In Exchange 2010 DAG, the asynchronous replication no longer uses SMB like it used to be in 2007. Exchange 2007 uses Server Message Blocks (SMB) for log shipping and port 445 has to be opened across datacentres if you have multi-site CCRs or SCRs.
Exchange 2010 uses TCP/IP for copying of log files and seeding. The DAG uses 64327 port for replication by default, but you can change the port. Check my previous article on how to change the replication port used by the DAG.