The alert message is from the event maxclientbufferdrop
Dropped connection, request exceeded max_client_buffer limit
The traffic manager is still reading the request, but the amount of data read in is larger than max_client_buffer
therefore it abandons the connection.
These settings are configured under Services > Virtual Servers > (select desired VS) > Protocol Settings > Memory Limits > max_client_buffer.
How much memory should the virtual server use to store data sent by the client? Larger values will use more memory, but will minimize the number of read() and write() system calls that Stingray must perform.
Note that for the HTTP protocol, Stingray will reject requests whose HTTP headers are larger than this setting, since it cannot decide what to do with a request until it has seen all the headers.
These settings can help prevent DoS (Denial of Service) attacks as well.