To use the larger 1K packet size, at the Autolog command prompt enter:
In general, you can use the larger packet size when you have a reasonably "clean," noise-free connection with the remote system, and when the remote file transfer software also supports the 1K packet size and has been appropriately set up to use 1K packets.
Using a larger packet size will make file transfers go faster on good
connections but will make them go slower over noisy connections. Using
the x1k option when it isn't supported by the remote file transfer
software may make the file transfer fail. To turn off the x1k
option and use 128-byte packets, enter: