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docs/docbook/projdoc/NetworkBrowsing.xml
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@ -22,6 +22,58 @@ means for resolution of MS Windows machine names is via DNS and Active Directory
The following information assumes that your site is running NetBIOS over TCP/IP.
</para></note>
<sect1>
<title>Features and Benefits</title>
<para>
Someone once referred to the past in terms of: <emphasis>They were the worst of times,
they were the best of times. The more we look back, them more we long for what was and
hope it never returns!</emphasis>.
</para>
<para>
For many MS Windows network administrators that statement sums up their feelings about
NetBIOS networking precisely. For those who mastered NetBIOS networking it's fickle
nature was just par for the course. For those who never quite managed to tame it's
lusty features NetBIOS is like Paterson's Curse.
</para>
<para>
For those not familiar with botanical problems in Australia: Paterson's curse,
Echium plantagineum, was introduced to Australia from Europe during the mid-nineteenth
century. Since then it has spread rapidly. The high seed production, with densities of
thousands of seeds per square metre, a seed longevity of more than seven years, and an
ability to germinate at any time of year, given the right conditions, are some of the
features which make it such a persistent weed.
</para>
<para>
In this chapter we explore vital aspects of SMB (Server Message Block) networking with
a particular focus on SMB as implmented through running NetBIOS (Network Basic
Input / Output System) over TCP/IP. Since Samba does NOT implement SMB or NetBIOS over
any other protocols we need to know how to configure our network environment and simply
remember to use nothing but TCP/IP on all our MS Windows network clients.
</para>
<para>
Samba provides the ability to implement a WINS (Windows Internetworking Name Server)
and implements extensions to Microsoft's implementation of WINS. These extensions
help Samba to affect stable WINS operations beyond the normal scope of MS WINS.
</para>
<para>
Please note that WINS is exclusively a service that applies only to those systems
that run NetBIOS over TCP/IP. MS Windows 200x / XP have the capacity to turn off
support for NetBIOS, in which case WINS is of no relevance. Samba-3 supports this also.
</para>
<para>
For those networks on which NetBIOS has been disabled (ie: WINS is NOT required)
the use of DNS is necessary for host name resolution.
</para>
</sect1>
<sect1>
<title>What is Browsing?</title>
@ -76,28 +128,36 @@ called <filename>nmbd</filename>. The configuration parameters involved in nmbd'
</programlisting></para>
<para>
WINS Server and WINS Support are mutually exclusive options. Those marked with an '*' are
the only options that commonly MAY need to be modified. Even if not one of these parameters
is set nmbd will still do it's job.
For Samba the WINS Server and WINS Support are mutually exclusive options. Those marked with
an '*' are the only options that commonly MAY need to be modified. Even if not one of these
parameters is set nmbd will still do it's job.
</para>
</sect1>
<sect1>
<title>Discussion</title>
<para>
Firstly, all MS Windows networking is based on SMB (Server Message
Block) based messaging. SMB messaging may be implemented using NetBIOS or
without NetBIOS. Samba implements NetBIOS by encapsulating it over TCP/IP.
MS Windows products can do likewise. NetBIOS based networking uses broadcast
messaging to affect browse list management. When running NetBIOS over
TCP/IP this uses UDP based messaging. UDP messages can be broadcast or unicast.
Firstly, all MS Windows networking uses SMB (Server Message Block) based messaging.
SMB messaging may be implemented with or without NetBIOS. MS Windows 200x supports
NetBIOS over TCP/IP for backwards compatibility. Microsoft are intent on phasing out NetBIOS
support.
</para>
<sect2>
<title>NetBIOS over TCP/IP</title>
<para>
Samba implements NetBIOS, as does MS Windows NT / 200x / XP, by encapsulating it over TCP/IP.
MS Windows products can do likewise. NetBIOS based networking uses broadcast messaging to
affect browse list management. When running NetBIOS over TCP/IP this uses UDP based messaging.
UDP messages can be broadcast or unicast.
</para>
<para>
Normally, only unicast UDP messaging can be forwarded by routers. The
<command>remote announce</command>
parameter to smb.conf helps to project browse announcements
<command>remote announce</command> parameter to smb.conf helps to project browse announcements
to remote network segments via unicast UDP. Similarly, the
<command>remote browse sync</command> parameter of <filename>smb.conf</filename>
implements browse list collation using unicast UDP.
@ -121,20 +181,21 @@ the use of the <command>remote announce</command> and the
<para>
As of Samba 3 WINS replication is being worked on. The bulk of the code has
been committed, but it still needs maturation.
been committed, but it still needs maturation. This is NOT a supported feature
of the Samba-3.0.0 release. Hopefully, this will become a supported feature
of one of the samba-3 release series.
</para>
<para>
Right now samba WINS does not support MS-WINS replication. This means that
when setting up Samba as a WINS server there must only be one <filename>nmbd</filename> configured
as a WINS server on the network. Some sites have used multiple Samba WINS
when setting up Samba as a WINS server there must only be one <filename>nmbd</filename>
configured as a WINS server on the network. Some sites have used multiple Samba WINS
servers for redundancy (one server per subnet) and then used
<command>remote browse sync</command> and <command>remote announce</command>
to affect browse list collation across all
segments. Note that this means clients will only resolve local names,
and must be configured to use DNS to resolve names on other subnets in
order to resolve the IP addresses of the servers they can see on other
subnets. This setup is not recommended, but is mentioned as a practical
to affect browse list collation across all segments. Note that this means clients
will only resolve local names, and must be configured to use DNS to resolve names
on other subnets in order to resolve the IP addresses of the servers they can see
on other subnets. This setup is not recommended, but is mentioned as a practical
consideration (ie: an 'if all else fails' scenario).
</para>
@ -145,15 +206,140 @@ that it will take time to establish a browse list and it can take up to 45
minutes to stabilise, particularly across network segments.
</para>
</sect2>
<sect2>
<title>TCP/IP - without NetBIOS</title>
<para>
All TCP/IP using systems use various forms of host name resolution. The primary
methods for TCP/IP hostname resolutions involves either a static file (<filename>/etc/hosts
</filename>) or DNS (the Domain Name System). DNS is the technology that makes
the Internet usable. DNS based host name resolution is supported by nearly all TCP/IP
enabled systems. Only a few embedded TCP/IP systems do not support DNS.
</para>
<para>
When an MS Windows 200x / XP system attempts to resolve a host name to an IP address
it follows a defined path:
</para>
<orderedlist>
<listitem><para>
Checks the <filename>hosts</filename> file. It is located in
<filename>C:\WinNT\System32\Drivers\etc</filename>.
</para></listitem>
<listitem><para>
Does a DNS lookup
</para></listitem>
<listitem><para>
Checks the NetBIOS name cache
</para></listitem>
<listitem><para>
Queries the WINS server
</para></listitem>
<listitem><para>
Does a broadcast name lookup over UDP
</para></listitem>
<listitem><para>
Looks up entries in LMHOSTS. It is located in
<filename>C:\WinNT\System32\Drivers\etc</filename>.
</para></listitem>
</orderedlist>
<para>
Windows 200x / XP can register it's host name with a Dynamic DNS server. You can
force register with a Dynamic DNS server in Windows 200x / XP using:
<command>ipconfig /registerdns</command>
</para>
<para>
With Active Directory (ADS), a correctly functioning DNS server is absolutely
essential. In the absence of a working DNS server that has been correctly configured
MS Windows clients and servers will be totally unable to locate each other,
consequently network services will be severely impaired.
</para>
<para>
The use of Dynamic DNS is highly recommended with Active Directory, in which case
the use of BIND9 is preferred for it's ability to adequately support the SRV (service)
records that are needed for Active Directory.
</para>
</sect2>
<sect2>
<title>DNS and Active Directory</title>
<para>
Occasionally we hear from Unix network administrators who want to use a Unix based Dynamic
DNS server in place of the Microsoft DNS server. While this might be desirable to some, the
MS Windows 200x DNS server is auto-configured to work with Active Directory. It is possible
to use BIND version 8 or 9, but it will almost certainly be necessary to create service records
so that MS Active Directory clients can resolve host names to locate essential network services.
The following are some of the default service records that Active Directory requires:
</para>
<itemizedlist>
<listitem><para>_ldap._tcp.pdc.ms-dcs.<emphasis>Domain</emphasis></para>
<para>
This provides the address of the Windows NT PDC for the Domain.
</para>
</listitem>
<listitem><para>_ldap._tcp.pdc.ms-dcs.<emphasis>DomainTree</emphasis></para>
<para>
Resolves the addresses of Global Catalog servers in the domain.
</para>
</listitem>
<listitem><para>_ldap._tcp.<emphasis>site</emphasis>.sites.writable.ms-dcs.<emphasis>Domain</emphasis></para>
<para>
Provides list of domain controllers based on sites.
</para>
</listitem>
<listitem><para>_ldap._tcp.writable.ms-dcs.<emphasis>Domain</emphasis></para>
<para>
Enumerates list of domain controllers that have the writable
copies of the Active Directory data store.
</para>
</listitem>
<listitem><para>_ldap._tcp.<emphasis>GUID</emphasis>.domains.ms-dcs.<emphasis>DomainTree</emphasis></para>
<para>
Entry used by MS Windows clients to locate machines using the
Global Unique Identifier.
</para>
</listitem>
<listitem><para>_ldap._tcp.<emphasis>Site</emphasis>.gc.ms-dcs.<emphasis>DomainTree</emphasis></para>
<para>
Used by MS Windows clients to locate site configuration dependant
Global Catalog server.
</para>
</listitem>
</itemizedlist>
</sect2>
</sect1>
<sect1>
<title>How Browsing Functions</title>
<para>
As stated above, MS Windows machines register their NetBIOS names
MS Windows machines register their NetBIOS names
(ie: the machine name for each service type in operation) on start
up. Also, as stated above, the exact method by which this name registration
up. The exact method by which this name registration
takes place is determined by whether or not the MS Windows client/server
has been given a WINS server address, whether or not LMHOSTS lookup
is enabled, or if DNS for NetBIOS name resolution is enabled, etc.