Windows PowerShell 2.0 commands

An A-Z Index of Windows PowerShell 2.0 commands


a

Get-Acl Get permission settings for a file or registry key

Set-Acl Set permissions

Active Directory Account, Computer, Group and User cmdlets

Get-Alias gal Return alias names for Cmdlets

Import-Alias ipal Import an alias list from a file

New-Alias nal Create a new alias.

Set-Alias sal Create or change an alias

Get-AuthenticodeSignature Get the signature object associated with a file

Set-AuthenticodeSignature Place a signature in a .ps1 script or other file

b

Begin Function BEGIN block

BITS Background Intelligent Transfer Service cmdlets

c

Set-Location cd/chdir/sl Set the current working location

Get-ChildItem dir/ls/gci Get child items (contents of a folder or registry key)

Clear-Host clear/cls Clear the screen

Clear-Item cli Remove content from a variable or an alias

Get-Command gcm Retrieve basic information about a command

Measure-Command Measure running time

Trace-Command Trace an expression or command

Add-Computer Add a computer to the domain

Checkpoint-Computer Create a system restore point (XP)

Remove-Computer Remove the local computer from a workgroup or domain

Restart-Computer Restart the operating system on a computer

Restore-Computer Restore the computer to a previous state

Stop-Computer Stop (shut down) a computer

Reset-ComputerMachinePassword Reset the machine account password for the computer

Test-ComputerSecureChannel Test and repair the secure channel to the domain

Add-Content ac Add to the content of the item

Get-Content cat/type/gc Get content from item (specific location)

Set-Content sc Set content in the item (specific location)

Clear-Content clc Remove content from a file/item

Get-Command gcm Get basic information about cmdlets

Invoke-Command icm Run command

Enable-ComputerRestore Enable System Restore on a drive

Disable-ComputerRestore Disable System Restore on a drive

Get-ComputerRestorePoint Get the restore points on the local computer

Test-Connection Ping one or more computers

ConvertFrom-CSV Convert object properties (in CSV format) into CSV objects

ConvertTo-CSV Convert .NET Framework objects into CSV variable-length strings

ConvertTo-Html Convert the input into an HTML table

ConvertTo-Xml Convert the input into XML

ConvertFrom-SecureString Convert a secure string into an encrypted standard string

ConvertTo-SecureString Convert an encrypted standard string into a secure string

Copy-Item copy/cp/ci Copy an item from a namespace location

Export-Counter Export Performance Counter data to log files

Get-Counter Get performance counter data

Import-Counter Import performance counter log files

Get-Credential Get a security credential (username/password)

Get-Culture Get region information (language and keyboard layout)

d

Get-ChildItem Dir/ls/gci Get child items (contents of a folder or registry key)

Get-Date Get current date and time

Set-Date Set system time on the host system

Remove-Item Del/erase/rd/rm/rmdir Delete an item

Compare-Object diff/compare Compare the properties of objects

Do Loop while a condition is True

e

End Function END block

Get-Event Get events in the event queue

Get-WinEvent Get events from event logs and event trace logs

New-Event Create a new event

Remove-Event Delete events from the event queue

Unregister-Event Cancel an event subscription

Wait-Event Wait until a particular event is raised

Clear-EventLog Delete all entries from an event log

Get-Eventlog Get event log data

Limit-EventLog Limit the size of the event log

New-Eventlog Create a new event log and a new event source

Remove-EventLog Delete an event log

Show-EventLog Display an event log

Write-EventLog Write an event to an event log

Get-EventSubscriber Get event subscribers

Register-EngineEvent Subscribe to powershell events

Register-ObjectEvent Subscribe to .NET events

Register-WmiEvent Subscribe to a WMI event

Get-ExecutionPolicy Get the execution policy for the shell

Set-ExecutionPolicy Change the execution policy (user preference)

Export-Alias epal Export an alias list to a file

Export-Clixml Produce a clixml representation of powershell objects

Export-Console Export console configuration to a file

Export-Csv epcsv Export to Comma Separated Values (spreadsheet)

Exit-PSSession Exit Exit Powershell (or exit a script)

f

ForEach-Object foreach Loop for each object in the pipeline ( % )

ForEach Loop through values in the pipeline

For Loop through items that match a condition

Format-Custom fc Format output using a customized view

Format-List fl Format output as a list of properties, each on a new line

Format-Table ft Format output as a table

Format-Wide fw Format output as a table listing one property only

Export-FormatData Save formatting data from the current session

Get-FormatData Get the formatting data in the current session

g

Get-Item gi Get a file/registry object (or any other namespace object)

Get-ChildItem dir/ls/gci Get child items (contents of a folder or registry key)

h

Get-Help help Open the help file

Add-History Add entries to the session history

Clear-History clhy Delete entries from the session history

Get-History history/h/ghy Get a listing of the session history

Invoke-History r/ihy Invoke a previously executed Cmdlet

Get-Host Get host information (PowerShell Version and Region)

Clear-Host clear/cls Clear the screen

Read-Host Read a line of input from the host console

Write-Host Write customized output to the host/screen

Get-HotFix Get Installed hotfixes

i

if Conditionally perform a command

Import-Clixml Import a clixml file and rebuild the PS object

Import-Csv ipcsv Take values from a CSV list and send objects down the pipeline

Invoke-Command Run commands on local and remote computers

Invoke-Expression iex Run a PowerShell expression

Get-Item gi Get a file object or get a registry (or other namespace) object

Invoke-Item ii Invoke an executable or open a file (START)

New-Item ni Create a new item in a namespace

Remove-Item rm/del/erase/rd/ri/rmdir Remove an item

Set-Item si Change the value of an item

Clear-ItemProperty clp Remove the property value from a property

Copy-ItemProperty cpp Copy a property along with it's value

Get-ItemProperty gp Retrieve the properties of an object

Move-ItemProperty mp Move a property from one location to another

New-ItemProperty Set a new property

Remove-ItemProperty rp Remove a property and its value

Rename-ItemProperty rnp Renames a property at its location

Set-ItemProperty sp Set a property at the specified location to a specified value

j

Get-Job gjb Get PowerShell background jobs that are running

Receive-Job rcjb Get PowerShell background job results

Remove-Job rjb Delete a PowerShell background job

Start-Job sajb Start a PowerShell background job

Stop-Job spjb Stop a PowerShell background job

Wait-Job wjb Wait for a background job

k

Stop-Process kill/spps Stop a running process

l

Update-List Add and remove items from a collection

Get-Location pwd / gl Get and display the current location

Pop-Location popd Set the current working location from the stack

Push-Location pushd Push a location to the stack

Set-Location cd/chdir/sl Set the current working location

m

Send-MailMessage Send an email message

Add-Member Add a member to an instance of a PowerShell object

Get-Member gm Enumerate the properties of an object

Get-Module gmo Get the modules imported to the session

Import-Module ipmo Add a module to the session

New-Module nmo Create a new dynamic module (only in memory)

Remove-Module rmo Remove a module from the current session

Move-Item mv/move/mi Move an item from one location to another

o

Compare-Object diff/compare Compare the properties of objects

Group-Object group Group objects that contain the same value

Measure-Object Measure the properties of an object

New-Object Create a new .Net object

Select-Object select Select properties of objects

Sort-Object sort Sort objects by property value

Where-Object Filter the objects passed along the command pipeline

Out-Default Send output to default

Out-File Send output to a file

Out-GridView ogv Send output to an interactive table

Out-Host oh Send output to the host

Out-Null Send output to null

Out-Printer lp Send the output to a printer

Out-String Send objects to the host as strings

p

Param Script Parameters

Powershell Launch a powershell session

Convert-Path cvpa Convert a ps path to a provider path

Join-Path Combine a path and child-path

Resolve-Path rvpa Resolves the wildcards in a path

Split-Path Return part of a path

Test-Path Return true if the path exists, otherwise return false

Get-Pfxcertificate Get pfx certificate information

Pop-Location popd Set the current working location from the stack

Push-Location pushd Push a location to the stack

Process Function PROCESS block

Get-Process ps/gps Get a list of processes on a machine

Debug-Process Attach a debugger to a running process

Start-Process start/saps Start one or more processes

Stop-Process kill/spps Stop a running process

Wait-Process Wait for a process to stop

Enable-PSBreakpoint ebp Enable a breakpoint in the current console

Disable-PSBreakpoint dbp Disable a breakpoint in the current console

Get-PSBreakpoint gbp Get the currently set breakpoints

Set-PSBreakpoint sbp Set a breakpoint on a line, command, or variable

Remove-PSBreakpoint rbp Delete breakpoints from the current console

Get-PSDrive gdr Get drive information (DriveInfo)

New-PSDrive mount/ndr Install a new drive on the machine

Remove-PSDrive rdr Remove a provider/drive from its location

Get-PSProvider Get information for the specified provider

Set-PSdebug Turn script debugging on or off

Enter-PSSession etsn Start an interactive session with a remote computer

Exit-PSSession exsn End an interactive session with a remote computer

Export-PSSession epsn Import commands and save them in a PowerShell module

Get-PSSession gsn Get the PSSessions in the current session

Import-PSSession ipsn Import commands from another session

New-PSSession nsn Create a persistent connection to a local or remote computer

Remove-PSSession rsn Close PowerShell sessions

Disable-PSSessionConfiguration Deny access to PS session configuration

Enable-PSSessionConfiguration Enable PS session configuration

Get-PSSessionConfiguration Get the registered PS session configuration

Register-PSSessionConfiguration Create and register a new PS session configuration

Set-PSSessionConfiguration Change properties of a registered session configuration

Unregister-PSSessionConfiguration Delete registered PS session configuration

New-PSSessionOption Advanced options for a PSSession

Add-PsSnapIn asnp Add snap-ins to the console

Get-PsSnapin gsnp List PowerShell snap-ins on this computer

Remove-PSSnapin rsnp Remove PowerShell snap-ins from the console

q

Quest AD cmdlets Read and write to Active Directory

r

Get-Random Get a random number

Read-Host Read a line of input from the host console

Remove-Item rm/del/erase/rd/ri/rmdir Remove an item

Rename-Item ren/rni Change the name of an existing item

Rename-ItemProperty Rename a property of an item

Run/Call & Run a command (call operator)

s

Select-Object select Select properties of objects

Select-XML Find text in an XML string or document

Send-MailMessage Send an email message

Get-Service gsv Get a list of services

New-Service Create a new service

Restart-Service Stop and then restart a service

Resume-Service Resume a suspended service

Set-Service Change the start mode/properties of a service

Start-Service sasv Start a stopped service

Stop-Service spsv Stop a running service

Suspend-Service Suspend a running service

Sort-Object sort Sort objects by property value

Set-StrictMode Enforce coding rules in expressions & scripts

Start-Sleep sleep Suspend shell, script, or runspace activity

Switch Multiple if statements

ConvertFrom-StringData Convert a here-string into a hash table

Select-String Search through strings or files for patterns

t

Tee-Object tee Send input objects to two places

New-Timespan Create a timespan object

Trace-Command Trace an expression or command

Get-Tracesource Get components that are instrumented for tracing.

Set-Tracesource Trace a PowerShell component

Start-Transaction Start a new transaction

Complete-Transaction Commit the transaction

Get-Transaction Get information about the active transaction

Use-Transaction Add a command or expression to the transaction

Undo-Transaction Roll back a transaction

Start-Transcript Start a transcript of a command shell session

Stop-Transcript Stop the transcription process

Add-Type Add a .NET Framework type to a PowerShell session

Update-TypeData Update extended type configuration

u

Get-Uiculture Get the ui culture information

Get-Unique gu Get the unique items in a collection

Update-Formatdata Update and append format data files

Update-Typedata Update the current extended type configuration

v

Clear-Variable clv Remove the value from a variable

Get-Variable gv Get a powershell variable

New-Variable nv Create a new variable

Remove-Variable rv Remove a variable and its value

Set-Variable set/sv Set a variable and a value

w

New-WebServiceProxy Create a Web service proxy object

Where-Object where/? Filter input from the pipeline

Where Filter objects from the pipeline

While Loop while a condition is True

Write-Debug Write a debug message to the host display

Write-Error Write an object to the error pipeline

Write-Host Write customized output to the host/screen

Write-Output write/echo Write an object to the pipeline

Write-Progress Display a progress bar

Write-Verbose Write a string to the host's verbose display

Write-Warning Write a warning message

Set-WmiInstance Create or update an instance of an existing WMI class

Invoke-WmiMethod iwmi Call WMI methods

Get-WmiObject gwmi Get WMI class information

Remove-WmiObject rwmi Delete an instance of a WMI class

Connect-WSMan Connect to the WinRM service on a remote computer

Disconnect-WSMan Disconnect from the WinRM service on a remote computer

Test-WSMan Test whether the WinRM service is running

Invoke-WSManAction Invoke an action on a specified object

Disable-WSManCredSSP Disable Credential Security Service Provider (SSP) authentication

Enable-WSManCredSSP Enable Credential SSP authentication

Get-WSManCredSSP Get the Credential SSP configuration

New-WSManInstance Create a new instance of a management resource

Get-WSManInstance Display management information (XML or value)

Set-WSManInstance Modify the management information related to a resource

Remove-WSManInstance Delete a management resource instance

Set-WSManQuickConfig Configure the local computer for remote management

New-WSManSessionOption Options for WSMan commands

# Comment / Remark

. (source) Run a command script in the current shell

& (call) Run a command script

? Alias for Where-Object

$variable = "value" Define a variable also: ${n!a#me} = "value"

@(...) Force an expression to be evaluated as an array





Active Directory module PowerShell cmdlets

The Active Directory (AD) module may be installed as part of the RSAT feature on a Windows 7 / 2008 R2 server (or by default, with the AD DS or AD LDS server roles.) Once installed, load the Active Directory module with Import-Module ActiveDirectory or click Start, Administrative Tools, Active Directory Module for Windows PowerShell.

Disable-adAccount Disable an Active Directory account.

Enable-adAccount Enable an Active Directory account.

Search-adAccount Get AD user, computer, and service accounts.

Unlock-adAccount Unlock an AD account.

Get-adAccountAuthorizationGroup Get the groups in which an account is a direct or indirect member.

Set-adAccountControl Modify user account control (UAC) values for an AD account.

Clear-adAccountExpiration Clear the expiration date for an AD account.

Set-adAccountExpiration Set the expiration date for an AD account.

Set-adAccountPassword Modify the password of an AD account.

Get-adAccountResultantPasswordReplicationPolicy Resultant password replication policy for an AD account.

c

Get-adComputer Get one or more AD computers.

New-adComputer Create a new AD computer.

Remove-adComputer Remove an AD computer.

Set-adComputer Modify an AD computer.

Add-adComputerServiceAccount Add one or more service accounts to an AD computer.

Get-adComputerServiceAccount Get the service accounts that are hosted by an AD computer.

Remove-adComputerServiceAccount Remove one or more service accounts from a computer.

d

Get-adDefaultDomainPasswordPolicy Get the default password policy for an AD domain.

Set-adDefaultDomainPasswordPolicy Modify the default password policy for an AD domain.

Move-adDirectoryServer Move a domain controller in AD DS to a new site.

Move-adDirectoryServerOperationMasterRole Move the operation master (FSMO) roles to an AD domain controller.

Get-adDomain Get an AD domain.

Set-adDomain Modify an AD domain.

Get-adDomainController Get one or more AD domain controllers.

Add-adDomainControllerPasswordReplicationPolicy

Add users, computers, and groups to the Allowed List or the Denied List

of the read-only domain controller (RODC) Password Replication Policy (PRP).

Get-adDomainControllerPasswordReplicationPolicy RODC PRP Allowed/Denied List.

Remove-adDomainControllerPasswordReplicationPolicy RODC PRP Allowed/Denied List.

Get-adDomainControllerPasswordReplicationPolicyUsage Get the resultant password policy of the specified

AD Account on the specified RODC.

Set-adDomainMode Set the domain functional level for an AD domain.

f

Get-adFineGrainedPasswordPolicy Get one or more AD fine-grained password policies.

New-adFineGrainedPasswordPolicy Create a new AD fine-grained policy.

Remove-adFineGrainedPasswordPolicy Remove an AD fine-grained password policy.

Set-adFineGrainedPasswordPolicy Modify an AD fine-grained password policy.

Add-adFineGrainedPasswordPolicySubject Apply a fine-grained password policy to one more users and groups.

Get-adFineGrainedPasswordPolicySubject Get the users and groups to which a fine-grained policy is applied.

Remove-adFineGrainedPasswordPolicySubject Remove one or more users from a fine-grained policy.

Get-adForest Get an AD forest.

Set-adForest Modify an AD forest.

Set-adForestMode Set the forest mode for an AD forest.

g

Get-adGroup Get one or more AD groups.

New-adGroup Create an AD group.

Remove-adGroup Remove an AD group.

Set-adGroup Modify an AD group.

Add-adGroupMember Add one or more members to an AD group.

Get-adGroupMember Get the members of an AD group.

Remove-adGroupMember Remove one or more members from an AD group.

o

Get-adObject Get one or more AD objects.

Move-adObject Move an AD object or a container of objects to a different container or domain.

New-adObject Create an AD object.

Remove-adObject Remove an AD object.

Rename-adObject Change the name of an AD object.

Restore-adObject Restore an AD object.

Set-adObject Modify an AD object.

Disable-adOptionalFeature Disable an AD optional feature.

Enable-adOptionalFeature Enable an AD optional feature.

Get-adOptionalFeature Get one or more AD optional features.

Get-adOrganizationalUnit Get one or more AD OUs.

New-adOrganizationalUnit Create a new AD OU.

Remove-adOrganizationalUnit Remove an AD OU.

Set-adOrganizationalUnit Modify an AD OU.

p

Add-adPrincipalGroupMembership Add a member to one or more AD groups.

Get-adPrincipalGroupMembership Get the AD groups that have a specified user, computer, or group.

Remove-adPrincipalGroupMembership Remove a member from one or more AD groups.

r

Get-adRootDSE Get the root of a domain controller information tree.

s

Get-adServiceAccount Get one or more AD service accounts.

Install-adServiceAccount Install an AD service account on a computer.

New-adServiceAccount Create a new AD service account.

Remove-adServiceAccount Remove an AD service account.

Set-adServiceAccount Modify an AD service account.

Uninstall-adServiceAccount UnInstall an AD service account from a computer.

Reset-adServiceAccountPassword Reset the service account password for a computer.

u

Get-adUser Get one or more AD users.

New-adUser Create a new AD user.

Remove-adUser Remove an AD user.

Set-adUser Modify an AD user.

Get-adUserResultantPasswordPolicy Get the resultant password policy for a user.

If your machine is joined to a domain then a default PSDrive named AD: is created. Use all the regular file system commands to navigate this:

PS C:\> cd AD:

PS AD:\> dir

To use the AD module to manage an Active Directory domain, the Windows Server 2008 R2 Active Directory Web Services (ADWS) service must be installed on at least one domain controller in the domain. To list all the Active Directory cmdlets installed, type Get-Command *-AD*

Windows Server 2012

Builds


A Milestone 3 build (6.2.7959.0) was reportedly leaked to file-sharing sites.[8] A new window style, but little else, was present. Windows Server 2012's developer preview was released on 9 September 2011 along with that of Windows 8, but unlike Windows 8's developer preview, it was only made available to MSDN subscribers. It was branded as the Windows Server "8" Developer Preview"[3] The Modern UI (formerly Metro) user interface is present, as well as the new Server Manager, along with the other new features. On 16 February 2012, Microsoft announced that the developer preview build, after installing a particular update, will be set to expire on 15 January 2013, instead of the original 8 April 2012.[9]

Screenshots of a build suspected to be (but was not) the beta of Windows Server 2012, then referred to as Windows Server "8", were reportedly leaked on 3 January 2012. A new dashboard UI is present.[10] Build 8180 was leaked on 13 January 2012, and contains some revisions to the Server Manager interface and Storage Spaces.[11]

The beta was released along with the Windows 8 Consumer Preview on 29 February 2012.[12]

The Release Candidate of Windows Server 2012 was released on 31 May 2012, along with the Windows 8 Release Preview.[13]

Features

Windows Server 2012 includes a number of new features or feature changes.

User interface

Server Manager has been redesigned with an emphasis on easing management of multiple servers.[14] The operating system, like Windows 8, uses the Metro UI unless installed in Server Core mode.[15] Windows PowerShell in this version has over 2300 commandlets, compared with around 200 in Windows Server 2008 R2.[16] There is also command auto-completion.[16]

Task Manager

Main article: Windows Task Manager in Windows 8

Windows 8 and Windows Server 2012 include a new version of Windows Task Manager together with the old version. In the new version the tabs are hidden by default showing applications only. In the new Processes tab, the processes are displayed in various shades of yellow, with darker shades representing heavier resource use. It lists application names, application status, and overall utilization data for CPU, memory, hard disk, and network resources, moving the process information found in the older Task Manager to the new Details tab. The Performance tab is split into CPU, memory (RAM), disk, ethernet, and, if applicable, wireless network sections with graphs for each. The CPU tab no longer displays individual graphs for every logical processor on the system by default; instead, it can display data for each NUMA node. When displaying data for each logical processor for machines with more than 64 logical processors, the CPU tab now displays simple utilization percentages on heat-mapping tiles.[17] The color used for these heat maps is blue, with darker shades again indicating heavier utilization. Hovering the cursor over any logical processor's data now shows the NUMA node of that processor and its ID, if applicable. Additionally, a new Startup tab has been added that lists startup applications.[18] The new task manager recognizes when a WinRT application has the "Suspended" status.

Installation options

Unlike its predecessor, Windows Server 2012 can switch between Server Core and the GUI (full) installation options without a full reinstallation. There is also a new third installation option that allows MMC and Server Manager to run, but without Windows Explorer or the other parts of the normal GUI shell.[19]

IP address management (IPAM)

Windows Server 2012 has an IPAM role for discovering, monitoring, auditing, and managing the IP address space used on a corporate network. IPAM provides for administration and monitoring of servers running Dynamic Host Configuration Protocol (DHCP) and Domain Name Service (DNS). IPAM includes components for:

• Automatic IP address infrastructure discovery: IPAM discovers domain controllers, DHCP servers, and DNS servers in the domains you choose. You can enable or disable management of these servers by IPAM.

• Custom IP address space display, reporting, and management: The display of IP addresses is highly customizable and detailed tracking and utilization data is available. IPv4 and IPv6 address space is organized into IP address blocks, IP address ranges, and individual IP addresses. IP addresses are assigned built-in or user-defined fields that can be used to further organize IP address space into hierarchical, logical groups.

• Audit of server configuration changes and tracking of IP address usage: Operational events are displayed for the IPAM server and managed DHCP servers. IPAM also enables IP address tracking using DHCP lease events and user logon events collected from Network Policy Server (NPS), domain controllers, and DHCP servers. Tracking is available by IP address, client ID, host name, or user name.

• Monitoring and management of DHCP and DNS services: IPAM enables automated service availability monitoring for Microsoft DHCP and DNS servers across the forest. DNS zone health is displayed, and detailed DHCP server and scope management is available using the IPAM console.

Both IPv4 and IPv6 are fully supported.[20][21]

Active Directory

Windows Server 2012 has a number of changes to Active Directory from the version shipped with Windows Server 2008 R2. The Active Directory Domain Services installation wizard has been replaced by a new section in Server Manager, and the Active Directory Administrative Center has been enhanced. A GUI has been added to the Active Directory Recycle Bin. Password policies can differ more easily within the same domain. Active Directory in Windows Server 2012 is now aware of any changes resulting from virtualization, and virtualized domain controllers can be safely cloned. Upgrades of the domain functional level to Windows Server 2012 are simplified; it can be performed entirely in Server Manager. Active Directory Federation Services is no longer required to be downloaded when installed as a role, and claims which can be used by the Active Directory Federation Services have been introduced into the Kerberos token. Windows Powershell commands used by Active Directory Administrative Center can be viewed in a "Powershell History Viewer".[22][23]

Hyper-V

Main article: Hyper-V#Future

Windows Server 2012, along with Windows 8, includes a new version of Hyper-V,[24] as presented at the Microsoft Build Event.[25] Many new features have been added to Hyper-V, including network virtualization, multi-tenancy, storage resource pools, cross-premise connectivity, and cloud backup. Additionally, many of the former restrictions on resource consumption have been greatly lifted. Each virtual machine in this version of Hyper-V can access up to 32 virtual processors, up to 512 gigabytes of random-access memory, and up to 16 terabytes of virtual disk space per virtual hard disk (using a new .vhdx format). Up to 1024 virtual machines can be active per host, and up to 4000 can be active per failover cluster.[26][27] The version of Hyper-V shipped with the client version of Windows 8 requires a processor that supports SLAT and for SLAT to be turned on, while the version in Windows Server 2012 only requires it if the RemoteFX role is installed.[28]

ReFS

ReFS (Resilient File System, originally codenamed "Protogon") is a new file system in Windows Server 2012 initially intended for file servers that improves on NTFS. Major new features of ReFS include:[29]

Improved reliability for on-disk structures

ReFS uses B+ trees for all on-disk structures including metadata and file data. The file size, total volume size, number of files in a directory and number of directories in a volume are limited by 64-bit numbers, which translates to maximum file size of 16 Exabytes, maximum volume size of 1 Yottabyte (with 64 KB clusters), which allows large scalability with no practical limits on file and directory size (hardware restrictions still apply). Metadata and file data are organized into tables similar to relational database. Free space is counted by a hierarchal allocator which includes three separate tables for large, medium, and small chunks. File names and file paths are each limited to a 32 KB Unicode text string.

Built-in resilience

ReFS employs an allocation-on-write update strategy for metadata, which allocates new chunks for every update transaction and uses large IO batches. All ReFS metadata has built-in 64-bit checksums which are stored independently. The file data can have an optional checksum in a separate "integrity stream", in which case the file update strategy also implements allocation-on-write; this is controlled by a new "integrity" attribute applicable to both files and directories. If nevertheless file data or metadata becomes corrupt, the file can be deleted without taking down the whole volume offline for maintenance, then restored from the backup. As a result of built-in resiliency, administrators do not need to periodically run error-checking tools such as CHKDSK when using ReFS.

Compatibility with existing APIs and technologies

ReFS does not require new system APIs and most file system filters continue to work with ReFS volumes. ReFS supports many existing Windows and NTFS features such as BitLocker encryption, Access Control Lists, USN Journal, change notifications,[30] symbolic links, junction points, mount points, reparse points, volume snapshots, file IDs, and oplock. ReFS seamlessly[31] integrates with Storage Spaces, a storage virtualization layer that allows data mirroring and striping, as well as sharing storage pools between machines.[32] ReFS resiliency features enhance the mirroring feature provided by Storage Spaces and can detect whether any mirrored copies of files become corrupt using background data scrubbing process, which periodically reads all mirror copies and verifies their checksums then replaces bad copies with good ones.

Some NTFS features are not supported in ReFS, including named streams, object IDs, short names, file compression, file level encryption (EFS), user data transactions, sparse files, hard links, extended attributes, and disk quotas.[29][33] ReFS does not itself offer data deduplication. Dynamic disks with mirrored or striped volumes are replaced with mirrored or striped storage pools provided by Storage Spaces. However, in Windows Server 2012, automated error-correction is only supported on mirrored spaces, and booting from ReFS is not supported either.

ReFS was first shown in screenshots from leaked build 6.2.7955, where it went by code name "Protogon".[34][35][36][37] Support for ReFS is absent in the developer preview (build 8102). ReFS is not readable by Windows 7 or earlier.[34]

IIS 8.0

Windows Server 2012 includes version 8.0 of Internet Information Services (IIS). The new version contains new features such as CPU usage caps for particular websites.[

Basic Network

What is a computer Network?


A network is any collection of independent computers that communicate with one another over a shared network medium.A computer network is a collection of two or more connected computers. When these computers are joined in a network, people can share files and peripherals such as modems, printers, tape backup drives, or CD-ROM drives. When networks at multiple locations are connected using services available from phone companies, people can send e-mail, share links to the global Internet, or conduct video conferences in real time with other remote users. As companies rely on applications like electronic mail and database management for core business operations, computer networking becomes increasingly more important.

Every network includes:



• At least two computers Server or Client workstation.

• Networking Interface Card's (NIC)

• A connection medium, usually a wire or cable, although wireless communication between networked computers and peripherals is also possible.

• Network Operating system software, such as Microsoft Windows NT or 2000, Novell NetWare, Unix and Linux.

Types of Networks:

LANs (Local Area Networks)

A network is any collection of independent computers that communicate with one another over a shared network medium. LANs are networks usually confined to a geographic area, such as a single building or a college campus. LANs can be small, linking as few as three computers, but often link hundreds of computers used by thousands of people. The development of standard networking protocols and media has resulted in worldwide proliferation of LANs throughout business and educational organizations.

WANs (Wide Area Networks)

Wide area networking combines multiple LANs that are geographically separate. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone lines (both synchronous and asynchronous), satellite links, and data packet carrier services. Wide area networking can be as simple as a modem and remote access server for employees to dial into, or it can be as complex as hundreds of branch offices globally linked using special routing protocols and filters to minimize the expense of sending data sent over vast distances.

Internet

The Internet is a system of linked networks that are worldwide in scope and facilitate data communication services such as remote login, file transfer, electronic mail, the World Wide Web and newsgroups.



With the meteoric rise in demand for connectivity, the Internet has become a communications highway for millions of users. The Internet was initially restricted to military and academic institutions, but now it is a full-fledged conduit for any and all forms of information and commerce. Internet websites now provide personal, educational, political and economic resources to every corner of the planet.

Intranet

With the advancements made in browser-based software for the Internet, many private organizations are implementing intranets. An intranet is a private network utilizing Internet-type tools, but available only within that organization. For large organizations, an intranet provides an easy access mode to corporate information for employees.

MANs (Metropolitan area Networks)

The refers to a network of computers with in a City.

VPN (Virtual Private Network)

VPN uses a technique known as tunneling to transfer data securely on the Internet to a remote access server on your workplace network. Using a VPN helps you save money by using the public Internet instead of making long–distance phone calls to connect securely with your private network. There are two ways to create a VPN connection, by dialing an Internet service provider (ISP), or connecting directly to Internet.

Categories of Network:

Network can be divided in to two main categories:

• Peer-to-peer.

• Server – based.

In peer-to-peer networking there are no dedicated servers or hierarchy among the computers. All of the computers are equal and therefore known as peers. Normally each computer serves as Client/Server and there is no one assigned to be an administrator responsible for the entire network.



Peer-to-peer networks are good choices for needs of small organizations where the users are allocated in the same general area, security is not an issue and the organization and the network will have limited growth within the foreseeable future.



The term Client/server refers to the concept of sharing the work involved in processing data between the client computer and the most powerful server computer.

The client/server network is the most efficient way to provide:

• Databases and management of applications such as Spreadsheets, Accounting, Communications and Document management.

• Network management.

• Centralized file storage.

The client/server model is basically an implementation of distributed or cooperative processing. At the heart of the model is the concept of splitting application functions between a client and a server processor. The division of labor between the different processors enables the application designer to place an application function on the processor that is most appropriate for that function. This lets the software designer optimize the use of processors--providing the greatest possible return on investment for the hardware.



Client/server application design also lets the application provider mask the actual location of application function. The user often does not know where a specific operation is executing. The entire function may execute in either the PC or server, or the function may be split between them. This masking of application function locations enables system implementers to upgrade portions of a system over time with a minimum disruption of application operations, while protecting the investment in existing hardware and software.

The OSI Model:

Open System Interconnection (OSI) reference model has become an International standard and serves as a guide for networking. This model is the best known and most widely used guide to describe networking environments. Vendors design network products based on the specifications of the OSI model. It provides a description of how network hardware and software work together in a layered fashion to make communications possible. It also helps with trouble shooting by providing a frame of reference that describes how components are supposed to function.



There are seven to get familiar with and these are the physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and the application layer.

• Physical Layer, is just that the physical parts of the network such as wires, cables, and there media along with the length. Also this layer takes note of the electrical signals that transmit data throughout system.

• Data Link Layer, this layer is where we actually assign meaning to the electrical signals in the network. The layer also determines the size and format of data sent to printers, and other devices. Also I don't want to forget that these are also called nodes in the network. Another thing to consider in this layer is will also allow and define the error detection and correction schemes that insure data was sent and received.

• Network Layer, this layer provides the definition for the connection of two dissimilar networks.

• Transport Layer, this layer allows data to be broken into smaller packages for data to be distributed and addressed to other nodes (workstations).

• Session Layer, this layer helps out with the task to carry information from one node (workstation) to another node (workstation). A session has to be made before we can transport information to another computer.

• Presentation Layer, this layer is responsible to code and decode data sent to the node.

• Application Layer, this layer allows you to use an application that will communicate with say the operation system of a server. A good example would be using your web browser to interact with the operating system on a server such as Windows NT, which in turn gets the data you requested.

Network Architectures:

Ethernet

Ethernet is the most popular physical layer LAN technology in use today. Other LAN types include Token Ring, Fast Ethernet, Fiber Distributed Data Interface (FDDI), Asynchronous Transfer Mode (ATM) and LocalTalk. Ethernet is popular because it strikes a good balance between speed, cost and ease of installation. These benefits, combined with wide acceptance in the computer marketplace and the ability to support virtually all popular network protocols, make Ethernet an ideal networking technology for most computer users today. The Institute for Electrical and Electronic Engineers (IEEE) defines the Ethernet standard as IEEE Standard 802.3. This standard defines rules for configuring an Ethernet network as well as specifying how elements in an Ethernet network interact with one another. By adhering to the IEEE standard, network equipment and network protocols can communicate efficiently.

Fast Ethernet

For Ethernet networks that need higher transmission speeds, the Fast Ethernet standard (IEEE 802.3u) has been established. This standard raises the Ethernet speed limit from 10 Megabits per second (Mbps) to 100 Mbps with only minimal changes to the existing cable structure. There are three types of Fast Ethernet: 100BASE-TX for use with level 5 UTP cable, 100BASE-FX for use with fiber-optic cable, and 100BASE-T4 which utilizes an extra two wires for use with level 3 UTP cable. The 100BASE-TX standard has become the most popular due to its close compatibility with the 10BASE-T Ethernet standard. For the network manager, the incorporation of Fast Ethernet into an existing configuration presents a host of decisions. Managers must determine the number of users in each site on the network that need the higher throughput, decide which segments of the backbone need to be reconfigured specifically for 100BASE-T and then choose the necessary hardware to connect the 100BASE-T segments with existing 10BASE-T segments. Gigabit Ethernet is a future technology that promises a migration path beyond Fast Ethernet so the next generation of networks will support even higher data transfer speeds.

Token Ring

Token Ring is another form of network configuration which differs from Ethernet in that all messages are transferred in a unidirectional manner along the ring at all times. Data is transmitted in tokens, which are passed along the ring and viewed by each device. When a device sees a message addressed to it, that device copies the message and then marks that message as being read. As the message makes its way along the ring, it eventually gets back to the sender who now notes that the message was received by the intended device. The sender can then remove the message and free that token for use by others.



Various PC vendors have been proponents of Token Ring networks at different times and thus these types of networks have been implemented in many organizations.

FDDI

FDDI (Fiber-Distributed Data Interface) is a standard for data transmission on fiber optic lines in a local area network that can extend in range up to 200 km (124 miles). The FDDI protocol is based on the token ring protocol. In addition to being large geographically, an FDDI local area network can support thousands of users.

Protocols:

Network protocols are standards that allow computers to communicate. A protocol defines how computers identify one another on a network, the form that the data should take in transit, and how this information is processed once it reaches its final destination. Protocols also define procedures for handling lost or damaged transmissions or "packets." TCP/IP (for UNIX, Windows NT, Windows 95 and other platforms), IPX (for Novell NetWare), DECnet (for networking Digital Equipment Corp. computers), AppleTalk (for Macintosh computers), and NetBIOS/NetBEUI (for LAN Manager and Windows NT networks) are the main types of network protocols in use today.



Although each network protocol is different, they all share the same physical cabling. This common method of accessing the physical network allows multiple protocols to peacefully coexist over the network media, and allows the builder of a network to use common hardware for a variety of protocols. This concept is known as "protocol independence,"



Some Important Protocols and their job:

Protocol Acronym Its Job

Point-To-Point TCP/IP The backbone protocol of the internet. Popular also for intranets using the internet

Transmission Control Protocol/internet Protocol TCP/IP The backbone protocol of the internet. Popular also for intranets using the internet

Internetwork Package Exchange/Sequenced Packet Exchange IPX/SPX This is a standard protocol for Novell Network Operating System

NetBIOS Extended User Interface NetBEUI This is a Microsoft protocol that doesn't support routing to other networks

File Transfer Protocol FTP Used to send and receive files from a remote host

Hyper Transfer Protocol HTTP Used for the web to send documents that are encoded in HTML.

Network File Services NFS Allows network nodes or workstations to access files and drives as if they were their own.

Simple Mail Transfer Protocol SMTP Used to send Email over a network

Telnet Used to connect to a host and emulate a terminal that the remote server can recognize

Introduction to TCP/IP Networks:

TCP/IP-based networks play an increasingly important role in computer networks. Perhaps one reason for their appeal is that they are based on an open specification that is not controlled by any vendor.

What Is TCP/IP?

TCP stands for Transmission Control Protocol and IP stands for Internet Protocol. The term TCP/IP is not limited just to these two protocols, however. Frequently, the term TCP/IP is used to refer to a group of protocols related to the TCP and IP protocols such as the User Datagram Protocol (UDP), File Transfer Protocol (FTP), Terminal Emulation Protocol (TELNET), and so on.

The Origins of TCP/IP

In the late 1960s, DARPA (the Defense Advanced Research Project Agency), in the United States, noticed that there was a rapid proliferation of computers in military communications. Computers, because they can be easily programmed, provide flexibility in achieving network functions that is not available with other types of communications equipment. The computers then used in military communications were manufactured by different vendors and were designed to interoperate with computers from that vendor only. Vendors used proprietary protocols in their communications equipment. The military had a multi vendor network but no common protocol to support the heterogeneous equipment from different vendors

Net work Cables and Stuff:

In the network you will commonly find three types of cables used these are the, coaxial cable, fiber optic and twisted pair.

Thick Coaxial Cable

This type cable is usually yellow in color and used in what is called thicknets, and has two conductors. This coax can be used in 500-meter lengths. The cable itself is made up of a solid center wire with a braided metal shield and plastic sheathing protecting the rest of the wire.

Thin Coaxial Cable

As with the thick coaxial cable is used in thicknets the thin version is used in thinnets. This type cable is also used called or referred to as RG-58. The cable is really just a cheaper version of the thick cable.

Fiber Optic Cable

As we all know fiber optics are pretty darn cool and not cheap. This cable is smaller and can carry a vast amount of information fast and over long distances.

Twisted Pair Cables

These come in two flavors of unshielded and shielded.

Shielded Twisted Pair (STP)

Is more common in high-speed networks. The biggest difference you will see in the UTP and STP is that the STP use's metallic shield wrapping to protect the wire from interference.



-Something else to note about these cables is that they are defined in numbers also. The bigger the number the better the protection from interference. Most networks should go with no less than a CAT 3 and CAT 5 is most recommended.



-Now you know about cables we need to know about connectors. This is pretty important and you will most likely need the RJ-45 connector. This is the cousin of the phone jack connector and looks real similar with the exception that the RJ-45 is bigger. Most commonly your connector are in two flavors and this is BNC (Bayonet Naur Connector) used in thicknets and the RJ-45 used in smaller networks using UTP/STP.

Unshielded Twisted Pair (UTP)

This is the most popular form of cables in the network and the cheapest form that you can go with. The UTP has four pairs of wires and all inside plastic sheathing. The biggest reason that we call it Twisted Pair is to protect the wires from interference from themselves. Each wire is only protected with a thin plastic sheath.

Ethernet Cabling

Now to familiarize you with more on the Ethernet and it's cabling we need to look at the 10's. 10Base2, is considered the thin Ethernet, thinnet, and thinwire which uses light coaxial cable to create a 10 Mbps network. The cable segments in this network can't be over 185 meters in length. These cables connect with the BNC connector. Also as a note these unused connection must have a terminator, which will be a 50-ohm terminator.



10Base5, this is considered a thicknet and is used with coaxial cable arrangement such as the BNC connector. The good side to the coaxial cable is the high-speed transfer and cable segments can be up to 500 meters between nodes/workstations. You will typically see the same speed as the 10Base2 but larger cable lengths for more versatility.



10BaseT, the “T” stands for twisted as in UTP (Unshielded Twisted Pair) and uses this for 10Mbps of transfer. The down side to this is you can only have cable lengths of 100 meters between nodes/workstations. The good side to this network is they are easy to set up and cheap! This is why they are so common an ideal for small offices or homes.



100BaseT, is considered Fast Ethernet uses STP (Shielded Twisted Pair) reaching data transfer of 100Mbps. This system is a little more expensive but still remains popular as the 10BaseT and cheaper than most other type networks. This on of course would be the cheap fast version.



10BaseF, this little guy has the advantage of fiber optics and the F stands for just that. This arrangement is a little more complicated and uses special connectors and NIC's along with hubs to create its network. Pretty darn neat and not to cheap on the wallet.



An important part of designing and installing an Ethernet is selecting the appropriate Ethernet medium. There are four major types of media in use today: Thickwire for 10BASE5 networks, thin coax for 10BASE2 networks, unshielded twisted pair (UTP) for 10BASE-T networks and fiber optic for 10BASE-FL or Fiber-Optic Inter-Repeater Link (FOIRL) networks. This wide variety of media reflects the evolution of Ethernet and also points to the technology's flexibility. Thickwire was one of the first cabling systems used in Ethernet but was expensive and difficult to use. This evolved to thin coax, which is easier to work with and less expensive.

Network Topologies:

What is a Network topology?

A network topology is the geometric arrangement of nodes and cable links in a LAN,



There are three topology's to think about when you get into networks. These are the star, rind, and the bus.



Star, in a star topology each node has a dedicated set of wires connecting it to a central network hub. Since all traffic passes through the hub, the hub becomes a central point for isolating network problems and gathering network statistics.



Ring, a ring topology features a logically closed loop. Data packets travel in a single direction around the ring from one network device to the next. Each network device acts as a repeater, meaning it regenerates the signal



Bus, the bus topology, each node (computer, server, peripheral etc.) attaches directly to a common cable. This topology most often serves as the backbone for a network. In some instances, such as in classrooms or labs, a bus will connect small workgroups

Collisions:

Ethernet is a shared media, so there are rules for sending packets of data to avoid conflicts and protect data integrity. Nodes determine when the network is available for sending packets. It is possible that two nodes at different locations attempt to send data at the same time. When both PCs are transferring a packet to the network at the same time, a collision will result.



Minimizing collisions is a crucial element in the design and operation of networks. Increased collisions are often the result of too many users on the network, which results in a lot of contention for network bandwidth. This can slow the performance of the network from the user's point of view. Segmenting the network, where a network is divided into different pieces joined together logically with a bridge or switch, is one way of reducing an overcrowded network.

Ethernet Products:

The standards and technology that have just been discussed help define the specific products that network managers use to build Ethernet networks. The following text discusses the key products needed to build an Ethernet LAN.

Transceivers

Transceivers are used to connect nodes to the various Ethernet media. Most computers and network interface cards contain a built-in 10BASE-T or 10BASE2 transceiver, allowing them to be connected directly to Ethernet without requiring an external transceiver. Many Ethernet devices provide an AUI connector to allow the user to connect to any media type via an external transceiver. The AUI connector consists of a 15-pin D-shell type connector, female on the computer side, male on the transceiver side. Thickwire (10BASE5) cables also use transceivers to allow connections.



For Fast Ethernet networks, a new interface called the MII (Media Independent Interface) was developed to offer a flexible way to support 100 Mbps connections. The MII is a popular way to connect 100BASE-FX links to copper-based Fast Ethernet devices.

Network Interface Cards:

Network interface cards, commonly referred to as NICs, and are used to connect a PC to a network. The NIC provides a physical connection between the networking cable and the computer's internal bus. Different computers have different bus architectures; PCI bus master slots are most commonly found on 486/Pentium PCs and ISA expansion slots are commonly found on 386 and older PCs. NICs come in three basic varieties: 8-bit, 16-bit, and 32-bit. The larger the number of bits that can be transferred to the NIC, the faster the NIC can transfer data to the network cable.



Many NIC adapters comply with Plug-n-Play specifications. On these systems, NICs are automatically configured without user intervention, while on non-Plug-n-Play systems, configuration is done manually through a setup program and/or DIP switches.



Cards are available to support almost all networking standards, including the latest Fast Ethernet environment. Fast Ethernet NICs are often 10/100 capable, and will automatically set to the appropriate speed. Full duplex networking is another option, where a dedicated connection to a switch allows a NIC to operate at twice the speed.

Hubs/Repeaters:

Hubs/repeaters are used to connect together two or more Ethernet segments of any media type. In larger designs, signal quality begins to deteriorate as segments exceed their maximum length. Hubs provide the signal amplification required to allow a segment to be extended a greater distance. A hub takes any incoming signal and repeats it out all ports.



Ethernet hubs are necessary in star topologies such as 10BASE-T. A multi-port twisted pair hub allows several point-to-point segments to be joined into one network. One end of the point-to-point link is attached to the hub and the other is attached to the computer. If the hub is attached to a backbone, then all computers at the end of the twisted pair segments can communicate with all the hosts on the backbone. The number and type of hubs in any one-collision domain is limited by the Ethernet rules. These repeater rules are discussed in more detail later.

Network Type Max Nodes

Per Segment Max Distance

Per Segment

10BASE-T

10BASE2

10BASE5

10BASE-FL 2

30

100

2 100m

185m

500m

2000m

Adding Speed:

While repeaters allow LANs to extend beyond normal distance limitations, they still limit the number of nodes that can be supported. Bridges and switches, however, allow LANs to grow significantly larger by virtue of their ability to support full Ethernet segments on each port. Additionally, bridges and switches selectively filter network traffic to only those packets needed on each segment - this significantly increases throughput on each segment and on the overall network. By providing better performance and more flexibility for network topologies, bridges and switches will continue to gain popularity among network managers.

Bridges:

The function of a bridge is to connect separate networks together. Bridges connect different networks types (such as Ethernet and Fast Ethernet) or networks of the same type. Bridges map the Ethernet addresses of the nodes residing on each network segment and allow only necessary traffic to pass through the bridge. When a packet is received by the bridge, the bridge determines the destination and source segments. If the segments are the same, the packet is dropped ("filtered"); if the segments are different, then the packet is "forwarded" to the correct segment. Additionally, bridges do not forward bad or misaligned packets.



Bridges are also called "store-and-forward" devices because they look at the whole Ethernet packet before making filtering or forwarding decisions. Filtering packets, and regenerating forwarded packets enable bridging technology to split a network into separate collision domains. This allows for greater distances and more repeaters to be used in the total network design.

Ethernet Switches:

Ethernet switches are an expansion of the concept in Ethernet bridging. LAN switches can link four, six, ten or more networks together, and have two basic architectures: cut-through and store-and-forward. In the past, cut-through switches were faster because they examined the packet destination address only before forwarding it on to its destination segment. A store-and-forward switch, on the other hand, accepts and analyzes the entire packet before forwarding it to its destination.



It takes more time to examine the entire packet, but it allows the switch to catch certain packet errors and keep them from propagating through the network. Both cut-through and store-and-forward switches separate a network into collision domains, allowing network design rules to be extended. Each of the segments attached to an Ethernet switch has a full 10 Mbps of bandwidth shared by fewer users, which results in better performance (as opposed to hubs that only allow bandwidth sharing from a single Ethernet). Newer switches today offer high-speed links, FDDI, Fast Ethernet or ATM. These are used to link switches together or give added bandwidth to high-traffic servers. A network composed of a number of switches linked together via uplinks is termed a "collapsed backbone" network.

Routers:

Routers filter out network traffic by specific protocol rather than by packet address. Routers also divide networks logically instead of physically. An IP router can divide a network into various subnets so that only traffic destined for particular IP addresses can pass between segments. Network speed often decreases due to this type of intelligent forwarding. Such filtering takes more time than that exercised in a switch or bridge, which only looks at the Ethernet address. However, in more complex networks, overall efficiency is improved by using routers.

What is a network firewall?

A firewall is a system or group of systems that enforces an access control policy between two networks. The actual means by which this is accomplished varies widely, but in principle, the firewall can be thought of as a pair of mechanisms: one which exists to block traffic, and the other which exists to permit traffic. Some firewalls place a greater emphasis on blocking traffic, while others emphasize permitting traffic. Probably the most important thing to recognize about a firewall is that it implements an access control policy. If you don't have a good idea of what kind of access you want to allow or to deny, a firewall really won't help you. It's also important to recognize that the firewall's configuration, because it is a mechanism for enforcing policy, imposes its policy on everything behind it. Administrators for firewalls managing the connectivity for a large number of hosts therefore have a heavy responsibility.

Network Design Criteria:

Ethernets and Fast Ethernets have design rules that must be followed in order to function correctly. Maximum number of nodes, number of repeaters and maximum segment distances are defined by the electrical and mechanical design properties of each type of Ethernet and Fast Ethernet media.



A network using repeaters, for instance, functions with the timing constraints of Ethernet. Although electrical signals on the Ethernet media travel near the speed of light, it still takes a finite time for the signal to travel from one end of a large Ethernet to another. The Ethernet standard assumes it will take roughly 50 microseconds for a signal to reach its destination.



Ethernet is subject to the "5-4-3" rule of repeater placement: the network can only have five segments connected; it can only use four repeaters; and of the five segments, only three can have users attached to them; the other two must be inter-repeater links.



If the design of the network violates these repeater and placement rules, then timing guidelines will not be met and the sending station will resend that packet. This can lead to lost packets and excessive resent packets, which can slow network performance and create trouble for applications. Fast Ethernet has modified repeater rules, since the minimum packet size takes less time to transmit than regular Ethernet. The length of the network links allows for a fewer number of repeaters. In Fast Ethernet networks, there are two classes of repeaters. Class I repeaters have a latency of 0.7 microseconds or less and are limited to one repeater per network. Class II repeaters have a latency of 0.46 microseconds or less and are limited to two repeaters per network. The following are the distance (diameter) characteristics for these types of Fast Ethernet repeater combinations:

Fast Ethernet Copper Fiber

No Repeaters

One Class I Repeater

One Class II Repeater

Two Class II Repeaters 100m

200m

200m

205m 412m*

272m

272m

228m

* Full Duplex Mode 2 km





When conditions require greater distances or an increase in the number of nodes/repeaters, then a bridge, router or switch can be used to connect multiple networks together. These devices join two or more separate networks, allowing network design criteria to be restored. Switches allow network designers to build large networks that function well. The reduction in costs of bridges and switches reduces the impact of repeater rules on network design.



Each network connected via one of these devices is referred to as a separate collision domain in the overall network.

Types of Servers:

Device Servers

A device server is defined as a specialized, network-based hardware device designed to perform a single or specialized set of server functions. It is characterized by a minimal operating architecture that requires no per seat network operating system license, and client access that is independent of any operating system or proprietary protocol. In addition the device server is a "closed box," delivering extreme ease of installation, minimal maintenance, and can be managed by the client remotely via a Web browser.



Print servers, terminal servers, remote access servers and network time servers are examples of device servers which are specialized for particular functions. Each of these types of servers has unique configuration attributes in hardware or software that help them to perform best in their particular arena.

Print Servers

Print servers allow printers to be shared by other users on the network. Supporting either parallel and/or serial interfaces, a print server accepts print jobs from any person on the network using supported protocols and manages those jobs on each appropriate printer.



Print servers generally do not contain a large amount of memory; printers simply store information in a queue. When the desired printer becomes available, they allow the host to transmit the data to the appropriate printer port on the server. The print server can then simply queue and print each job in the order in which print requests are received, regardless of protocol used or the size of the job.

Multiport Device Servers

Devices that are attached to a network through a multiport device server can be shared between terminals and hosts at both the local site and throughout the network. A single terminal may be connected to several hosts at the same time (in multiple concurrent sessions), and can switch between them. Multiport device servers are also used to network devices that have only serial outputs. A connection between serial ports on different servers is opened, allowing data to move between the two devices.



Given its natural translation ability, a multi-protocol multiport device server can perform conversions between the protocols it knows, like LAT and TCP/IP. While server bandwidth is not adequate for large file transfers, it can easily handle host-to-host inquiry/response applications, electronic mailbox checking, etc. And it is far more economical than the alternatives of acquiring expensive host software and special-purpose converters. Multiport device and print servers give their users greater flexibility in configuring and managing their networks.



Whether it is moving printers and other peripherals from one network to another, expanding the dimensions of interoperability or preparing for growth, multiport device servers can fulfill your needs, all without major rewiring.

Access Servers

While Ethernet is limited to a geographic area, remote users such as traveling sales people need access to network-based resources. Remote LAN access, or remote access, is a popular way to provide this connectivity. Access servers use telephone services to link a user or office with an office network. Dial-up remote access solutions such as ISDN or asynchronous dial introduce more flexibility. Dial-up remote access offers both the remote office and the remote user the economy and flexibility of "pay as you go" telephone services. ISDN is a special telephone service that offers three channels, two 64 Kbps "B" channels for user data and a "D" channel for setting up the connection. With ISDN, the B channels can be combined for double bandwidth or separated for different applications or users. With asynchronous remote access, regular telephone lines are combined with modems and remote access servers to allow users and networks to dial anywhere in the world and have data access. Remote access servers provide connection points for both dial-in and dial-out applications on the network to which they are attached. These hybrid devices route and filter protocols and offer other services such as modem pooling and terminal/printer services. For the remote PC user, one can connect from any available telephone jack (RJ45), including those in a hotel rooms or on most airplanes.

Network Time Servers

A network time server is a server specialized in the handling of timing information from sources such as satellites or radio broadcasts and is capable of providing this timing data to its attached network. Specialized protocols such as NTP or udp/time allow a time server to communicate to other network nodes ensuring that activities that must be coordinated according to their time of execution are synchronized correctly. GPS satellites are one source of information that can allow global installations to achieve constant timing.

IP Addressing:

An IP (Internet Protocol) address is a unique identifier for a node or host connection on an IP network. An IP address is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 (known as octets) separated by decimal points. This is known as "dotted decimal" notation.



Example: 140.179.220.200



It is sometimes useful to view the values in their binary form.



140 .179 .220 .200



10001100.10110011.11011100.11001000



Every IP address consists of two parts, one identifying the network and one identifying the node. The Class of the address and the subnet mask determine which part belongs to the network address and which part belongs to the node address.

Address Classes:

There are 5 different address classes. You can determine which class any IP address is in by examining the first 4 bits of the IP address.



Class A addresses begin with 0xxx, or 1 to 126 decimal.



Class B addresses begin with 10xx, or 128 to 191 decimal.



Class C addresses begin with 110x, or 192 to 223 decimal.



Class D addresses begin with 1110, or 224 to 239 decimal.



Class E addresses begin with 1111, or 240 to 254 decimal.



Addresses beginning with 01111111, or 127 decimal, are reserved for loopback and for internal testing on a local machine. [You can test this: you should always be able to ping 127.0.0.1, which points to yourself] Class D addresses are reserved for multicasting. Class E addresses are reserved for future use. They should not be used for host addresses.



Now we can see how the Class determines, by default, which part of the IP address belongs to the network (N) and which part belongs to the node (n).



Class A -- NNNNNNNN.nnnnnnnn.nnnnnnn.nnnnnnn



Class B -- NNNNNNNN.NNNNNNNN.nnnnnnnn.nnnnnnnn



Class C -- NNNNNNNN.NNNNNNNN.NNNNNNNN.nnnnnnnn



In the example, 140.179.220.200 is a Class B address so by default the Network part of the address (also known as the Network Address) is defined by the first two octets (140.179.x.x) and the node part is defined by the last 2 octets (x.x.220.200).



In order to specify the network address for a given IP address, the node section is set to all "0"s. In our example, 140.179.0.0 specifies the network address for 140.179.220.200. When the node section is set to all "1"s, it specifies a broadcast that is sent to all hosts on the network. 140.179.255.255 specifies the example broadcast address. Note that this is true regardless of the length of the node section.

Private Subnets:

There are three IP network addresses reserved for private networks. The addresses are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. They can be used by anyone setting up internal IP networks, such as a lab or home LAN behind a NAT or proxy server or a router. It is always safe to use these because routers on the Internet will never forward packets coming from these addresses



Subnetting an IP Network can be done for a variety of reasons, including organization, use of different physical media (such as Ethernet, FDDI, WAN, etc.), preservation of address space, and security. The most common reason is to control network traffic. In an Ethernet network, all nodes on a segment see all the packets transmitted by all the other nodes on that segment. Performance can be adversely affected under heavy traffic loads, due to collisions and the resulting retransmissions. A router is used to connect IP networks to minimize the amount of traffic each segment must receive.

Subnet Masking

Applying a subnet mask to an IP address allows you to identify the network and node parts of the address. The network bits are represented by the 1s in the mask, and the node bits are represented by the 0s. Performing a bitwise logical AND operation between the IP address and the subnet mask results in the Network Address or Number.



For example, using our test IP address and the default Class B subnet mask, we get:



10001100.10110011.11110000.11001000 140.179.240.200 Class B IP Address



11111111.11111111.00000000.00000000 255.255.000.000 Default Class B Subnet Mask



10001100.10110011.00000000.00000000 140.179.000.000 Network Address

Default subnet masks:

Class A - 255.0.0.0 - 11111111.00000000.00000000.00000000



Class B - 255.255.0.0 - 11111111.11111111.00000000.00000000



Class C - 255.255.255.0 - 11111111.11111111.11111111.00000000



CIDR -- Classless InterDomain Routing.



CIDR was invented several years ago to keep the internet from running out of IP addresses. The "classful" system of allocating IP addresses can be very wasteful; anyone who could reasonably show a need for more that 254 host addresses was given a Class B address block of 65533 host addresses. Even more wasteful were companies and organizations that were allocated Class A address blocks, which contain over 16 Million host addresses! Only a tiny percentage of the allocated Class A and Class B address space has ever been actually assigned to a host computer on the Internet.



People realized that addresses could be conserved if the class system was eliminated. By accurately allocating only the amount of address space that was actually needed, the address space crisis could be avoided for many years. This was first proposed in 1992 as a scheme called Supernetting.



The use of a CIDR notated address is the same as for a Classful address. Classful addresses can easily be written in CIDR notation (Class A = /8, Class B = /16, and Class C = /24)



It is currently almost impossible for an individual or company to be allocated their own IP address blocks. You will simply be told to get them from your ISP. The reason for this is the ever-growing size of the internet routing table. Just 5 years ago, there were less than 5000 network routes in the entire Internet. Today, there are over 90,000. Using CIDR, the biggest ISPs are allocated large chunks of address space (usually with a subnet mask of /19 or even smaller); the ISP's customers (often other, smaller ISPs) are then allocated networks from the big ISP's pool. That way, all the big ISP's customers (and their customers, and so on) are accessible via 1 network route on the Internet.



It is expected that CIDR will keep the Internet happily in IP addresses for the next few years at least. After that, IPv6, with 128 bit addresses, will be needed. Under IPv6, even sloppy address allocation would comfortably allow a billion unique IP addresses for every person on earth

Examining your network with commands:

Ping



PING is used to check for a response from another computer on the network. It can tell you a great deal of information about the status of the network and the computers you are communicating with.



Ping returns different responses depending on the computer in question. The responses are similar depending on the options used.



Ping uses IP to request a response from the host. It does not use TCP



.It takes its name from a submarine sonar search - you send a short sound burst and listen for an echo - a ping - coming back.



In an IP network, `ping' sends a short data burst - a single packet - and listens for a single packet in reply. Since this tests the most basic function of an IP network (delivery of single packet), it's easy to see how you can learn a lot from some `pings'.



To stop ping, type control-c. This terminates the program and prints out a nice summary of the number of packets transmitted, the number received, and the percentage of packets lost, plus the minimum, average, and maximum round-trip times of the packets.



Sample ping session



PING localhost (127.0.0.1): 56 data bytes

64 bytes from 127.0.0.1: icmp_seq=0 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=1 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=2 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=3 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=4 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=5 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=6 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=7 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=8 ttl=255 time=2 ms

64 bytes from 127.0.0.1: icmp_seq=9 ttl=255 time=2 ms



localhost ping statistics



10 packets transmitted, 10 packets received, 0% packet loss

round-trip min/avg/max = 2/2/2 ms

meikro$



The Time To Live (TTL) field can be interesting. The main purpose of this is so that a packet doesn't live forever on the network and will eventually die when it is deemed "lost." But for us, it provides additional information. We can use the TTL to determine approximately how many router hops the packet has gone through. In this case it's 255 minus N hops, where N is the TTL of the returning Echo Replies. If the TTL field varies in successive pings, it could indicate that the successive reply packets are going via different routes, which isn't a great thing.



The time field is an indication of the round-trip time to get a packet to the remote host. The reply is measured in milliseconds. In general, it's best if round-trip times are under 200 milliseconds. The time it takes a packet to reach its destination is called latency. If you see a large variance in the round-trip times (which is called "jitter"), you are going to see poor performance talking to the host

NSLOOKUP

NSLOOKUP is an application that facilitates looking up hostnames on the network. It can reveal the IP address of a host or, using the IP address, return the host name.



It is very important when troubleshooting problems on a network that you can verify the components of the networking process. Nslookup allows this by revealing details within the infrastructure.

NETSTAT

NETSTAT is used to look up the various active connections within a computer. It is helpful to understand what computers or networks you are connected to. This allows you to further investigate problems. One host may be responding well but another may be less responsive.

IPconfig

This is a Microsoft windows NT, 2000 command. It is very useful in determining what could be wrong with a network.



This command when used with the /all switch, reveal enormous amounts of troubleshooting information within the system.



Windows 2000 IP Configuration



Host Name . . . . . . . . . . . . : cowder

Primary DNS Suffix . . . . . . . :

Node Type . . . . . . . . . . . . : Broadcast

IP Routing Enabled. . . . . . . . : No

WINS Proxy Enabled. . . . . . . . : No

WINS Proxy Enabled. . . . . . . . : No

Connection-specific DNS Suffix . :

Description . . . . . . . . . . . :

WAN (PPP/SLIP) Interface

Physical Address. . . . . . . . . : 00-53-45-00-00-00

DHCP Enabled. . . . . . . . . . . : No

IP Address. . . . . . . . . . . . : 12.90.108.123

Subnet Mask . . . . . . . . . . . : 255.255.255.255

Default Gateway . . . . . . . . . : 12.90.108.125

DNS Servers . . . . . . . . . . . : 12.102.244.2

204.127.129.2

Traceroute

Traceroute on Unix and Linux (or tracert in the Microsoft world) attempts to trace the current network path to a destination. Here is an example of a traceroute run to www.berkeley.edu:



$ traceroute www.berkeley.edu



traceroute to amber.Berkeley.EDU (128.32.25.12), 30 hops max, 40 byte packets



1 sf1-e3.wired.net (206.221.193.1) 3.135 ms 3.021 ms 3.616 ms



2 sf0-e2s2.wired.net (205.227.206.33) 1.829 ms 3.886 ms 2.772 ms



3 paloalto-cr10.bbnplanet.net (131.119.26.105) 5.327 ms 4.597 ms 5.729 ms



4 paloalto-br1.bbnplanet.net (131.119.0.193) 4.842 ms 4.615 ms 3.425 ms



5 sl-sj-2.sprintlink.net (4.0.1.66) 7.488 ms 38.804 ms 7.708 ms



6 144.232.8.81 (144.232.8.81) 6.560 ms 6.631 ms 6.565 ms



7 144.232.4.97 (144.232.4.97) 7.638 ms 7.948 ms 8.129 ms



8 144.228.146.50 (144.228.146.50) 9.504 ms 12.684 ms 16.648 ms



9 f5-0.inr-666-eva.berkeley.edu (198.128.16.21) 9.762 ms 10.611 ms 10.403 ms



10 f0-0.inr-107-eva.Berkeley.EDU (128.32.2.1) 11.478 ms 10.868 ms 9.367 ms



11 f8-0.inr-100-eva.Berkeley.EDU (128.32.235.100) 10.738 ms 11.693 ms 12.520 ms





Windows Internet Name Service (WINS) is Microsoft's implementation of NetBIOS Name Service (NBNS), a name server and service for NetBIOS computer names. Effectively WINS is to NetBIOS names, what DNS is to domain names — a central mapping of host names to network addresses. Like DNS it is broken into two parts, a Server Service (that manages the encoded Jet Database, server to server replication, service requests, and conflicts) and a TCP/IP Client component which manages the client's registration and renewal of names, and takes care of queries.

Network address mappings are dynamically updated so that when a client needs to contact another computer on the network it can get its up-to-date IP address which may be issued by a DHCP server, aside from this the WINS functionality provides a way of keeping the client names unique on the network.

Networks normally have more than one WINS server and each WINS server should be in push/pull replication; where more than two WINS servers are required the best practice replication model is the hub and spoke, thus the WINS design is not central but distributed. Each WINS server holds a full copy of every other related WINS system's records. There is no hierarchy in WINS (unlike DNS), but like DNS its database can be queried for the address to contact rather than broadcasting a request for which address to contact. The system therefore reduces broadcast traffic on the network, however replication traffic can add to WAN/LAN traffic, although this can be set to replicate in non busy periods. By design any WINS client can register any name with any WINS server. This makes the system prone to abuse or unreliable through poor administration.

All WINS clients should be configured to use a primary WINS server and a different secondary WINS server. The secondary would normally be the hub server, The setting of which WINS servers to use is either in the DHCP scope options or a per client hard coded value.

As of Windows 2000, DNS provides the favored alternative to WINS, as part of Active Directory

In theory, if DNS is available, WINS is only necessary if pre-Windows 2000 clients or servers need to resolve names. In reality, especially in large enterprise environments, applications such as SMS 2003 with its use of the 1A record, SQL Server 2000 for use of named pipes, and Exchange Server 2000 and 2003 both require WINS for full functionality.

The WINS server from Microsoft is only available as a service to run on the Windows Server family of operating systems. The WINS client from Microsoft is common across all its operating systems including DOS. WINS clients can also be devices such as IP phones and printers



Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network.

DHCP assigns an IP address when a system is started, for example:

A user turns on a computer with a DHCP client.

The client computer sends a broadcast request (called a DISCOVER or DHCPDISCOVER), looking for a DHCP server to answer.

The router directs the DISCOVER packet to the correct DHCP server.

The server receives the DISCOVER packet. Based on availability and usage policies set on the server, the server determines an appropriate address (if any) to give to the client. The server then temporarily reserves that address for the client and sends back to the client an OFFER (or DHCPOFFER) packet, with that address information. The server also configures the client's DNS servers, WINS servers, and sometimes other services as well.

The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know that it intends to use the address.

The server sends an ACK (or DHCPACK) packet, confirming that the client has a been given a lease on the address for a server-specified period of time.

When a computer uses a static IP address, it means that the computer is manually configured to use a specific IP address. One problem with static assignment, which can result from user error or inattention to detail, occurs when two computers are configured with the same IP address. This creates a conflict that results in loss of service. Using DHCP to dynamically assign IP addresses minimizes these conflicts.

Why DHCP

1. Networks with large numbers of workstations that are not permanently on line (e.g. customers-workstations-of ISP that connect only when required).

2. There are more workstations (customers) than there are public ip numbers available in an ISP.

3. DHCP's purpose is to enable individual computers on an IP network to extract their configurations from a server (the 'DHCP server') or servers, in particular, servers that have no exact information about the individual computers until they request the information. The overall purpose of this is to reduce the work necessary to administer a large IP network. The most significant piece of information distributed in this manner is the IP address.

What is a DHCP lease?

A DHCP lease is the amount of time that the DHCP server grants to the DHCP client permission to use a particular IP address. A typical server allows its administrator to set the lease time.

Netwok Basic

Networking is the practice of linking computing devices together with hardware and software that supports data communications across these devices.

There are two main types of the computer networking client-server and peer to peer. In the client server computing, a computer plays a major role known as server, where the files, data in the form of web pages, docs or spread sheet files, video, database & resources are placed.

All the other computers in the client/server networks are called clients and they get the data from the server. In the peer to peer networks all the computers play the same role and no computer act as a centralized server. In the major businesses around the world client-server networks model is in major use.

A network topology defines the structure, design or layout of a network. There are different topologies like bus, ring, star, mesh, hybrid etc. The star topology is most commonly used topology. In the star topology, all the computers in the network are connected with a centralized device such as hub or switch. Thus forms a star like structure. If the hubs/switch fails to work for any reason then all the connectivity and communication between the computers will be halted.

A common communication language is used by the computers and the communication devices is known as protocols. The most commonly used and popular protocol on the internet and in the home and other networks is called TCP/IP. TCP/IP is not a single protocol but it is a suite of several protocols. A computer network can be a wired or wireless and TCP/IP protocol can work both in types of a network. Data flow or communication can be divided into seven logical layers called OSI layers model that was developed by Intel and Xerox Corporation and was standardized by ISO.

1. Application layer

2. Presentation layer

3. Session layer

4. Transport layer

5. Network layer

6. Data Link layer

a. Media access control sub-layer

b. Logical link control sub-layer

7. Physical layer

A network can be divided into different scales and ranges and it depends on the requirement of the organization and the geographical location. Computer Network can be divided into Local Area Network, Personal Area Network, Campus Area Network, Wireless Local Area Network, Metropolitan Area Network and Wide Area Network.



There are several communication connection methods like Home PNA, Power line communication, Ethernet and Wi-Fi connection method.

A network can also be categorized into several different types based on the services it provides like Server farms, Storage area networks, Value control networks, Value-Added networks, SOHO networks, Wireless and Jungle networks.



I have explained the basic and advance data communication technologies, Router commands, communication devices, certifications, IP addressing basics, subnetting, networking tips, networking interview questions, windows networking, mobile technology and wireless computing. I have tried to cover all the hot topics in the area of computer networking so that maximum users can get benefit from this website.

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Local area network (LAN): A computer network that covers a relatively small area. Most LANs cover a single building or group of buildings. A system of LANs can be connected over any distance through telephone lines and radio waves, creating a wide-area network.



Workgroup: In computer networking, a workgroup is a collection of computers on a local area network (LAN) that share common resources and responsibilities. The Microsoft Windows family of operating systems supports assigning of personal computers to named workgroups



MAC Address In TCP/IP computer networks, each device possesses a Media Access Control (MAC) address used to uniquely identify the network adapter hardware.

MAC is the technology used for access control and identification of computers on an Internet Protocol (IP) network.

The MAC address is used by network adapters to uniquely identify themselves on a LAN. MAC addresses are 12-digit hexadecimal numbers that map to IP addresses through an address resolution protocol (ARP).

TCP/IP is an extremely popular network protocol that enables communication between most of today's computers. Did you know that TCP/IP is over 30 years old

Definition TCP/IP : Transmission Control Protocol (TCP) and Internet Protocol (IP) are two distinct network protocols, technically speaking. TCP and IP are so commonly used together; however, that TCP/IP has become standard terminology to refer to either or both of the protocols.

IP addresses are the fundamental method for computers to identify themselves on the Internet and many other computer networks.

An IP address is a logical address of a network adapter. Home computers and many other devices acquire IP addresses to join Internet Protocol networks.

IP corresponds to the Network layer (Layer 3) in the OSI model, whereas TCP corresponds to the Transport layer (Layer 4) in OSI. In other words, the term TCP/IP refers to network communications where the TCP transport is used to deliver data across IP networks.

The average person on the Internet works in a predominately TCP/IP environment. Web browsers, for example, use TCP/IP to communicate with Web servers.

IP (Internet Protocol) is the primary network protocol used on the Internet, developed in the 1970s. On the Internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.

IP supports unique addressing for computers on a network. Most networks use the Internet Protocol version 4 (IPv4) standards that features IP addresses four bytes (32 bits) in length. The newer Internet Protocol version 6 (IPv6) standard features addresses 16 bytes (128 bits) in length.







An IP address is considered private if the IP number falls within one of the IP address ranges reserved for private uses by Internet standards groups. These private IP address ranges exist:

10.0.0.0 through 10.255.255.255

169.254.0.0 through 169.254.255.255 (APIPA only)

172.16.0.0 through 172.31.255.255

192.168.0.0 through 192.168.255.255

Private IP addresses are typically used on local networks including home, school and business LANs including airports and hotels.

Devices with private IP addresses cannot connect directly to the Internet. Likewise, computers outside the local network cannot connect directly to a device with a private IP. Instead, access to such devices must be brokered by a router or similar device that supports

Subnet : A subnet is a logical grouping of connected network devices. When a subnet is properly implemented, both the performance and security of networks can be improved.

Network/Subnet Masks

A network mask helps you which portion of the address identifies the network portion and the host portion of an IP address. The three different classes of the IP addresses have their own default masks as shown below.

Class Subnet Mask

Class A: 255.0.0.0

Class B: 255.255.0.0

Class C: 255.255.255.0

Default Gateway: In computer networking, a default gateway is the device that passes traffic from the local subnet to devices on other subnets. The default gateway often connects a local network to the Internet, although internal gateways for local networks also exist.

Ping is the name of a standard software utility (tool) used to test network connections. It can be used to determine if a remote device (such as Web or game server) can be reached across the network and, if so, the connection's latency. Ping tools are part of Windows, Mac OS X and Linux as well as some routers and game consoles.



Most ping tools use Internet Control Message Protocol (ICMP). They send request messages to a target network address at periodic intervals and measure the time it takes for a response message to arrive. These tools typically support options like



DNS - Domain Name System

DNS technology allows hosts on TCP/IP networks (such as Internet Web sites) to be addressed by names. DNS includes a network protocol and a distributed data store for lookup of host names and addresses.

DNS technology allows hosts on TCP/IP networks (such as Internet Web sites) to be addressed by names. DNS includes a network protocol and a distributed data store for lookup of host names and addresses.

DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites.

A DNS server is a special type of computer on the Internet used to support the Domain Name System. Numerous DNS servers across the Internet maintain a distributed database of domain names and IP addresses.

A DNS cache is a small database maintained by a computer's operating system. The database contains records of all recently accessed Internet domains.



RJ-45 connectors are the ones you are most likely going to encounter in your network travels. RJ-45 connectors are used with twisted-pair cabling, the most prevalent network cable in use today. RJ-45 connectors resemble the aforementioned RJ-11 phone jacks, but support up to eight wires instead of the six supported by RJ-11 connectors. RJ-45 connectors are also larger. Figure 6 shows the RJ-45 connectors.



switches are the connectivity points of an Ethernet network. Devices connect to switches via twisted-pair cabling, one cable for each device. The difference between hubs and switches is in how the devices deal with the data that they receive. Whereas a hub forwards the data it receives to all of the ports on the device, a switch forwards it only to the port that connects to the destination device. It does this by learning the MAC address of the devices attached to it, and then by matching the destination MAC address in the data it receives. Figure 1 shows how a switch works

Routers In a common configuration, routers are used to create larger networks by joining two network segments. Such as a SOHO (small office and home network) router used to connect a user to the Internet. A router can be a dedicated hardware device or a computer system with more than one network interface and the appropriate routing software. All modern network operating systems include the functionality to act as a router.

A router derives its name from the fact that it can route data it receives from one network onto another. When a router receives a packet of data, it reads the header of the packet to determine the destination address. Once it has determined the address, it looks in its routing table to determine whether it knows how to reach the destination and, if it does, it forwards the packet to the next hop on the route. The next hop might be the final destination, or it might be another router