Understanding and Deploying LDAP Directory Services > 2. A Brief History of Directories > Network Operating System Directories |
Network Operating System DirectoriesThe term network operating system (NOS) describes a category of products that provide a variety of services to clients and servers on LANs. LANs take many forms, but they typically operate at relatively high speeds and are used within organizations to connect a set of related computer systems. LANs, and later NOSs, originally became popular as a way to share expensive resources such as printers and file servers. Arguably, the success of LANs can be traced to the invention of Ethernet in 1973 by some clever engineers at Xerox PARC. Today the majority of LANs are connected to the global Internet, although they also continue in their original role as providers of high-speed local connectivity within organizations. A typical configuration is shown in Figure 2.3. Figure 2.3 A local area network (LAN).The best-known example of a NOS is Novell NetWare, which made its debut in the mid-1980s. Other popular NOSs include Microsoft Windows NT (a relatively late arrival), Banyan VINES (which has a sophisticated directory service called StreetTalk), and Apple Computer's Appleshare service. NOS directories grew out of the need for network operating systems to authenticate users, track network resources, and provide efficient, centralized management capabilities. Novell Directory ServicesEarly versions of Novell NetWare relied on a simple directory of user - and network-related information called the Bindery. With the debut of NetWare 4.0 in 1993, NetWare gained a full-fledged distributed directory service called NetWare Directory Services, which was eventually renamed Novell Directory Services (NDS). NDS is a mature product whose underlying models and design are closely modeled after the X.500 standards, except that it uses a proprietary suite of directory protocols. NDS can support a highly distributed network environment and offers excellent management utilities. It includes directories that can be highly replicated (even across slow WAN links), along with other sophisticated capabilities, such as a network login that allows users to type their password just once to access all network services. NDS, which has historically focused on serving the needs of NetWare, is still weak in the areas of performance and scalability. Currently, NDS supports LDAP only through a gateway. One telling fact is that Novell's own GroupWise messaging and collaboration suite does not use NDS ”it uses its own application-specific directory. Nevertheless, NDS is one of the most widely deployed directory services. Microsoft's Active DirectoryMicrosoft's LAN Manager and Windows NT Server products prior to version 5.0 include a simple directory service called the NT Domain Directory. This directory has a number of shortcomings. Although machines are grouped into related groups called domains, the NT Domain Directory does not provide a hierarchical view of the directory contents. It is not a general-purpose directory and can't be extended for use by third-party applications. An NT Domain directory is also difficult to manage when it gets large, and it does not scale up easily to accommodate tens of thousands of directory entries. Finally, LDAP is not supported by the NT Domain Directory; all access is through proprietary protocols and APIs. To improve on the weaknesses inherent in its previous offering, Microsoft will include a new, native LDAPv3 directory called Active Directory with Windows NT Server version 5.0. Although Active Directory is primarily aimed at meeting the needs of the Windows NT 5.0 operating system, it is much closer to a general-purpose directory service than the NT Domain Directory is. Unlike most NOS directories, Active Directory uses LDAP as its core protocol, and it actually supports a variety of Internet protocols, including LDAPv3, HTTP, and DNS. Following the lead of Netscape, Microsoft has placed Active Directory at the center of its intranet application and security strategy. Active Directory boasts advanced features such as multimaster replication, a global directory catalog to ease lookups in large-scale deployments, and support for dynamic directory applications such as chat clients and servers. At the time of this writing, Active Directory is scheduled to ship in late 1999. Status of NOS DirectoriesAs evidenced by Active Directory, NOS directories are embracing open standards such as LDAP and opening themselves to a wider variety of directory-enabled applications. NOS directories such as NDS boast the largest installed base of any kind of distributed directory services.
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Index terms contained in this sectionAppleShareBanyan VINES directories history of NOS (network operating system) directories 2nd 3rd 4th 5th 6th domains Ethernet history of directories NOS (network operating system) directories application support Microsoft Active Directory 2nd Novell Directory Services 2nd Microsoft Active Directory 2nd network operating system directories application support Microsoft Active Directory 2nd Novell Directory Services 2nd NOS (network operating system) directories application support Microsoft Active Directory 2nd Novell Directory Services 2nd Novell Directory Services 2nd Windows NT |
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