File transfert using In Band Bytestream ( jep-0047 )
Jep-0096 ( file transfer ) mandate the usage of two file transfer method, socks 5 ( already in gajim ) and in band bytestream ( jep-0047 ), but the second is not implemented at the moment.
Ibb is useful when you cannot use socks5, ie restricting firewall. I also think it is much easier to implement than socks5.