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Active Directory CSIT 320
What is Active Directory? • Just as the combination of a database and a database management system collects and organizes information about an institution/company/… as well as manages access to that information, Active Directory collects, organizes and manages access to information about network “objects” – such as computers, servers, printers, users, groups, etc. • For instance, one component is a Directory Service • Often likened to a phone book which one to look up numbers (from names) or services (yellow pages) • Active Directory is often just called AD • For example AD-DS is active CSIT 320
Standards • Active Directory is based upon some of the following standards (though not fully compliant with all of them) • DNS – AD needs DNS to work, follows its organization and naming conventions • X.500 – directory service protocol based on the OSI model (AD does not use the full X.500 standard) • LDAP (Lightweight Directory Access Protocol ) – part of the X.500 standard was Directory Access Protocol – LDAP is a scaled down, easier version of that • Kerberos – network authentication protocol – adds the security to AD CSIT 320
Hierarchical Arrangement • Whereas a database has a “relational” structure, the objects in AD have a hierarchical, tree-like structure. • Thus there is a root • Every object other than the root has one and only one parent. • However, it can get complicated in that there are various levels (domains, organizational units, groups) as well as distinctions between logical separations and physical separations. CSIT 320
Domain • A domain is one of the main organizational units in Active Directory. • It collects resources and manages access to them for a set of users. • For instance users being logged in the same domain typically implies that those users will for the most part have access to the same resources and follow the same policies • In Active Directory diagrams , domains are represented by triangles. CSIT 320
Domain Controller • An AD domain must have at least one AD domain controller. • The domain controller manages the authentication of users granting them access to the domain and the resources it contains. • Best Practices suggests that there are at least two domain controllers in a domain so that access to the domain can still be granted if one controller is down. CSIT 320
Tree • A tree is a set of domains that obey a DNS-type hierarchical naming structure. They belong to the same “namespace”. • A namespace provides a context in which a name has a well defined meaning. lasalle.edu luna.lasalle.edu student.lasalle.edu CSIT 320
Forest • As the name suggests a forest is a collection of trees. Each tree has a its own namespace, but the different trees in the forest have different namespaces. However you may want them to be connected in some way – have some kind of trust relationship, some sharing of resources or just want to administer them as a unit. lasalle.edu lasalle.museum CSIT 320 student.lasalle.edu
The first tree is the root • The trees in a forest still share a common root. • The first tree in the forest serves as the root. • It will have (at least initially) the global catalog – the collection of definitions, how the forests are organized, what the trust relationships are, names for all of the objects, etc. CSIT 320
Trust • If two domains have a trust relationship, it means that users from one domain can access resources from another domain. • That way an administrator does not have to give users accounts in both domains. • The domain with the resource is said to be “trusting” and the domain with the user is said to be “trusted”. Trust can be but doesn’t have to be a two-way street. CSIT 320
Organizational Unit • Before we were moving up in the hierarchy from the original concept of a domain, an organizational unit on the other hand is lower in the hierarchy (farther from the root) • It is a container within a domain – resources like printers and file shares organized into smaller containers. • Example within the student.lasalle.edu domain, science students may be access to different shares and different printers from business students, etc. CSIT 320
Sites: • In a large company a logical container such as a domain might cover multiple physical locations. • This can cause a problem because a lot of information is passed between domain controllers. • So AD has the notion of a site to correspond to physical differences rather than logical differences • A site can have multiple domains • A domain may be spread over multiple sites CSIT 320
Some AD Objects • User • Group • Computer • Printer • Distribution Lists • System Policies CSIT 320
What is the Schema? • Just like in a database, Active Directory has a schema. • Definition of all AD objects, • For example , it will define a User, what attributes a User must have, what attributes a User might have, relationships between Users and Groups, etc. • ONE schema for a forest • Extensible • While a default set of definitions gets one started with AD, one can extend or create new objects CSIT 320
What is a Global Catalog? • A distributed data repository containing a searchable, partial representation of every object in every domain in a forest. • Answers AD Search Queries • Must be present to successfully logon • Holds a copy of all Objects of the whole Forest… • ...but holds only a subset of the Attribute CSIT 320
Which Role can a Server have? • Member Server – server on a domain offering a non-active directory service • Domain Controller – as the name suggests its manages access to the resources within a domain • Global Catalog – while a domain controller stores the objects for the domain it “controls”, a global catalog server stores the objects from all domains in the forest. • A global catalog server is a domain controller, but a domain controller may not be a global catalog server CSIT 320
Multi Master Replication • Updates can be applied to ANY Domain Controller • Will be Replicated to each other Domain Controls (inside that Domain) within 15 Minutes • Optimized Algorithm reduces Replication Traffic • Not time based (triggered on demand, only)! CSIT 320
Active Directory Security • Improved Authentication • Permissions applied via ACLs • To Objects as whole • To specific Attributes • Fine-Tuning of Access Permissions possible CSIT 320
References • Windows Server 2008 R2 Unleashed, Rand Morimoto, Michael Noel, Omar Droubi, Ross Mistry and Chris Amaris, SAMS. • Active Directory for Dummies, Steve Clines and Marcia Loughry, Wiley. • http://www.tech-faq.com/active-directory-terminology-and-concepts.html CSIT 320