We recently had a customer complain that FTP transfers were being truncated - but only for files with a PGP extension! When a 56K file was transferred using Filezilla, only 54K arrived at the server.
The problem turned out to be a feature of network interface cards called TCP offloading, which takes the load off the CPU for network processing and hands it to the NIC.
TCP uploading is known to cause some issues, and the solution was to disable TCP offloading as described
here.
