Windows :- Top Interview Questions with Answers Part 1

1)  What is Active Directory

Active Directory is a directory service used to store information about the network resources across a domain.

An Active Directory (AD) structure is a hierarchical framework of objects. The objects fall into three broad categories - resources (e.g. printers , services (e.g. e-mail ), and users (accounts, or users and groups). The AD provides information on the objects, organizes the objects, controls access, and sets security.

2)  What are FSMO Roles? Explain Each Role

Domain naming master. This domain controller manages the addition and removal of domains in the forest. A forest can have only one domain naming master, which can be transferred to another domain controller through the Active Directory Domains and Trusts snap-in.

Schema master. The schema master controls updates to the domain schema data. There is one schema master in the entire forest. It can be transferred to another domain controller through the Active Directory Schema Master snap-in.

PDC Emulator master. In a mixed Windows 2000 and Windows NT environment, the PDC Emulator master supports the BDCs. Thus, it manages user account and password changes, and forwards that information to the Windows NT BDC. In a native mode Windows 2000 environment, the PDC Emulator master receives preference in the replication of user account passwords. Before a logon fails, it is checked for updated information. This master role can be transferred to another domain controller through the Active Directory Users and Computers snap-in.

Relative ID master. A single relative ID master in each domain of a tree manages the allocation of sequential relative IDs (RIDs) to each of the domain controllers. This makes all security IDs (SIDs) created in a domain relative to the domain controller. This master role can be transferred to another domain controller through the Active Directory Users and Computers snap-in.

Infrastructure master. The infrastructure master is responsible for managing group and user references. Expect a delay in changes to user g when they are made across domains. Updates to other domains are made by the infrastructure master domain controller via a process called multimaster replication. This master role can be transferred to another domain controller through the Active Directory Users and Computers snap-in.

3)  What is a Global Catalog

The Global Catalog (GC) has two primary functions. First, it acts as a domain controller that stores object data and manages queries about objects and their most common attributes (called the Global Catalog Partial Attribute Set, or PAS). Second, it provides data that permits network logon. In single domain controller environments, the Active Directory and GC reside on the same server. Where multiple domain controllers exist, as we discuss later, it is often advisable to move the GC to its own dedicated domain controller. All domain trees have a GC, and must reside on a domain controller.

4)  What are Group Policies

Group policies are used by administrators to configure and control user environment settings. Group Policy Objects (GPOs) are used to configure group policies which are applied to sites, domains, and organizational units (OUs).

5)  What is the difference between a Domain and Workgroup

Windows has two modes of operation - Workgroup and Domain. Depending on the environment that your computer is in, you will be running in one of these two modes. Most home and small business environments will be Workgroup, and most mid- to large businesses will run in domain mode. There are different features and capabilities depending on each, and each serve a purpose

Workgroups can be best understood as a loosely connected group of computers. They rely on each other for nothing, but they are there to share resources should the need arise. There is no centralized management and so there is a low barrier to use. By default, Windows XP is in this mode.

Domains, on the other hand, provide centralized management and security. User access is controlled from a separate server called a domain controller and there is a “trust” built between systems in a domain. There are much more robust differences as well.

Workgroup
A workgroup is best understood as a peer-to-peer network. That is, each computer is sustainable on its own. It has its own user list, it’s own access control and its own resources. In order for a user to access resources on another workgroup computer, that exact user must be setup on the other computer.

In addition, workgroups offer little security outside of basic access control. Windows “share permissions” are very basic and do not offer any kind of granularity for “who” can access “what”, etc.
Workgroups are more than adequate, though, for most small business and home use.

Domain
A domain is a trusted group of computers that share security, access control and have data passed down from a centralized domain controller server or servers. Domain Controllers handle all aspects of granting users permission to login. They are the gatekeeper. In addition, most modern domains use Active Directory which allows and even more centralized point for software distribution, user management and computer controls.

6)  What is the relationship between tree and a forest

Forests, trees, and domains

The framework that holds the objects is viewed at a number of levels. At the top of the structure is the Forest - the collection of every object, its attributes and rules (attribute syntax) in the AD. The forest holds one or more transitive, trust-linked Trees. A tree holds one or more Domains and domain trees, again linked in a transitive trust hierarchy. Domains are identified by their DNS  name structure, the namespace. A domain has a single DNS name.

The objects held within a domain can be grouped into containers called Organizational Units (OUs). OUs give a domain a hierarchy, ease its administration, and can give a semblance of the structure of the AD's company in organizational or geographical terms. OUs can contain OUs - indeed, domains are containers in this sense - and can hold multiple nested OUs. Microsoft recommends as few domains as possible in AD and a reliance on OUs to produce structure and improve the implementation of policies and administration. The OU is the common level at which to apply group policies , which are AD objects themselves called Group Policy Objects (GPOs), although policies can also be applied to domains or sites (see below). The OU is the lowest level at which administrative powers can be delegated.

As a further subdivision AD supports the creation of Sites, which are physical, rather than logical, groupings defined by one or more IP subnets. Sites distinguish between locations connected by low-speed (e.g. WAN , VPN ) and high-speed (e.g. LAN ) connections. Sites can contain one or more domains and domains can contain one or more sites. This is important to control network traffic generated by replication.

The actual division of the company's information infrastructure into a hierarchy of one or more domains and top-level OUs is a key decision. Common models are by business, by geographical location, or by IT roles. These models are also often used in combination.

7)  What is the file name of Active directory and where is it stored

File name : NTDS.DIT

Location : %SystemRoot%\ntds

8)  What are the different types of backups explain them

The Backup utility supports five methods of backing up data on your computer or network.

Copy backup

A copy backup copies all the files you select, but does not mark each file as having been backed up (in other words, the archive attribute is not cleared). Copying is useful if you want to back up files between normal and incremental backups because copying does not affect these other backup operations.

Daily backup

Daily backup copies all the files that you select that have been modified on the day the daily backup is performed. The backed-up files are not marked as having been backed up (in other words, the archive attribute is not cleared).

Differential backup

A differential backup copies files that have been created or changed since the last normal or incremental backup. It does not mark files as having been backed up (in other words, the archive attribute is not cleared). If you are performing a combination of normal and differential backups, restoring files and folders requires that you have the last normal as well as the last differential backup.

Incremental backup

An incremental backup backs up only those files that have been created or changed since the last normal or incremental backup. It marks files as having been backed up (in other words, the archive attribute is cleared). If you use a combination of normal and incremental backups, you will need to have the last normal backup set as well as all incremental backup sets to restore your data.

Normal backup

A normal backup copies all the files you select and marks each file as having been backed up (in other words, the archive attribute is cleared). With normal backups, you only need the most recent copy of the backup file or tape to restore all of the files. You usually perform a normal backup the first time you create a backup set.

Backing up your data using a combination of normal backups and incremental backups requires the least amount of storage space and is the quickest backup method. However, recovering files can be time-consuming and difficult because the backup set might be stored on several disks or tapes.

Backing up your data using a combination of normal backups and differential backups is more time-consuming, especially if your data changes frequently, but it is easier to restore the data because the backup set is usually stored on only a few disks or tapes.

10) What is the difference between NTFS and FAT file system

file allocation table. FAT is ancient in computer terms. Because of its age, most operating systems-including Windows NT, Windows 98, MacOS, and some versions of UNIX-offer support for FAT.

Microsoft created the new technology file system (NTFS) to compensate for the features it felt FAT lacked. These features include increased fault tolerance, enhanced security, and so on.

Compatibility
Before you decide which type of file system to use on a partition, you must consider compatibility. If multiple operating systems will access the partition, you must use a file system that all operating systems can read. Usually, this means using FAT, because of its universal compatibility. Only Windows NT supports NTFS partitions.

Keep in mind, however, that this limitation applies only to the local machine. For example, if Windows NT and Windows 98 are loaded on the same machine and both operating systems require access to a common partition, you must format that partition as FAT. However, if Windows NT is the only operating system on the PC, you can format the partition as NTFS, even if computers running other operating systems will access the partition across the network.

Volume size
Another determining factor is the physical size of your partition. FAT supports partition sizes only up to 2 GB. If your partition size is larger than 2 GB, you must either format it as NTFS or break it into smaller partitions. Keep in mind that NTFS has more overhead than FAT. If your partition size is smaller than 200 MB, you should use FAT to avoid losing a major chunk of disk space to the overhead associated with NTFS. The maximum size of an NTFS partition is 16 EB (exabytes-an exabyte is 2^64 bytes, or 1,024 terabytes).

Fault tolerance
Once you've considered your partition size and compatibility issues, you have some flexibility in determining which file system is right for you. When making this decision, you should consider fault tolerance. Windows NT offers software support for several alternate disk-access methods that increase speed and/or fault tolerance. These options include disk striping and disk striping with parity. Many of these options require NTFS. If you're planning to use a hardware-based stripe set, you can use either file system.

Even without these advanced fault-tolerant options, NTFS includes built-in fault-tolerant capabilities well beyond the capabilities of FAT. For example, when NTFS writes a change to the hard disk, it makes a record of the change in a log file. In the event of a power failure or a disk error, Windows NT can use these log files to repair your data.

NTFS also repairs hard disk errors automatically without displaying an error message. When Windows NT writes a file to an NTFS partition, it keeps a copy of the file in memory. It then reads back the file to make sure it matches the copy stored in memory. If the copies don't match, Windows NT marks that section of the hard disk as corrupted and won't try to use it again. It then uses the copy of the file stored in memory to rewrite the file to an alternate location on the hard disk.

The FAT file system doesn't offer any of these safety features. While FAT does maintain two copies of the file-allocation table, in case one copy is damaged, it's incapable of automatically fixing errors. Instead, you must run a utility such as Scandisk.

Security
As we mentioned before, NTFS has a built-in security system. You can grant various permissions to directories and to individual files. These permissions protect files and directories locally and remotely. For example, if someone were to sit down at a PC containing restricted files, NTFS would protect those files.

If you're using FAT, you're dependent on share permissions for security. Share permissions will protect a file across the network, but they offer no local protection. A person trying to access restricted files could simply sit down at the local PC and gain full access to these files. Another disadvantage to share permissions is that they can be messy to manage. Suppose you have hundreds of users on a server, each with his or her own directories. You could potentially end up with hundreds of shares-and some of them may overlap, which creates additional complications.

File compression
Another advantage to NTFS is its native support for file compression. NTFS compression is much better than its predecessors. It offers you the chance to compress individual files and directories of your choice. Because it compresses individual files, a minor hard disk problem won't foul up your compression scheme and make you lose everything. Compressing individual files and directories also lets you limit compression to seldom-used files. By doing so, you won't slow your operating system by making it decompress files each time it needs to access them.

The system partition
This article may seem to say that NTFS is superior to FAT and that unless you have a small partition or need compatibility with other operating systems, you should always use NTFS. However, this isn't the case.

As we mentioned earlier, NTFS partitions are accessible only via Windows NT. If you have a fatal error with Windows NT, you can't simply boot a system disk to a command prompt and fix a problem on an NTFS partition. To get around this problem, Microsoft recommends installing a second copy of Windows NT on your hard disk and using this copy to repair problems that occur on NTFS partitions.

Unfortunately, this method has some serious drawbacks. For starters, a second copy of Windows NT could consume up to 150 MB, depending on which options you choose to load. Second, during the boot process, both copies share common files. Therefore, if your system partition (the partition your PC boots from) is formatted as NTFS and has a problem, you may not be able to boot either copy of Windows NT to fix the problem. While you may think the odds of a system partition error are slim, remember that many changes you might make to your disk partitions result in having to manually update the Boot.ini file. If you incorrectly update this file, Windows NT will become unbootable. Since this is an initial boot file on the system partition, every installed copy of Windows NT would share this file.

A better solution is to format your system partition as FAT. If you're concerned about security, simply make the system partition small and don't place anything other than the Windows NT system files on it. Remember, a FAT partition is safe from a security standpoint, as long as no unauthorized person has physical access to the machine.

Converting to NTFS
If you've read this article and wish you could use NTFS on some of your partitions that already contain data, you can easily convert a partition to NTFS. To do so, open an MS-DOS Prompt window and type the following command:

CONVERT drive: /FS:NTFS

For example, if you want to convert your D drive to NTFS, you'd replace the word drive with the letter D, as follows:

CONVERT D: /FS:NTFS

12) How do you install Active Directory

Procedure

 To install Active Directory on Windows Server 2003

1. Click Start, click Run, type dcpromo, and then click OK.
2. On the first page of the Active Directory Installation Wizard, click Next.

Note:

If this is the first time you have installed Active Directory, you can click Active Directory Help to learn more about Active Directory before clicking Next.

3. On the next page of the Active Directory Installation Wizard, click Next.
4. On the Domain Controller Type page, click Domain Controller for a new domain, and then click Next.
5. On the Create New Domain page, click Domain in a new forest, and then click Next.
6. On the New Domain Name page, in the Full DNS name for new domain box, type corp.contoso.com, and then click Next.
7. On the Database and Log Folders page, accept the defaults in the Database folder box and the Log folder box, and then click Next.
8. On the Shared System Volume page, accept the default in the Folder location box, and then click Next.
9. On the DNS Registration Diagnostics page, click Install and configure the DNS server on this computer and set this computer to use this DNS server as its preferred DNS Server, and then click Next.
10. On the Permissions page, click Permissions compatible only with Windows 2000 or Windows Server 2003 operating systems, and then click Next.
11. On the Directory Services Restore Mode Administrator Password page, enter a password in the Restore Mode Password box, retype the password to confirm it in the Confirm password box, and then click Next.
12. On the Summary page, confirm the information is correct, and then click Next.
13. When prompted to restart the computer, click Restart now.

14) What is DNS?

15) what is DHCP?

Dynamic Host Configuration Protocol (DHCP) is a network application protocol used by devices (DHCP clients) to obtain configuration information for operation in an Internet Protocol network. This protocol reduces system administration workload, allowing devices to be added to the network with little or no manual intervention.

DHCP discovery

The client broadcasts on the physical subnet to find available servers. Network administrators can configure a local router to forward DHCP packets to a DHCP server on a different subnet. This client-implementation creates a UDP packet with the broadcast destination of 255.255.255.255 or subnet broadcast address.

A client can also request its last-known IP address (in the example below, 192.168.1.100). If the client is still in a network where this IP is valid, the server might grant the request. Otherwise, it depends whether the server is set up as authoritative or not. An authoritative server will deny the request, making the client ask for a new IP immediately. A non-authoritative server simply ignores the request, leading to an implementation-dependent timeout for the client to give up on the request and ask for a new IP address.

DHCP offers

When a DHCP server receives an IP lease request from a client, it reserves an IP address for the client and extends an IP lease offer by sending a DHCPOFFER message to the client. This message contains the client's MAC address, the IP address that the server is offering, the subnet mask, the lease duration, and the IP address of the DHCP server making the offer.

The server determines the configuration, based on the client's hardware address as specified in the CHADDR field. Here the server, 192.168.1.1, specifies the IP address in the YIADDR field.

DHCP requests

A client can receive DHCP offers from multiple servers, but it will accept only one DHCP offer and broadcast a DHCP request message. Based on Transaction ID field in the request, servers are informed whose offer the client has accepted. When other DHCP servers receive this message, they withdraw any offers that they might have made to the client and return the offered address to the pool of available addresses.

DHCP acknowledgement

When the DHCP server receives the DHCPREQUEST message from the client, the configuration processes enters its final phase. The acknowledgement phase involves sending a DHCPACK packet to the client. This packet includes the lease duration and any other configuration information that the client might have requested. At this point, the IP configuration process is complete

17) what is ping (packet internet gropher) & its protocol (ICMP) -- ping is used to check connectivity to an IP

18) what are the boot options for a PC. list them & which option do we use & when (the option we get by pressing F8 - safe mode , safe mode with networking .. 7 so on.)

19) what is LAN, WAN

21) wht is firewall,

22) proxy server

26) boot sequence of PC

27) MBR (master boot record)

28) other general OS based questions as what options u hv in manage (rt click my comp -> manage), which logs u hv in event viewer, etc..

29)Different Servers???

WinNT/2000/2003/2008

30)Can Win Home Edition be added in a Domain?..if no Why?

No,

31)why does safe mode have a black background?

Video card is disabled or not loaded

32)What is RAID?

In computing , the acronym  RAID (originally redundant array of inexpensive disks, now also known as redundant array of independent disks) refers to a data storage  scheme using multiple hard drives  to share or replicate data  among the drives. Depending on the version chosen, the benefit of RAID is one or more of increased data integrity , fault-tolerance , throughput  or capacity  compared to single drives. In its original implementations, its key advantage was the ability to combine multiple low-cost devices using older technology into an array that offered greater capacity, reliability, speed, or a combination of these things, than was affordably available in a single device using the newest technology.

Standard RAID levels

A quick summary of the most commonly used RAID levels:

·         RAID 0: Striped Set

·         RAID 1: Mirrored Set

·         RAID 5: Striped Set with Parity

33)System requirements for different servers.?

34)How much Ram does win server 2003 standard edition support?

>4 GB

35)Explain Dhcp?.(explain DORA)

36)Event viewer? LOG files

With Event Viewer, you can monitor events recorded in event logs. Typically a computer stores the Application, Security, and System logs

38) What is NAT, how it work?

NAT is like the receptionist in a large office. Let's say you have left instructions with the receptionist not to forward any calls to you unless you request it. Later on, you call a potential client and leave a message for them to call you back. You tell the receptionist that you are expecting a call from this client and to put them through.
The client calls the main number to your office, which is the only number the client knows. When the client tells the receptionist who they are looking for, the receptionist checks a lookup table that matches up the person's name and extension. The receptionist knows that you requested this call, therefore the receptionist forwards the caller to your extension.

Developed by Cisco, Network Address Translation is used by a device (firewall, router or computer) that sits between an internal network and the rest of the world. NAT has many forms and can work in several ways:

39)what is OU?

Organizational Units", are administrative-level containers on a computer network that allow network administrators to organize groups of users together so that any changes, security privileges or any other administrative tasks could be accomplished more efficiently.

A network administrator will typically create organizational units that resemble their company's business organization. An OU can be set up for each department. Within that department OU, there could be subsets, or objects that represent users, groups, customers, partners, vendors or even computers and printers on the network.

Applying a set of policies or restrictions to an organizational unit applies it to all subsets within that organization unit. An object, placed into a new organization unit, inherits all the policies and rights associated with that organizational unit.

Organizational Units are used on systems as a form of identity management, a method of technology used to automate various administrative applications such as password synchronization, resetting passwords, user provisioning, meta directories, and consolidated reporting and auditing. 

42) classes of IP

Short for Internet Protocol, IP is an address of a computer or other network device on a network using IP or TCP/IP . For example, the number "166.70.10.23" is an example of such an address. These addresses are similar to addresses used on houses and help data reach its appropriate destination on a network.

There are five classes of available IP ranges: Class A, Class B, Class C, Class D and Class E, while only A, B and C are commonly used. Each class allows for a range of valid IP addresses. Below is a listing of these addresses.

Class	Address Range	Supports
Class A	1.0.0.1 to 126.255.255.254	Supports 16 million hosts on each of 127 networks.
Class B	128.1.0.1 to 191.255.255.254	Supports 65,000 hosts on each of 16,000 networks.
Class C	192.0.1.1 to 223.255.254.254	Supports 254 hosts on each of 2 million networks.
Class D	224.0.0.0 to 239.255.255.255	Reserved for multicast groups.
Class E	240.0.0.0 to 254.255.255.254	Reserved.

43)what is MAC address..mention the Bit?

In computer networking, a Media Access Control address (MAC address), Ethernet Hardware Address (EHA), hardware address, adapter address or physical address is a quasi-unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification. If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number.

Three numbering spaces, managed by the Institute of Electrical and Electronics Engineers (IEEE), are in common use for formulating a MAC address:

44)Explain Hub, Switch and Router:-

A hub is typically the least expensive, least intelligent, and least complicated of the three. Its job is very simple: anything that comes in one port is sent out to the others. That's it. Every computer connected to the hub "sees" everything that every other computer on the hub sees. The hub itself is blissfully ignorant of the data being transmitted. For years, simple hubs have been quick and easy ways to connect computers in small networks.

A switch does essentially what a hub does but more efficiently. By paying attention to the traffic that comes across it, it can "learn" where particular addresses are. For example, if it sees traffic from machine A coming in on port 2, it now knows that machine A is connected to that port and that traffic to machine A needs to only be sent to that port and not any of the others. The net result of using a switch over a hub is that most of the network traffic only goes where it needs to rather than to every port. On busy networks this can make the network significantly faster.

A router is the smartest and most complicated of the bunch. Routers come in all shapes and sizes from the small four-port broadband routers that are very popular right now to the large industrial strength devices that drive the internet itself. A simple way to think of a router is as a computer that can be programmed to understand, possibly manipulate, and route the data its being asked to handle. For example, broadband routers include the ability to "hide" computers behind a type of firewall which involves slightly modifying the packets of network traffic as they traverse the device. All routers include some kind of user interface for configuring how the router will treat traffic. The really large routers include the equivalent of a full-blown programming language to describe how they should operate as well as the ability to communicate with other routers to describe or determine the best way to get network traffic from point A to point B.

45)Explain the Registry ?

The Windows registry is a directory which stores settings and options for the operating system for Microsoft Windows 32-bit versions, 64-bit versions, and Windows Mobile. It contains information and settings for all the hardware, operating system software, most non-operating system software, users, preferences of the PC, etc. Whenever a user makes changes to Control Panel settings, file associations, system policies, or most installed software, the changes are reflected and stored in the registry. The registry also provides a window into the operation of the kernel, exposing runtime information such as performance counters and currently active hardware

Keys and values

The registry contains two basic elements: keys and values

Hives

The Registry is split into a number of logical sections, or "hives".[3] Hives are generally named by their Windows API definitions, which all begin "HKEY". They are abbreviated to a three- or four-letter short name starting with "HK" (e.g. HKCU and HKLM).

The HKEY_LOCAL_MACHINE and HKEY_CURRENT_USER nodes have a similar structure to each other; applications typically look up their settings by first checking for them in "HKEY_CURRENT_USER\Software\Vendor's name\Application's name\Version\Setting name", and if the setting is not found look instead in the same location under the HKEY_LOCAL_MACHINE key. When writing settings back, the reverse approach is used — HKEY_LOCAL_MACHINE is written first, but if that cannot be written to (which is usually the case if the logged-in user is not an administrator), the setting is stored in HKEY_CURRENT_USER instead.

HKEY_CLASSES_ROOT (HKCR)

Abbreviated HKCR, HKEY_CLASSES_ROOT stores information about registered applications, such as file associations and OLE Object Class IDs tying them to the applications used to handle these items. On Windows 2000 and above, HKCR is a compilation of HKCU\Software\Classes and HKLM\Software\Classes. If a given value exists in both of the subkeys above, the one in HKCU\Software\Classes is used.[4]

HKEY_CURRENT_USER (HKCU)

Abbreviated HKCU, HKEY_CURRENT_USER stores settings that are specific to the currently logged-in user. The HKCU key is a link to the subkey of HKEY_USERS that corresponds to the user; the same information is reflected in both locations. On Windows-NT based systems, each user's settings are stored in their own files called NTUSER.DAT and USRCLASS.DAT inside their own Documents and Settings subfolder (or their own Users subfolder in Windows Vista). Settings in this hive follow users with a roaming profile from machine to machine.

HKEY_LOCAL_MACHINE (HKLM)

Abbreviated HKLM, HKEY_LOCAL_MACHINE stores settings that are general to all users on the computer. On NT-based versions of Windows, HKLM contains four subkeys, SAM, SECURITY, SOFTWARE and SYSTEM, that are found within their respective files located in the %SystemRoot%\System32\Config folder. A fifth subkey, HARDWARE, is volatile and is created dynamically, and as such is not stored in a file. Information about system hardware drivers and services are located under the SYSTEM subkey, while the SOFTWARE subkey contains software and Windows settings.

HKEY_USERS (HKU): Abbreviated HKU, HKEY_USERS contains subkeys corresponding to the HKEY_CURRENT_USER keys for each user profile actively loaded on the machine, though user hives are usually only loaded for currently logged-in users.

HKEY_CURRENT_CONFIG :Abbreviated HKCC, HKEY_CURRENT_CONFIG contains information gathered at runtime; information stored in this key is not permanently stored on disk, but rather regenerated at the boot time.

46)Windows Advanced boot options :-

use a Safe Boot option, follow these steps:

Restart your computer and start pressing the F8 key on your keyboard. On a computer that is configured for booting to multiple operating systems, you can press the F8 key when the Boot Menu appears.

Select an option when the Windows Advanced Options menu appears, and then press ENTER.

When the Boot menu appears again, and the words "Safe Mode" appear in blue at the bottom, select the installation that you want to start, and then press ENTER.

Back to the top

Description of Safe Boot options

Safe Mode (SAFEBOOT_OPTION=Minimal): This option uses a minimal set of device drivers and services to start Windows.

Safe Mode with Networking (SAFEBOOT_OPTION=Network): This option uses a minimal set of device drivers and services to start Windows together with the drivers that you must have to load networking.

Safe Mode with Command Prompt (SAFEBOOT_OPTION=Minimal(AlternateShell)): This option is the same as Safe mode, except that Cmd.exe starts instead of Windows Explorer.

Enable VGA Mode: This option starts Windows in 640 x 480 mode by using the current video driver (not Vga.sys). This mode is useful if the display is configured for a setting that the monitor cannot display.

Note Safe mode and Safe mode with Networking load the Vga.sys driver instead.

Last Known Good Configuration: This option starts Windows by using the previous good configuration.

Directory Service Restore Mode: This mode is valid only for Windows-based domain controllers. This mode performs a directory service repair.

Debugging Mode: This option turns on debug mode in Windows. Debugging information can be sent across a serial cable to another computer that is running a debugger. This mode is configured to use COM2.

Enable Boot Logging: This option turns on logging when the computer is started with any of the Safe Boot options except Last Known Good Configuration. The Boot Logging text is recorded in the Ntbtlog.txt file in the %SystemRoot% folder.

Starts Windows Normally: This option starts Windows in its normal mode.

Reboot: This option restarts the computer.

Return to OS Choices Menu: On a computer that is configured to starting to more than one operating system, this option returns to the Boot menu.

An environment variable is set when you use one of the Safe Boot options. The environment variable is SAFEBOOT_OPTION. This variable is set to either Network or to Minimal.

The default Microsoft VGA driver is used for display at 640 x 480 resolution and in 16 colors. You must log on in all modes by a domain or by the local Security Accounts Manager, depending on which Safe Boot mode you select.

47)OSI layers

Characteristics of the OSI Layers

The seven layers of the OSI reference model can be divided into two categories: upper layers and lower layers.

The upper layers of the OSI model deal with application issues and generally are implemented only in software. The highest layer, the application layer, is closest to the end user. Both users and application layer processes interact with software applications that contain a communications component. The term upper layer is sometimes used to refer to any layer above another layer in the OSI model.

The lower layers of the OSI model handle data transport issues. The physical layer and the data link layer are implemented in hardware and software. The lowest layer, the physical layer, is closest to the physical network medium (the network cabling, for example) and is responsible for actually placing information on the medium.

Figure 1-3 illustrates the division between the upper and lower OSI layers.

Figure 1-3 Two Sets of Layers Make Up the OSI Layers

OSIModel Physical Layer

The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical layer implementations can be categorized as either LAN or WAN specifications. Figure 1-7 illustrates some common LAN and WAN physical layer implementations.

Figure 1-7 Physical Layer Implementations Can Be LAN or WAN Specifications

OSI Model Data Link Layer

The data link layer provides reliable transit of data across a physical network link. Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control. Physical addressing (as opposed to network addressing) defines how devices are addressed at the data link layer. Network topology consists of the data link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Error notification alerts upper-layer protocols that a transmission error has occurred, and the sequencing of data frames reorders frames that are transmitted out of sequence. Finally, flow control moderates the transmission of data so that the receiving device is not overwhelmed with more traffic than it can handle at one time.

The Institute of Electrical and Electronics Engineers (IEEE) has subdivided the data link layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC). Figure 1-8 illustrates the IEEE sublayers of the data link layer.

Figure 1-8 The Data Link Layer Contains Two Sublayers

The Logical Link Control (LLC) sublayer of the data link layer manages communications between devices over a single link of a network. LLC is defined in the IEEE 802.2 specification and supports both connectionless and connection-oriented services used by higher-layer protocols. IEEE 802.2 defines a number of fields in data link layer frames that enable multiple higher-layer protocols to share a single physical data link. The Media Access Control (MAC) sublayer of the data link layer manages protocol access to the physical network medium. The IEEE MAC specification defines MAC addresses, which enable multiple devices to uniquely identify one another at the data link layer.

OSI Model Network Layer

The network layer defines the network address, which differs from the MAC address. Some network layer implementations, such as the Internet Protocol (IP), define network addresses in a way that route selection can be determined systematically by comparing the source network address with the destination network address and applying the subnet mask. Because this layer defines the logical network layout, routers can use this layer to determine how to forward packets. Because of this, much of the design and configuration work for internetworks happens at Layer 3, the network layer.

OSI Model Transport Layer

The transport layer accepts data from the session layer and segments the data for transport across the network. Generally, the transport layer is responsible for making sure that the data is delivered error-free and in the proper sequence. Flow control generally occurs at the transport layer.

Flow control manages data transmission between devices so that the transmitting device does not send more data than the receiving device can process. Multiplexing enables data from several applications to be transmitted onto a single physical link. Virtual circuits are established, maintained, and terminated by the transport layer. Error checking involves creating various mechanisms for detecting transmission errors, while error recovery involves acting, such as requesting that data be retransmitted, to resolve any errors that occur.

The transport protocols used on the Internet are TCP and UDP.

OSI Model Session Layer

The session layer establishes, manages, and terminates communication sessions. Communication sessions consist of service requests and service responses that occur between applications located in different network devices. These requests and responses are coordinated by protocols implemented at the session layer. Some examples of session-layer implementations include Zone Information Protocol (ZIP), the AppleTalk protocol that coordinates the name binding process; and Session Control Protocol (SCP), the DECnet Phase IV session layer protocol.

OSI Model Presentation Layer

The presentation layer provides a variety of coding and conversion functions that are applied to application layer data. These functions ensure that information sent from the application layer of one system would be readable by the application layer of another system. Some examples of presentation layer coding and conversion schemes include common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes.

Common data representation formats, or the use of standard image, sound, and video formats, enable the interchange of application data between different types of computer systems. Conversion schemes are used to exchange information with systems by using different text and data representations, such as EBCDIC and ASCII. Standard data compression schemes enable data that is compressed at the source device to be properly decompressed at the destination. Standard data encryption schemes enable data encrypted at the source device to be properly deciphered at the destination.

Presentation layer implementations are not typically associated with a particular protocol stack. Some well-known standards for video include QuickTime and Motion Picture Experts Group (MPEG). QuickTime is an Apple Computer specification for video and audio, and MPEG is a standard for video compression and coding.

Among the well-known graphic image formats are Graphics Interchange Format (GIF), Joint Photographic Experts Group (JPEG), and Tagged Image File Format (TIFF). GIF is a standard for compressing and coding graphic images. JPEG is another compression and coding standard for graphic images, and TIFF is a standard coding format for graphic images.

OSI Model Application Layer

The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application.

This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication.

When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit.
When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer. Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).