In which scenario would you likely use a TFTP server?

A TFTP (Trivial File Transfer Protocol) server is commonly used for backing up router configurations due to its simplicity and lightweight nature. The protocol is designed for quick and straightforward file transfers, making it ideal for transferring configuration files to and from network devices like routers and switches.

When a network technician wants to save or restore device configurations, using TFTP allows them to easily transfer these files over the network without the complex overhead associated with more advanced protocols. Since TFTP operates over UDP, it lacks some of the features found in more robust protocols like FTP or SFTP, such as authentication and larger file support, but this lightness is beneficial in the context of transferring configuration files where speed and efficiency are prioritized.

In contrast, the other scenarios presented involve operations for which TFTP is not well-suited. For example, transferring large video files would be impractical due to TFTP's limitations on file size and lack of error recovery features. Similarly, tasks related to email operations and deploying web applications require more sophisticated protocols that can handle large data sets, provide error correction, and ensure security, which TFTP is not designed to manage. Thus, using a TFTP server for backing up router configurations is the most suitable scenario among the options provided.