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\title{Samba and SMB Tutorial}
\author{Andrew Tridgell\\
E-mail: tridge@samba.anu.edu.au}

\begin{document}
\maketitle

This tutorial will be divided into four sections:

\begin{itemize}
\item The SMB protocol - what's on the wire
\item Configuring Samba - installing and tuning Samba
\item The future of SMB - where the protocol is going
\item Discussion - we discuss your SMB needs
\end{itemize}

\section{The SMB Protocol}

Samba implements the SMB protocol and a number of associated
protocols. It is sometimes useful to compare SMB to NFS

\begin{itemize}
\item SMB has scores of top level commands some with dozens of
  subcommands and subsubcommands
\item NFS has around a dozen commands in total
\item SMB is connection oriented with a client-maintains-state
  architecture to handle reconnect
\item NFS is stateless
\item SMB has sophisticated command chaining, client caching and
  locking capabilities.
\item NFS is well documented and was designed before being implemented
\item SMB is badly documented with the documentation being written
  retrospectively from the existing implementations
\end{itemize}

\subsection{The anatomy of SMB}

The SMB protocol can work over many transports, but the most
interesting these days is TCP/IP. SMB on TCP/IP uses three ports:

\begin{itemize}
\item UDP/137 is used for name resolution and registration
\item UDP/138 is used for browsing
\item TCP/139 is used for the main file and print sharing transactions
\end{itemize}

This is a simplification, but it is close


\subsection{NBT on UDP/137}

UDP/137 carries name registrations and name queries. When the queries
are unicast this protocol if often referred to as WINS (or Windows
Internet Name Server). It is a inappropriate name as WINS does not
work at all well on large WANs.

We will now observe a Win95 machine called VAAREKE starting up and
watch the traffic on UDP/137. Note particularly the differences in the
startup for WINS and non-WINS.

\subsection{NBT on UDP/138}

UDP/138 carries browsing traffic. This is mostly local broadcast
traffic with the occasional message between subnets for cross subnet
browsing. 

We will take a look at the following situations:

\begin{itemize}
\item a browse client (such as a win95 PC) boots up
\item a browse server restarts
\end{itemize}

One thing to note about these packets is that they actually have a
mixed byte order! It is a rare thing for a internet protocol to mix
byte orders. Can you work out how it happened?

\section{SMB on TCP/139}

TCP/139 is where the main action happens with the SMB protocol. All
file and printer sharing happens on this port. It is a complex
protocol but its structure is fairly easy to understand. We will look
at a number of situations:

\begin{itemize}
\item connecting to a SMB server
\item copying a file
\item obtaining and breaking oplocks
\item printing a file
\end{itemize}

\subsection{SMB authentication}

SMB authentication is a thorny issue. There are two main
authentication models available but unfortunately many people want
something that is a combination of the two.

We will examine the authentication process for the two security
models:

\begin{itemize}
\item user level security - where the client first authenticates then
  chooses a share to access
\item share level security - where the client authenticates as part of
  accessing a share
\end{itemize}

\subsection{Domain logons}

The SMB protocol (or more accurately the MS implementations) support
two quite different methods for ``network logons'', one being used by
Windows95 and the other by WindowsNT. 

The Windows95 domain logon protocol is fairly simple but is a useful
way of allowing users to move between workstations while maintaining a
single point of logon and single place where profiles are stored. 

A Windows95 domain logon works by:

\begin{itemize}
\item The client doing a broadcast on UDP/138 to ask for a logon
  server
\item The logon server responding with its netbios name 
\item The client doing a SMB connect to the logon server
\item The client asking the logon server for information on its domain
  logon configuration, such as logon scripts, home directories and
  profile paths.
\end{itemize}

A WindowsNT domain logon works by:

\begin{itemize}
\item The client doing a broadcast on UDP/138 to ask for a NT domain 
  server
\item The domain server responding with its netbios name 
\item The client doing a SMB connect to the logon server
\item The client establishes an encrypted secure pipe using a shared
  secret key and a RC4 encryption stream
\item The client asks the logon server for information on its domain
  logon configuration, such as logon scripts, home directories and
  profile paths.
\end{itemize}

The NT domain protocol may look a lot more secure, but it actually has
some major flaws. unfortunately we have been forced to reproduce some
of those flaws in the Samba implementation in order to remain
compatible with NT clients.

\subsection{Locking and client caching}

One area where SMB is particularly rich is in the range of locking
capabilities available. They are divided into 3 types of locks:

\begin{itemize}
\item byte range locking - for locking records in a file
\item share modes - for specifying what other users can do with a file
  at the same time
\item opportunistic locks - not really locking at all, oplocks are a
  safe client caching mechanism
\end{itemize}

\newpage
\section{Configuring Samba}

Samba is really fairly easy to install as long as you read the
documentation. Unfortunately most people seem to skip the
documentation and instead write to us (hint: read the docs first!).

\subsection{Installing Samba}

It's simple:

\begin{itemize}
\item unpack the archive
\item read the documentation
\item edit the Makefile
\item compile - use ``make''
\item install - use ``make install''
\item build a config file, starting with the sample
\end{itemize}

I'll give a quick demo 

\subsection{The smb.conf file}

The smb.conf file should be familiar to anyone who has dealt with the
old win.ini style config files. 

Here are some tips:

\begin{itemize}
\item don't just guess the meaning of an option from its name. Look in
  the man page!
\item take advantage of the \% macros to allow for per host and per
  user customization
\item smb.conf access controls are not a replacement for good unix
  file permissions
\item use the include option and macros to allow you to test configs
  on one guinea pig machine 
\end{itemize}

\subsection{performance tuning}

Lots of people ask how to tune Samba performance. The best way to tune
anything is to first understand why is is running slower than you
expect. For this I suggest you use a sniffer and your system trace
utility.

There are some common ``quick fixes'' however:

\begin{itemize}
\item socket options, particularly TCP\_NODELAY
\item client TCP tuning options
\item oplocks
\end{itemize}

The biggest problem with SMB performance is the way that MS have
written their clients. A less efficient client is hard to
imagine. Let's look at a couple of examples:

\begin{itemize}
\item file properties
\item copying a file
\end{itemize}

\subsection{SWAT - the Samba Web Administration Tool}

Samba is finally coming out of the dark ages as far as GUI
administration tools are concerned. The next major release will come
with a web based GUI config tool called SWAT. 

I'll give you a quick demo to whet your appetites

\newpage
\section{The future of SMB and Samba}

SMB and Samba are rapidly evolving things. While Samba is constantly
improving we also have to track major changes in the SMB
protocol. 

\subsection{CIFS specification effort}

A couple of years ago MS started a standardization effort for
CIFS. The motivations for this are sure to be complex but the result
is definitely a good thing for the SMB community. The SMB protocol is
finally being (at least partly) documented!

The protocol is still really defined by the MS implementations, but at
least its a start.

\subsection{What's new in CIFS}

CIFS adds a few new things

\begin{itemize}
\item formalizes the new ``NT LM 0.12'' subprotocol
\item adds some rather unsatisfactory methods for solving the flat
  name space issue using DNS
\item finally removes some SMB commands - some bloat is removed
\end{itemize}

\subsection{LDAP}

Microsoft have stated that LDAP is the way of the future for name
resolution and some other aspects of SMB. It is still very unclear
exactly how this will work.

\subsection{Kerberos}

Microsoft have decided that the proprietary domain protocols will be
replaced with Kerberos. This is certainly a good thing, but there are
some gotchas.

\subsection{netbios-less operation}

NT5 will include netbios-less operation on a new TCP port number. This
sparked the most heated debate we have yet seen in the CIFS
community. I'll try to explain the issues as I see them.

\subsection{PDC support in Samba}

Samba is continuing to develop NT4 style Primary Domain Controller
support. I'll give a demo and a brief rundown on why this is
important. 

\newpage
\section{Discussion}

This final section I'd like to leave open ended. I'm hoping that a
number of the tutorial attendees will describe their network setup so
that we can discuss the role that SMB and Samba plays in their
network.

I'm hoping to learn as much from this section as you do! I'm always
looking for feedback on Samba so I know where effort needs to be
concentrated. 

\section{Further info}

There is lots of Samba info available!

\begin{itemize}
\item The first stop for Samba info is the Samba web site at
  http://samba.anu.edu.au/samba/
\item John Blair has written a Samba book. It is well worth reading if
  you run a Samba server. See the Samba web site for details. More
  books are being written as well.
\item The Samba mailing lists, see http://samba.anu.edu.au/listproc/
\item you can contact me at tridge@samba.anu.edu.au, but please be
  patient in waiting for a reply, I get far more email than I can
  handle. 
\end{itemize}

\end{document}
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