Some General IT Questions Part 2

Active Directory

An active directory is a directory structure used on Microsoft Windows based computers and servers to store information and data about networks and domains. It is primarily used for online information and was originally created in 1996. It was first used with Windows 2000.

An active directory (sometimes referred to as an AD) does a variety of functions including the ability to provide information on objects, helps organize these objects for easy retrieval and access, allows access by end users and administrators and allows the administrator to set security up for the directory.

An active directory can be defined as a hierarchical structure and this structure is usually broken up into three main categories, the resources which might include hardware such as printers, services for end users such as web email servers and objects which are the main functions of the domain and network.

Understanding Active Directories

It is interesting to note the framework for the objects. Remember that an object can be a piece of hardware such as a printer, end user or security settings set by the administrator. These objects can hold other objects within their file structure. All objects have an ID, usually an object name (folder name). In addition to these objects being able to hold other objects, every object has its own attributes which allows it to be characterized by the information it contains. Most IT professionals call these settings or characterizations schemas.

The type of schema created for a folder will ultimately determine how these objects are used. For instance, some objects with certain schemas cannot be deleted, they can only be deactivated. Others types of schemas with certain attributes can be deleted entirely. For instance, a user object can be deleted, but the administrator object cannot be deleted.

When understanding active directories, it is important to know the framework that objects can be viewed at. In fact, an active directory can be viewed at either one of three levels, these levels are called forests, trees or domains. The highest structure is called the forest because you can see all objects included within the active directory.

Within the Forest structure are trees, these structures usually hold one or more domains. Going further down the structure of an active directory are single domains. To put the forest, trees and domains into perspective, consider the following example.

A large organization has many dozens of users and processes. The forest might be the entire network of end users and specific computers at a set location. Within this forest directory are now trees that hold information on specific objects such as domain controllers, program data and system, among others. Within these objects are even more objects which can then be controlled and categorized.

How are Active Directories used?

If you are a computer administrator for a large corporation or organization, you can easily update all end users computers with new software, patches and files simply by updating one object in a forest or tree.

Because each object fits into a set schema and has specific attributes, a network administrator can easily clear a person on a set tree or instantly give or deny access to select users for certain applications. The Microsoft servers use trust to determine whether or not access should be allowed. Two types of trusts that Microsoft active directories incorporate are transitive trusts and one way non transitive trusts. A transitive trust is when there is a trust that goes further than two domains in a set tree, meaning two entities are able to access each other's domains and trees.

A one way transitive trust is when a user is allowed access to another tree or domain; however, the other domain does not allow access to the further domains. This can be summed up as a network administrator and end user. The network administrator can access most trees in the forest including a specific end user's domain. However, the end user, while able to access his or her own domain, cannot access other trees.

It is important to note that active directories are a great way to organize a large organization or corporation's computers' data and network. Without an active directory, most end users would have computers that would need to be updated individually and would not have access to a larger network where data can be processed and reports can be created. While active directories can be technical to a good extent and require considerable expertise to navigate, they are essential to storing information and data on networks.

Switches

In a telecommunications network, a switch is a device that channels incoming data from any of multiple input ports to the specific output port that will take the data toward its intended destination. In the traditional circuit-switched telephone network, one or more switches are used to set up a dedicated though temporary connection or circuit for an exchange between two or more parties. On an Ethernet local area network (LAN), a switch determines from the physical device (Media Access Control or MAC) address in each incoming message frame which output port to forward it to and out of. In a wide area packet-switched network such as the Internet, a switch determines from the IP address in each packet which output port to use for the next part of its trip to the intended destination.

In the Open Systems Interconnection (OSI) communications model, a switch performs the Layer 2 or Data-link layer function. That is, it simply looks at each packet or data unit and determines from a physical address (the "MAC address") which device a data unit is intended for and switches it out toward that device. However, in wide area networks such as the Internet, the destination address requires a look-up in a routing table by a device known as a router. Some newer switches also perform routing functions (Layer 3 or the Network layer functions in OSI) and are sometimes called IP switches.

On larger networks, the trip from one switch point to another in the network is called a hop. The time a switch takes to figure out where to forward a data unit is called its latency. The price paid for having the flexibility that switches provide in a network is this latency. Switches are found at the backbone and gateway levels of a network where one network connects with another and at the subnetwork level where data is being forwarded close to its destination or origin. The former are often known as core switches and the latter as desktop switches.

In the simplest networks, a switch is not required for messages that are sent and received within the network. For example, a local area network may be organized in a token ring or bus arrangement in which each possible destination inspects each message and reads any message with its address.

Circuit-Switching version Packet-Switching

A network's paths can be used exclusively for a certain duration by two or more parties and then switched for use to another set of parties. This type of "switching" is known as circuit-switching and is really a dedicated and continuously connected path for its duration. Today, an ordinary voice phone call generally uses circuit-switching.

Most data today is sent, using digital signals, over networks that use packet-switching. Using packet-switching, all network users can share the same paths at the same time and the particular route a data unit travels can be varied as conditions change. In packet-switching, a message is divided into packets, which are units of a certain number of bytes. The network addresses of the sender and of the destination are added to the packet. Each network point looks at the packet to see where to send it next. Packets in the same message may travel different routes and may not arrive in the same order that they were sent. At the destination, the packets in a message are collected and reassembled into the original message.

Router

In packet-switched networks such as the Internet, a router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. 

The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks it is connected to. A router is located at any gateway (where one network meets another), including each point-of-presence on the Internet. A router is often included as part of a network switch.

A router may create or maintain a table of the available routes and their conditions and use this information along with distance and cost algorithms to determine the best route for

a given packet. Typically, a packet may travel through a number of network points with routers before arriving at its destination. Routing is a function associated with the Network layer (layer 3) in the standard model of network programming, the Open Systems Interconnection (OSI) model. A layer-3 switch is a switch that can perform routing functions.

An edge router is a router that interfaces with an asynchronous transfer mode (ATM) network. A brouter is a network bridge combined with a router.

For home and business computer users who have high-speed Internet connections such as cable, satellite, or DSL, a router can act as a hardware firewall. This is true even if the home or business has only one computer. Many engineers believe that the use of a router provides better protection against hacking than a software firewall, because no computer Internet Protocol address are directly exposed to the Internet. This makes port scans (a technique for exploring weaknesses) essentially impossible. In addition, a router does not consume computer resources as a software firewall does. Commercially manufactured routers are easy to install, reasonably priced, and available for hard-wired or wireless networks.

Also see bridge, gateway, hub, and switch.

Microsoft Exchange Server

Microsoft Exchange Server is the server side of a client–server, collaborative application product developed by Microsoft. It is part of the Microsoft Servers line of server products and is used by enterprises using Microsoft infrastructure products. Exchange's major features consist of electronic mail, calendaring, contacts and tasks; support for mobile and web-based access to information; and support for data storage.

History

Planning the migration from Microsoft's internal "legacy XENIX-based messaging system" to Exchange Server environment began in April 1993, and by January 1995 some 500 users were running on Exchange Server Beta 1. By April 1996 32,000 users were migrated to that environment.

Exchange 1.0

Windows Messaging, initially called Microsoft Exchange, is an e-mail client that was included with Windows 95 (beginning with OSR2), 98 and Windows NT 4.0. In Windows 98, it is not installed by default, but available as a separate program in the setup CD. Microsoft Exchange gained wider usage with the release of Windows 95, as this was the only e-mail client that came bundled with it. Exchange was included throughout later releases of Windows up until the initial release of Windows 98, which by then also included Outlook Express 4.0.

Exchange Server 4.0

Exchange Server 4.0, released on June 11, 1996, was the original version of Exchange Server sold to the public, positioned as an upgrade to Microsoft Mail 3.5. The original version of Microsoft Mail (written by Microsoft) had been replaced, several weeks after Lotus acquired cc:Mail, by a package called Network Courier, acquired during the purchase of Consumer Software Inc. in April 1991. Exchange Server was however an entirely new X.400-based client–server mail system with a single database store that also supported X.500 directory services. The directory used by Exchange Server eventually became Microsoft's Active Directory service, an LDAP-compliant directory server. Active Directory was integrated into Windows 2000 as the foundation of Windows Server domains.

Exchange Server 5.0

On May 23, 1997, Exchange Server 5.0 was released, which introduced the new Exchange Administrator console, as well as opening up "integrated" access to SMTP-based networks for the first time. Unlike Microsoft Mail (which required a standalone SMTP relay), Exchange Server 5.0 could, with the help of an add-in called the Internet Mail Connector, communicate directly with servers using (reference missing) . Version 5.0 also introduced a new Web-based e-mail interface Exchange Web Access, this was rebranded as Outlook Web Access in a later Service pack. Along with Exchange Server version 5.0, Microsoft released version 8.01 of Microsoft Outlook, version 5.0 of the Microsoft Exchange Client and version 7.5 of Microsoft Schedule+ to support the new features in the new version of Exchange Server.

Exchange Server 5.5, introduced November, 1997, was sold in two editions, Standard and Enterprise. They differ in database store size, mail transport connectors and clustering capabilities. The Standard Edition had the same 16 GB database size limitation as earlier versions of Exchange Server, while the Enterprise Edition had an increased limit of 16 TB (although Microsoft's best practices documentation recommends that the message store not exceed 100 GB). The Standard Edition includes the Site Connector, MS Mail Connector, Internet Mail Service (previously "Internet Mail Connector"), and Internet News Service (previously "Internet News Connector"), as well as software to interoperate with cc:Mail, Lotus Notes and Novell GroupWise. The Enterprise Edition adds an X.400 connector, and interoperability software with SNADS and PROFS. The Enterprise Edition also introduced two node clustering capability. Exchange Server 5.5 introduced a number of other new features including a new version of Outlook Web Access with Calendar support, support for IMAP4 and LDAP v3 clients and the Deleted Item Recovery feature. Exchange Server 5.5 was the last version of Exchange Server to have separate directory, SMTP and NNTP services. There was no new version of Exchange Client and Schedule+ for version 5.5, instead version 8.03 of Microsoft Outlook was released to support the new features of Exchange Server 5.5.

Exchange 2000 Server

Exchange 2000 Server (v6.0, code name Platinum), released on November 29, 2000, overcame many of the limitations of its predecessors. For example, it raised the maximum sizes of databases and increased the number of servers in a cluster from two to four. However, many customers were deterred from upgrading by the requirement for a full Microsoft Active Directory infrastructure to be in place, as unlike Exchange Server 5.5, Exchange 2000 Server had no built-in Directory Service, and had a dependency upon Active Directory. The migration process from Exchange Server 5.5 did not have any in-place upgrade path, and necessitated having the two systems online at the same time, with user-to-mailbox mapping and a temporary translation process between the two directories. Exchange 2000 Server also added support for instant messaging, but that capability was later spun off to Microsoft Office Live Communications Server.

Exchange Server 2003

Exchange Server 2003 (v6.5, code name Titanium) debuted on September 28, 2003. Exchange Server 2003 (currently at Service Pack 2) can be run on Windows 2000 Server (only if Service Pack 4 is first installed) and 32-bit Windows Server 2003, although some new features only work with the latter. Like Windows Server 2003, Exchange Server 2003 has many compatibility modes to allow users to slowly migrate to the new system. This is useful in large companies with distributed Exchange Server environments who cannot afford the downtime and expense that comes with a complete migration.

Exchange Server 2007

Exchange Server 2007 was released on November 30, 2006, to business customers as part of Microsoft's roll-out wave of new products. It includes new clustering options, 64-bit support for greater scalability, voice mail integration, better search and support for Web services, better filtering options, and a new Outlook Web Access interface. Exchange 2007 also dropped support for Exchange 5.50 migrations, routing groups, admin groups, Outlook Mobile Access, X.400, and some API interfaces, amongst other features.

Exchange Server 2007 (v8, code name E12, or with SP1 v8.1) runs only on 64-bit x86-64 versions of Windows Server. This requirement applies to supported production environments only; a 32-bit trial version is available for download and testing. Hence, companies currently running Exchange Server on 32-bit hardware will be required to replace or migrate hardware if they wish to upgrade to the new version. Companies that are currently running Exchange Server on 64-bit capable hardware are still required to migrate from their existing Exchange 2000/2003 servers to a new 2007 server since in-place upgrades are not supported in 2007.

Microsoft Exchange 2010

Microsoft reached the RTM (Release To Manufacturing) milestone for Exchange Server 2010 on October 8, 2009, and was officially launched on November 9, 2009;. A 120 day trial is downloadable from Microsoft. Exchange Server 2010 is available in two server editions; Standard edition and Enterprise edition.

Major changes from previous versions of Exchange Server include:

• The high availability options for Mailbox Databases (SCC: Single Copy Clustering, CCR: Clustered Continuous Replication and LCR: Local Continuous Replication) and site resiliency functionality (SCR: Standby Continuous Replication) have been replaced by Database Availability Groups (DAGs) in Exchange Server 2010. Major DAG benefits include providing database level high availability (as opposed to server level), support for up to sixteen (16) copies of each database, and flexible configuration (databases copies may be added / removed at will without requiring major server reconfiguration). Each server that runs the Enterprise edition of Exchange Server 2010 can host up to 100 database copies.

·          High availability for the Client Access Server role in Exchange Server 2010 is provided by using Client Access Server (CAS) arrays. A CAS array can contain multiple Client Access Servers in an Active Directory site and provide a single name endpoint for client connections. CAS arrays cannot span multiple Active Directory sites.

·         In Exchange Server 2007, a clustered mailbox server could not be combined with any other roles. In Exchange Server 2010, the Mailbox Server Role may be combined with the Client Access Server and/or Hub Transport roles, regardless of whether or not the mailbox server participates in a Database Availability Group. (However, since Database Availability Groups use Windows Failover Clustering, and Microsoft does not support the combination of Windows Failover Clustering and Windows Network Load Balancing on the same server, a multi-role deployment will require the use of a 3rd party load balancer to provide load balancing and fault tolerance for the Client Access Server role).

·         With the introduction of the RPC Client Access service, all Outlook clients access their mailbox database through the Client Access Server role. This abstraction layer allows for improved load balancing and redundancy and minimal client impact in the event of a database level *-over ("switchover" or "failover") event.

·         Exchange Server 2010 provides cost savings in required hardware. Storage performance requirements (measured in IOPS: Input/Output operations Per Second) have been reduced by approximately 70% over Exchange Server 2007, and by approximately 90% over Exchange Server 2003. According to a case study, Microsoft IT was able to reduce hardware costs by 75% during the migration from Exchange Server 2007 to Exchange Server 2010.

·         Exchange Server 2010 extends the large mailbox support introduced in Exchange Server 2007, and also introduces a Personal Archive feature to allow messages to be retained longer without the need for a 3rd party archival system. The Personal Archive is implemented as a secondary mailbox for archive-enabled users, and in Exchange Server 2010 Service Pack 1, the Personal Archive may be located on a different database than the primary mailbox, which may reside on a different disk if desired.

Linux

Linux (often pronounced LIH-nuhks with a short "i") is a Unix-like operating system that was designed to provide personal computer users a free or very low-cost operating system comparable to traditional and usually more expensive Unix systems. Linux has a reputation as a very efficient and fast-performing system. Linux's kernel (the central part of the operating system) was developed by Linus Torvalds at the University of Helsinki in Finland. To complete the operating system, Torvalds and other team members made use of system components developed by members of the Free Software Foundation for the GNU Project.

Linux is a remarkably complete operating system, including a graphical user interface, an X

Window System, TCP/IP, the Emacs editor, and other components usually found in a comprehensive Unix system. Although copyrights are held by various creators of Linux's components, Linux is distributed using the Free Software Foundation's copyleft stipulations that mean any modified version that is redistributed must in turn be freely available.

Unlike Windows and other proprietary systems, Linux is publicly open and extendible by contributors. Because it conforms to the Portable Operating System Interface standard user and programming interfaces, developers can write programs that can be ported to other operating systems. Linux comes in versions for all the major microprocessor platforms including the Intel, PowerPC, Sparc, and Alpha platforms. It's also available on IBM's S/390. Linux is distributed commercially by a number of companies. A magazine, Linux Journal, is published as well as a number of books and pocket references.

Linux is sometimes suggested as a possible publicly-developed alternative to the desktop predominance of Microsoft Windows. Although Linux is popular among users already familiar with Unix, it remains far behind Windows in numbers of users. However, its use in the business enterprise is growing.

Linux is a contraction for Linus' Unix; the short i sound preferred by most (including Torvalds) derives from the Swedish pronunciation of Linus.

Thanks & Regards,

"Remember Me When You Raise Your Hand For Dua"
Raheel Ahmed Khan
System Engineer
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sirraheel@gmail.com

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