the upload side, causing those ACKs not not arrive in a timely fashion. Depending on the severity, this could definitely make an impact on your download speed!

Video Explanation