Understanding and Deploying LDAP Directory Services > 2. A Brief History of Directories > Prehistory and Early Electronic Directories |
Prehistory and Early Electronic DirectoriesEven before the birth of the computer, people had access to a variety of directories. Examples include the following:
Typically, these directories are printed on paper and updated relatively infrequently. Many of these directories are still in use today. Early Electronic DirectoriesElectronic directories were born shortly after the digital computer itself was created. One of the first widespread uses of electronic directories was to store information about accounts within multiuser timesharing systems. Many of these directories have their roots in the 1960s and early 1970s, and some of them are still in use today. Examples include the following:
These directories were used to authenticate users, control access to resources, and account for the resources consumed by individual users. As people began to use computer systems to collaborate and communicate with others, the role of these directories was expanded to include basic contact information about the users of the systems. Distributed Computing Research and the Grapevine SystemSome of the most important developments that led to the general-purpose, highly distributed directories that are increasingly popular today took place in the late 1970s and early 1980s within the research laboratories of commercial companies and universities. Distributed systems emerged as a popular research topic, growing out of the interest created by the availability of open operating systems such as UNIX and by the availability of inexpensive, relatively high-speed networking technology. The early distributed systems research covered a lot of territory, ranging from the design of simple email systems to the creation of large distributed computers based on Remote Procedure Calls (RPC). One of the most significant early distributed systems, Grapevine, was developed and deployed at Xerox Palo Alto Research Center (PARC) by the early 1980s. Grapevine was implemented using the Mesa programming language on Xerox Alto computers. The computers were connected by Ethernet local area networks (LAN) and 56Kbps wide area network (WAN) links. All communication within the Grapevine system was via a replicated, store-and-forward message-passing system. Figure 2.1 shows the major components of Grapevine. Figure 2.1 The Grapevine distributed system.Grapevine included a Registration Database that served many of the same purposes as the directory systems of today. The Registration Database contained information about people, groups of people, and sites on the network (servers). It was highly replicated and designed for fault tolerance. Administration was decentralized and the entire system was designed to be very scalable. Xerox eventually produced a commercial directory service called Clearinghouse that was based in part on the Grapevine work. The Arrival of the InternetIn the mid-1980s, computer networks in the form of both LANs and WANs became increasingly popular. WANs typically connect independent organizations over long distances; the best-known WAN is the Internet itself, which has its roots in Arpanet. Arpanet was a distributed research project funded by the U.S. Defense Advanced Research Projects Agency (DARPA) in the 1970s and early 1980s. Large WANs such as the Internet are actually networks of networks that join together thousands of WANs, each of which is made up of many LANs. The Internet has spawned many interesting directory services developments, including the development of LDAP itself. The Domain Name SystemIn 1984, the Domain Name System (DNS) came online on the Internet to provide a mapping between textual names (e.g., whitehouse.gov ) and the IP addresses (e.g., 198.137.241.30 ) that the Internet uses behind the scenes. DNS is a widely distributed service that replaced an unwieldy scheme in which each computer on the network had a copy of a file that contained the names and IP addresses of all hosts on the Internet. DNS has evolved some since 1984, but it is still used today when a user of the Internet accesses a service using a textual name. Figure 2.2 shows the DNS hierarchical namespace. Figure 2.2 The Domain Name System's hierarchical namespace.DNS was designed to serve a specific, limited function ”not to be a general-purpose directory service. It also was not designed to be as extensive as to meet the extensive directory needs of applications; it was designed to hold a limited set of data about Internet hosts and networks and to respond to a few types of queries. Nevertheless, DNS was novel for its day. It was designed from the start to be a widely distributed system with distributed administration and control. It was also designed to allow the data to be replicated among multiple servers on the network. Finally, DNS has proven itself to be extremely scalable, growing with amazing aptitude from servicing a few hundred thousand hosts in 1990 to an estimated 37 million by mid-1998. Part of the reason for DNS's success is that it provides a simple, limited set of services. The Internet WHOIS DatabaseAnother early Internet directory was the WHOIS database, which still serves as a network-accessible registry of contact information for hosts, networks, and individual IP addresses. WHOIS accepts a limited number of text-based queries and returns text-based results to clients on the Internet. Listing 2.1 shows an example of a WHOIS query in bold, along with the results returned by the service. Listing 2.1 An example of a WHOIS query% whois excite.com Registrant: Excite, Inc (EXCITE-DOM) 555 Broadway Redwood City, CA 94063 USA Domain Name: EXCITE.COM Administrative Contact, Technical Contact, Zone Contact: DNS admin (DA1596-ORG) dnsadmin@EXCITE.COM (415)943-1200 Fax- (415)943-1299 Billing Contact: Accounts Payable (AP707-ORG) ap@EXCITE.COM (415)943-1200 Fax- (415)943-1299 Record last updated on 09-Jun-97. Record created on 19-Sep-95. Database last updated on 24-Aug-98 04:10:05 EDT. Domain servers in listed order: NS00.EXCITE.COM 198.3.98.250 NS01.EXCITE.COM 198.3.98.251 NSE00.EXCITE.COM 198.3.102.250 NSE01.EXCITE.COM 198.3.102.251 As previously mentioned, the Internet spawned a variety of other directory services developments, the most important of which are covered in other sections of this chapter.
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Index terms contained in this section*UserDirectory (University of Michigan)Arpanet DARPA (U.S. Defense Advanced Research Projects Agency) databases Internet WHOIS directories history of 2nd distributed computing research 2nd 3rd 4th DNS (Domain Name System) 2nd 3rd early electronic multiuser timesharing systems WHOIS database distributed computing research 2nd Grapevine 2nd DNS (Domain Name System) 2nd 3rd Domain Name System, see DNS early electronic directories Grapevine distributed computing system 2nd history of directories distributed computing research 2nd Grapevine distributed system 2nd early electronic Internet development DNS (Domain Name System 2nd 3rd WHOIS database multiuser timesharing systems Internet DNS (Domain Name System) 2nd 3rd WHOIS database listings WHOIS queries Mesa programming language Michigan Terminal System (MTS) multiuser timesharing systems MVS PROFS (IBM) PARC (Xerox Palo Alto Research Center) Grapevine distributed system 2nd queries WHOIS database Registration Database Grapevine distributed system Remote Procedure Calls, see RPCs RPCs (Remote Procedure Calls) U.S. Defense Advanced Research Projects Agency (DARPA) UNIX /etc/passwd (Bell Labs) WANs (Wide Area Networks) Internet development DNS (Domain Name System) 2nd 3rd WHOIS database WHOIS database query example Wide Area Networks, see WANs |
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