bao cao wlan

8/9/2019 Bao cao wlan

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I. Khi nim tng qut v WLAN.II. Phn loi.

1.Cu hnh mng WLAN ph thuc.

2.Cu hnh mng WLAN c lp.III. Cc kiu tn cng trong WLAN.IV. M haV. Bo mt.


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WLAN l mt loi mng my tnh,vic kt ni

gia cc thnh phn trong mng khng s dng cc

loi cp nh mt mng thng thng, mi trngtruyn thng l khng kh. Cc thnh phn trongmng s dngsng in t truyn thng vi nhau.


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WLAN cung cp tt c cc tnh nng v li ch cccng ngh LAN truyn thng nh Ethernet v TokenRing, nhng khng b gii hn bi dy dn hay cp ni .


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Thay v s dng UTP (ph bin cho LAN hin nay),WLAN s dng:

+ Tia hng ngoiInfrared (IR): c nhiu hn ch, d dng b chn/cn, khng c sn

phm thc t.

+ Tn s radio (RFs): C th xuyn qua phn ln cc vt cn trong vn

phng.


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WLAN s dng cc di tn 2.4 GHz v 5-GHz.

+ Chun 802.11b v 802.11g: 2.4-2.5 GHz.+ Chun 802.11a: 5.725 5.875 GHz .


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V sao s dng WLAN?

+ Cc li ch ca mng cc b khng dy.

+ Tnh di ng.+ Kh nng m rng.+ Tit kim chi ph cho cn ngn v di hn.+ Cc li th v ci t.+ Vn c c tin cy trong mi trng khc nghit.+Thi gian ci t mng gim xung.


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Hn ch:

+Bo mt:kh nng b tn cng ca ngi dng l rt cao.

+ tin cy: d b nhiu, tn hiu b gim do tc ng ca ccthit b khc(l vi sng,.). Lm gim ng k hiu qu hotng ca mng.

+ Tc : Tc ca mng khng dy (1- 125 Mbps) rt chmso vi mng s dng cp(100Mbps n hng Gbps).


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C hai m hnh chnh :1. M hnh mng c lp.

2. M hnh mng ph thuc.


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+ Khng c base station.

+ Cc nodes ch c th truyn cho nhau cc nodes khc

bn trongvng bao ph kt ni.

+ Nodes t chc vi nhau thnh mt mng: nh tuyngia chng .


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+ Cc nodes hnh thnh mt mng li lin kt vinhau bng sng v tuyn.

+ Cc nodes chia s cc thng s chung nh: knh tns, thit lp nhn dng, phng thc mt m ha.


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+ c s dng ph bin.+ S dng m hnh my trm/ my phc v(client/server).

+ Cc im truy nhp (Access Point (AP)) thc hinchc nng cng chuyn tip cho cc my trm.+ Mt nhm cc my trm cng chia s mt AP trongphm vi mt cell ng vi mt vng ph sng ca mt

AP n l.


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_ Tn cng Access Point.

_ Tn cng yu cu xc thc li.

_ Tn cng da trn s cm nhn sng mang lp vt l.

_ Tn cng ngt kt ni .


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Access Point gi mo c dng m t nhngAccess Point c to ra mt cch v tnh hay c lmnh hng n h thng mng hin c.

Kiu tn cng ny xy ra khi:

+ Access Point c cu hnh khng hon chnh .

+Access Point gi mo t cc mng WLAN ln cn .+ Access Point gi mo do k tn cng to ra


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Chn cc frame yu cu xc thc li vo mngWLAN bng cch gi mo a ch MAC ngun v chln lt ca Access Point v cc ngi dng.

Ngi dng khi nhn c frame yu cu xc thc lith ngh rng chng do Access Point gi n.

Thng thng ngi dng s kt ni li phc hidch v, nhng k tn cng nhanh chng tip tc gicc gi yu cu xc thc li cho ngi dng.


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K tn cng li dng giao thc chng ng , lm

cho ngi dng ngh rng lc no trong mng cng c1 my tnh ang truyn thng. iu ny lm cho ccmy tnh khc lun lun trng thi ch i dn ntnh trng ngn trong mng.


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K tn cng gi mo Source v Destination MAC nAP v cc client tng ng.

Client s nhn cc yu cu hy kt ni n t AP.ng thi k tn cng cng gi yu cu n AP.


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M ha l bin i d liu ch c cc thnh phnc xc nhn mi c th gii m c n.

C hai loi :

+ M ha dng (stream ciphers).+ M ha khi ( block ciphers).


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M ha dng phng thc m ha theo tng bit, mha dng pht sinh chui kha lin tc da trn gi trca kha.

V d mt m ha dng c th sinh ra mt chuikha di 15 byte m ha mt frame v mt chuikha khc di 200 byte m ha mt frame khc.


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M ha khi sinh ra mt chui kha duy nht v c

kch thc c nh(64 hoc 128 bit). Chui k t chac m ha( plaintext) s c phn mnh thnhnhng khi(block) v mi khi s c trn vi chuikha mt cch c lp.


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+ Xc nh ai c quyn s dng WLAN :c ch xcthc( authentication) .

+ Tnh ring t cho cc d liu khng dy : thut tonm ha ( encryption).


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S dng hai phng php :

+ WPA ( wifi protected access ).

+ WEP ( wired equivalent privacy ).


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WEP da trn m ha dng i xngRC4 ( Rons code 4) .

Thut ton m ha RC4 l thut ton m ha ixng , s dng cng mt kha cho vic m ha v giim.


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Kha WEP c s dng nh danh xc thcclient .

Kha WEP c dng m ha d liu. Khi clients dng WEP mun kt ni vi AP th AP s xc nhxem client c gi tr kha chnh xc hay khng.


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Gii php WEP ti u:

+S dng kha WEP c di 128 bit.

+ Thc thi chnh sch thay i kha WEP nh k.+ S dng cc cng c theo di s liu thng k d liutrn ng truyn khng dy.


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+ Phng php WPA khc phc c nhiu nhcim ca WEP.

+ WPA thay i kho cho mi gi tin.

+ WPA s dng hm thay i kho TKIP (TemporalKey Integrity Protocol).+ S dng nhng kho khi to phc tp lm mt

khu.

+ WPA cn bao gm kim tra tnh ton vn ca thngtin .

bao cao wlan

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