How parallelize the SST network transfer

I know the xtrabackup option to parallelize the xtrabackup dump, but I would also like to parallelize the network transfer during the SST from the donor to the joiner.

The reason is that the joiner is an AWS instance that has a bandwidth capping of 8Mbit/s per process (the donor is not an AWS instance). A known workaround is to spread the replication between multiple processes, but I can’t find a way to achieve this with XtraDB Cluster.

Any ideas how to solve this problem ?