cong nghe wifi

8/7/2019 cong nghe wifi

1/18

KHOA CNG NGH THNG TIN

B Mn in T Vin Thng

BO CO:

MN THNG TIN S

BI BO CO:

Cng Ngh WiFi

Gio vin hng dn : Thc S : HONG QUANG TRUNG

Sinh vinthc hin : Nhm 5

Thi Nguyn 11-2009

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Nhim v ti

ti: Tm Hiu V Cng Ngh Mng WiFi

DANH SCH NHM 5:

1. Nguyn B Thnh

2. Kim Vn Linh

3. Phan Anh Tun

4. Vng Th Thu

5. Phm Vn Tng

Mc Lc:

1:Gii Thiu T3

2: Cc loi Wireless Networks T3

3: Cc chun ca Wireless LANs T4

4: nh ngha mng Wifi 5 T5

5: Hot ng ca mng Wifi T6

6: Sng Wifi T6

7: Cc thnh phn c bn ca mng T8

8: Cu hnh ca Wireless LANs T9

9: Cc Thit b T11

10: u v nhc im ca Wireless LANs T13

11: Mt s ng dng ca mng khng dy: T14

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1:Gii Thiu

Trong nhng nm gn y,vic b i cc dy ni cho in thoi c nh v pht

trin sn phm khng dy cho th trng doanh nghip v tiu dng tr nn rt d

dng. Bi vy nn khng c g ngc nhin khi cng ngh khng dy ang bt u c

p dng cho lnh vc in ton c nhn v in ton doanh nghip.Chng ta thy rt r

s pht trin vt bc ca vin thng v cng ngh thng tin. Nhu cu trao i thng tin

mi lc mi ni lm cho cm t "Wireless" xut hin trong nhng nm gn y.

Mt trong nhng ng dng mnh nht ca n hin nay, m i u ta cng thy l "in

thoi di ng", phc v cho ci s "nhiu chuyn" ca chng ta. Tng t nh vy, trong

ngnh Mng, IEEE 802.11 cng lm mt cuc cch mng v tr thnh mt standard,

gp phn cho s pht trin mnh m ca cng ngh Wireless trong nhng nm gn y.

2:Cc loi Wireless Networks:

C th phn chia tm nh sau:

Wireless LAN ( Wifi ): Kt ni wireless trong mt phm vi nh nh trong mt phng,

mt to nh, hoc gia hai to nh gn nhau Bn knh ph sng bn trong ( indoor )

khong vi trm mt Bn ngoi ( outdoor ) khong vi km. Thng c s dng

nhng ni ng c nh khch sn, sn bay, ga tu in, trng hcS dng chun

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802.11..

Wireless-MAN ( WiMax ): Kt ni wireless gia nhng building khc nhau, hay gia cc

building trong cng mt thnh phBn knh ph sng c th ln ti vi chc km.

Thng c s dng nhng ni tha tht dn c hay ni c ia hnh phc tp.

Wireless-PAN:Dng cho cc thit b di ng cm tay nh :in thoi i ng,Laptop ng

dng Bluetooh truyn ti d liu vi nhau.V mng cm bin khng dy s dng phc v

cho mc ch dn s v qun s,o c cm ng.

3:Cc chun ca Wireless LANs

802.11

IEEE c pht trin chun 802.11 cho WLANs, c 4 c t mi bao gm 802.11,

802.11a, 802.11b v 802.11g. Mi chun 802.11 hot ng mt phm vi khc nhau v

mt tc khc nhau. 802.11 p dng cho mng Lan khng dy v cung cp 1 hoc 2

Mbps truyn trong di 2.4Ghz dng tn s quang ph ph bin (FHSS Frequency

hopping speard spectrum) hoc hoc qun l trnh t quang ph (direct sequence spreadspectrum - DSSS).

802.11a

c t hot ng 802.11a trong phm vi 5GHz v cung cp tc d liu n 54Mbps.

Phm vi 5GHz khng cn c ng c v n to c hi thun li bng tc trn c

t 802.11b vi quyn s dng nhiu hn phm vi 2.4GHz. Tuy nhin, phm vi v tc

ca 802.11a ngc li vy ti sao 802.11a khng c chp nhn nh l mt chunWiFi. 802.11a s dng mt lc iu bin nhn bit nh tn s trc giao ranh gii

a thnh phn (orthogonal frequency-division multiplexing (OFDM)) chng li FHSS v

DSSS. Phn ln sn phm 802.11a khng tng thch vi sn phm 802.11b hoc

802.11g .

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802.11b

Chun 802.11b hot ng trong phm vi 2.4GHz v cung cp tc d liu l 11Mbps,

802.11b l chun thc t cho cng ngh WiFi bi v n rt c ch v gi r . Trong khi

chm hn 802.11a, 802.11b nhanh nh dch v 10BaseT Ethernet. 802.11b s dng qun

l trnh t quang ph (DSSS) v b sung m kha iu bin (complementary code keying

- CCK). 802.11b c chng nhn bi IEEE vo nm 1999.

802.11g

802.11g c ph chun vo ngy 11 thng 7 nm 2003 v cung cp tc d liu l

54Mbps, hot ng trong di 2.4GHz v 5GHz , tng thch ngc vi 802.11b. Ngay c

truc khi IEEE ph chun, 802.11g s tr thnh chun ca cng ngh WiFi v nh sn

xut chnh bt u bn sn phm trong nm 2003. 802.11g s dng s iu bin

OFDM nhng, tng thch ngc vi 802.11b, n cng h tr iu bin b sung m

kha iu bin (CCK)

y l chun mi nht cho tc nhanh, hon ton tng thch vi chun 802.11b v gi

c cng kh hp l. Mng khng dy 802.11b hin thi c tc truyn l 11mbps, kh

thch hp cho internet c bng thng rng nhng hoi hn ch truyn cc tp tin dunglng ln hay xem phim.

Tuy nhin chun 802.11a c tc truyn 54mbps li qu t bi v tn sng 802.11a

5GHz v 802.11b 2,4GHz nn nng cp ln mng 802.1a c ngha l phi b hn

802.11b hay mua phn cng h tr hai chun ny (nhng gi thng cao)

Do , chun 802.11g c cng tc vi 802.11a v c kh nng cng tn ti vi thit b

802.11b trong cng mt mng v n cng dng bng tn 2,4 GHz.

Cn v tc , chun 802.11g trn thc t tc truyn l 10 n 15mpbs, hay gp 4 ln

tc thc t ca chun 802.11b l t 2,5 n 4mpbs.

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Khi ta bt m ha WEP (Wired Equivalent Privacy) hay khi ta dng c hai card 802.11b

v 802.11g trn cng mt mng khng bt WEP th tc gim, nu mun tc truyn

cao hn th ch dng mi 802.11b. Thm ch card 802.11b chy nhanh hn khong 15%

khi kt ni vi gateway 802.11b.

Mng khng dy (wireless network) l mng in thoi hoc mng my tnh s dng

sng radio lm sng truyn dn (carrier wave) hay tng vt l.

Mt s thut ng:

Mng MAN khng dy (WMAN) - mng th khng dy

Mng LAN khng dy (WLAN) - mng cc b khng dy

Mng PAN khng dy (WPAN) - mng c nhn khng dy

GSM - Chun ton cu cho truyn thng di ng s, thng dng ti hu ht cc nc

ngoi tr Hn Quc v Nht Bn.

Wi-Fi - mt tp cc chun tng thch sn phm dnh cho cc mng WLAN da trn

c t IEEE 802.11

4: nh ngha mng Wifi

Wi-Fi (Wireless Fidelity)hay mng 802.11 l h thng mng khng dy s dng

sng v tuyn, ging nh in thoi di ng, truyn hnh v radio.H thng ny hot

ng mt s sn bay, qun caf, th vin hoc khch sn. H thng cho php truy cp

Internet ti nhng khu vc c sng ca h thng ny, hon ton khng cn n cp ni.

Ngoi cc im kt ni cng cng (hotspots), WiFi c th c thit lp ngay ti nh

ring.

Tn gi 802.11 bt ngun t vin IEEE (Institute of Electrical and Electronics

Engineers). Vin ny to ra nhiu chun cho nhiu giao thc k thut khc nhau, v n s

dng mt h thng s nhm phn loi chng; 3 chun thng dng ca WiFi hin nay l

802.11a/b/g.

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5:Hot ng ca mng Wifi

Truyn thng qua mng khng dy l truyn thng v tuyn hai chiu. C th:

Thit b adapter khng dy (hay b chuyn tn hiu khng dy) ca my tnh chuyn i

d liu sang tn hiu v tuyn v pht nhng tn hiu ny i bng mt ng-ten.

Thit b router khng dy nhn nhng tn hiu ny v gii m chng. N gi thng tin ti

Internet thng qua kt ni hu tuyn Ethenet.

Qui trnh ny vn hot ng vi chiu ngc li, router nhn thng tin t Internet, chuyn

chng thnh tn hiu v tuyn v gi n adapter khng dy ca my tnh.

6:Sng Wifi

Cc sng v tuyn s dng cho WiFi gn ging vi cc sng v tuyn s dng cho

thit b cm tay, in thoi di ng v cc thit b khc. N c th chuyn v nhn sng

v tuyn, chuyn i cc m nh phn 1 v 0 sang sng v tuyn v ngc li.

Tuy nhin, sng WiFi c mt s khc bit so vi cc sng v tuyn khc ch:

Chng truyn v pht tn hiu tn s 2.4 GHz hoc 5GHz. Tn s ny cao hn so vi

cc tn s s dng cho in thoi di ng, cc thit b cm tay v truyn hnh. Tn s cao

hn cho php tn hiu mang theo nhiu d liu hn. Chng dng chun 802.11

Chun 802.11b l phin bn u tin trn th trng. y l chun chm nht v r tin

nht, v n tr thnh t ph bin hn so vi cc chun khc. 802.11b pht tn hiu tng

s 2.4 GHz, n c th x l n 11 MB/giy, v n s dng m CCK (complimentary

code keying).

Chun 802.11g cng pht tng s 2.4 GHz, nhng nhanh hn so vi chun 802.11b, tc

x l t 54 MB/giy. Chun 802.11g nhanh hn v n s dng m OFDM(orthogonal frequency-division multiplexing), mt cng ngh m ha hiu qu hn.

Chun 802.11a pht tng s 5 GHz v c th t n 54 MB/ giy. N cng s dng m

OFDM. Nhng chun mi hn sau ny nh 802.11n cn nhanh hn chun 802.11n,

nhng 802.11n vn cha phi l chun cui cng.

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WiFi c th hot ng trn c ba tn s v c th nhy qua li gia cc tn s khc nhau

mt cch nhanh chng. Vic nhy qua li gia cc tn s gip gim thiu s nhiu sng

v cho php nhiu thit b kt ni khng dy cng mt lc.

7:Cc thnh phn c bn ca mng:

- Stations (cc my trm): cc mng c xy dng truyn d liu gia cc trm,

station l cc thit b tnh ton c giao tip mng khng dy, in hnh nh cc my tnh

bn hay my tnh xch tay s dng pin. Trong mt s mi trng, mng khng dy

c s dng nhm trnh phi ko cp mi v cc my bn c kt ni vi mng

LAN khng dy. Nhng khu vc ln hn cng c li khi s dng mng khng dy nh

xng sn xut s dng mng cc b khng dy kt ni cc b phn. 802.11 nhanh

chng tr thnh chun thc t lin kt nhng ngi s dng thit b in t vi nhau.

- Access points (cc im truy cp): cc khung d liu trn mng 802.11 phi c

chuyn thnh dng khung d liu khc phn phi trong cc mng khc. Thit b c

gi l im truy cp th hin cc chc nng chuyn i t khng dy sang c dy (im

truy cp bao gm nhiu chc nng khc nhau, nhng thc hin chuyn i l chc nng

quan trng nht). Cc chc nng im truy cp c t ti nhng thit b c lp.Tuy

nhin, nhiu sn phm mi hn tch hp cc giao thc 802.11 vo hai loi access point

cp thp (thin access point) v b iu khin access point (access point Controller).

- Wireless medium (mi trng khng dy): chuyn cc khung d liu t trm ny

sang trm khc trong mi trng khng dy, ngi ta xy dng nhiu chun vt l khc

nhau. Nhiu lp vt l c pht trin h tr 802.11 MAC, lp vt l v tuyn (radio

frequency)vlpvtlhngngoicchunha.

- Distribution system (h thng phn tn): Khi cc im truy cp c kt ni vi nhau

trong mt khu vc, chng phi lin lc vi nhau kim sot qu trnh di chuyn ca ccthit b di ng. H thng phn tn l mt thnh phn logic ca 802.11 c dng

chuyn cc khung d liu n ch. 802.11 khng yu cu bt c k thut ring bit no

cho h thng phn tn. i vi hu ht cc sn phm thng mi, h thng phn tn bao

gm cc phn t chuyn i v mi trng hot ng phn tn, chnh l mng ng trc

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c dng chuyn tip khung d liu gia cc im truy cp. Trong cc sn phm

thng mi chim lnh th trng th Ethernet c s dng lm mng ng trc chnh.

8:Cu hnh ca Wireless LANs

Cu hnh ca WLAN c hai loi:

- Cu hnh ad-hoc hay cn gi l mng ngang hng: mi my tnh km theo card khngdy, pht v nhn d liu ti v t tt c cc my tnh thu pht khc vi khong cch tia gia 2 my l 300 feet (khong 900m).

M hnh ad-hoc: ABCD kt ni vi nhau trc tip

A - - - C

| \ / |

| /\ |

| / \ |

B - - - D

Hnh 5: M hnh mng Ad-hoc

-Cu hnh h tng: mi my tnh gi v nhn d liu t cc im truy cp- trngging nh cc hp nh c anten gn trn tng hoc trn gi . Khi im truy nhp

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nhn d liu, n c th gi tn hiu qua cc tn s radio ti cc my tnh trong vngph sng ca mnh hay gi ti mng dy Ethernet

M hnh infrastructure: ABCDEF kt ni thng qua AP

Extended Service Set (ESS)

A - - - | - ------- Access Point (AP)------- | - - - D

B - - - | | - - - E

C - - - | | - - - F

Hnh 6: Mng WLAN vi m hnh Infrastructure.

h thng mng khng dy thnh 2 loi:

- Mng khng dy trong nh (Indoor):

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- Mng khng dy ngoi tri (Outdoor):

9:Cc Thit b:

Product Name Type Features

D-Link_DWL-650+AirPlus

PCMCIAWireless Adapter

802.11b, 22Mbps withAirPlus products

D-Link_DWL-6000AP AirPro

Multimode_Wireless AccessPoint

802.11a, 802.11b22Mbps with AirPluproducts and 72Mbps withAirPro products

D-Link_DI-714P+AirPlus

Wireless Router and Print

802.11b, 22Mbps withAirPlus products

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http://www.dlink.com/products/digitalHome/wireless/11b+/dwl650+/http://www.dlink.com/products/digitalHome/wireless/11b+/dwl650+/http://www.dlink.com/products/dwl6000ap/http://www.dlink.com/products/dwl6000ap/http://www.dlink.com/products/digitalHome/wireless/11b+/di714p+/http://www.dlink.com/products/digitalHome/wireless/11b+/di714p+/http://www.dlink.com/products/digitalHome/wireless/11b+/dwl650+/http://www.dlink.com/products/digitalHome/wireless/11b+/dwl650+/http://www.dlink.com/products/dwl6000ap/http://www.dlink.com/products/dwl6000ap/http://www.dlink.com/products/digitalHome/wireless/11b+/di714p+/http://www.dlink.com/products/digitalHome/wireless/11b+/di714p+/


12/18

Server

D-Link_DWL-AB520AirPro

Wireless PCI Adapter

802.11a, 802.11b

Linksys BEFW11S4

Wireless Access Point with4-port switch

802.11b only

Linksys WAP51AB

DualBandWireless AccessPoint

802.11a, 802.11b, 7

Mbps with other Linksy802.11a products

Linksys WPC51AB


802.11a only

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http://www.dlink.com/products/wireless/dwlab520/http://www.dlink.com/products/wireless/dwlab520/http://www.linksys.com/Products/product.asp?grid=23&prid=415http://www.linksys.com/products/product.asp?grid=33&scid=35&prid=452http://www.linksys.com/products/product.asp?grid=33&scid=36&prid=477http://www.dlink.com/products/wireless/dwlab520/http://www.dlink.com/products/wireless/dwlab520/http://www.linksys.com/Products/product.asp?grid=23&prid=415http://www.linksys.com/products/product.asp?grid=33&scid=35&prid=452http://www.linksys.com/products/product.asp?grid=33&scid=36&prid=477


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Linksys WPC11


802.11b only

10:u v nhc im ca Wireless LANs

u im- Khng phi khoan tng, bm v i dy.- Khng phi ngi ti nhng v tr c nh.- Chia s ngun ti nguyn.- Trong nhiu trng hp l gii php r hn cho mng LAN- C th kt ni khong cch xa hn so vi cc thit b Bluetoothhoc IR.- Cng sut v tc c th chp nhn c..- u im chnh ca Wireless chnh l tnh linh hot, tnh chuynng, thi gian lp t nhanh, t nh hng n c s h tng , lm vic,c th g b nhanh nu khng dng na, cc selection cng a dng hn, t bao ph cho n gc pht sng.

Nhc im- Phc tp hn trong vic thit lp, qun l v vn hnh mng.- Thng tin c truyn trn khng trung trn tn s dng chung dnn cc vn an ninh v nhiu.- Tn s cng cao th tc cng cao, nhng ng thi suy gim

cng cng cao...

11:Ro cn ca mng khng dy

Khng cn i cp mng v th thi gian s nhanh hn nhng tht ra cn c qu nhiu rocn khi trin khai mng khng dy.

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Chi ph: Hin nay hu ht cc my tinh dng cho vn phng v my tnh xch tay u ctrang b card mng 10/100Mbps, cn cc mainboard tch hp thm card mng10/100Mbps cng ch cao hn 5USD, ch cn 5-6USD l c th mua c card mng10/100Mbps ri. V vy, nu khng ngi khoan tng i dy mng th lp t mng c

dy vn r hn nhiu.Bo mt: Bo mt WPA an ton hn WEP, nhng hin tai cha c nhiu sn phm htr WPA, c bit l cc my tnh khng chy h iu hnh WindowsXP. Mt mng cdy d cha c bin php bo mt, nu mun tn cng th tin tc phi truy cp mc vtl.

n nh: Nhiu c th lm gim tc , thm ch lm mt lun tn hiu WiFi, c bit l cc khu vc giao nhau vi cc mng WiFi. Vi chun 802.11a th y khng phi l trngi ln, v 802.11a hot ng tn s 5GHz, trong khi 802.11b v 802.11g hot ng

tn s 2.4GHz, cng tn s hot ng ca nhiu thit b khc nh Bluetooth, in thoiv tuyn, l vi sng.

4.Bng thng: D bng thng hin ti ca 802.11b qu duyt web bng kt niADSL hoc thnh thong truyn tp tin qua li, nhng thng sut ca mng khng dy likhng cho nhng ai thng xuyn phi truyn hoc m trc tip cc tp tin dunglng ln.

11:Mt s ng dng ca mng khng dy:

Gii php cho vn phng di ng:

Vi s xut hin v pht trin ca cng ngh mng khng dy, cc vn phng lm

vic thc s tr thnh 1 Vn phng M. Cc kt ni mng ngi dng c duy tr

mt cch d dng, lin tc m khng ph thuc vo s thay i v tr lm vic hay s

b sung cc im kt ni mi.

Gii php ny khng ch n thun l tng kh nng trao i thng tin trong Vn

phng m cn gip ngi s dng nng cao nng lc lm vic v hiu qu kinh

doanh.

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Mi Wireless Access Point hot ng nh l mt im trung tm kt ni ti cc

my trm s dng card khng dy. Tm ph sng ca mt Access Point n l (trong

vn phng) khong 30 mt.

Cc Access Point c lin kt vi nhau bng mt thit b chuyn mnh (Switch),

iu c ngha l mt mng c th bao gm nhiu Access Point hot ng cng vi

nhau m rng phm vi ph sng.

Gii php lin kt cc mng (Building-to-Building)

i vi nhiu T chc v doanh nghip ln, ngoi Vn phng chnh cn c rt

nhiu cc vn phng chi nhnh, nhu cu lin kt cc H thng mng thnh vin vi

H thng mng trung tm c xem nh 1 iu kin tin quyt cho vic ng b ho

phng thc Qun l v cc trao i thng tin, d liu hot ng.

Vi cc phng thc kt ni mng truyn thng i hi 1 chi ph rt cao v cc

ng dy kt ni i hi nhiu cng thi cng cng nh nhng chi ph bo dng.Phng thc kt ni thng qua ng in thoi cng cng p ng c phn

no nhu cu ny nhng li c tc qu thp so vi 1 ng truyn khng dy thng

thng s dng chun IEEE802.11b.

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S la chn l khng bt buc, nhng gii php kt ni khng dy hin nay

ang c xem l gii php hp l nht v kinh t nht cho cc doanh nghip ln, cc

khu cng nghip, cc B - Ban - Ngnh trong vic lin kt cc mng thng tin.

Cc thit b mng khng dy cng cho php ngi dng thc hin cc phng thc

kt ni:

- im - im (Point to Point)

- im nhiu im (Point to MultiPoint)

im truy cp mng Cng cng (Hotspot):

Gii php ny c bit ph hp vi cc nh cung cp dch v Internet nh:

- Cc ISP: cung cp dch v truy cp internet cng cng cho cc im cng

cng nh: Sn bay, Nh ga, Trng hc, Bnh vin, Trung tm Hi ngh, Trin lm,Sn vn ng, ....

- Cc khch sn, nh hng: cung cp dch v Internet ti tng phng nh:

Guest Room, Lobby, Meeting room, Restaurant,...

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- Cc to nh thng mi: cung cp dch v truy cp internet cho cc Vn

phng cho thu, cc khch hng,...

- ...v..v...

Ti mi im cung cp dch v truy cp Internet khng dy ny, nh cung cp

dch v t cc Access Point, hoc cc Antenna thu pht tn hiu, cho php nhng

khch hng c my tnh xch tay hoc thit b di ng c tch hp cng ngh khng

dy Wi-Fi truy cp Internet m khng cn dy dn. Cng ngh Zero-Configuration

c p dng nhm nng cao tnh bo mt v to iu kin thun li nht cho ngi

s dng trong vic ng nhp (thng thng ngi dng c cung cp 1 Account

ng nhp vo mng m khng cn phi thay i bt k mt thit lp cu hnh notrong thit b ca mnh nh: IP, DNS, Gateway, Subnet mask,...).

p ng nhng yu cu ng nhp s dng, cc nh cung cp tch hp cc

thit b nh: PMS (Property Management System), Billing Server, Radius Server,...

cung cp, qun l cc account truy cp v tnh cc truy cp.

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Internet

Service Provider

Server

Farms

RADIUSCorporate

LAN(s)

Universities

SchoolsMDU/MTU

Airports

Train Stations

Hotels

Restaurants

Malls

Backbone: leased

line, DSL, Cable,

Wireless...


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Kt Lun:

Ngy nay chng ta c th thy rt r cc ng dng LAN khng dy ang pht trin rtnhanh v c nhiu tin li cho tng lai. Trong mt vi nm qua chng ngy cng cci thin nhiu v tc , tnh bo mt, cht lng dch v v s qun l tp trung. iu c th cho rng vi thi gian chng ta c th hon ton b li cc thit k chy dytruyn thng ny hay khng?

Ti Liu Tham Kho:Ch yu tham kho trn mng Internet v mt s din n:

http://google.comhttp://wirelessvn.com

Page 18
http://google.com/http://wirelessvn.com/http://google.com/http://wirelessvn.com/

cong nghe wifi

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