The SMB protocol has evolved over time from CIFS to SMB1 to SMB2, with implementations by dozens of vendors including most major Operating Systems and NAS solutions. The SMB 3.0 protocol, announced at the SNIA Storage Developer Conference in September 2011, now has commercial implementations by Microsoft, NetApp, EMC, and other vendors (some available for licensing), along with recent versions of Samba 4.x, and others in development. This SNIA tutorial describes the basic architecture of the SMB protocol and basic operations, including connecting to a share, negotiating a dialect, executing operations, and disconnecting from a share. The second part of the talk will cover improvements in version 2.0 of the protocol, including a reduced command set, support for asynchronous operations, compounding of operations, durable and resilient file handles, file leasing, and large MTU support.