Novell Directory Services is a fully-replicated, globally distributed, object-oriented, hierarchical database of physical network objects. This type of hierarchical database implements a tree structure that is composed of a root segment, parent segments, and child segments. The segment is the equivalent of file’s record type. The hierarchical database model depicts a set of one-to-many (1:M) relationships between a parent and its children. The hierarchical model uses a hierarchic sequence or preorder traversal to navigate through its structures, always starting at the left side of the tree. Given its parent/child structure, the hierarchical model yields database integrity and consistency: There cannot be a child record without a parent. In addition, a well-designed hierarchical database is very efficient when handling large amounts of data or many transactions (Rob,Coronell, page44, Database Systems).
The NDS type of computing infrastructure stores information about all Internet, intranet, and network resources on a network (WebPages). NDS arranges network resources independently from their physical location (CNE 93). NDS provides network simplicity by representing any network resource such as faxes, routers, switches, printers on the network.. Software applications such as database and word processing functions as well as the volumes in the network file system are simplified by objects as well. The interaction and relationships between these objects can be controlled by the access control services of NDS. With simple drag and drop operation individual objects, groups of objects, or entire branches of the NDS tree can be moved to different locations (Website).
THE BENEFITS OF NDS:
Logging onto several servers individually can be time consuming and inefficient as well as costly. NDS allows the user to logon to the network from a single point with only one password.
NDS Properties and attributes: NetWare 5 page 150 2nd paragraph 154
A network administrators primary responsibilities include maintaining the servers, volumes, users, groups, printers, and other resources in the network. NDS enables you to view all network resources as objects within a distributed or networkwide name service known as the NDS tree. A decision as to how resources are created and placed as objects in the name service must be made by the administrator.
How NDS works:
NDS is made up of objects and properties that are defined by a set of rules in the Directory call a schema. These schema rules dictate the naming and relationship of the objects and properties that can exist in the Directory. The schema consists of three main components called the object class, the property definitions, and the property syntax’s. Working together, these components establish the rules that control the creation of a particular object type in the Directory.
Users, groups, printers, servers, volumes, and computers are the types of objects implemented.
Novell may have outsmarted itself by promoting NDS while waiting for Windows 2000 to come out. The changes in NDS are more evolutionary than revolutionary and therefore may be interpreted as "nothing new" according to Garret Hayes, a systems controls manager at Client/Server Labs. Inc. in Atlanta, a primary test lab partner for Computerworld. The biggest problem according to Hayes is that there are few if any "killer" applications already out there which make use of any directory services concept. This puts Novell in the difficult position of being to good to early. The opposite side to this it is that NDS is here and can be used right now while its difficult to tell exactly when Windows 2000 will be available.
Microsoft over the past few years has been waging a cold war
using propaganda and promises to slander Novell. This campaign involves directories that in theory let you find anything attached to the network such users, servers, and printers. A directory also allows you to manage all these resources from a single point especially when they share computers and move among PC’s.
When Microsoft countered with the Windows NT product that is
extremely more capable, Novell got its ass kicked. Novell now finds itself on the verge of reversing this trend permanently. It has separated NDS from NetWare and has built NT and Unix versions. NDS for Linux (Linux is a flavor of Unix) was given a pubic demonstration at Brain share ‘99 in Utah.
The NDS for telecomms and Internet Service Providers will
standardize NDS. Once this happens there will be little reason to go with Microsoft’s Active Directory.
How NDS has provided company solutions:
"Tradition...with a Vision." Saint Andrew’s School in Boca Raton,
Saint Andrew’s, an independent Episcopal school, offers a comprehensive educational curriculum to 660 students in grades 6-12, including 80 boarding students from 22 countries. The school is best known for providing an excellent education in a nurturing environment exemplified by small class sizes and student/teacher ratios often falling below 10/1.
Results To Date
Supporting the treasury operations of the bank is the Capital Markets Group, located in ABN AMRO’s North American headquarters in Chicago. The Capital Market Group’s network consists of 35 Novell NetWare servers connected to 1200 workstations, and is serviced by the ABN AMRO Information Technology Services Group.
NDS has been modified to make it more secure, manageable, flexible and scalable. Transitive synchronization, transitive vector, replica change caching, multiple objects per packet, randomized replica lists, distributive and WAN Traffic Manager. Role based administration using the inheritable ACL’s or the password property.
Replica synchronization process in NetWare 5 uses transitive synchronization, which is the method of using transitive vectors while synchronizing two NetWare 5 servers. The transitive vector replaces the synchronized up to property that was used in NetWare 4.
With NetWare 5, replication no longer happens within a replica ring or list. The transitive server implements time synchronization. If a source server’s transitive vector is more recent than a target server’s vector, the source server does not need to synchronize with that target server. Synchronization traffic is thereby reduced, freeing up bandwidth. It uses either the IPX or IP protocol.
The transitive vector is a new structure that has been added to the partition on root
It’s actually a group of modification timestamps representing the values held by each replica.. One transitive vector is used for each replica. The synchronized up to property is different from the transitive vector in that it holds up to one value for each replica in the partition. Another major difference is that transitive vectoring is synchronized between servers.
A specific server does not have to contact each of the other servers in the partition to complete the replica sychronization process.
In NetWare 4, when the replica synchronization starts, it contacts and updates each of the replicas in the replica ring in sequential order. Therefore, the first replica in the replica ring is updated first, followed by the second one, and so on. Since the replica
Is updated first, followed by the second one, and so on. Since the replica ring is identical on all the servers holding copies of this partition, the synchronization process updates all the replicas for each partition in the same order. The effect of this may be undesirable if multiple servers are trying synchronize with the same replica on the same server simultaneously. Since only on inbound synchronization is supported per partition (not per server), one of the sychronizaiton processes will have to back off and make the attempt again at a latter time. This situation only arises if the synchronization process tends to execute at approximately the same time on multiple servers.
To help solve this problem, NetWare 5 changes the sequence in which replicas are processed by randomizing the replica ring list before attempting to contact the server. This greatly reduces the chances that one of the servers will have to back off and attempt to resynchronize with a replica. By randomizing which replica receives the first update, transitive synchronization will more quickly converge the data for each partition.
Cache object changes to the NDS objects enhances the performance of the replica synchronization process.