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CIFS = SMB + Tweaks CIFS is Microsoft's Internet file system offering. Just as Sun tweaked its previously existing technology to produce WebNFS, Microsoft tweaked its Server Message Block (SMB) to produce CIFS. SMB, the file-sharing protocol at the heart of Windows networking, is the protocol spoken by Windows NT, Windows95, Windows f or Workgroups and OS/2 LAN Manager. CIFS is not so much a new protocol as a renaming of future versions of Microsoft's existing SMB protocol. Therefore, what used to be referred to as SMB is now CIFS.

CIFS avoided several of the changes that WebNFS needed. SMB already runs on static, well-known TCP/IP ports, so firewalls are not a problem. In addition, network turnarounds in SMB are minimized via the protocol's "AndX" mechanism, which lets SMB and CIFS clients batch multiple protocol-level requests.

But unlike NFS, which grew up in the TCP/IP world, SMB emerged in the early 1980s as a protocol for small PC workgroups and used NetBIOS/

NetBEUI as a network transport. Although a specification for running NetBIOS over TCP/IP was devised (it was referred to as NBT and detailed in RFC 1001 and 1002), SMB networking still relies on NetBIOS name services for translating machine host names into IP addresses.

Microsoft's Windows Internet Na me Service (WINS) and the LMHOSTS file are methods of performing NetBIOS name searches. But on the Internet, host name-to-IP address translation is performed via Domain Name System (DNS) servers. As a result, Microsoft made several tweaks to the protocol to let CIFS clients perform host name searches directly via DNS. Microsoft's previous incarnations of SMB, prior to the most recent CIFS specification, never managed to get the DNS integration quite right.

Microsoft also added support for its Distributed File System (DFS). Don't confuse Microsoft's DFS with the Distributed Computing Environment's (DCE) DFS; although they solve some similar problems, they are completely different animals. Microsoft DFS support in CIFS lets it handle logical volume names. For instance, network volumes can exist across multiple shares and multiple servers, but they are accessed via one common subdirectory.

Microsoft's DFS is a suitable enhancement to CIFS, letting you move volumes from one server to the next without changing your users' paths or URLs. The closest equivalent service in WebNFS is the NFS Automounter, which is not universally available from all NFS vendors and is harder to administer than Microsoft DFS.

Once past these minor tweaks, the proposed CIFS protocol is largely a description of how SMB file sharing runs in Windows95 and NT. However, Microsoft has more radical plans for CIFS down the road. In Windows NT 5.0, Microsoft will let CIFS run by itself over TCP/IP without any NetBIOS-isms. So instead of NetBIOS name service schemes (broadcasts, WINS, LMHOSTS), NT 5.0 CIFS will use Lightweight Directory Access Protocol (LDAP).

WebNFS versus CIFS Which protocol is better for your system? A side-by-side comparison of the important issues involved should help you decide.

· Performance and Capacity Issues Proxy servers and file caching onto the client's disk are two primary mechanisms HTTP employs to aid performance over low-bandwidth links. Neither WebNFS nor CIFS protocols supports proxy servers the way HTTP does. Additionally, CIFS does not currently c ache to the client's hard drive.

Likewise, most NFS implementations do not cache to hard disk. However, a few NFS implementations (such as SunSoft's Solaris and PC-NFS products) include CacheFS, which handles disk caching.