News about the new release of OS X, "Mavericks," is trickling out as developers and other WWDC attendees post information about it to the Internet. However, hidden a bit down in Apple's OS X Mavericks Technology Overview document is an interesting tidbit: SMB2 is replacing AFP as the default file sharing protocol for OS X.

AFP—Apple Filing Protocol—has a long pedigree that stretches all the way back to the Mac's early days (and even a bit before that). Contemporary AFP piggybacks on top of TCP/IP for transport, but it supports a few Mac-specific things that other network file protocols don't, like type and creator codes. These don't matter as much as they used to, but OS X's HFS+ file system supports a pretty rich amount of metadata, and AFP transports and preserves that metadata.

But AFP isn't particularly friendly to non-Apple systems, and no operating systems other than OS X support it natively. This wouldn't be such a big deal, except that one of OS X's killer features, Time Machine, only works over a LAN with destinations that support AFP. This is at least in part because of Time Machine's reliance on Unix hard links, and also in part because it has to be able to ensure that any OS X files with HFS+ specific metadata are correctly preserved. This in turn means that third-party Time Capsule devices have to rely on reverse-engineered implementations of AFP to continue functioning, and OS X updates occasionally break third-party Time Capsule devices, sometimes for weeks.

It is interesting, then, that SMB2 is the new default protocol. SMB ("Server Message Block") is Microsoft's proprietary network file sharing protocol, and it's in most cases the only network file protocol that Windows computers understand. Most versions of OS X prior to OS X 10.7 relied on an open-source implementation of SMB called Samba for accessing Windows file shares and sharing files with Windows clients. However, as of OS X 10.7, Apple replaced Samba with its own SMB implementation, called SMBX.

SMBX's introduction drew some fire because Apple focused SMBX on compatibility with a newer version of the SMB spec, SMB2, at the expense of compatibility with the original (and still widely used) SMB1. However, Apple's choice to support SMB2 dovetailed nicely with Microsoft's own push since SMB2 became the default protocol for Microsoft operating systems on the desktop starting with Windows Vista and for servers starting with Windows Server 2008. It's faster, less chatty (SMB1 is notoriously "talkative," with a tremendous and tremendously inefficient amount of back-and-forth between clients and servers), and much more robust.

The break from AFP as OS X's default network file protocol ought to help OS X mesh better with PCs, both at home and in the office. The operating system will even use SMB2 as its first protocol choice between two Macs running OS X Mavericks. However, AFP is still hanging around, both for legacy Mac communication and also for connectivity with "Time Machine–based backup systems." Time Machine, at least for now, remains bound to AFP.