I have been using ls = f.mlsd() to get list of files and timestamp from ftp but it gives me
ftplib.error_perm: 500 Unknown command
Is there any problem with ftp server? do i need to install anything on the server to get this command working
In the fact, MLSD is nothing but a protocol extension introduced in RFC 3659 that may be not supported by some FTP servers. If you care about portability, it's better to use f.nlst() instead.
If changing something on server is acceptable for you, then I suggest you switching to proftpd which has MLSD support as a part of it's mod_facts extension.