Network Guide Part 5 - Network Operating Systems

Network Guide Part 5 - Network Operating Systems

Every network today uses some form of software to manage its resources. This software runs on a special, high-powered computer and is called a network operating system (or NOS, for short). The NOS is one of the most important components of the network. We will look at four of the most popular network operating systems:

* Novell NetWare

* Microsoft Windows NT

* Unix

* Macintosh OS (Mac OS)

NetWare, developed by Novell, was the first network operating system to gain wide acceptance in the PC market. Windows NT, introduced by Microsoft in 1993, is gaining market share as of late because of its ease of use. Unix, while being the oldest network operating system, is only starting to gain popularity with PC users through PC-based flavors of Unix, such as Linux. This rise in popularity is due in part to the Internet, which is based on Unix standards and protocols. The fourth network operating system in use today—though used in a much smaller part of the networking market—is Apple’s Macintosh OS, also known as the Mac OS

Novell NetWare

NetWare is one of the more powerful network operating systems on the market today. It is almost infinitely scalable and has support for multiple client platforms. Although many companies larger than a few hundred stations are running NetWare, this NOS enjoys success in many different types of networks.
At the time of this writing, the current version of NetWare is version 5 (NetWare 6 beta version has been released) and includes workstation management support, Internet connectivity, web proxy, native TCP/IP ( Transmission Control Protocol/Internet Protocol) support, and continued support for its award-winning directory service, NDS.
Note For more information on NetWare, check out Novell’s website at www.novell.com.

Features of NetWare

NetWare is popular in large networks (more than 20 servers) because of features such as centralized administration of all users and their properties. The most important features of NetWare 4.x and later are the following:

The directory service (NDS)
The simple user interface
Fairly minimal hardware requirements
Scalable hardware support
Third-party support Interoperability with many types of computer systems

NetWare has always been an excellent directory, file, and print server, but with its acquisition of many Java technologies, it is starting to encroach on the application server market. These features make NetWare an excellent choice in the directory, file, and print environments.

The NetWare Server User Interface With NetWare 5 servers, you can choose from three interfaces:

The command-line console
The menu-based utilities
The new Java-based graphical interface

The new graphical interface is based on the Unix X Window standard and has been a long time coming. You can interact with a NetWare 5 server using the mouse to issue commands in this graphical environment, which is an option that was previously unavailable.

Even though the NetWare graphical interface (called Console 1) looks like X Window, it is a Java-based approximation, not the real thing. You can’t run X Window programs on a NetWare server. You can, however, run programs written in Java.


Scalable Hardware Requirements

In the days of NetWare 3.x , you could run NetWare on a server that had as little as 4MB of RAM; other network operating systems of the time required a minimum of 24MB. This made NetWare popular among hardware buyers, but not with those who made the hardware.

Other hardware support also makes NetWare a popular choice. For example, out of the box, the NetWare 5 kernel supports as many as 32 processors, as long as the hardware configuration complies with Intel Multiprocessor Specification 1.1 or 1.4. In addition, NetWare 5 supports hot-pluggable PCI cards. Many other operating systems must be specially modified to include this support, but NetWare comes with it.

Note A hot-pluggable PCI card enables you to install or remove a device while the server is powered up and functioning


Third-Party Support

If you want to write your own operating system, you can. Other people have done it, such as the developers of Linux (discussed later in this chapter). However, you won’t sell many copies without third-party software support. This means making your source code available to other developers so that they can write software for it. If source code isn’t made available, no one can write programs to run on it, and if there aren’t any programs available to run on the operating system, how much sense does it make for anyone to buy it? The same holds true for network operating systems. Without support for popular network services (such as backup programs), the platform will not be widely used.

Fortunately, servers are big business. It is in the interest of many third parties to write server-based software for new network operating systems. Server-based software includes, but is not limited to, the following:

Backup programs
E-mail
Internet access

Until recently being surpassed by Windows NT, NetWare had the largest base of third-party programs. However, NetWare use and support are climbing again now that Novell is embracing Java technologies.


NetWare Interoperability

NetWare can communicate with just about any computing environment, including:

Windows 95/98
Windows NT
Mac OS
VMS
OS/400
Unix
OS/2

When each of these operating systems tries to communicate with a NetWare server, the server appears as though it were a member of that network type. For example, on a Mac OS network, a NetWare server can appear to be just another Macintosh server, but in reality it’s a Pentium-class box running NetWare. I have found that a NetWare server makes a better server for Macs than Apple’s own servers running the AppleShare network operating system.


NetWare Architecture

NetWare, like most other network operating systems, is modular. It consists of a core component and other pieces that can be loaded into memory as necessary. In NetWare parlance, the core component is called the core OS (or kernel ), and the other modules are called NetWare Loadable Modules (NLMs). This design makes efficient use of the hardware resources (memory and hard-disk space, for example) of the computer on which it is running. Unneeded services or components can be unloaded, thus conserving memory

NLMs fall into four categories:

Disk drivers
LAN drivers
Name space modules
Utilities


Disk Drivers

These NLMs give NetWare access to the disk channel. Older disk-driver NLM files have a .DSK extension, whereas newer disk drivers (those that conform to the NetWare Peripheral Architecture, or NPA) have the extension .HAM or .CDM . For NetWare 5, a combination of IDEATA.HAM and

IDEHD.CDM provides access to local Integrated Drive Electronics (IDE) drives. NetWare versions 4.1 and later can use this technology, which is the only type of disk-driver technology available for NetWare 5. For example, the IDE.DSK file is the disk driver that allows NetWare 3.x to access local IDE drives, but this file won’t work on NetWare 5 servers. You would have to use the IDEATA.HAM and IDEHD.CDM combination.

LAN Drivers
Every network board installed in a NetWare server must have a corresponding LAN driver, which is the interface between the NetWare kernel and the network interface card. These files typically have the file extension .LAN. For example, the 3C5X9.LAN file is the driver that allows NetWare to access a 3Com EtherLink III NIC.

Name Space Modules
As mentioned, NetWare can “look” like another type of server. Part of that functionality is configured by the protocols in use. A name space module controls how files look or how they are stored on a disk. By default, Net-Ware stores files using the DOS naming convention (eight alphanumeric characters, a period, and then a three-letter extension; also called 8.3). Different operating systems use different naming conventions for files, and the name space modules make it possible to store those files on volumes on a NetWare server. The extension of these name space modules is .NAM. For example, the NFS.NAM name space module enables NetWare to store files on a disk using the Unix NFS (Network File System) naming convention. Additionally, if you want to store files that use the Windows long filename naming convention, you load the LONG.NAM names.

Warning Be careful when loading multiple name space modules. Loading multiple modules not only requires more memory, but also reduces the total number of files that can be stored on that volume.


Utility NLMs
This category includes any kind of NLM that doesn’t fall into the other three categories. More than 70 percent of NLMs on a NetWare server are of this type. These NLMs typically have the file extension .NLM. Examples include:

MONITOR.NLM, which monitors the server
NWCONFIG.NLM, which is a NetWare configuration NLM
NDPSMGR.NLM, which is the NDPS (Novell Distributed Print Services) manager that loads the NetWare printing manager

As mentioned, a great deal of third-party support is available for Net-Ware. Manufacturers write software for NetWare servers in the form of NLMs. Most hardware manufacturers write LAN and disk-driver NLMs so that NetWare will run on their server platforms. Additionally, some companies write special utility NLMs, such as backup and management utilities, for NetWare servers. But, with the advent of NetWare 5 and the inclusion of server-based JVM (see the sidebar titled “Java, Anyone?” that appeared earlier in this chapter), several hundred more server applications will soon become available.

Note One type of utility NLM that deserves special mention is new with NetWare 5. The Platform Support Module (PSM) enables NetWare 5 to communicate with a multiprocessor architecture. Each PSM is characterized by the extension .PSM. For example, the MPS14.PSM file provides NetWare with support for Intel Multiprocessor Specification version 1.4. Once loaded, this file enables Net-Ware to use the multiprocessor functions of any server that follows the MPS 1.4 specification.

Major Versions of NetWare in Use
Three major versions of NetWare are in use today:

NetWare 3.x
NetWare 4.x
NetWare 5

Each version has unique characteristics. Let’s take a brief look at each one.

NetWare 3.x
NetWare 3.x includes NetWare 3.11 and 3.12. Based on the Novell product known as NetWare 386 (introduced about the same time as the Intel 80386 processor), NetWare 3.x made NetWare the de facto standard for business networks.

NetWare 3.x supports multiple, cross-platform clients and has minimal hardware requirements (4MB of RAM, 75MB of hard-disk space). It uses a database called the bindery, which will be discussed later in this chapter, to keep track of users and groups, and it is administered with a menu-based DOS utility known as SYSCON.

The design of NetWare 3.x included one utility for every function: SYSCON for user administration, PCONSOLE for printing setup, and FILER for file operations. This was nice for basic operations, but complete network administration was difficult because you had to switch between utilities to perform any network administration function. (For example, you would have to add the user in SYSCON and assign the user rights in FILER.) This drawback was resolved in NetWare 4 with the introduction of NetWare Administrator.

From its introduction in the early 1990s until the mid-1990s when newer versions were released, NetWare 3.x was the most popular NOS. Because of this popularity and a loyal installed user base, Novell released an upgrade for NetWare 3.x in 1998, NetWare 3.2. It keeps the same architecture and basic kernel, but applies some patches and adds some new features (such as a Windows administration utility) to keep it up-to-date without changing the basic operating system features that users and administrators love.

NetWare 4.x
Introduced in 1993, NetWare 4 was the first version to include a new, centralized administration service, Novell Directory Services (NDS). This new feature simplified the administration of multiple servers. With NetWare 3.x and previous versions, if a user wanted access to multiple servers, you had to make a user on each server and then assign that user rights on all servers. With the introduction of NDS, all administration was centralized. You could make a user once instead of 10 times for 10 servers. Version 4 was a radical departure from the way network administrators were used to thinking about administering a NetWare network. Unfortunately, NetWare 4 was also fairly buggy. Novell quickly made and released patches until the version number was up to 4.02—the first version considered stable.

Many versions have come and gone since 4.02. Versions 4.1 and 4.11 are the most popular versions of NetWare 4.x used in corporate networks today. At the time of this writing, there has been a new release of NetWare 4.x, NetWare 4.2. A stepping-stone upgrade toward NetWare 5, it gives a Novell network administrator some features of NetWare 5 (such as the ZENworks starter pack that provides workstation management) in order to prepare for a full migration from NetWare 4.x to 5.

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Real World Scenario: What Is intraNetWare?
Novell released NetWare 4.11 as a package called intraNetWare. The name change capitalized on the popularity of the intranet craze. IntraNetWare included a web server and an FTP (File Transfer Protocol) server, as well as an IPX/IP (Internet Packet eXchange/Internet Protocol) gateway to facilitate connection to the Internet and to a corporate intranet.

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Industry analysts were skeptical, to say the least. Novell threw away several years’ worth of brand recognition by changing the product name. The actual operating system was still NetWare, but the package that included all the products was called intraNetWare. With the release of NetWare 5, the package name was changed back to NetWare.

You may run into this package, or some mention of it, while you’re working on a network. Just know that intraNetWare is just NetWare by another name. I don’t really know why they changed it, but then again, why did they change the formula for Coca-Cola?

NetWare 5
At the time of this writing, the most current version of NetWare is NetWare 5. NetWare 6 will be released soon, as it is in the beta version now. Probably the most talked-about feature of NetWare 5 is its capability to use TCP/IP in its pure form. Other companies tout “native” IP, but that usually means encapsulating some other protocol inside TCP/IP. In the NetWare 5 TCP/IP implementation, only TCP/IP RFC (Request for Comment) protocols are used to communicate between clients and servers as well as between servers. Using the NetWare 5 TCP/IP implementation is becoming popular because an administrator can use the same protocol on a LAN and a WAN.

As with any major version change, NetWare 5 includes a few important function changes. As previously mentioned, NetWare 5 includes a multiprocessing kernel. Although earlier versions supported multiple processors, you had to load several additional NLMs (including SMP.NLM). Also, NetWare 5 includes a five-user version of Oracle8, the leading relational database software for NetWare. Finally, NetWare 5 includes many expansions to the NDS database, such as the ZENworks workstation management software.

Directory Services

A directory service is a feature of a network operating system that enables users to find network resources. There are two main types of directory services for NetWare:

The bindery (pronounced with a long i) is a simple, flat database of users, groups, and security information that resides on a server. It is available in versions of NetWare prior to version 4.

NDS, which provides access to a global, hierarchical database of network entities (called objects), is available in version 4 and later. Based on the X.500 Internet directory standard (a standard way of naming network entities), this database (called the Directory with a capital D, not to be confused with a DOS directory) is distributed and replicated to all NetWare servers on the network. Each server contains a part of the directory database. Additionally, all servers know about one another and the directory information that each contains.

A major advantage of NDS over the bindery is that with NDS, the entire network is organized into a hierarchical structure, called an NDS Tree. This tree is a logical representation of a network. It includes objects that represent the network’s users, servers, printers, and other resources. On the other hand, the bindery contains user information for that server only. NDS is described as a network-centric directory service, whereas the bindery is server-centric.

To contrast these two directory services, let’s look at an example. If a user on a NetWare 3.x network wants to log in to multiple servers, the administrator must create users on every server. If there are 20 servers on the network, the administrator must create that user 20 times, once on each server. With NDS, however, the administrator simply creates a single user object in the Directory. The user can then log in to the network on any server. The administrator simply assigns rights to the resources that the user needs to access.

To change the Directory database, a NetWare network administrator uses a program called NetWare Administrator. Although this graphical Windows utility has gone through several iterations in the past six years since its introduction, it is the only administrative utility you need to modify NDS objects and their properties. Many utilities are available for specific functions, but NetWare Administrator is the one utility that can do it all.

Design Issues
When designing a NetWare network, you must consider a couple of issues:

The number of servers you will need
Your NDS tree design

Because NetWare is infinitely scalable, you are limited only by the amount and performance of the server’s hardware. Single NetWare servers that support hundreds (sometimes thousands) of users are not uncommon. It is possible to load a single server with all the services (including file, print, Internet, and e-mail functionality) you’ll need for your small business network. Assuming you have enough RAM, the server will run fine. A typical design guideline is approximately one server for every 100 to 200 users, a ratio that is more flexible than that for other network operating systems.

If you are running a version of NetWare that uses NDS, your NDS tree should mimic your network

Note There are no “wrong” NDS tree designs. Some are just better for a particular network than others.

Note There are other, more detailed NDS design concepts. For more information on NDS design, see Mastering Novell Directory Services

Available Client Software

Diverse clients can talk to a NetWare server. To facilitate this, Novell developed client software that allows many client operating systems to take advantage of all NetWare features. Specifically, Novell’s clients (sometimes called NDS clients) enable access to the NDS database. Even though some clients are included with various operating systems and the vendors themselves design them, you should implement Novell’s client on the client operating systems you are running to get the most functionality out of NetWare—including being able to administer NetWare. The NetWare client written by Novell for the particular operating system provides full NDS functionality and is therefore the best choice for connecting that operating system to a NetWare network.

Microsoft Windows NT

With the same graphical interface as other versions of Windows and simple administration possible from the server console, Windows NT is a force to be reckoned with. Microsoft introduced Windows NT in 1993 with version 3.1 (about the same time Windows 3.1 was taking off as a desktop graphical interface for DOS). No one paid it much heed because it was fairly buggy, and a mountain of hardware was required to run it. This NOS went pretty much unnoticed until version 3.51 was introduced about a year later. Windows NT 3.51 was quite stable and, by this time, hardware vendors had met the challenge with the 486 and Pentium processors. Because of its similarity to Windows 3.1 and its powerful networking features, Windows NT gained popularity. Microsoft began to put its significant marketing muscle behind it, and Windows NT started to become a viable alternative in the network operating system market previously dominated by Novell NetWare and the various flavors of Unix.

Note For more information on Windows NT, check out Microsoft’s website at www.microsoft.com.

Windows NT Features

Windows NT is the first choice of developers because of the similarity in programming for Windows 95/98 and Windows NT. Additionally, the installation CD includes a complete Internet server suite (including WWW, FTP, and DNS [Domain Name Service] server programs). Finally, because the look and feel of Windows NT is almost identical to that of Microsoft’s Desktop operating systems, Windows 3.x and Windows 95/98, training administrators requires much less time. These features along with many others have skyrocketed Windows NT use in the corporate network infrastructure. It is important to note that “Windows NT” actually refers to two separate products: Window NT Server (the NOS) and Windows NT Workstation (the client OS, designed to be a high-security desktop OS). Let’s take a look at a few of the more popular features of Windows NT.

The Windows NT User Interface
The Windows NT interface is the same as the Windows interface we’ve come to love (or hate, depending on your view). Windows NT 3.1 and 3.5x use the same basic look and feel as Windows 3.1. Windows NT 4 uses the interface from Windows 95 and Windows 98.

Although there might be subtle differences between the desktop operating systems and their Windows NT counterparts, the basic look and feel is the same. Because of this, a novice administrator can easily learn to use Windows NT. Analysts refer to this as a shallow learning curve.

Third-Party Support
Because of its ease of use and relatively inexpensive cost, Windows NT is selling well. Third-party vendors are writing thousands of software titles for Windows NT. Currently the number of third-party network programs for Windows NT surpasses the number for NetWare.

One reason for the range of software available for Windows NT is that developers can create these programs using many of the development tools they use to write Windows programs. Additionally, Microsoft makes much of the code available to developers for little or no charge. Other vendors often charge to download their development tools, although that trend is rapidly changing. Finally, a program that is certified as Windows Compatible must work on both Windows 95/98 and Windows NT. Because it’s so easy to develop programs for both versions and because Microsoft requires it for Windows certification, the number of programs available for NT is constantly growing. That isn’t to say that all NT programs are network enabled, but when given the choice, developers usually choose to create programs for NT rather than for other network operating system platforms.

Windows NT Interoperability
With the vast diversity of client operating systems out there, any network operating system must be able to provide services to multiple clients. For this reason, Windows NT Server includes file and print services for Apple Macintosh. The Windows NT server appears as if it were a Macintosh server.

Additionally, Windows NT can run text-mode native OS/2 programs without modification. For example, administrators with multiple OS/2 computers running OS/2 text mode e-mail gateways can consolidate them into a single Windows NT server and run each gateway in a separate window.

NetWare Integration
When Windows NT Server was released in 1993, NetWare was the primary network operating system available. As a matter of fact, it had more than 75 percent of the installed network operating system base. For this reason, Microsoft has software for Windows NT that allows it to coexist in a Net-Ware environment. Three main programs facilitate the integration of Windows NT and NetWare:

Gateway Services for NetWare (GSNW)
Client Services for NetWare (CSNW)
File and Print Services for NetWare (FPNW)

Gateway Services for NetWare installs as a service on a Windows NT server and translates requests for Windows NT resources into NetWare requests. At a lower level, GSNW is translating SMB (Server Message Block) protocol requests into NCP (NetWare Core Protocol) requests. GSNW allows multiple Windows NT clients to connect through a Windows NT server to NetWare servers using only Windows NT client software and protocols

Note GSNW has a relatively undocumented feature: Any number of Windows NT clients can connect to NetWare resources through GSNW and use only one license on the NetWare server being accessed. With this capability, it is theoretically possible to build a network of mostly NetWare servers, but license all of them for five users or fewer. Novell is understandably peeved. However, GSNW performance is very poor in this application. Microsoft doesn’t recommend GSNW for high NetWare traffic environments.

Client Services for NetWare (CSNW) is probably the simplest of all the software, but it requires the most overhead to implement. You must install CSNW on every Windows NT Workstation computer that needs access to NetWare resources.

Additionally, all users who want to access NetWare resources need user accounts and rights on the NetWare servers they access.

File and Print Services for NetWare (FPNW) is really a method for providing files and printers hosted by Windows NT Server to Novell clients. When installed and configured on a Windows NT server, this service makes a Windows NT server look like a NetWare server to Novell clients. This service is good when you have a small number of NT servers and a large number of NetWare servers.


Windows NT Architecture
Windows NT sports a fairly complex architecture that’s hidden behind a nice graphical front end. This powerful operating system is available in two packages:

Windows NT Server
Windows NT Workstation

The two share the same basic underlying architecture, but there are several key differences.


Application Support Subsystems

Windows NT is designed as a modular system. Components fall into either the user mode or the kernel mode. This simply indicates which entity uses those components. The two components to note in this diagram are the Hardware Abstraction Layer (HAL) and the many subsystems that can run applications. These two components enable NT to run many types of applications on many hardware types.

Win16 Applications (Win16 Subsystem)
Windows NT can run just about any 16-bit Windows application, providing that it conforms to the Microsoft standards for writing Windows 3.x applications. Each application can run in a separate Virtual DOS Machine (VDM) with its own memory protection.

Win32 Applications (Win32 Subsystem)
Windows NT can run applications designed for both Windows 95/98 and Windows NT.

OS/2 Applications (OS/2 Subsystem)
Windows NT can run OS/2 applications in character mode if these applications use only the pure OS/2 development tools. Windows NT cannot run OS/2 graphical applications.

Unix Applications (POSIX Subsystem)
One of the most talked-about features when Windows NT was introduced was its support for a standard Unix programming environment known as POSIX (Portable Operating System Interface for Computer Environments). Programs written to the POSIX standard can run on any POSIX implementation (including that of Windows NT). Windows NT can run any application that adheres strictly to the Institute of Electrical and Electronics Engineers (IEEE) POSIX standards.

Processor Options for Windows NT
In addition to the application support subsystems, Windows NT can run on many processor types. Before NT, most network operating systems ran only on the Intel platform. But the Hardware Abstraction Layer of the Windows NT architecture allows NT to run on different hardware platforms by simply using a different HAL. Currently, Windows NT supports the following CPU types:

Intel 386 (I386) Architecture Arguably the most popular platform for NT. This type includes the 80386, 80486, Pentium, Pentium Pro, Pentium II, and Pentium III as well as any newer processors in that line. A rule of thumb: If an I386 architecture runs DOS, it will run NT.

Digital Equipment Corporation (DEC) Alpha AXP Architecture Second only to the Intel architecture, this architecture has become popular because of the sheer speed of the DEC Alpha processor (now called Compaq Alpha). This is due, in part, to its Reduced Instruction Set Computing, or RISC, design.

MIPS R4x00 Architecture Another RISC processor that is gaining popularity. Windows NT and Unix are among the operating systems that run on the MIPS architecture.

Motorola PowerPC Architecture A RISC processor developed jointly by IBM, Motorola, and Apple. The Apple Power Mac and a version of the IBM PC use this processor. The Power Mac is now so popular among Macintosh users that all of Apple’s current line of Macintosh computers contains PowerPC-based units. The only operating system that the IBM PC implementation runs is Windows NT. And, unfortunately, Microsoft has announced plans to discontinue support for this architecture.

NT loads network applications as services. A service is a Windows program (a file with either an .EXE or a .DLL extension) that is loaded automatically by the server or manually by the administrator. Network applications that are written specifically for Windows NT are written as Windows NT services.


The Major Versions of Windows NT

In 1993, amid the increased popularity of networking PCs, Microsoft released Windows NT 3.1 as a high-end server platform for Windows networks. It was a powerful operating system that could take advantage of the 32-bit features of the Intel 386 processor, including support for as much as 4GB of memory and preemptive multitasking. However, its greater memory requirements and lack of stability with some programs made people nervous about adopting it as their only network operating system, and it was not widely adopted.

The release of Windows NT 3.51 in 1994 didn’t elicit an enthusiastic response. People quickly realized, however, that it was a stable, robust server platform that could be easily implemented in small- to medium-sized networks. Popularity and support for Windows NT grew in the computing community.

Windows NT 4, which was released in 1996, has the look and feel of Windows 95/98 and includes Internet Information Server (IIS), a web server, and the Internet Explorer web browser. This, in addition to simple server administration and RAID support, made Windows NT 4 the choice for many small- to medium-sized networks. It is becoming more widely used as an enterprise network, but has not been accepted as the backbone NOS for many large networks.

Microsoft changed that with Windows 2000 (formerly known as Windows NT 5), which was released in early 2000. The major difference between Windows 2000 and NT 4 is the replacement of the NT Directory Service (NTDS) with Microsoft Active Directory ( AD). AD is supposedly a true X.500-based Directory, similar to Novell’s NDS. In reality, it is a hierarchy of DNS names for domains


Directory Services

As you already know, a directory service provides access to a central database of information that contains details about the resources available on a network. In Windows NT, the Security Accounts Manager (SAM) database (also called the domain database) contains information about all the users and groups within a domain. A domain is a group of computers that share a single SAM database. There can be more than one domain on a network. For the users in one domain to use resources that reside in a different domain, a relationship known as a trust must exist. This system of domains and trusts for a Windows NT Server network is known as Windows NT Directory Service (NTDS). In an NTDS network, any computer that has Windows NT Server installed can have a copy of the domain database on it. However, only one copy of the database can be considered the master copy. This master copy is the only database responsible for initiating changes on the network. The computer that contains this master copy of the SAM is called the Primary Domain Controller, or PDC. Any other Windows NT server can have a copy of the SAM for backup purposes, in case something happens to the PDC. These computers are called Backup Domain Controllers (BDCs). Further, any computer that has NT Server installed, but doesn’t have a copy of the SAM, is called a Member Server. All of these server types are shown in Figure 5.9.

The importance of these distinctions is that all network administration for a domain happens at a PDC. BDCs can authenticate users, but if the PDC is down, you can’t make administrative changes (such as adding users) until the PDC comes back up. Member servers typically offer services to the network, but don’t take part in authentication (other than to indicate on which server the SAM database resides).

Note You can promote a BDC to a PDC without reinstalling, but, unfortunately, you can’t promote a Member Server to either a BDC or a PDC without completely reinstalling NT Server.

In contrast to Novell NetWare, Windows NT has no one utility that you can use to manage all network entities and resources. Instead, user and group information is managed with User Manager for Domains. Even though Windows NT has its own directory service, Novell has been hard at work to implement its NDS on the Windows NT platform. NDS for NT completely replaces the Windows NT directory service while maintaining compatibility with Windows NT programs that rely on the NTDS.
Many people have tried to compare User Manager for Domains to Net-Ware Administrator, but their functionality is not the same. User Manager can deal with only one domain at a time, and then only with the users, groups, and policies of that domain. NetWare Administrator can manage the entire NDS tree and all network entities.


Minimum Requirements for Windows NT

Because of its graphical nature and complexity, Windows NT has greater hardware requirements than any of the other network operating systems. With each successive version, the hardware requirements seem to at least double, if not triple. Microsoft recommends running NT 4 Server on only the hardware in its Hardware Compatibility List (HCL). You’ll find the HCL at www.microsoft.com/hwtest/hcl/. If the hardware you are trying to use with Windows NT Server or Workstation isn’t on the HCL and you call Microsoft with a problem, you may have support difficulties.


Available Client Software

The nicest feature of Windows NT is less a feature than a fact of the state of networking today. If you implement Windows NT Server on your network, chances are you have Windows 95/98 as your client. All Windows 95/98 and Windows NT workstations install the Microsoft Client for Microsoft Networks by default whenever a network card is installed in a client workstation. This client enables the workstation to access any machine running a Microsoft operating system with networking components (for example, Windows NT Server or Workstation or Windows 95/98). This client must be installed to access the resources of a Windows NT network. Really the only client operating systems that can access a Windows NT network without additional gateway software on the server (such as the products for NetWare that were mentioned earlier) are Windows 95/98 and Windows NT versions of the Microsoft Client for Microsoft Networks.

Macintoshes can also access a Windows NT server, but Services for Macintosh (SFM) must be installed and configured. There is no Microsoft client for a Macintosh, per se. But there is an authentication module for the Macintosh that makes logons easier and provides a secure logon session for the Mac user.

In addition to the Microsoft Client for Microsoft Networks, Windows 95/ 98 and Windows NT include the Microsoft Client for NetWare Networks, which allows users to log in to NetWare servers. This client supports an NDS login, but doesn’t allow administration of an NDS tree using NetWare Administrator. When used in conjunction with the Microsoft Client for Microsoft Networks, this solution provides the most interoperability for clients in a network that has mostly NT servers and only a few NetWare servers, since they can log in to both Microsoft and Novell networks. The only caveat is that a user may not be able to access all the features on a NetWare server (including NDS, since this client performs bindery logins only).

Unix Flavors

Of the other network operating systems available, the various forms of Unix are probably the most popular. It is probably also the oldest of the network operating systems. Bell Labs developed Unix, in part, in 1969. I say “in part” because there are now so many iterations, commonly called flavors, of Unix that it is almost a completely different operating system.

Although the basic architecture of all flavors is the same (32-bit kernel, command-line based, capable of having a graphical interface, as in X Window), the subtle details of each make one flavor better in a particular situation than another.

Unix flavors incorporate a kernel, which constitutes the core of the operating system. The kernel can access hardware and communicate with various types of user interfaces. The two most popular user interfaces are the command-line interface (called a shell) and the graphical interface (X Window). The Unix kernel is similar to the core operating system components of Windows NT and NetWare. In Unix, the kernel is typically simple and, therefore, powerful. Additionally, the kernel can be recompiled to include support for more devices. As a matter of fact, some flavors include the source code so that you can create your own flavor of Unix.


Linux

The Unix flavor that has been receiving the most attention lately is Linux. Linux is a fairly easy-to-use (as Unix goes, anyway) flavor developed by Linus Torvalds at the University of Helsinki, Finland. He started his work in 1991 and released version 1 of the Linux kernel in 1994. At the time of this writing, the current Linux kernel is version 2.2. Since Torvalds adds features daily, it’s only a matter of time before a new release.

Linux runs mainly on the Intel platform, although some distributions run on RISC processors such as the MIPS and Alpha. Attempts have been made, successfully, to run the RISC version on other platforms, such as the Macintosh. Linux is easy to install, and most distributions are free and include the source code. Hardware requirements can vary widely with each distribution.

And there are various flavors of Linux. People acquire Linux, come up with a new feature, recompile Linux with the new feature, and then redistribute Linux. According to Linux’s distribution agreement (called the GNU public license), any sale or distribution must include the source code so that others can also develop custom Linux applications.

Most Linux distributions include a full suite of applications, such as a word processor, the X Window graphical interface, and source code compilers. Additionally, most Unix applications that comply with the POSIX standard should run on Linux with little or no modification.

Because Linux is a flavor of Unix, it comes with network support for TCP/ IP. In particular, Caldera’s OpenLinux is making its mark in the networking world. OpenLinux was developed for corporate networking, so it supports multiple protocols (including PPP [Point-to-Point Protocol], AppleTalk, IPX, and SMB). It also includes support for integration with other network operating systems.

Note For more detailed information on Linux, as well as locations to download Linux, check out www.linux.org.


Two other distributions of Linux should be noted: Red Hat and Slackware. Red Hat Linux is the most portable version of Linux, with code that runs natively on the Intel, Alpha, and SPARC processors. The Slackware distribution was specifically designed for the Intel platform and, as such, supports many PC hardware devices, including Ethernet and multiple (up to 16) processors.

Note For a list of the various English Linux distributions, check out www.linux.org/dist/english.html.


SCO Unix

The Santa Cruz Operation (SCO), in California, makes two main flavors of Unix: OpenServer and UnixWare. OpenServer is considered the Intel Unix flavor of choice because it is robust and scalable. Corporate networks are favorably inclined toward OpenServer because SCO provides excellent support for its product.

In 1997, Novell sold its Unix product, UnixWare, to SCO. The distinguishing feature of this product is its interoperability with Novell-based networks. Additionally, it is easy to install and administer.

Note For more information on OpenServer and other SCO products, check out SCO’s home page at www.sco.com.


Solaris Unix

Of the non-Intel Unix flavors, the most popular is probably Solaris, made by Sun Microsystems. This flavor was designed to run primarily on the SPARC family, a RISC platform developed by Sun. Sun sells both the Solaris operating system and the hardware to run it on, which includes both the logic boards and the systems. These computers running Solaris are widely used as Internet servers.

Not to be outdone by Linux and the SCO flavors, Sun released a version of Solaris for the Intel architecture called Solaris for x86 in 1995. It is designed for use on low-end application and Internet servers.

Solaris is based on the original version of Unix that came out of Bell Labs and, as such, is widely compatible with a number of Unix server applications.

Note For more information on Solaris, check out Sun Microsystems’s website at www.sun.com.

Macintosh OS

The Macintosh interface is considered to be the easiest to use of all graphical user interfaces. Developed in 1983, the Macintosh OS (or Mac OS) is seeing a resurgence of popularity with the introduction of several cool new models, like the iMac, the G4 cube, and the Titanium PowerBook G4 Macintosh. Macintosh has always had a very loyal following, and with good reason. The Macintosh OS (combined with the Macintosh hardware platform) is a very user-friendly computer. As such, many people who have never used computers before are buying Macs.

Note With very few exceptions, the Mac OS will not run on any hardware platform except the Macintosh.

In this section, you will learn about the following items relating to the Mac OS:
Versions
Compatibility and interoperability
Services
Security

Versions
The Mac OS has gone through several major revisions so far, with each version having many more features than the one before it. No discussion of the Mac OS would be complete without a brief discussion of the major releases of the Mac OS, including:

System 1
System 6
System 7
Mac OS 8
Mac OS 9
Mac OS 10 (Mac OS X)


System 1
When the original Macintosh was released in 1984, the Mac OS interface (simply called the Finder in those days) was pretty bare. It contained the basic elements of the current Mac OS, but in non-color form. It had no support for color, but it did have a very powerful graphical user interface (GUI) that made many people go out and buy it.

System 6
System 6 was introduced around 1986 and quickly made the Macintosh world even more exciting with the introduction of color to the operating system. Depending on the video card, a Mac with System 6 could display thousands, even millions, of colors. This was very exciting stuff for the time.

System 7
As good as System 6 was, it didn’t have good support for multitasking. (It could switch between programs using a product known as Multifinder, but it wasn’t great.) Macintosh System 7, therefore, gave Mac users the ability to run multiple programs at once. In addition, it gave users support for True-Type fonts (automatically scalable fonts) and the ability to share out a disk onto the network so that other Mac users could access it. It also gave users the ability to use virtual memory (using a portion of the hard disk as memory).

Mac OS 8
In 1997, Apple made a few changes with the operating system. First of all, they now actively promoted the fact that the Macintosh system software was to be known as Mac OS. Also, due to a partnership with Microsoft (and an infusion of capital from the same), Internet Explorer was installed as the default browser. Apple also increased their cross-platform connectivity with the introduction of an updated version of their PC Exchange product, which now had support for Windows 9x long filenames. Finally, the OS contained its own Java Virtual Machine for running Java applications.

Mac OS 9
With Mac OS 9, Apple brought the Mac OS up to speed with Microsoft’s multiuser offerings. It was now possible to specify different settings and environments for multiple users of the same Macintosh. Along with that, Apple introduced the Keychain, which stored the various online passwords for a user so that only one password was required when a user went online. Finally, they included a network browser so that a user could browse the network easily for a network server.

Mac OS X (OS 10)
Amid much hoopla, Apple introduced OS X, the current version and first major rewrite of the Mac OS in years, in 2001. The basic interface still looks the same; however, the use of color, graphics, and moving graphics is much improved over previous versions. Also, it is based on a Unix kernel, which makes it more stable, more scalable, and generally more powerful than previous versions. Windows “fly” open and get “squished” onto a bar (called the Dock) when minimized. Also, for the first time, you can save directly to PDF format in most applications. This new OS, in addition to being extremely powerful, is also extremely user- and Internet-friendly.


Compatibility and Interoperability

As a server platform, the Mac OS is reliable and fairly scalable. It really can’t compete with the largest Unix and high-end server platforms in the enterprise, but it makes for a good workgroup web-server platform. In that respect, the Mac OS is compatible with many different clients. As a client, though, there is one major problem with the Mac OS: The predominant business client platform is the Windows platform. As such, most business applications are written for that platform, and translations of all those applications for the Mac OS are few and far between. Still, there are translations of the most popular business applications (e.g., Microsoft Word) for the Mac OS that make it viable to use in the workplace.

Another compatibility and interoperability benefit is the support of other server operating systems for Mac OS clients. Windows NT and 2000 have built-in support for Mac OS clients. In fact, the support is so good that Mac OS clients can’t tell the difference between a Windows server with Mac OS file and print support and an actual Macintosh server. Novell NetWare has similar support for Mac OS clients, as previously mentioned in this chapter.


Services

The Mac OS can perform many functions on a network. In addition to being a client, a Macintosh can be a file and print server using AppleShare (Apple’s proprietary networking software) as well as an Internet server using various Apple and third-party software. The advantage of having a Macintosh as a server is that it is extremely easy to administrate. It is so easy, in fact, that many first-time users have no problems networking Macs and making them into file (or other) servers.

There are also some higher-level network software programs available for the Mac OS. For example, there are several e-mail server software packages that allow not only workgroup e-mail, but enterprise-wide Internet e-mail. Also, there are several database packages (Filemaker Pro, for example) that allow the Mac OS to be a database server as well.

Security

The Mac OS offers reliable security. Mac OS X has local user account security built in as part of the OS. Network security has also been taken into account. Many services that would be susceptible to a hack are turned off by default, so a Mac is more secure than other OSes right out of the box. Additionally, there are many third-party security products (including some that implement Kerberos security, which is the type used by Windows 2000) that can make the Mac OS extremely secure over the network.

Summary

You learned about the various client- and server-related topics for four main operating systems: NetWare, Windows NT, Unix, and the Mac OS. For each, you learned the basics of the interface and OS, as well as its use on a network.

First, you learned about Novell NetWare and its former dominance in the networking market. You learned of its flexibility in client support, ease of administration (using NDS), and scalability. Next you learned about Windows NT and its prevalent use as an application server platform. You learned of its extreme ease of administration and shallow learning curve. Then you learned that Unix has great power, but a more complex administration. You also learned of its different flavors and their main applications. Finally, you learned about the Mac OS and its ease of use as well as its presence in the networking arena. Although it is easy to use, the enterprise has not yet adopted it as a standard client platform.

thanx for the info

Hi Mind Reader!

Am a new entrant to this forum. I have read your articles and find them useful. I would like to do a course on networking. SInce you are a wiz in this field, please guide me on where I can start it on line.

Thank you.

Amos Kwira Bwambale
Former Student from Uganda

Kurukshetra University
Haryana
India.

Hi Amos,
Try using the PM system to contact the user directly :)