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<?xml version="1.0" encoding="iso-8859-1"?>
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<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
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<chapter id="2000users">
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<title>A Distributed 2000-User Network</title>
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There is something indeed mystical about things that are
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big. Large networks exhibit a certain magnetism and exude a sense of
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importance that obscures reality. You and I know that it is no more
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difficult to secure a large network than it is a small one. We all
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know that over and above a particular number of network clients, the
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rules no longer change; the only real dynamic is the size of the domain
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(much like a kingdom) over which the network ruler (oops, administrator)
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has control. The real dynamic then transforms from the technical to the
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political. Then again, that point is often reached well before the
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kingdom (or queendom) grows large.
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If you have systematically worked your way to this chapter, hopefully you
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have found some gems and techniques that are applicable in your
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world. The network designs you have worked with in this book have their
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strong points as well as weak ones. That is to be expected given that
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they are based on real business environments, the specifics of which are
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molded to serve the purposes of this book.
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This chapter is intent on wrapping up issues that are central to
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implementation and design of progressively larger networks. Are you ready
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for this chapter? Good, it is time to move on.
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In previous chapters, you made the assumption that your network
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administration staff need detailed instruction right down to the
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nuts and bolts of implementing the solution. That is still the case,
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but they have graduated now. You decide to document only those issues,
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methods, and techniques that are new or complex. Routine tasks such as
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implementing a DNS or a DHCP server are under control. Even the basics of
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Samba are largely under control. So in this section you focus on the
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specifics of implementing LDAP changes, Samba changes, and approach and
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design of the solution and its deployment.
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<title>Introduction</title>
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Abmas is a miracle company. Most businesses would have collapsed under
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the weight of rapid expansion that this company has experienced. Samba
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is flexible, so there is no need to reinstall the whole operating
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system just because you need to implement a new network design. In fact,
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you can keep an old server running right up to the moment of cutover
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and then do a near-live conversion. There is no need to reinstall a
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Samba server just to change the way your network should function.
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<indexterm><primary>LDAP</primary></indexterm>
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Network growth is common to all organizations. In this exercise,
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your preoccupation is with the mechanics of implementing Samba and
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LDAP so that network users on each network segment can work
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<title>Assignment Tasks</title>
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Starting with the configuration files for the server called
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<constant>MASSIVE</constant> in <link linkend="happy"/>, you now deal with the
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issues that are particular to large distributed networks. Your task
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is simple &smbmdash; identify the challenges, consider the
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alternatives, and then design and implement a solution.
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<indexterm><primary>VPN</primary></indexterm>
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Remember, you have users based in London (UK), Los Angeles,
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Washington. DC, and, three buildings in New York. A significant portion
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of your workforce have notebook computers and roam all over the
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world. Some dial into the office, others use VPN connections over the
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Internet, and others just move between buildings.i
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What do you say to an employee who normally uses a desktop
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system but must spend six weeks on the road with a notebook computer?
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She is concerned about email access and how to keep coworkers current
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with changing documents.
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To top it all off, you have one network support person and one
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help desk person based in London, a single person dedicated to all
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network operations in Los Angeles, five staff for user administration
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and help desk in New York, plus one <emphasis>floater</emphasis> for
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You have outsourced all desktop deployment and management to
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DirectPointe. Your concern is server maintenance and third-level
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support. Build a plan and show what must be done.
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<title>Dissection and Discussion</title>
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<indexterm><primary>passdb backend</primary></indexterm>
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<indexterm><primary>LDAP</primary></indexterm>
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In <link linkend="happy"/>, you implemented an LDAP server that provided the
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<parameter>passdb backend</parameter> for the Samba servers. You
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explored ways to accelerate Windows desktop profile handling and you
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took control of network performance.
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<indexterm><primary>ldapsam</primary></indexterm>
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<indexterm><primary>tdbsam</primary></indexterm>
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<indexterm><primary>smbpasswd</primary></indexterm>
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<indexterm><primary>replicated</primary></indexterm>
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The implementation of an LDAP-based passdb backend (known as
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<emphasis>ldapsam</emphasis> in Samba parlance), or some form of database
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that can be distributed, is essential to permit the deployment of Samba
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Primary and Backup Domain Controllers (PDC/BDCs). You see, the problem
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is that the <emphasis>tdbsam</emphasis>-style passdb backend does not
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lend itself to being replicated. The older plain-text-based
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<emphasis>smbpasswd</emphasis>-style passdb backend can be replicated
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using a tool such as <command>rsync</command>, but
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<emphasis>smbpasswd</emphasis> suffers the drawback that it does not
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support the range of account facilities demanded by modern network
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<indexterm><primary>XML</primary></indexterm>
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<indexterm><primary>SQL</primary></indexterm>
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The new <emphasis>tdbsam</emphasis> facility supports functionality
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that is similar to an <emphasis>ldapsam</emphasis>, but the lack of
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distributed infrastructure sorely limits the scope for its
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deployment. This raises the following questions: Why can't I just use
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an XML-based backend, or for that matter, why not use an SQL-based
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backend? Is support for these tools broken? Answers to these
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questions require a bit of background.</para>
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<indexterm><primary>directory</primary></indexterm>
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<indexterm><primary>database</primary></indexterm>
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<indexterm><primary>transaction processing</primary></indexterm>
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<indexterm><primary>LDAP</primary></indexterm>
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<emphasis>What is a directory?</emphasis> A directory is a
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collection of information regarding objects that can be accessed to
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rapidly find information that is relevant in a particular and
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consistent manner. A directory differs from a database in that it is
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generally more often searched (read) than updated. As a consequence, the
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information is organized to facilitate read access rather than to
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support transaction processing.</para>
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<indexterm><primary>Lightweight Directory Access Protocol</primary><see>LDAP</see></indexterm>
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<indexterm><primary>LDAP</primary></indexterm>
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<indexterm><primary>master</primary></indexterm>
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<indexterm><primary>slave</primary></indexterm>
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The Lightweight Directory Access Protocol (LDAP) differs
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considerably from a traditional database. It has a simple search
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facility that uniquely makes a highly preferred mechanism for managing
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user identities. LDAP provides a scalable mechanism for distributing
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the data repository and for keeping all copies (slaves) in sync with
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the master repository.</para>
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<indexterm><primary>identity management</primary></indexterm>
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<indexterm><primary>Active Directory</primary></indexterm>
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<indexterm><primary>OpenLDAP</primary></indexterm>
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Samba is a flexible and powerful file and print sharing
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technology. It can use many external authentication sources and can be
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part of a total authentication and identity management
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infrastructure. The two most important external sources for large sites
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are Microsoft Active Directory and LDAP. Sites that specifically wish to
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avoid the proprietary implications of Microsoft Active Directory
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naturally gravitate toward OpenLDAP.</para>
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<indexterm><primary>network</primary><secondary>routed</secondary></indexterm>
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In <link linkend="happy"/>, you had to deal with a locally routed
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network. All deployment concerns focused around making users happy,
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and that simply means taking control over all network practices and
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usage so that no one user is disadvantaged by any other. The real
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lesson is one of understanding that no matter how much network
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bandwidth you provide, bandwidth remains a precious resource.</para>
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<para>In this chapter, you must now consider how the overall network must
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function. In particular, you must be concerned with users who move
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between offices. You must take into account the way users need to
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access information globally. And you must make the network robust
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enough so that it can sustain partial breakdown without causing loss of
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<title>Technical Issues</title>
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There are at least three areas that need to be addressed as you
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approach the challenge of designing a network solution for the newly
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<listitem><para><indexterm><primary>mobility</primary></indexterm>
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User needs such as mobility and data access</para></listitem>
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<listitem><para>The nature of Windows networking protocols</para></listitem>
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<listitem><para>Identity management infrastructure needs</para></listitem>
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<para>Let's look at each in turn.</para>
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<title>User Needs</title>
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The new company has three divisions. Staff for each division are spread across
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the company. Some staff are office-bound and some are mobile users. Mobile
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users travel globally. Some spend considerable periods working in other offices.
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Everyone wants to be able to work without constraint of productivity.
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The challenge is not insignificant. In some parts of the world, even dial-up
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connectivity is poor, while in other regions political encumbrances severely
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curtail user needs. Parts of the global Internet infrastructure remain shielded
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off for reasons outside the scope of this discussion.
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<indexterm><primary>synchronize</primary></indexterm>
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Decisions must be made regarding where data is to be stored, how it will be
245
replicated (if at all), and what the network bandwidth implications are. For
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example, one decision that can be made is to give each office its own master
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file storage area that can be synchronized to a central repository in New
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York. This would permit global data to be backed up from a single location.
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The synchronization tool could be <command>rsync,</command> run via a cron
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job. Mobile users may use off-line file storage under Windows XP Professional.
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This way, they can synchronize all files that have changed since each logon
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<indexterm><primary>bandwidth</primary><secondary>requirements</secondary></indexterm>
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<indexterm><primary>roaming profile</primary></indexterm>
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No matter which way you look at this, the bandwidth requirements
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for acceptable performance are substantial even if only 10 percent of
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staff are global data users. A company with 3,500 employees,
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280 of whom are mobile users who use a similarly distributed
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network, found they needed at least 2 Mb/sec connectivity
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between the UK and US offices. Even over 2 Mb/sec bandwidth, this
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company abandoned any attempt to run roaming profile usage for
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mobile users. At that time, the average roaming profile took 480
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KB, while today the minimum Windows XP Professional roaming
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profile involves a transfer of over 750 KB from the profile
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server to and from the client.
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<indexterm><primary>wide-area</primary></indexterm>
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Obviously then, user needs and wide-area practicalities dictate the economic and
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technical aspects of your network design as well as for standard operating procedures.
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<title>The Nature of Windows Networking Protocols</title>
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<indexterm><primary>profile</primary><secondary>mandatory</secondary></indexterm>
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Network logons that include roaming profile handling requires from 140 KB to 2 MB.
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The inclusion of support for a minimal set of common desktop applications can push
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the size of a complete profile to over 15 MB. This has substantial implications
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for location of user profiles. Additionally, it is a significant factor in
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determining the nature and style of mandatory profiles that may be enforced as
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part of a total service-level assurance program that might be implemented.
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<indexterm><primary>logon traffic</primary></indexterm>
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<indexterm><primary>redirected folders</primary></indexterm>
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One way to reduce the network bandwidth impact of user logon
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traffic is through folder redirection. In <link linkend="happy"/>, you
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implemented this in the new Windows XP Professional standard
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desktop configuration. When desktop folders such as <guimenu>My
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Documents</guimenu> are redirected to a network drive, they should
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also be excluded from synchronization to and from the server on
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logon or logout. Redirected folders are analogous to network drive
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<para><indexterm><primary>application servers</primary></indexterm>
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Of course, network applications should only be run off
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local application servers. As a general rule, even with 2 Mb/sec
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network bandwidth, it would not make sense at all for someone who
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is working out of the London office to run applications off a
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server that is located in New York.
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<indexterm><primary>affordability</primary></indexterm>
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When network bandwidth becomes a precious commodity (that is most
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of the time), there is a significant demand to understand network
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processes and to mold the limits of acceptability around the
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constraints of affordability.
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When a Windows NT4/200x/XP Professional client user logs onto
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the network, several important things must happen.
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<indexterm><primary>DHCP</primary></indexterm>
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The client obtains an IP address via DHCP. (DHCP is
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necessary so that users can roam between offices.)
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<indexterm><primary>WINS</primary></indexterm>
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<indexterm><primary>DNS</primary></indexterm>
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The client must register itself with the WINS and/or DNS server.
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<indexterm><primary>Domain Controller</primary><secondary>closest</secondary></indexterm>
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The client must locate the closest domain controller.
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The client must log onto a domain controller and obtain as part of
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that process the location of the user's profile, load it, connect to
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redirected folders, and establish all network drive and printer connections.
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The domain controller must be able to resolve the user's
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credentials before the logon process is fully implemented.
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Given that this book is about Samba and that it implements the Windows
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NT4-style domain semantics, it makes little sense to compare Samba with
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Microsoft Active Directory insofar as the logon protocols and principles
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of operation are concerned. The following information pertains exclusively
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to the interaction between a Windows XP Professional workstation and a
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Samba-3.0.20 server. In the discussion that follows, use is made of DHCP and WINS.
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As soon as the Windows workstation starts up, it obtains an
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IP address. This is immediately followed by registration of its
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name both by broadcast and Unicast registration that is directed
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<indexterm><primary>Unicast</primary></indexterm>
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<indexterm><primary>broadcast</primary><secondary>directed</secondary>
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</indexterm><indexterm><primary>NetBIOS</primary></indexterm>
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Given that the client is already a domain member, it then sends
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a directed (Unicast) request to the WINS server seeking the list of
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IP addresses for domain controllers (NetBIOS name type 0x1C). The
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WINS server replies with the information requested.</para>
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<indexterm><primary>broadcast</primary><secondary>mailslot</secondary></indexterm>
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<indexterm><primary>Unicast</primary></indexterm>
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<indexterm><primary>WINS</primary></indexterm>
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The client sends two netlogon mailslot broadcast requests
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to the local network and to each of the IP addresses returned by
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the WINS server. Whichever answers this request first appears to
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be the machine that the Windows XP client attempts to use to
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process the network logon. The mailslot messages use UDP broadcast
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to the local network and UDP Unicast directed at each machine that
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was listed in the WINS server response to a request for the list of
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<indexterm><primary>protocol</primary><secondary>negotiation</secondary></indexterm>
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<indexterm><primary>logon server</primary></indexterm>
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<indexterm><primary>fail</primary></indexterm>
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The logon process begins with negotiation of the SMB/CIFS
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protocols that are to be used; this is followed by an exchange of
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information that ultimately includes the client sending the
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credentials with which the user is attempting to logon. The logon
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server must now approve the further establishment of the
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connection, but that is a good point to halt for now. The priority
405
here must center around identification of network infrastructure
406
needs. A secondary fact we need to know is, what happens when
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local domain controllers fail or break?
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<indexterm><primary>Domain Controller</primary></indexterm>
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<indexterm><primary>PDC</primary></indexterm>
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<indexterm><primary>BDC</primary></indexterm>
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<indexterm><primary>netlogon</primary></indexterm>
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Under most circumstances, the nearest domain controller
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responds to the netlogon mailslot broadcast. The exception to this
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norm occurs when the nearest domain controller is too busy or is out
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of service. Herein lies an important fact. This means it is
419
important that every network segment should have at least two
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domain controllers. Since there can be only one PDC, all additional
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domain controllers are by definition BDCs.
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<indexterm><primary>authentication</primary></indexterm>
426
<indexterm><primary>Identity Management</primary></indexterm>
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The provision of sufficient servers that are BDCs is an
428
important design factor. The second important design factor
429
involves how each of the BDCs obtains user authentication
430
data. That is the subject of the next section, which involves key
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decisions regarding Identity Management facilities.
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<title>Identity Management Needs</title>
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<indexterm><primary>privacy</primary></indexterm>
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<indexterm><primary>user credentials</primary></indexterm>
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<indexterm><primary>validated</primary></indexterm>
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<indexterm><primary>privileges</primary></indexterm>
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Network managers recognize that in large organizations users
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generally need to be given resource access based on needs, while
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being excluded from other resources for reasons of privacy. It is
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therefore essential that all users identify themselves at the
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point of network access. The network logon is the principal means
449
by which user credentials are validated and filtered and appropriate
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rights and privileges are allocated.
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<indexterm><primary>Identity Management</primary></indexterm>
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<indexterm><primary>Yellow Pages</primary></indexterm>
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<indexterm><primary>NIS</primary></indexterm>
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Unfortunately, network resources tend to have their own Identity
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Management facilities, the quality and manageability of which varies
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from quite poor to exceptionally good. Corporations that use a mixture
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of systems soon discover that until recently, few systems were
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designed to interoperate. For example, UNIX systems each have an
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independent user database. Sun Microsystems developed a facility that
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was originally called <constant>Yellow Pages</constant>, and was renamed
464
when a telephone company objected to the use of its trademark.
465
What was once called <constant>Yellow Pages</constant> is today known
466
as <constant>Network Information System</constant> (NIS).
470
<indexterm><primary>NIS+</primary></indexterm>
471
NIS gained a strong following throughout the UNIX/VMS space in a short
472
period of time and retained that appeal and use for over a decade.
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Security concerns and inherent limitations have caused it to enter its
474
twilight. NIS did not gain widespread appeal outside of the UNIX world
475
and was not universally adopted. Sun updated this to a more secure
476
implementation called NIS+, but even it has fallen victim to changing
477
demands as the demand for directory services that can be coupled with
478
other information systems is catching on.
483
<indexterm><primary>NIS</primary></indexterm>
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<indexterm><primary>government</primary></indexterm>
485
<indexterm><primary>education</primary></indexterm>
486
Nevertheless, both NIS and NIS+ continue to hold ground in
487
business areas where UNIX still has major sway. Examples of
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organizations that remain firmly attached to the use of NIS and
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NIS+ include large government departments, education institutions,
490
and large corporations that have a scientific or engineering
495
<indexterm><primary>scalable</primary></indexterm>
496
<indexterm><primary>distributed</primary></indexterm>
497
Today's networking world needs a scalable, distributed Identity
498
Management infrastructure, commonly called a directory. The most
499
popular technologies today are Microsoft Active Directory service
500
and a number of LDAP implementations.
504
<indexterm><primary>multiple directories</primary></indexterm>
505
The problem of managing multiple directories has become a focal
506
point over the past decade, creating a large market for
507
metadirectory products and services that allow organizations that
508
have multiple directories and multiple management and control
509
centers to provision information from one directory into
510
another. The attendant benefit to end users is the promise of
511
having to remember and deal with fewer login identities and
515
<indexterm><primary>network</primary><secondary>bandwidth</secondary></indexterm>
516
The challenge of every large network is to find the optimum
517
balance of internal systems and facilities for Identity
518
Management resources. How well the solution is chosen and
519
implemented has potentially significant impact on network bandwidth
520
and systems response needs.</para>
523
<indexterm><primary>LDAP server</primary></indexterm>
524
<indexterm><primary>LDAP</primary><secondary>master</secondary></indexterm>
525
<indexterm><primary>LDAP</primary><secondary>slave</secondary></indexterm>
526
In <link linkend="happy"/>, you implemented a single LDAP server for the
527
entire network. This may work for smaller networks, but almost
528
certainly fails to meet the needs of large and complex networks. The
529
following section documents how you may implement a single
530
master LDAP server with multiple slave servers.</para>
533
What is the best method for implementing master/slave LDAP
534
servers within the context of a distributed 2,000-user network is a
535
question that remains to be answered.</para>
538
<indexterm><primary>distributed domain</primary></indexterm>
539
<indexterm><primary>wide-area</primary></indexterm>
540
One possibility that has great appeal is to create a single,
541
large distributed domain. The practical implications of this
542
design (see <link linkend="chap7net"/>) demands the placement of
543
sufficient BDCs in each location. Additionally, network
544
administrators must make sure that profiles are not transferred
545
over the wide-area links, except as a totally unavoidable
546
measure. Network design must balance the risk of loss of user
547
productivity against the cost of network management and
552
<indexterm><primary>domain name space</primary></indexterm>
553
The network design in <link linkend="chap7net2"/> takes the approach
554
that management of networks that are too remote to be managed
555
effectively from New York ought to be given a certain degree of
556
autonomy. With this rationale, the Los Angeles and London networks,
557
though fully integrated with those on the East Coast, each have their
558
own domain name space and can be independently managed and controlled.
559
One of the key drawbacks of this design is that it flies in the face of
560
the ability for network users to roam globally without some compromise
561
in how they may access global resources.
565
<indexterm><primary>interdomain trusts</primary></indexterm>
566
Desk-bound users need not be negatively affected by this design, since
567
the use of interdomain trusts can be used to satisfy the need for global
572
<indexterm><primary>LDAP</primary></indexterm>
573
<indexterm><primary>LDAP</primary><secondary>backend</secondary></indexterm>
574
<indexterm><primary>SID</primary></indexterm>
575
When Samba-3 is configured to use an LDAP backend, it stores the domain
576
account information in a directory entry. This account entry contains the
577
domain SID. An unintended but exploitable side effect is that this makes it
578
possible to operate with more than one PDC on a distributed network.
582
<indexterm><primary>WINS</primary></indexterm>
583
<indexterm><primary>wins.dat</primary></indexterm>
584
<indexterm><primary>SID</primary></indexterm>
585
How might this peculiar feature be exploited? The answer is simple. It is
586
imperative that each network segment have its own WINS server. Major
587
servers on remote network segments can be given a static WINS entry in
588
the <filename>wins.dat</filename> file on each WINS server. This allows
589
all essential data to be visible from all locations. Each location would,
590
however, function as if it is an independent domain, while all sharing the
591
same domain SID. Since all domain account information can be stored in a
592
single LDAP backend, users have unfettered ability to roam.
596
<indexterm><primary>NetBIOS name</primary><secondary>aliases</secondary></indexterm>
597
<indexterm><primary>fail-over</primary></indexterm>
598
This concept has not been exhaustively validated, though we can see no reason
599
why this should not work. The important facets are the following: The name of
600
the domain must be identical in all locations. Each network segment must have
601
its own WINS server. The name of the PDC must be the same in all locations; this
602
necessitates the use of NetBIOS name aliases for each PDC so that they can be
603
accessed globally using the alias and not the PDC's primary name. A single master
604
LDAP server can be based in New York, with multiple LDAP slave servers located
605
on every network segment. Finally, the BDCs should each use failover LDAP servers
606
that are in fact slave LDAP servers on the local segments.
610
<indexterm><primary>LDAP</primary><secondary>updates</secondary></indexterm>
611
<indexterm><primary>domain tree</primary></indexterm>
612
<indexterm><primary>LDAP</primary><secondary>database</secondary></indexterm>
613
<indexterm><primary>LDAP</primary><secondary>directory</secondary></indexterm>
614
With a single master LDAP server, all network updates are effected on a single
615
server. In the event that this should become excessively fragile or network
616
bandwidth limiting, one could implement a delegated LDAP domain. This is also
617
known as a partitioned (or multiple partition) LDAP database and as a distributed
622
As the LDAP directory grows, it becomes increasingly important
623
that its structure is implemented in a manner that mirrors
624
organizational needs, so as to limit network update and
625
referential traffic. It should be noted that all directory
626
administrators must of necessity follow the same standard
627
procedures for managing the directory, because retroactive correction of
628
inconsistent directory information can be exceedingly difficult.
637
<title>Political Issues</title>
640
As organizations grow, the number of points of control increases
641
also. In a large distributed organization, it is important that the
642
Identity Management system be capable of being updated from
643
many locations, and it is equally important that changes made should
644
become usable in a reasonable period, typically
645
minutes rather than days (the old limitation of highly manual
654
<title>Implementation</title>
657
<indexterm><primary>winbind</primary></indexterm>
658
<indexterm><primary>LDAP</primary></indexterm>
659
<indexterm><primary>UID</primary></indexterm>
660
<indexterm><primary>GID</primary></indexterm>
661
Samba-3 has the ability to use multiple password (authentication and
662
identity resolution) backends. The diagram in <link linkend="chap7idres"/>
663
demonstrates how Samba uses winbind, LDAP, and NIS, the traditional system
664
password database. The diagram only documents the mechanisms for
665
authentication and identity resolution (obtaining a UNIX UID/GID)
666
using the specific systems shown.
669
<figure id="chap7idres">
670
<title>Samba and Authentication Backend Search Pathways</title>
671
<imagefile scale="55">chap7-idresol</imagefile>
675
<indexterm><primary>smbpasswd</primary></indexterm>
676
<indexterm><primary>xmlsam</primary></indexterm>
677
<indexterm><primary>SMB passwords</primary></indexterm>
678
<indexterm><primary>tdbsam</primary></indexterm>
679
<indexterm><primary>mysqlsam</primary></indexterm>
680
<indexterm><primary>LDAP</primary></indexterm>
681
<indexterm><primary>distributed</primary></indexterm>
682
Samba is capable of using the <constant>smbpasswd</constant>,
683
<constant>tdbsam</constant>, <constant>xmlsam</constant>,
684
and <constant>mysqlsam</constant> authentication databases. The SMB
685
passwords can, of course, also be stored in an LDAP ldapsam
686
backend. LDAP is the preferred passdb backend for distributed network
691
<indexterm><primary>passdb backend</primary></indexterm>
692
Additionally, it is possible to use multiple passdb backends
693
concurrently as well as have multiple LDAP backends. As a result, you
694
can specify a failover LDAP backend. The syntax for specifying a
695
single LDAP backend in &smb.conf; is:
698
passdb backend = ldapsam:ldap://master.abmas.biz
701
This configuration tells Samba to use a single LDAP server, as shown in <link linkend="ch7singleLDAP"/>.
702
<figure id="ch7singleLDAP">
703
<title>Samba Configuration to Use a Single LDAP Server</title>
704
<imagefile scale="65">ch7-singleLDAP</imagefile>
706
<indexterm><primary>LDAP</primary><secondary>fail-over</secondary></indexterm>
707
<indexterm><primary>fail-over</primary></indexterm>
708
The addition of a failover LDAP server can simply be done by adding a
709
second entry for the failover server to the single <parameter>ldapsam</parameter>
710
entry, as shown here (note the particular use of the double quotes):
713
passdb backend = ldapsam:"ldap://master.abmas.biz \
714
ldap://slave.abmas.biz"
717
This configuration tells Samba to use a master LDAP server, with failover to a slave server if necessary,
718
as shown in <link linkend="ch7dualLDAP"/>.
719
<figure id="ch7dualLDAP">
720
<title>Samba Configuration to Use a Dual (Fail-over) LDAP Server</title>
721
<imagefile scale="65">ch7-fail-overLDAP</imagefile>
726
Some folks have tried to implement this without the use of double quotes. This is the type of entry they
730
passdb backend = ldapsam:ldap://master.abmas.biz \
731
ldapsam:ldap://slave.abmas.biz
734
<indexterm><primary>contiguous directory</primary></indexterm>
735
The effect of this style of entry is that Samba lists the users
736
that are in both LDAP databases. If both contain the same information,
737
it results in each record being shown twice. This is, of course, not the
738
solution desired for a failover implementation. The net effect of this
739
configuration is shown in <link linkend="ch7dualadd"/>
742
<figure id="ch7dualadd">
743
<title>Samba Configuration to Use Dual LDAP Databases - Broken - Do Not Use!</title>
744
<imagefile scale="55">ch7-dual-additive-LDAP</imagefile>
748
If, however, each LDAP database contains unique information, this may
749
well be an advantageous way to effectively integrate multiple LDAP databases
750
into one seemingly contiguous directory. Only the first database will be updated.
751
An example of this configuration is shown in <link linkend="ch7dualok"/>.
754
<figure id="ch7dualok">
755
<title>Samba Configuration to Use Two LDAP Databases - The result is additive.</title>
756
<imagefile scale="55">ch7-dual-additive-LDAP-Ok</imagefile>
760
When the use of ldapsam is specified twice, as shown here, it is imperative
761
that the two LDAP directories must be disjoint. If the entries are for a
762
master LDAP server as well as its own slave server, updates to the LDAP
763
database may end up being lost or corrupted. You may safely use multiple
764
LDAP backends only if both are entirely separate from each other.
768
It is assumed that the network you are working with follows in a
769
pattern similar to what was covered in <link linkend="happy"/>. The following steps
770
permit the operation of a master/slave OpenLDAP arrangement.
774
<title>Implementation Steps for an LDAP Slave Server</title>
777
<indexterm><primary>SUSE Linux</primary></indexterm>
778
<indexterm><primary>Red Hat Linux</primary></indexterm>
779
Log onto the master LDAP server as <constant>root</constant>.
780
You are about to change the configuration of the LDAP server, so it
781
makes sense to temporarily halt it. Stop OpenLDAP from running on
782
SUSE Linux by executing:
784
&rootprompt; rcldap stop
786
On Red Hat Linux, you can do this by executing:
788
&rootprompt; service ldap stop
793
<indexterm><primary>/etc/openldap/slapd.conf</primary></indexterm>
794
Edit the <filename>/etc/openldap/slapd.conf</filename> file so it
795
matches the content of <link linkend="ch7-LDAP-master"/>.
799
Create a file called <filename>admin-accts.ldif</filename> with the following contents:
801
dn: cn=updateuser,dc=abmas,dc=biz
805
userPassword: not24get
807
dn: cn=sambaadmin,dc=abmas,dc=biz
811
userPassword: buttercup
816
Add an account called <quote>updateuser</quote> to the master LDAP server as shown here:
818
&rootprompt; slapadd -v -l admin-accts.ldif
823
<indexterm><primary>LDIF</primary></indexterm>
824
<indexterm><primary>LDAP</primary><secondary>preload</secondary></indexterm>
825
Change directory to a suitable place to dump the contents of the
826
LDAP server. The dump file (and LDIF file) is used to preload
827
the slave LDAP server database. You can dump the database by executing:
829
&rootprompt; slapcat -v -l LDAP-transfer-LDIF.txt
831
Each record is written to the file.
835
<indexterm><primary>LDAP-transfer-LDIF.txt</primary></indexterm>
836
Copy the file <filename>LDAP-transfer-LDIF.txt</filename> to the intended
837
slave LDAP server. A good location could be in the directory
838
<filename>/etc/openldap/preload</filename>.
842
Log onto the slave LDAP server as <constant>root</constant>. You can
843
now configure this server so the <filename>/etc/openldap/slapd.conf</filename>
844
file matches the content of <link linkend="ch7-LDAP-slave"/>.
848
Change directory to the location in which you stored the
849
<filename>LDAP-transfer-LDIF.txt</filename> file (<filename>/etc/openldap/preload</filename>).
850
While in this directory, execute:
852
&rootprompt; slapadd -v -l LDAP-transfer-LDIF.txt
854
If all goes well, the following output confirms that the data is being loaded
857
added: "dc=abmas,dc=biz" (00000001)
858
added: "cn=sambaadmin,dc=abmas,dc=biz" (00000002)
859
added: "cn=updateuser,dc=abmas,dc=biz" (00000003)
860
added: "ou=People,dc=abmas,dc=biz" (00000004)
861
added: "ou=Groups,dc=abmas,dc=biz" (00000005)
862
added: "ou=Computers,dc=abmas,dc=biz" (00000006)
863
added: "uid=Administrator,ou=People,dc=abmas,dc=biz" (00000007)
864
added: "uid=nobody,ou=People,dc=abmas,dc=biz" (00000008)
865
added: "cn=Domain Admins,ou=Groups,dc=abmas,dc=biz" (00000009)
866
added: "cn=Domain Users,ou=Groups,dc=abmas,dc=biz" (0000000a)
867
added: "cn=Domain Guests,ou=Groups,dc=abmas,dc=biz" (0000000b)
868
added: "uid=bobj,ou=People,dc=abmas,dc=biz" (0000000c)
869
added: "sambaDomainName=MEGANET2,dc=abmas,dc=biz" (0000000d)
870
added: "uid=stans,ou=People,dc=abmas,dc=biz" (0000000e)
871
added: "uid=chrisr,ou=People,dc=abmas,dc=biz" (0000000f)
872
added: "uid=maryv,ou=People,dc=abmas,dc=biz" (00000010)
873
added: "cn=Accounts,ou=Groups,dc=abmas,dc=biz" (00000011)
874
added: "cn=Finances,ou=Groups,dc=abmas,dc=biz" (00000012)
875
added: "cn=PIOps,ou=Groups,dc=abmas,dc=biz" (00000013)
880
Now start the LDAP server and set it to run automatically on system reboot by executing:
882
&rootprompt; rcldap start
883
&rootprompt; chkconfig ldap on
885
On Red Hat Linux, execute the following:
887
&rootprompt; service ldap start
888
&rootprompt; chkconfig ldap on
893
<indexterm><primary>chkconfig</primary></indexterm>
894
<indexterm><primary>service</primary></indexterm>
895
<indexterm><primary>rcldap</primary></indexterm>
896
Go back to the master LDAP server. Execute the following to start LDAP as well
897
as <command>slurpd</command>, the synchronization daemon, as shown here:
899
&rootprompt; rcldap start
900
&rootprompt; chkconfig ldap on
901
&rootprompt; rcslurpd start
902
&rootprompt; chkconfig slurpd on
904
<indexterm><primary>slurpd</primary></indexterm>
905
On Red Hat Linux, check the equivalent command to start <command>slurpd</command>.
909
<indexterm><primary>smbldap-useradd</primary></indexterm>
910
On the master LDAP server you may now add an account to validate that replication
911
is working. Assuming the configuration shown in <link linkend="happy"/>, execute:
913
&rootprompt; /var/lib/samba/sbin/smbldap-useradd -a fruitloop
918
On the slave LDAP server, change to the directory <filename>/var/lib/ldap</filename>.
919
There should now be a file called <filename>replogfile</filename>. If replication worked
920
as expected, the content of this file should be:
923
dn: uid=fruitloop,ou=People,dc=abmas,dc=biz
925
replace: sambaProfilePath
926
sambaProfilePath: \\MASSIVE\profiles\fruitloop
928
replace: sambaHomePath
929
sambaHomePath: \\MASSIVE\homes
932
entryCSN: 2003122700:43:38Z#0x0005#0#0000
934
replace: modifiersName
935
modifiersName: cn=Manager,dc=abmas,dc=biz
937
replace: modifyTimestamp
938
modifyTimestamp: 20031227004338Z
944
Given that this first slave LDAP server is now working correctly, you may now
945
implement additional slave LDAP servers as required.
949
On each machine (PDC and BDCs) after the respective &smb.conf; files have been created as shown in
950
<link linkend="ch7-massmbconfA">Primary Domain Controller &smb.conf; File &smbmdash; Part A + B + C</link> and
951
on BDCs the <link linkend="ch7-slvsmbocnfA">Backup Domain Controller &smb.conf; File &smbmdash; Part A
952
+ B + C</link> execute the following:
954
&rootprompt; smbpasswd -w buttercup
956
This will install in the <filename>secrets.tdb</filename> file the password that Samba will need to
957
manage (write to) the LDAP Master server to perform account updates.
962
<example id="ch7-LDAP-master">
963
<title>LDAP Master Server Configuration File &smbmdash; <filename>/etc/openldap/slapd.conf</filename></title>
965
include /etc/openldap/schema/core.schema
966
include /etc/openldap/schema/cosine.schema
967
include /etc/openldap/schema/inetorgperson.schema
968
include /etc/openldap/schema/nis.schema
969
include /etc/openldap/schema/samba.schema
971
pidfile /var/run/slapd/slapd.pid
972
argsfile /var/run/slapd/slapd.args
975
suffix "dc=abmas,dc=biz"
976
rootdn "cn=Manager,dc=abmas,dc=biz"
979
rootpw {SSHA}86kTavd9Dw3FAz6qzWTrCOKX/c0Qe+UV
981
replica host=lapdc.abmas.biz:389
982
suffix="dc=abmas,dc=biz"
983
binddn="cn=updateuser,dc=abmas,dc=biz"
984
bindmethod=simple credentials=not24get
986
access to attrs=sambaLMPassword,sambaNTPassword
987
by dn="cn=sambaadmin,dc=abmas,dc=biz" write
990
replogfile /var/lib/ldap/replogfile
992
directory /var/lib/ldap
994
# Indices to maintain
998
index uid pres,sub,eq
999
index displayName pres,sub,eq
1004
index sambaPrimaryGroupSID eq
1005
index sambaDomainName eq
1010
<example id="ch7-LDAP-slave">
1011
<title>LDAP Slave Configuration File &smbmdash; <filename>/etc/openldap/slapd.conf</filename></title>
1013
include /etc/openldap/schema/core.schema
1014
include /etc/openldap/schema/cosine.schema
1015
include /etc/openldap/schema/inetorgperson.schema
1016
include /etc/openldap/schema/nis.schema
1017
include /etc/openldap/schema/samba.schema
1019
pidfile /var/run/slapd/slapd.pid
1020
argsfile /var/run/slapd/slapd.args
1023
suffix "dc=abmas,dc=biz"
1024
rootdn "cn=Manager,dc=abmas,dc=biz"
1027
rootpw {SSHA}86kTavd9Dw3FAz6qzWTrCOKX/c0Qe+UV
1030
by dn=cn=updateuser,dc=abmas,dc=biz write
1033
updatedn cn=updateuser,dc=abmas,dc=biz
1034
updateref ldap://massive.abmas.biz
1036
directory /var/lib/ldap
1038
# Indices to maintain
1039
index objectClass eq
1040
index cn pres,sub,eq
1041
index sn pres,sub,eq
1042
index uid pres,sub,eq
1043
index displayName pres,sub,eq
1048
index sambaPrimaryGroupSID eq
1049
index sambaDomainName eq
1054
<example id="ch7-massmbconfA">
1055
<title>Primary Domain Controller &smb.conf; File &smbmdash; Part A</title>
1057
<smbconfcomment>Global parameters</smbconfcomment>
1058
<smbconfsection name="[global]"/>
1059
<smbconfoption name="unix charset">LOCALE</smbconfoption>
1060
<smbconfoption name="workgroup">MEGANET2</smbconfoption>
1061
<smbconfoption name="passdb backend">ldapsam:ldap://massive.abmas.biz</smbconfoption>
1062
<smbconfoption name="username map">/etc/samba/smbusers</smbconfoption>
1063
<smbconfoption name="log level">1</smbconfoption>
1064
<smbconfoption name="syslog">0</smbconfoption>
1065
<smbconfoption name="log file">/var/log/samba/%m</smbconfoption>
1066
<smbconfoption name="max log size">0</smbconfoption>
1067
<smbconfoption name="smb ports">139</smbconfoption>
1068
<smbconfoption name="name resolve order">wins bcast hosts</smbconfoption>
1069
<smbconfoption name="time server">Yes</smbconfoption>
1070
<smbconfoption name="printcap name">CUPS</smbconfoption>
1071
<smbconfoption name="add user script">/opt/IDEALX/sbin/smbldap-useradd -m '%u'</smbconfoption>
1072
<smbconfoption name="delete user script">/opt/IDEALX/sbin/smbldap-userdel '%u'</smbconfoption>
1073
<smbconfoption name="add group script">/opt/IDEALX/sbin/smbldap-groupadd -p '%g'</smbconfoption>
1074
<smbconfoption name="delete group script">/opt/IDEALX/sbin/smbldap-groupdel '%g'</smbconfoption>
1075
<smbconfoption name="add user to group script">/opt/IDEALX/sbin/smbldap-groupmod -m '%g' '%u'</smbconfoption>
1076
<smbconfoption name="delete user from group script">/opt/IDEALX/sbin/smbldap-groupmod -x '%g' '%u'</smbconfoption>
1077
<smbconfoption name="set primary group script">/opt/IDEALX/sbin/smbldap-usermod -g '%g' '%u'</smbconfoption>
1078
<smbconfoption name="add machine script">/opt/IDEALX/sbin/smbldap-useradd -w '%u'</smbconfoption>
1079
<smbconfoption name="shutdown script">/var/lib/samba/scripts/shutdown.sh</smbconfoption>
1080
<smbconfoption name="abort shutdown script">/sbin/shutdown -c</smbconfoption>
1081
<smbconfoption name="logon script">scripts\logon.bat</smbconfoption>
1082
<smbconfoption name="logon path">\\%L\profiles\%U</smbconfoption>
1083
<smbconfoption name="logon drive">X:</smbconfoption>
1084
<smbconfoption name="domain logons">Yes</smbconfoption>
1085
<smbconfoption name="domain master">Yes</smbconfoption>
1086
<smbconfoption name="wins support">Yes</smbconfoption>
1087
<smbconfoption name="ldap suffix">dc=abmas,dc=biz</smbconfoption>
1088
<smbconfoption name="ldap machine suffix">ou=People</smbconfoption>
1089
<smbconfoption name="ldap user suffix">ou=People</smbconfoption>
1090
<smbconfoption name="ldap group suffix">ou=Groups</smbconfoption>
1091
<smbconfoption name="ldap idmap suffix">ou=Idmap</smbconfoption>
1092
<smbconfoption name="ldap admin dn">cn=sambaadmin,dc=abmas,dc=biz</smbconfoption>
1093
<smbconfoption name="idmap backend">ldap://massive.abmas.biz</smbconfoption>
1094
<smbconfoption name="idmap uid">10000-20000</smbconfoption>
1095
<smbconfoption name="idmap gid">10000-20000</smbconfoption>
1096
<smbconfoption name="printer admin">root</smbconfoption>
1097
<smbconfoption name="printing">cups</smbconfoption>
1101
<example id="ch7-massmbconfB">
1102
<title>Primary Domain Controller &smb.conf; File &smbmdash; Part B</title>
1104
<smbconfsection name="[IPC$]"/>
1105
<smbconfoption name="path">/tmp</smbconfoption>
1107
<smbconfsection name="[accounts]"/>
1108
<smbconfoption name="comment">Accounting Files</smbconfoption>
1109
<smbconfoption name="path">/data/accounts</smbconfoption>
1110
<smbconfoption name="read only">No</smbconfoption>
1112
<smbconfsection name="[service]"/>
1113
<smbconfoption name="comment">Financial Services Files</smbconfoption>
1114
<smbconfoption name="path">/data/service</smbconfoption>
1115
<smbconfoption name="read only">No</smbconfoption>
1117
<smbconfsection name="[pidata]"/>
1118
<smbconfoption name="comment">Property Insurance Files</smbconfoption>
1119
<smbconfoption name="path">/data/pidata</smbconfoption>
1120
<smbconfoption name="read only">No</smbconfoption>
1122
<smbconfsection name="[homes]"/>
1123
<smbconfoption name="comment">Home Directories</smbconfoption>
1124
<smbconfoption name="valid users">%S</smbconfoption>
1125
<smbconfoption name="read only">No</smbconfoption>
1126
<smbconfoption name="browseable">No</smbconfoption>
1128
<smbconfsection name="[printers]"/>
1129
<smbconfoption name="comment">SMB Print Spool</smbconfoption>
1130
<smbconfoption name="path">/var/spool/samba</smbconfoption>
1131
<smbconfoption name="guest ok">Yes</smbconfoption>
1132
<smbconfoption name="printable">Yes</smbconfoption>
1133
<smbconfoption name="browseable">No</smbconfoption>
1137
<example id="ch7-massmbconfC">
1138
<title>Primary Domain Controller &smb.conf; File &smbmdash; Part C</title>
1140
<smbconfsection name="[apps]"/>
1141
<smbconfoption name="comment">Application Files</smbconfoption>
1142
<smbconfoption name="path">/apps</smbconfoption>
1143
<smbconfoption name="admin users">bjones</smbconfoption>
1144
<smbconfoption name="read only">No</smbconfoption>
1146
<smbconfsection name="[netlogon]"/>
1147
<smbconfoption name="comment">Network Logon Service</smbconfoption>
1148
<smbconfoption name="path">/var/lib/samba/netlogon</smbconfoption>
1149
<smbconfoption name="admin users">root, Administrator</smbconfoption>
1150
<smbconfoption name="guest ok">Yes</smbconfoption>
1151
<smbconfoption name="locking">No</smbconfoption>
1153
<smbconfsection name="[profiles]"/>
1154
<smbconfoption name="comment">Profile Share</smbconfoption>
1155
<smbconfoption name="path">/var/lib/samba/profiles</smbconfoption>
1156
<smbconfoption name="read only">No</smbconfoption>
1157
<smbconfoption name="profile acls">Yes</smbconfoption>
1159
<smbconfsection name="[profdata]"/>
1160
<smbconfoption name="comment">Profile Data Share</smbconfoption>
1161
<smbconfoption name="path">/var/lib/samba/profdata</smbconfoption>
1162
<smbconfoption name="read only">No</smbconfoption>
1163
<smbconfoption name="profile acls">Yes</smbconfoption>
1165
<smbconfsection name="[print$]"/>
1166
<smbconfoption name="comment">Printer Drivers</smbconfoption>
1167
<smbconfoption name="path">/var/lib/samba/drivers</smbconfoption>
1168
<smbconfoption name="write list">root</smbconfoption>
1169
<smbconfoption name="admin users">root, Administrator</smbconfoption>
1173
<example id="ch7-slvsmbocnfA">
1174
<title>Backup Domain Controller &smb.conf; File &smbmdash; Part A</title>
1176
<smbconfcomment># Global parameters</smbconfcomment>
1177
<smbconfsection name="[global]"/>
1178
<smbconfoption name="unix charset">LOCALE</smbconfoption>
1179
<smbconfoption name="workgroup">MEGANET2</smbconfoption>
1180
<smbconfoption name="netbios name">BLDG1</smbconfoption>
1181
<smbconfoption name="passdb backend">ldapsam:ldap://lapdc.abmas.biz</smbconfoption>
1182
<smbconfoption name="username map">/etc/samba/smbusers</smbconfoption>
1183
<smbconfoption name="log level">1</smbconfoption>
1184
<smbconfoption name="syslog">0</smbconfoption>
1185
<smbconfoption name="log file">/var/log/samba/%m</smbconfoption>
1186
<smbconfoption name="max log size">50</smbconfoption>
1187
<smbconfoption name="smb ports">139</smbconfoption>
1188
<smbconfoption name="name resolve order">wins bcast hosts</smbconfoption>
1189
<smbconfoption name="printcap name">CUPS</smbconfoption>
1190
<smbconfoption name="show add printer wizard">No</smbconfoption>
1191
<smbconfoption name="logon script">scripts\logon.bat</smbconfoption>
1192
<smbconfoption name="logon path">\\%L\profiles\%U</smbconfoption>
1193
<smbconfoption name="logon drive">X:</smbconfoption>
1194
<smbconfoption name="domain logons">Yes</smbconfoption>
1195
<smbconfoption name="os level">63</smbconfoption>
1196
<smbconfoption name="domain master">No</smbconfoption>
1197
<smbconfoption name="wins server">192.168.2.1</smbconfoption>
1198
<smbconfoption name="ldap suffix">dc=abmas,dc=biz</smbconfoption>
1199
<smbconfoption name="ldap machine suffix">ou=People</smbconfoption>
1200
<smbconfoption name="ldap user suffix">ou=People</smbconfoption>
1201
<smbconfoption name="ldap group suffix">ou=Groups</smbconfoption>
1202
<smbconfoption name="ldap idmap suffix">ou=Idmap</smbconfoption>
1203
<smbconfoption name="ldap admin dn">cn=sambaadmin,dc=abmas,dc=biz</smbconfoption>
1204
<smbconfoption name="utmp">Yes</smbconfoption>
1205
<smbconfoption name="idmap backend">ldap://massive.abmas.biz</smbconfoption>
1206
<smbconfoption name="idmap uid">10000-20000</smbconfoption>
1207
<smbconfoption name="idmap gid">10000-20000</smbconfoption>
1208
<smbconfoption name="printing">cups</smbconfoption>
1210
<smbconfsection name="[accounts]"/>
1211
<smbconfoption name="comment">Accounting Files</smbconfoption>
1212
<smbconfoption name="path">/data/accounts</smbconfoption>
1213
<smbconfoption name="read only">No</smbconfoption>
1215
<smbconfsection name="[service]"/>
1216
<smbconfoption name="comment">Financial Services Files</smbconfoption>
1217
<smbconfoption name="path">/data/service</smbconfoption>
1218
<smbconfoption name="read only">No</smbconfoption>
1222
<example id="ch7-slvsmbocnfB">
1223
<title>Backup Domain Controller &smb.conf; File &smbmdash; Part B</title>
1225
<smbconfsection name="[pidata]"/>
1226
<smbconfoption name="comment">Property Insurance Files</smbconfoption>
1227
<smbconfoption name="path">/data/pidata</smbconfoption>
1228
<smbconfoption name="read only">No</smbconfoption>
1230
<smbconfsection name="[homes]"/>
1231
<smbconfoption name="comment">Home Directories</smbconfoption>
1232
<smbconfoption name="valid users">%S</smbconfoption>
1233
<smbconfoption name="read only">No</smbconfoption>
1234
<smbconfoption name="browseable">No</smbconfoption>
1236
<smbconfsection name="[printers]"/>
1237
<smbconfoption name="comment">SMB Print Spool</smbconfoption>
1238
<smbconfoption name="path">/var/spool/samba</smbconfoption>
1239
<smbconfoption name="guest ok">Yes</smbconfoption>
1240
<smbconfoption name="printable">Yes</smbconfoption>
1241
<smbconfoption name="browseable">No</smbconfoption>
1243
<smbconfsection name="[apps]"/>
1244
<smbconfoption name="comment">Application Files</smbconfoption>
1245
<smbconfoption name="path">/apps</smbconfoption>
1246
<smbconfoption name="admin users">bjones</smbconfoption>
1247
<smbconfoption name="read only">No</smbconfoption>
1249
<smbconfsection name="[netlogon]"/>
1250
<smbconfoption name="comment">Network Logon Service</smbconfoption>
1251
<smbconfoption name="path">/var/lib/samba/netlogon</smbconfoption>
1252
<smbconfoption name="guest ok">Yes</smbconfoption>
1253
<smbconfoption name="locking">No</smbconfoption>
1255
<smbconfsection name="[profiles]"/>
1256
<smbconfoption name="comment">Profile Share</smbconfoption>
1257
<smbconfoption name="path">/var/lib/samba/profiles</smbconfoption>
1258
<smbconfoption name="read only">No</smbconfoption>
1259
<smbconfoption name="profile acls">Yes</smbconfoption>
1261
<smbconfsection name="[profdata]"/>
1262
<smbconfoption name="comment">Profile Data Share</smbconfoption>
1263
<smbconfoption name="path">/var/lib/samba/profdata</smbconfoption>
1264
<smbconfoption name="read only">No</smbconfoption>
1265
<smbconfoption name="profile acls">Yes</smbconfoption>
1270
<title>Key Points Learned</title>
1274
<indexterm><primary>LDAP</primary></indexterm><indexterm><primary>BDC</primary></indexterm>
1275
Where Samba-3 is used as a domain controller, the use of LDAP is an
1276
essential component to permit the use of BDCs.
1280
<indexterm><primary>wide-area</primary></indexterm>
1281
Replication of the LDAP master server to create a network of BDCs
1282
is an important mechanism for limiting WAN traffic.
1286
Network administration presents many complex challenges, most of which
1287
can be satisfied by good design but that also require sound communication
1288
and unification of management practices. This can be highly challenging in
1289
a large, globally distributed network.
1293
Roaming profiles must be contained to the local network segment. Any
1294
departure from this may clog wide-area arteries and slow legitimate network
1301
<figure id="chap7net">
1302
<title>Network Topology &smbmdash; 2000 User Complex Design A</title>
1303
<imagefile scale="80">chap7-net-Ar</imagefile>
1306
<figure id="chap7net2">
1307
<title>Network Topology &smbmdash; 2000 User Complex Design B</title>
1308
<imagefile scale="80">chap7-net2-Br</imagefile>
1314
<title>Questions and Answers</title>
1317
There is much rumor and misinformation regarding the use of MS Windows networking protocols.
1318
These questions are just a few of those frequently asked.
1321
<qandaset defaultlabel="chap07qa" type="number">
1326
<indexterm><primary>DHCP</primary></indexterm>
1327
<indexterm><primary>network</primary><secondary>bandwidth</secondary></indexterm>
1328
Is it true that DHCP uses lots of WAN bandwidth?
1335
<indexterm><primary>DHCP</primary><secondary>Relay Agent</secondary></indexterm>
1336
<indexterm><primary>routers</primary></indexterm>
1337
<indexterm><primary>DHCP</primary><secondary>servers</secondary></indexterm>
1338
It is a smart practice to localize DHCP servers on each network segment. As a
1339
rule, there should be two DHCP servers per network segment. This means that if
1340
one server fails, there is always another to service user needs. DHCP requests use
1341
only UDP broadcast protocols. It is possible to run a DHCP Relay Agent on network
1342
routers. This makes it possible to run fewer DHCP servers.
1346
<indexterm><primary>DHCP</primary><secondary>request</secondary></indexterm>
1347
<indexterm><primary>DHCP</primary><secondary>traffic</secondary></indexterm>
1348
A DHCP network address request and confirmation usually results in about six UDP packets.
1349
The packets are from 60 to 568 bytes in length. Let us consider a site that has 300 DHCP
1350
clients and that uses a 24-hour IP address lease. This means that all clients renew
1351
their IP address lease every 24 hours. If we assume an average packet length equal to the
1352
maximum (just to be on the safe side), and we have a 128 Kb/sec wide-area connection,
1353
how significant would the DHCP traffic be if all of it were to use DHCP Relay?
1357
I must stress that this is a bad design, but here is the calculation:
1359
Daily Network Capacity: 128,000 (Kbits/s) / 8 (bits/byte)
1360
x 3600 (sec/hr) x 24 (hrs/day)= 2288 Mbytes/day.
1362
DHCP traffic: 300 (clients) x 6 (packets)
1363
x 512 (bytes/packet) = 0.9 Mbytes/day.
1365
From this can be seen that the traffic impact would be minimal.
1369
<indexterm><primary>DNS</primary><secondary>Dynamic</secondary></indexterm>
1370
<indexterm><primary>DHCP</primary></indexterm>
1371
Even when DHCP is configured to do DNS update (dynamic DNS) over a wide-area link,
1372
the impact of the update is no more than the DHCP IP address renewal traffic and thus
1373
still insignificant for most practical purposes.
1383
<indexterm><primary>background communication</primary></indexterm>
1384
<indexterm><primary>LDAP</primary><secondary>master/slave</secondary><tertiary>background communication</tertiary></indexterm>
1385
How much background communication takes place between a master LDAP server and its slave LDAP servers?
1392
<indexterm><primary>slurpd</primary></indexterm>
1393
The process that controls the replication of data from the master LDAP server to the slave LDAP
1394
servers is called <command>slurpd</command>. The <command>slurpd</command> remains nascent (quiet)
1395
until an update must be propagated. The propagation traffic per LDAP slave to update (add/modify/delete)
1396
two user accounts requires less than 10KB traffic.
1406
LDAP has a database. Is LDAP not just a fancy database front end?
1413
<indexterm><primary>database</primary></indexterm>
1414
<indexterm><primary>LDAP</primary><secondary>database</secondary></indexterm>
1415
<indexterm><primary>SQL</primary></indexterm>
1416
<indexterm><primary>transactional</primary></indexterm>
1417
LDAP does store its data in a database of sorts. In fact, the LDAP backend is an application-specific
1418
data storage system. This type of database is indexed so that records can be rapidly located, but the
1419
database is not generic and can be used only in particular pre-programmed ways. General external
1420
applications do not gain access to the data. This type of database is used also by SQL servers. Both
1421
an SQL server and an LDAP server provide ways to access the data. An SQL server has a transactional
1422
orientation and typically allows external programs to perform ad hoc queries, even across data tables.
1423
An LDAP front end is a purpose-built tool that has a search orientation that is designed around specific
1424
simple queries. The term <constant>database</constant> is heavily overloaded and thus much misunderstood.
1434
<indexterm><primary>OpenLDAP</primary></indexterm>
1435
Can Active Directory obtain account information from an OpenLDAP server?
1442
<indexterm><primary>meta-directory</primary></indexterm>
1443
No, at least not directly. It is possible to provision Active Directory from and/or to an OpenLDAP
1444
database through use of a metadirectory server. Microsoft MMS (now called MIIS) can interface
1445
to OpenLDAP using standard LDAP queries and updates.
1455
What are the parts of a roaming profile? How large is each part?
1462
<primary>roaming profile</primary>
1464
A roaming profile consists of
1469
Desktop folders such as <constant>Desktop</constant>, <constant>My Documents</constant>,
1470
<constant>My Pictures</constant>, <constant>My Music</constant>, <constant>Internet Files</constant>,
1471
<constant>Cookies</constant>, <constant>Application Data</constant>,
1472
<constant>Local Settings,</constant> and more. See <link linkend="happy"/>, <link linkend="XP-screen001"/>.
1476
<indexterm><primary>folder redirection</primary></indexterm>
1477
Each of these can be anywhere from a few bytes to gigabytes in capacity. Fortunately, all
1478
such folders can be redirected to network drive resources. See <link linkend="redirfold"/>
1479
for more information regarding folder redirection.
1483
A static or rewritable portion that is typically only a few files (2-5 KB of information).
1487
<indexterm><primary>NTUSER.DAT</primary></indexterm>
1488
<indexterm><primary>HKEY_LOCAL_USER</primary></indexterm>
1489
The registry load file that modifies the <constant>HKEY_LOCAL_USER</constant> hive. This is
1490
the <filename>NTUSER.DAT</filename> file. It can be from 0.4 to 1.5 MB.
1495
<indexterm><primary>Microsoft Outlook</primary><secondary>PST files</secondary></indexterm>
1496
Microsoft Outlook PST files may be stored in the <constant>Local Settings\Application Data</constant>
1497
folder. It can be up to 2 GB in size per PST file.
1507
Can the <constant>My Documents</constant> folder be stored on a network drive?
1514
<indexterm><primary>UNC name</primary></indexterm>
1515
<indexterm><primary>Universal Naming Convention</primary><see>UNC name</see></indexterm>
1516
Yes. More correctly, such folders can be redirected to network shares. No specific network drive
1517
connection is required. Registry settings permit this to be redirected directly to a UNC (Universal
1518
Naming Convention) resource, though it is possible to specify a network drive letter instead of a
1519
UNC name. See <link linkend="redirfold"/>.
1529
<indexterm><primary>wide-area</primary></indexterm>
1530
<indexterm><primary>network</primary><secondary>bandwidth</secondary></indexterm>
1531
<indexterm><primary>WINS</primary></indexterm>
1532
How much WAN bandwidth does WINS consume?
1539
<indexterm><primary>NetBIOS</primary><secondary>name cache</secondary></indexterm>
1540
<indexterm><primary>WINS server</primary></indexterm>
1541
<indexterm><primary>domain replication</primary></indexterm>
1542
MS Windows clients cache information obtained from WINS lookups in a local NetBIOS name cache.
1543
This keeps WINS lookups to a minimum. On a network with 3500 MS Windows clients and a central WINS
1544
server, the total bandwidth demand measured at the WINS server, averaged over an 8-hour working day,
1545
was less than 30 KB/sec. Analysis of network traffic over a 6-week period showed that the total
1546
of all background traffic consumed about 11 percent of available bandwidth over 64 Kb/sec links.
1547
Background traffic consisted of domain replication, WINS queries, DNS lookups, and authentication
1548
traffic. Each of 11 branch offices had a 64 Kb/sec wide-area link, with a 1.5 Mb/sec main connection
1549
that aggregated the branch office connections plus an Internet connection.
1553
In conclusion, the total load afforded through WINS traffic is again marginal to total operational
1554
usage &smbmdash; as it should be.
1564
How many BDCs should I have? What is the right number of Windows clients per server?
1571
It is recommended to have at least one BDC per network segment, including the segment served
1572
by the PDC. Actual requirements vary depending on the working load on each of the BDCs and the
1573
load demand pattern of client usage. I have seen sites that function without problem with 200
1574
clients served by one BDC, and yet other sites that had one BDC per 20 clients. In one particular
1575
company, there was a drafting office that had 30 CAD/CAM operators served by one server, a print
1576
server; and an application server. While all three were BDCs, typically only the print server would
1577
service network logon requests after the first 10 users had started to use the network. This was
1578
a reflection of the service load placed on both the application server and the data server.
1582
As unsatisfactory as the answer might sound, it all depends on network and server load
1593
<indexterm><primary>NIS server</primary></indexterm><indexterm><primary>LDAP</primary></indexterm>
1594
I've heard that you can store NIS accounts in LDAP. Is LDAP not just a smarter way to
1602
The correct answer to both questions is yes. But do understand that an LDAP server has
1603
a configurable schema that can store far more information for many more purposes than
1614
Can I use NIS in place of LDAP?
1621
<indexterm><primary>NIS</primary></indexterm>
1622
<indexterm><primary>NIS schema</primary></indexterm>
1623
No. The NIS database does not have provision to store Microsoft encrypted passwords and does not deal
1624
with the types of data necessary for interoperability with Microsoft Windows networking. The use
1625
of LDAP with Samba requires the use of a number of schemas, one of which is the NIS schema, but also
1626
a Samba-specific schema extension.
added
removed
docs-xml/Samba3-ByExample/SBE-2000UserNetwork.xml
