What is the difference between upstream and downstream traffic?

Answer: Network traffic is often described as either upstream or downstream traffic. These terms are rarely used by most Internet users, but they are important to network administrators, who monitor the bandwidth usage of networks and individual systems.

Upstream traffic refers to data that is sent from a computer or network. This includes all types of outgoing data, such as sending an e-mail message or uploading a file. It may also include data sent over the Internet while playing an online multiplayer game.

Downstream traffic refers data that is received by a computer or network. This includes receiving e-mail messages, downloading files, or simply visiting Web pages. Online games also generate downstream traffic.

Some ISPs place monthly limits on upstream and downstream traffic for each user, collectively referred to as "bandwidth usage." However, these bandwidth limits are usually very high, which means most users don't need to monitor their monthly network traffic. Network administrators, on the other hand, usually keep a close eye on upstream and downstream traffic to make sure no single system is transferring an abnormal amount of data.

Published: May 28, 2010 — by Per Christensson