SMB2 is replacing AFP as the default sharing protocol.
SMB2
SMB2 is the new default protocol for sharing files in OS X Mavericks. SMB2 is superfast, increases security, and improves Windows compatibility.
Efficient. SMB2 features Resource compounding, allowing multiple requests to be sent in a single request. In addition, SMB2 can use large reads and writes to make better use of faster networks as well as large MTU support for blazing speeds on 10 Gigabit Ethernet. It aggressively caches file and folder properties and uses opportu- nistic locking to enable better caching of data. Its even more reliable, thanks to the ability to transparently reconnect to servers in the event of a temporary disconnect.
Secure. SMB2 supports Extended Authentication Security using Kerberos and NTLMv2.
Compatible. SMB2 is automatically used to share files between two Mac computers running OS X Mavericks, or when a Windows client running Vista, Windows 7, or Windows 8 connects to your Mac. Mavericks maintains support for AFP and SMB network file-sharing protocols, automatically selecting the appropriate protocol
as needed.