To avoid excessive usage of bandwidth, and protect your site from Denial Of Service attacks, you can limit bandwidth usage for a site and limit the number of simultaneous connections.
Important: To enable users to limit bandwidth in Plesk for Linux, the Plesk administrator must install the support for the Bandwidth Limiter for Apache through Tools & Settings > Updates and Upgrades > Add/Remove Components > Web hosting > Apache > mod_bw. Also, the administrator will need to stop nginx through Tools & Settings > Services management > stop Reverse Proxy Server (nginx). In Plesk for Windows, make sure that QoS Packet Scheduler is working in your system.
To limit bandwidth usage and number of connections to a site:
Note: This command is available only if your hosting provider has turned on the support for bandwidth limiting.