Downloads and Uploads on Computer Networks and the Internet

Example of a Web Browser File Download
Example of a Web Browser File Download. Bradley Mitchell

On computer networks, a download involves receiving a file or other data being sent from a remote device. An upload involves sending a copy of a file to a remote device. However, sending data and files across computer networks does not necessarily constitute an upload or a download.

Is it a Download or Just a Transfer?

All kinds of network traffic can be considered data transfers of some kind. Specific kinds network activity considered to be downloads are typically transfers from a server to a client in a client-server system.

 Examples include

  • downloading email from a mail server to their local client
  • downloading an application or an archive (like a .zip or a .tar file) from a Web server
  • using FTP to copy a file from an FTP server onto a local device

Conversely, examples of network uploads include

  • uploading photos and videos to a cloud storage system or a Web site like Pinterest
  • sending email
  • publishing HTML files to a Web server
  • using FTP to copy a file onto an FTP server

Downloading versus Streaming

The key difference between downloads (and uploads) and other kinds of data transfer on networks is persistent storage. After a download (or upload), a new copy of the data gets stored on the receiving device. With streaming, the data (typically audio or video) is received and viewed in real time but not stored for future use.

On computer networks, the term upstream refers to network traffic that flows away from the local device toward the remote destination.

 Downstream traffic, conversely, flows to a user's local device. Traffic on most networks flows in both upstream and downstream directions simultaneously. For example, a Web browser sends HTTP requests upstream to the Web server, and the server replies with downstream data in the form of Web page content.

Often, while application data flows in one direction, network protocols also send control instructions (generally invisible to the user) in the opposite direction. 

Typical Internet users create much more downstream than upstream traffic. For this reason, some Internet services like asymmetric DSL (ADSL) provide less network bandwidth in the upstream direction in order to reserve more bandwidth for downstream traffic.

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