Artikel ini adalah tutorial singkat mengenai instalasi Windows Server
2003 ke komputer PC untuk digunakan dalam sistem Voucha II. Jika Anda
menggunakan server built-up seperti IBM xSeries atau Dell PowerEdge,
anda harus baca manual instalasi yang disertakan bersama server
tersebut. Instalasi ini dapat diterapkan pada :
1. Windows Server 2003 x86
2. Windows Server 2003 x86 Service Pack 1
3. Windows Server 2003 x86 R2
4. Windows Server 2003 x86 Service Pack 2
Instalasi Windows Server 2003 hampir mirip dengan instalasi Windows XP dan sama mudahnya. Hal-hal yang perlu Anda siapkan:
1. CD/DVD instalasi Windows Server 2003 (Enterprise Edition)
2. CD/DVD driver untuk motherboard, video card, sound card, ethernet card, dll.
3.
PC dengan RAM minimum 256 (disarankan 512MB atau lebih), hardisk 20GB
(disarankan 40GB atau lebih), video card true-color dengan resolusi
1024×768.
Baiklah mari kita mulai:
Boot komputer dengan CD Windows Server 2003
Atur
konfigurasi BIOS agar melakukan boot ke CD/DVD ROM. Masukkan CD/DVD
Windows Server 2003. Anda akan mendapatkan layar selamat datang di setup
Windows Server 2003.
Tekan tombol ‘ENTER’ di keyboard. Anda akan menuju ke layar EULA
Tekan ‘F8′ di keyboard untuk persetujuan lisensi Windows Server 2003.
Membuat Partisi
Jika
hardisk Anda masih kosong, anda harus membuat partisi untuk sistem
Windows Server 2003. Tekan ‘C’ untuk membuat partisi dan masukkan ukuran
partisi yang dibutuhkan, misal 10000MB (1GB).
Jika sudah selesai, tekan ‘ENTER’.
Format partisi tersebut dengan filesystem NTFS dengan metode quickformat.
Tekan ‘ENTER’. Windows Server 2003 Setup memformat partisi hardisk Anda.
Setelah format selesai, Windows Server 2003 Setup meng-copy file-file ke partisi Windows.
Setelah selesai, Windows Server 2003 Setup akan me-restart komputer dan boot ulang
Windows Server Setup GUI
Tunggu beberapa saat sampai muncul Wizard berikut:
Pilih ‘Customize’, dan lakukan setting seperti screen di bawah ini.
Klik ‘OK’, kembali ke layar sebelumnya dan klik ‘Next’.
Isi dengan Nama Anda dan Nama Perusahaan Anda. Kemudian klik ‘Next’.
Isi dengan CD key Windows Server 2003 yang disertakan bersama CD Windows Server 2003. Klik ‘Next’
Pilih Licensing Mode ‘Per Server’ dan isi dengan jumlah koneksi yang dibutuhkan. Klik ‘Next’.
Isi ‘Computer Name’ dan password untuk Administrator. Klik ‘Next’.
Pilih ‘Time Zone’ dengan (GMT +07:00 ) Bangkok, Hanoi, Jakarta. Klik ‘Next’. Setup akan melakukan instalasi Network.
PIlih ‘Custom settings’ dan klik ‘Next’.
Pilih komponen ‘Internet Protocol (TCP/IP)’ dan klik ‘Properties’.
Isi ‘IP address’, ‘Subnet mask:’, ‘Default gateway:’ sesuai konfigurasi network Anda. Klik ‘OK’. Kemudian klik ‘Next’.
Isi nama Workgroup yang diinginkan, misalnya : ‘VOUCHA’. dan klik ‘Next’.
Setup mencopy file-file komponen ke partisi Windows. Setelah itu Setup akan melakukan restart dan boot ulang komputer Anda.
Selamat, Anda berhasil melakukan instalasi Windows Server 2003!
Technorati Tags: windows-server-2003
Setup Windows Server 2003 - Bagian 2
Pada
Setup Windows Server 2003 - Bagian 1, kita telah melakukan instalasi
Windows Server 2003 dengan konfigurasi standar. Beberapa konfigurasi
lainnya masih harus dicustomize agar sesuai dengan kebutuhan sistem yang
diharapkan.
Pada bagian ke-2 ini, kita akan melakukan instalasi
beberapa komponen tambahan yang diperlukan dan melakukan beberapa
konfigurasi minimum untuk Windows Server 2003.
Instalasi Windows Server 2003 Service Pack 2
1. Masukkan CD Windows Server 2003 Service Pack 2
2. Jika Autorun tidak aktif, jalankan melalui menu Start.
Caranya:
1. Klik ‘Start’->’Run
2. Klik ‘Browse’. Pilih lokasi CD-ROM, dan pilih file ‘SRSP2.CMD’
3. Setup akan mengekstrak file-file instalasi dan menampilkan kotak dialog seperti berikut.
4. Klik ‘Next’ dan lanjutkan sampai selesai.
5. Restart
Instalasi Driver
Anda
harus melakukan instalasi driver-driver hardware di komputer dengan
CD/DVD instalasi hardware bersangkutan. Jika driver untuk Windows Server
2003 tidak ditemukan, coba dengan driver untuk Windows XP atau download
dari website vendor bersangkutan.
Instalasi Internet Information Service (IIS)
1. Jalankan ‘Add or Remove Programs’ dari Control Panel
2. Klik button ‘Add/Remove Windows Components’
3. Double click ‘Application Server’
4. Double click ‘Internet Information Service (IIS)’
5. Pilih ‘File Transfer Protocol (FTP) Service’
6. Klik OK.
Membuat Partisi
Partisi
untuk dokumen, database, dan file-file temporer sebaiknya dipisah.
Untuk membuat partisi di Windows Server 2003, ikuti langkah berikut:
1. Jalankan ‘Control Panel’->’Administrative Tools’->’Computer Management’
2. Pilih ‘Disk Management’
3. Klik ‘Disk 0′ pada daftar disk dan klik kanan.
4. Pilih ‘New Partition’
5. Pilih ‘Extended Partition’, isi ukuran partisi yang dibutuhkan dan klik ‘Next’
6. Pilih filesystem ‘NTFS’.
7. Ulangi langkah 1-6 untuk partisi yang lain.
Membuat User Account
Anda
harus membuat user account khusus untuk pemakaian biasa dan jangan
gunakan account Administrator. Gunakan account Administrator jika
diperlukan, misalnya instalasi software atau hardware.
1. Jalankan ‘Control Panel’->’Administrative Tools’->’Computer Management’
2. Pilih ‘Local Users and Groups’
3. Pilih ‘Users’
4. Klik kanan di daftar user dan pilih ‘New User’
5. Isi dengan nama user yang Anda inginkan.
6. Klik ‘Create’
Selamat,
Windows Server 2003 telah siap digunakan sebagai Server. Untuk
menggunakan Voucha II, Anda perlu melakukan instalasi Microsoft SQL
Server 2000 dan Microsoft SQL Server 2000 - Service Pack 4.
Technorati Tags: windows-server-2003.
sumber : http://amanda2tkj.blogspot.com/
Jaringan
Minggu, 11 November 2012
Penjelasan WI-FI
Wi-Fi
Wi-Fi (
/ˈwaɪfaɪ/,
also spelled Wifi or WiFi) is a popular technology that allows an
electronic device to exchange data wirelessly
(using radio waves) over a computer network,
including high-speed Internet connections. The Wi-Fi Alliance
defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards".[1]
However, since most modern WLANs are based on these standards, the term
"Wi-Fi" is used in general English as a synonym for "WLAN".
A device that can use Wi-Fi (such as
a personal computer, video-game console, smartphone,
tablet, or digital audio player) can connect to a network resource
such as the Internet via a wireless network access point. Such an access point (or hotspot) has a
range of about 20 meters (65 feet) indoors and a greater range outdoors.
Hotspot coverage can comprise an area as small as a single room with walls that
block radio waves or as large as many square miles — this is achieved by using
multiple overlapping access points.
"Wi-Fi" is a trademark of
the Wi-Fi Alliance and the brand name for products using the IEEE 802.11
family of standards. Only Wi-Fi products that complete Wi-Fi Alliance interoperability
certification testing successfully may use the "Wi-Fi CERTIFIED"
designation and trademark.
Wi-Fi has had a checkered security
history. Its earliest encryption system, WEP, proved easy to break. Much higher quality protocols, WPA
and WPA2, were added later. However, an optional feature added in 2007, called Wi-Fi Protected Setup (WPS), has a flaw that allows a remote attacker to recover
the router's WPA or WPA2 password in a few hours on most implementations.[2]
Some manufacturers have recommended turning off the WPS feature. The Wi-Fi
Alliance has since updated its test plan and certification program to ensure
all newly certified devices resist brute-force AP PIN attacks.
Contents
|
History
Main article: History of IEEE 802.11
802.11 technology has its origins in
a 1985 ruling by the US Federal Communications Commission that released the ISM band for
unlicensed use.[3]
In 1991, NCR Corporation with AT&T Corporation
invented the precursor to 802.11 intended for use in cashier systems. The first
wireless products were under the name WaveLAN.
Vic Hayes has been called the "father of Wi-Fi" by some,
due to his involvement in negotiating the initial standards within the IEEE while
chairing the workgroup.[4][5]
A large number of patents by many
companies are used in 802.11 standard.[6]
In 1992 and 1996, Australian organisation CSIRO obtained patents for a method later used in Wi-Fi to
"unsmear" the signal.[7]
In April 2009, 14 tech companies agreed to pay CSIRO $250 million for
infringements on CSIRO patents.[8]
This led to WiFi being attributed as an Australian invention,[9] though this
has been the subject of some controversy.[10][11]
CSIRO won a further $220 million settlement for Wi-Fi patent infringements in
2012 with global firms in the United States required to pay the CSIRO licensing
rights estimated to be worth an additional $1 billion in royalties.[8][12][13]
In 1999, the Wi-Fi Alliance
was formed as a trade association to hold the Wi-Fi trademark under which most
products are sold.[14]
The key technologies behind Wi-Fi
were developed by the radioastronomer John O'Sullivan
as a by-product in a research project, "a failed experiment to detect
exploding mini black holes the size of an atomic particle".[15]
The
name
The term Wi-Fi, first used
commercially in August 1999,[16] was
coined by a brand-consulting firm called Interbrand
Corporation. The Wi-Fi Alliance had hired Interbrand to determine a name that
was "a little catchier than 'IEEE 802.11b Direct Sequence'".[17][18][19]
Belanger also stated that Interbrand invented Wi-Fi as a play
on words with Hi-Fi
(high fidelity), and also created the Wi-Fi logo.
The Wi-Fi Alliance initially used an
advertising slogan for Wi-Fi, "The Standard for Wireless Fidelity",[17] but
later removed the phrase from their marketing. Despite this, some documents
from the Alliance dated 2003 and 2004 still contain the term Wireless
Fidelity.[20][21]
There was no official statement related to the dropping of the term.
Non-Wi-Fi technologies intended for
fixed points such as Motorola Canopy
are usually described as fixed wireless.
Alternative wireless technologies include mobile phone standards such as 2G, 3G or 4G.
Wi-Fi
certification
See also: Wi-Fi Alliance
The IEEE does not test equipment for
compliance with their standards. The non-profit
Wi-Fi Alliance was formed in 1999 to fill this void — to establish and enforce
standards for interoperability and backward compatibility, and to promote wireless
local-area-network technology. As of 2010, the Wi-Fi Alliance consisted of more
than 375 companies from around the world.[22][23]
The Wi-Fi Alliance enforces the use of the Wi-Fi brand to technologies based on
the IEEE 802.11 standards from the Institute of Electrical and Electronics Engineers. This includes wireless local area network (WLAN) connections, device to device connectivity (such as
Wi-Fi Peer to Peer aka Wi-Fi Direct), Personal area network (PAN), local area network (LAN) and even some limited wide area network
(WAN) connections. Manufacturers with membership in the Wi-Fi Alliance, whose
products pass the certification process, gain the right to mark those products
with the Wi-Fi logo.
Specifically, the certification
process requires conformance to the IEEE 802.11 radio standards, the WPA and WPA2 security standards, and the EAP authentication standard. Certification may optionally
include tests of IEEE 802.11 draft standards, interaction with cellular-phone
technology in converged devices, and features relating to security set-up,
multimedia, and power-saving.[24]
Not every Wi-Fi device is submitted
for certification. The lack of Wi-Fi certification does not necessarily imply a
device is incompatible with other Wi-Fi devices. If it is compliant or partly
compatible, the Wi-Fi Alliance may not object to its description as a Wi-Fi
device[citation needed] though
technically only certified devices are approved. Derivative terms, such as Super Wi-Fi,
coined by the US Federal
Communications Commission (FCC) to
describe proposed networking in the UHF TV band in the US, may or may not be
sanctioned.
Uses
A sticker indicating to the public
that a location is within range of a Wi-Fi network. A dot with curved lines
radiating from it is a common symbol for Wi-Fi, representing a point
transmitting a signal.[25]
To connect to a Wi-Fi LAN, a
computer has to be equipped with a wireless
network interface controller.
The combination of computer and interface controller is called a station.
All stations share a single radio frequency communication channel.
Transmissions on this channel are received by all stations within range. The
hardware does not signal the user that the transmission was delivered and is
therefore called a best-effort delivery mechanism. A carrier wave is used to transmit the data in
packets, referred to as "Ethernet frames".
Each station is constantly tuned in on the radio frequency communication
channel to pick up available transmissions.
Internet
access
A Wi-Fi-enabled device can connect
to the Internet when within range of a wireless network.
The coverage of one or more (interconnected) access points — called hotspots — can extend from an area as small as a
few rooms to as large as many square miles. Coverage in the larger area may
require a group of access points with overlapping coverage. Outdoor public
Wi-Fi technology has been used successfully in wireless mesh networks in London, UK.
Wi-Fi provides service in private
homes, high street chains and independent businesses, as well as in public
spaces at Wi-Fi hotspots set up either free-of-charge or commercially.
Organizations and businesses, such as airports, hotels, and restaurants, often provide
free-use hotspots to attract customers. Enthusiasts or authorities who wish to
provide services or even to promote business in selected areas sometimes
provide free Wi-Fi access.
Routers that incorporate a digital subscriber line modem or a cable modem
and a Wi-Fi access point, often set up in homes and other buildings, provide
Internet access and internetworking
to all devices connected to them, wirelessly or via cable.
Similarly, there are battery-powered
routers that include a cellular mobile Internet radiomodem and Wi-Fi access
point. When subscribed to a cellular phone carrier, they allow nearby Wi-FI
stations to access the Internet over 2G, 3G, or 4G networks. Many smartphones
have a built-in capability of this sort, including those based on Android, Bada, iOS (iPhone), and Symbian, though carriers often disable the feature, or charge a
separate fee to enable it, especially for customers with unlimited data plans.[26]
"Internet pucks" provide standalone facilities of this type as well,
without use of a smartphone; examples include the MiFi- and WiBro-branded devices. Some laptops that have a cellular modem
card can also act as mobile Internet Wi-Fi access points.
Wi-Fi also connects places that
normally don't have network access, such as kitchens and garden sheds.
City-wide
Wi-Fi
Further information: Municipal
wireless network
An outdoor Wi-Fi access point
In the early 2000s, many cities
around the world announced plans to construct city-wide Wi-Fi networks. There
are many successful examples; in 2004, Mysore became India's first Wi-fi-enabled city and second in the
world after Jerusalem. A company called WiFiyNet has set up hotspots in Mysore,
covering the complete city and a few nearby villages.[27]
In 2005, Sunnyvale, California, became the first city in the United States to offer
city-wide free Wi-Fi,[28]
and Minneapolis has generated $1.2 million in profit annually for its
provider.[29]
In May 2010, London, UK, Mayor Boris Johnson
pledged to have London-wide Wi-Fi by 2012.[30]
Several boroughs including Westminster and Islington[31][32]
already have extensive outdoor Wi-Fi coverage.
Officials in South Korea's capital
are moving to provide free Internet access at more than 10,000 locations around
the city, including outdoor public spaces, major streets and densely populated
residential areas. Seoul will grant leases to KT, LG Telecom and SK Telecom.
The companies will invest $44 million in the project, which will be completed
in 2015.[33]
Campus-wide
Wi-Fi
Many traditional college campuses in
the United States provide at least partial wireless Wi-Fi Internet coverage. Carnegie
Mellon University built the first campus-wide
wireless Internet network, called Wireless Andrew
at its Pittsburgh campus in 1993 before Wi-Fi branding originated.[34][35][36]
In 2000, Drexel University
in Philadelphia became the United States's first major university to offer
completely wireless Internet access across its entire campus.[37]
The Far Eastern University in Manila is the first university in the Philippines
to implement a campus-wide WiFi coverage for its students, faculty, and staff.
Direct
computer-to-computer communications
Wi-Fi also allows communications
directly from one computer to another without an access point intermediary.
This is called ad hoc Wi-Fi transmission. This wireless ad hoc network mode has proven popular with multiplayer handheld game consoles, such as the Nintendo DS,
PlayStation Portable, digital cameras,
and other consumer electronics devices. Some devices can also share their Internet
connection using ad-hoc, becoming hotspots or "virtual routers".[38]
Similarly, the Wi-Fi Alliance
promotes a specification called Wi-Fi Direct
for file transfers and media sharing through a new discovery- and
security-methodology.[39]
Wi-Fi Direct launched in October 2010.[40]
Advantages
and limitations
A keychain-size Wi-Fi detector
Advantages
Wi-Fi allows cheaper deployment of local area networks (LANs). Also spaces where cables cannot be run, such as
outdoor areas and historical buildings, can host wireless LANs.
Manufacturers are building wireless
network adapters into most laptops. The price of chipsets for Wi-Fi
continues to drop, making it an economical networking option included in even
more devices.[citation needed]
Different competitive brands of access
points and client network-interfaces can inter-operate at a basic level of
service. Products designated as "Wi-Fi Certified" by the Wi-Fi
Alliance are backwards compatible. Unlike mobile phones,
any standard Wi-Fi device will work anywhere in the world.
Wi-Fi Protected Access encryption (WPA2) is considered secure, provided a strong passphrase
is used. New protocols for quality-of-service (WMM) make Wi-Fi more suitable for latency-sensitive
applications (such as voice and video). Power saving mechanisms (WMM Power
Save) extend battery life.
Limitations
Spectrum assignments and operational
limitations are not consistent worldwide: most of Europe allows for an
additional two channels beyond those permitted in the US for the 2.4 GHz
band (1–13 vs. 1–11), while Japan has one more on top of that (1–14). As of
2007, Europe is essentially homogeneous in this respect.
A Wi-Fi signal occupies five
channels in the 2.4 GHz band. Any two channels numbers that differ by five
or more, such as 2 and 7, do not overlap. The oft-repeated adage that channels
1, 6, and 11 are the only non-overlapping channels is, therefore, not
accurate. Channels 1, 6, and 11 are the only group of three
non-overlapping channels in the U.S. In Europe and Japan using Channels 1, 5,
9, and 13 for 802.11g and n is recommended.[citation needed]
The current 'fastest' norm, 802.11n,
uses double the radio spectrum/bandwidth (40 MHz) compared to 802.11a or
802.11g (20 MHz). This means there can be only one 802.11n network on the
2.4 GHz band at a given location, without interference to/from other WLAN
traffic. 802.11n can also be set to use 20 MHz bandwidth only to prevent
interference in dense community.
Range
See also: Long-range Wi-Fi
Wi-Fi networks have limited range. A
typical wireless access point using 802.11b or 802.11g with a
stock antenna might have a range of 32 m (120 ft) indoors and
95 m (300 ft) outdoors. IEEE 802.11n,
however, can more than double the range.[41]
Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequency
block has slightly better range than Wi-Fi in the 5 GHz frequency block
which is used by 802.11a and optionally by 802.11n. On wireless routers with
detachable antennas, it is possible to improve range by fitting upgraded
antennas which have higher gain in particular directions. Outdoor ranges can be
improved to many kilometers through the use of high gain directional antennas at the router and remote device(s). In general, the maximum
amount of power that a Wi-Fi device can transmit is limited by local
regulations, such as FCC Part 15 in the US.
Due to reach requirements for
wireless LAN applications, Wi-Fi has fairly high power consumption compared to
some other standards. Technologies such as Bluetooth
(designed to support wireless PAN applications) provide a much shorter propagation
range of <10m[42]
and so in general have a lower power consumption. Other low-power technologies
such as ZigBee have
fairly long range, but much lower data rate. The high power consumption of
Wi-Fi makes battery life in mobile devices a concern.
Researchers have developed a number
of "no new wires" technologies to provide alternatives to Wi-Fi for
applications in which Wi-Fi's indoor range is not adequate and where installing
new wires (such as CAT-5) is not
possible or cost-effective. For example, the ITU-T G.hn standard for high speed Local area networks uses existing home wiring (coaxial cables, phone lines and power
lines). Although G.hn does not provide some of the advantages of Wi-Fi (such as
mobility or outdoor use), it's designed for applications (such as IPTV distribution) where indoor range is more important than
mobility.
Due to the complex nature of radio propagation
at typical Wi-Fi frequencies, particularly the effects of signal reflection off
trees and buildings, algorithms can only approximately predict Wi-Fi signal
strength for any given area in relation to a transmitter.[43]
This effect does not apply equally to long-range Wi-Fi,
since longer links typically operate from towers that transmit above the
surrounding foliage.
The practical range of Wi-Fi
essentially confines mobile use to such applications as inventory-taking
machines in warehouses or in retail spaces, barcode-reading
devices at check-out stands, or receiving/shipping stations. Mobile use of
Wi-Fi over wider ranges is limited, for instance, to uses such as in an
automobile moving from one hotspot to another. Other wireless technologies are
more suitable for communicating with moving vehicles.
Data
security risks
The most common wireless encryption-standard,
Wired
Equivalent Privacy (WEP), has been shown to be easily breakable even when correctly configured. Wi-Fi Protected Access (WPA and WPA2) encryption, which became available in
devices in 2003, aimed to solve this problem. Wi-Fi access points typically default to an encryption-free (open) mode.
Novice users benefit from a zero-configuration device that works
out-of-the-box, but this default does not enable any wireless security, providing open wireless access to a LAN. To turn security
on requires the user to configure the device, usually via a software graphical
user interface (GUI). On unencrypted Wi-Fi
networks connecting devices can monitor and record data (including personal
information). Such networks can only be secured by using other means of
protection, such as a VPN or secure Hypertext
Transfer Protocol (HTTPS) over Transport
Layer Security.
Interference
Wi-Fi connections can be disrupted
or the internet speed lowered by having other devices in the same area. Many
2.4 GHz 802.11b and 802.11g
access-points default to the same channel on initial startup, contributing to
congestion on certain channels. Wi-Fi pollution, or an excessive number of access
points in the area, especially on the neighboring channel, can prevent access
and interfere with other devices' use of other access points, caused by
overlapping channels in the 802.11g/b spectrum, as well as with decreased signal-to-noise ratio (SNR) between access points. This can become a problem in
high-density areas, such as large apartment complexes or office buildings with
many Wi-Fi access points.
Additionally, other devices use the
2.4 GHz band: microwave ovens, ISM band devices,
security cameras, ZigBee devices, Bluetooth devices, video senders,
cordless phones, baby monitors, and (in some countries) Amateur radio
all of which can cause significant additional interference. It is also an issue
when municipalities[44] or other
large entities (such as universities) seek to provide large area coverage.
Hardware
Standard
devices
An embedded
RouterBoard 112 with U.FL-RSMA pigtail and R52 mini PCI Wi-Fi
card widely used by wireless Internet service providers (WISPs) in the Czech Republic
USB wireless adapter
A wireless access point (WAP) connects a group of wireless devices to an adjacent
wired LAN. An access point resembles a network hub,
relaying data between connected wireless devices in addition to a
(usually) single connected wired device, most often an ethernet hub or switch,
allowing wireless devices to communicate with other wired devices.
Wireless
adapters allow devices to connect to a
wireless network. These adapters connect to devices using various external or
internal interconnects such as PCI, miniPCI, USB, ExpressCard, Cardbus and PC Card. As of
2010, most newer laptop computers come equipped with built in internal
adapters.
Wireless routers integrate a Wireless Access Point, ethernet switch, and
internal router firmware application that provides IP routing, NAT, and DNS forwarding through an integrated WAN-interface.
A wireless router allows wired and wireless ethernet LAN devices to connect to
a (usually) single WAN device such as a cable modem
or a DSL modem.
A wireless router allows all three devices, mainly the access point and router,
to be configured through one central utility. This utility is usually an
integrated web server that is accessible to wired and wireless LAN clients and
often optionally to WAN clients. This utility may also be an application that
is run on a desktop computer, as is the case with as Apple's AirPort, which is
managed with the AirPort Utility on Mac OS X and Microsoft Windows.[45]
Wireless network bridges connect a wired network to a wireless network. A bridge
differs from an access point: an access point connects wireless devices to a
wired network at the data-link layer. Two wireless bridges may be used to connect two wired
networks over a wireless link, useful in situations where a wired connection
may be unavailable, such as between two separate homes.
Wireless range-extenders or wireless
repeaters can extend the range of an existing wireless network. Strategically
placed range-extenders can elongate a signal area or allow for the signal area
to reach around barriers such as those pertaining in L-shaped corridors.
Wireless devices connected through repeaters will suffer from an increased
latency for each hop, as well as from a reduction in the maximum data
throughput that is available. In addition, the effect of additional users using
a network employing wireless range-extenders is to consume the available bandwidth
faster than would be the case where but a single user migrates around a network
employing extenders. For this reason, wireless range-extenders work best in
networks supporting very low traffic throughput requirements, such as for cases
where but a single user with a Wi-Fi equipped tablet migrates around the
combined extended and non-extended portions of the total connected network.
Additionally, a wireless device connected to any of the repeaters in the chain
will have a data throughput that is also limited by the "weakest
link" existing in the chain between where the connection originates and
where the connection ends. Networks employing wireless extenders are also more
prone to degradation from interference from neighboring access points that border
portions of the extended network and that happen to occupy the same channel as
the extended network.
The security standard, Wi-Fi Protected Setup, allows embedded devices with limited graphical user
interface to connect to the Internet with ease. Wi-Fi Protected Setup has 2
configurations: The Push Button configuration and the PIN configuration. These
embedded devices are also called The Internet of Things and are low-power,
battery-operated embedded systems. A number of Wi-Fi manufacturers design chips
and modules for embedded Wi-Fi, such as GainSpan.[46]
Distance
records
Distance records (using non-standard
devices) include 382 km (237 mi) in June 2007, held by Ermanno
Pietrosemoli and EsLaRed of Venezuela, transferring about 3 MB of data between
the mountain-tops of El Águila
and Platillon.[47][48]
The Swedish
Space Agency transferred data 420 km
(260 mi), using 6 watt amplifiers to reach an overhead stratospheric
balloon.[49]
Embedded
systems
Embedded serial-to-Wi-Fi module
Increasingly in the last few years
(particularly as of 2007), embedded Wi-Fi modules have become available that
incorporate a real-time operating system and provide a simple means of
wirelessly enabling any device which has and communicates via a serial port.[50]
This allows the design of simple monitoring devices. An example is a portable
ECG device monitoring a patient at home. This Wi-Fi-enabled device can
communicate via the Internet.[51]
These Wi-Fi modules are designed by OEMs so that implementers need only minimal Wi-Fi knowledge to
provide Wi-Fi connectivity for their products.
Multiple
access points
Increasing the number of Wi-Fi
access points provides network redundancy, support for fast roaming and
increased overall network-capacity by using more channels or by defining
smaller cells. Except for the smallest implementations (such as home or
small office networks), Wi-Fi implementations have moved toward
"thin" access points, with more of the network intelligence housed in a centralized network appliance, relegating
individual access points to the role of "dumb" transceivers. Outdoor
applications may use mesh
topologies.
Network
security
The main issue with wireless network
security is its simplified access to the network compared to traditional wired
networks such as ethernet.[citation
needed] With wired networking one must either gain access to a
building (physically connecting into the internal network) or break through an
external firewall. Most business networks protect sensitive data and systems
by attempting to disallow external access. Enabling wireless connectivity
reduces security if the network uses inadequate or no encryption.[52]
An attacker who has gained access to
a Wi-Fi network router can initiate a DNS spoofing attack against any other
user of the network by forging a response before the queried DNS server has a
chance to reply.[53]
Securing
methods
A common measure to deter
unauthorized users involves hiding the access point's name by disabling the SSID broadcast. While effective against the casual user, it is
ineffective as a security method because the SSID is broadcast in the clear in
response to a client SSID query. Another method is to only allow computers with
known MAC addresses to join the network,[54] but
determined eavesdroppers may be able join the network by spoofing an
authorized address.
Wired
Equivalent Privacy (WEP) encryption was designed to
protect against casual snooping but it is no longer considered secure. Tools
such as AirSnort or Aircrack-ng
can quickly recover WEP encryption keys.[55]
Because of WEP's weakness the Wi-Fi Alliance
approved Wi-Fi Protected Access (WPA) which uses TKIP. WPA was specifically designed to work with older equipment
usually through a firmware upgrade. Though more secure than WEP, WPA has known
vulnerabilities.
The more secure WPA2 using Advanced
Encryption Standard was introduced in 2004 and is supported
by most new Wi-Fi devices. WPA2 is fully compatible with WPA.[56]
A flaw in a feature added to Wi-Fi
in 2007, called Wi-Fi Protected Setup, allows WPA and WPA2 security to be bypassed and
effectively broken in many situations. The only remedy as of late 2011 is to
turn off Wi-Fi Protected Setup,[57] which is
not always possible.
Piggybacking
Main article: Piggybacking
(Internet access)
Piggybacking refers to access to a
wireless Internet connection by bringing one's own computer within the range of
another's wireless connection, and using that service without the subscriber's
explicit permission or knowledge.
During the early popular adoption of
802.11,
providing open access points for anyone within range to use was encouraged[by
whom?] to cultivate wireless
community networks,[58]
particularly since people on average use only a fraction of their downstream
bandwidth at any given time.
Recreational logging and mapping of
other people's access points has become known as wardriving.
Indeed, many access points are intentionally installed without security turned
on so that they can be used as a free service. Providing access to one's
Internet connection in this fashion may breach the Terms of Service or contract
with the ISP. These activities do not result in sanctions in most
jurisdictions; however, legislation and case law differ
considerably across the world. A proposal to leave graffiti
describing available services was called warchalking.[59]
A Florida court
case determined that owner laziness was not to be a valid excuse.[citation needed]
Piggybacking often occurs
unintentionally, since most access points are configured without encryption by
default[citation needed] and operating
systems can be configured to connect automatically to any available wireless
network. A user who happens to start up a laptop in the vicinity of an access
point may find the computer has joined the network without any visible
indication. Moreover, a user intending to join one network may instead end up
on another one if the latter has a stronger signal. In combination with automatic
discovery of other network resources (see DHCP and Zeroconf) this could possibly lead wireless users to send sensitive
data to the wrong middle-man when seeking a destination (see Man-in-the-middle
attack). For example, a user could
inadvertently use an unsecure network to log in to a website, thereby
making the login credentials available to anyone listening, if the website uses
an unsecure protocol such as HTTP.
Safety
Further information: Wireless
electronic devices and health
The World
Health Organization (WHO) says "there is no risk
from low level, long-term exposure to wi-fi networks" and the United
Kingdom's Health
Protection Agency reports that exposure to Wi-Fi for
a year results in the "same amount of radiation from a 20-minute mobile
phone call." [60][61]
A small percentage of Wi-Fi users
have reported adverse health issues after repeat exposure and use of Wi-Fi,[62] though
there has been no publication of any effects being observable in double-blind studies. A review of studies involving 725 people that claimed electromagnetic
hypersensitivity found no evidence for their claims.[63]
One study speculated that
"laptops (Wi-Fi mode) on the lap near the testicles may result in
decreased male fertility".[64]
Another study found decreased working memory
among males during Wi-Fi exposure.[65]
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