--- /dev/null
+<chapter id="protocol">
+ <title>The SMB/CIFS protocol</title>
+
+ <!--
+ Some parts shamelessly borrowed from myself.
+ Original on http://jelmer.vernstok.nl/publications/cifs-developments.pdf
+ -->
+
+ <para>
+ "SMB" (also known as "CIFS") is a
+ file-sharing protocol that has been used since the mid-eighties.
+ Most people know SMB as the protocol behind the "Network Neighbourhood"
+ and remote printing in Windows.
+ </para>
+
+ <para>
+ Several parts of the protocol are not discussed in this chapter, such
+ as mailslots, browsing and dfs, to prevent it from getting too complex.
+ CIFS internals are documented in detail in <citation>Hertel, 2003</citation>.
+ </para>
+
+
+ <sect1>
+ <title>History</title>
+
+ <sect2>
+ <title>Invention by IBM</title>
+
+ <para>
+ SMB is not very old, but it has a long history of modifications and extensions.
+ The original protocol was meant to run over ``NetBIOS'', which was the
+ name of the DOS interface to a very simple LAN system developed by IBM.
+ NetBIOS was developed because SNA, IBM's other main
+ protocol at the time, was much too advanced for use in DOS.
+ </para>
+
+ <para>
+ The NetBIOS API in these days (early eighties) was nothing more then the
+ interface to a very simple link-layer protocol
+ over which several protocols, including SMB, were used. It could do reads and
+ writes to services on remote hosts, which were identified by case-insensitive
+ names, and discover all available hosts and services.
+ </para>
+
+ <para>
+ Dr. Barry Feigenbau, an IBM employee, invented the core of the original SMB protocol,
+ which he initially named after himself: ``BAF''. He later changed the name to
+ be ``SMB'' (for ``Server Message Block''). Every packet in the protocol
+ starts with a byte $0xFF$ and these three letters.
+ </para>
+
+ <para>
+ IBM, Microsoft, 3Com and Intel made up the rest of the initial protocol
+ together. The commands the protocol supported at this stage were basically
+ a mirror of the DOS File IO API calls, which meant the protocol wasn't very
+ efficient. The protocol also lacked authentication support. Everybody on the
+ network could do reads and writes, which meant this protocol
+ wasn't very suitable for large enterprises.
+ </para>
+
+ <para>
+ NetBIOS is an API that has had various implementations; there is
+ NetBIOS over TCP/IP (NBT), NetBIOS over IPX, NetBIOS over SNA and
+ even NetBIOS over DECNEt. Mostly used these days is
+ NetBIOS over TCP (NBT).
+ </para>
+
+ <para>
+ This is also were things are starting to get hairy. Since NetBIOS identifies
+ hosts by their name, NetBIOS clients had to start doing IP broadcasts to
+ figure out the IP of the host they had to connect to. Several schemes were
+ introduced to do name lookups crossing subnet boundaries, using name servers,
+ etc. We're basically emulating a NetBIOS LAN in order to be able to run SMB.
+ </para>
+
+ <para>
+ Doing NetBIOS over IP is not very sane, however, the NBT implementation itself
+ in Windows isn't very nice either. It has horrible
+ limits, special exceptions, several broken schemes for looking up
+ names (including two kinds of name servers). NetBIOS and NetBIOS over TCP/IP
+ are described in RFC1001 and RFC1002.
+ </para>
+ </sect2>
+
+ <sect2>
+ <title>The various incarnations of SMB</title>
+
+ <para>Over the years, several usage models for SMB have been developed. While SMB originally started out as a file sharing protocol, it was later extended to include support for network management and other network services
+ as well.</para>
+
+ <para>
+ One of the reasons for the various "upgrades" of the SMB
+ protocol is the fact that networks have become larger
+ and larger and with them the need for privilege separation
+ and scalability has increased.
+ </para>
+
+ <sect3>
+ <title>DOS</title>
+
+ <para>
+ The original model in which SMB was used was as a
+ simple file-sharing service in a NetBIOS-environment.
+ </para>
+
+ <para>
+ File sharing worked basically by specifying a list of directories that had
+ to be shared and what name they had to be shared under ("shares"). Eventually,
+ one could password-protect a share. At most one password per share could be set.
+ </para>
+ </sect3>
+
+ <sect3>
+ <title>Windows For Workgroups</title>
+
+ <para>
+ After the ``CORE'' dialect,
+ IBM and Microsoft implemented a new dialect known as ``LANMAN''.
+ This dialect was used by Windows for
+ Workgroups, OS/2 and Windows 9x which all know it under a different name. A
+ 'virtual' file system was also added, which was used for doing remote function
+ calls (RAP, for ``Remote Administration Protocol'').
+ </para>
+
+ <para>
+ Computers are grouped into "Workgroups" in this model. Everybody is equal to
+ the others and there is no central point of control.
+ </para>
+ </sect3>
+
+ <sect3>
+ <title>Windows NT</title>
+ <para>
+ For Windows NT, yet another dialect was added, named 'NT'. The NT dialect
+ had it's own set of file I/O functions (similar to the NT File I/O API)
+ and it had support for yet another way of doing remote function calls:
+ DCE/RPC. RPC's are used for DCOM and several of the subsystems in NT
+ that can be accessed remotely (registry, printing, user management, logging
+ on, etc).
+ </para>
+
+ <para>
+ Windows NT works with a new concept for grouping computers called ``domains''<footnote>In the protocol, domains are actually an upgraded version of a workgroup</footnote>. Each computer is member of exactly one domain. There are several roles a computer can have in the domain: PDC (primary domain controller, the "manager" of the domain, that coordinates all authentication and authorization), BDC (Backup domain controller, in case the PDC goes down) or just a regular domain member. The PDC decides who is to be a member of the domain.
+ </para>
+ </sect3>
+
+ <sect3>
+ <title>Windows 2000</title>
+ <para>
+ In Windows NT 5 (marketing name: Windows 2000), NetBIOS-less SMB was
+ introduced. This means SMB is used directly over TCP port 445 instead of
+ via NetBIOS over TCP/IP. DNS
+ is used for looking up machine names.
+ </para>
+
+ <para>Windows 2000 was also the first operating system from Microsoft
+ that had support for Active Directory. Active Directory is very
+ similar to the "domain" concept used by NT4, though it
+ is implemented differently (using modified open protocols),
+ and has some additional features (one of the most important ones being decentralized).
+ </para>
+
+ <para>
+ Active directory no longer uses a central point of authority
+ and there are fewer limits to the size of a domain. Several
+ DC's can exist, so there is no longer a single point of
+ failure as well as better scalability.
+ </para>
+ </sect3>
+ </sect2>
+
+ <sect2>
+ <title>Samba versions and their support for the SMB models</title>
+
+ <sect3>
+ <title>Samba 2.2</title>
+
+ <para>Full CORE and Workgroup support. Somewhat basic
+ NT4-style support.</para>
+ </sect3>
+
+ <sect3>
+ <title>Samba 3.0</title>
+
+ <para>Full CORE and Workgroup support. Almost complete
+ NT4-style support.
+ </para>
+ </sect3>
+
+ <sect3>
+ <title>Samba 3.2</title>
+
+ <para>FIXME</para>
+ </sect3>
+
+ <sect3>
+ <title>Samba 4.0</title>
+
+ <para>Full CORE, Workgroup, NT4 and ADS support.</para>
+
+ </sect3>
+ </sect2>
+ </sect1>
+</chapter>
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