Gii Thiu Cc Dng Thit B CiscoCisco System l hng chuyn sn xut v a ra cc gii php mng LAN&WAN ln nht th gii hin nay. Th phn ca hng chim 70% n 80% th trng thit b mng trn ton th gii. Cc thit b v gii php ca hng p ng nhu cu ca mi loi hnh doanh nghip t cc doanh nghip va v nh n cc doanh nghip c quy m ln v cc nh cung cp dch v Internet (ISP). Router and Routing Systems Switches Universal Gateway and Access Servers IP Communications Wireless Video Storages Contents and Optical Networking

I. Router and Routing SystemsCc sn phm thuc loi ny c tp chung ch yu vo cc dng sn phm di y: Cisco 7600 Series Routers

Cisco 7500 Series Routers Cisco 7200 Series Routers Cisco 3700 Series Multiservice Access Routers Cisco 3600 Series Multiservice Platforms Cisco 2600 Series Multiservice Platforms Cisco 2500 Series Routers Cisco 1700 Series Modular Access Routers Cisco 800 Series Routers Cisco 800 Series Router

Cisco 800 Series l gii php l tng cho cc kt ni Internet an ton v cc kt ni mng cho cc vn phng nh hoc nhng ngi lm vic t xa (teleworkers). Cisco 1700 Series Modular Acess Routers

Cisco 1700 Series Modular Access Router cung cp truy cp Inernet v mng nhanh, tin cy v an ton thng qua cc cng ngh WAN tc cao khc nhau. Cisco 1700 Series cho php rt nhiu kh nng bo mt nh wire-speed IP Security VPN, Firewall protection, v Intrusion detection. ng thi dng sn phm ny cng a ra cc dch v VoIP v IP Telephony thng qua mng hp nht Voice-Data vi cc tnh nng QoS cao. Dng sn phm ny l l tng cho Enterprise branch offices v Small and Medium-sized businesses. Cc models thuc dng 1700 series: Cisco 1760, 1751, 1721 Modular Access Router Cisco 1712, 1711, 1710 Security Access Router Cisco 1701 ADSL Security Access Router Cisco 2500 Series Routers

Hin ti Cisco ch sn xut hai dng 2509 v 2511, cn li tt c cc dng khc c thay th bi Cisco 2600 Series. Cisco 2509 v Cisco 2511 cung cp hai cng Serial WAN tc cao v 8 hoc 16 cng Async cho php cc truy cp t xa thng qua modem ngoi. Ruoter c kt ni vo mng LAN thng qua cng Ethernet 10Mbps. Loi Router ny hon ton ph hp vi cc doanh nghip loi trung bnh vi kh nng cung cp y cc tnh nng Routing, QoS v Security. Cisco 2600 Series Hin ti Cisco ch sn xut hai dng 2509 v 2511, cn li tt c cc dng khc c thay th bi Cisco 2600 Series. Cisco 2509 v Cisco 2511 cung cp hai cng Serial WAN tc cao v 8 hoc 16 cng Async cho php cc truy cp t xa thng qua modem ngoi. Ruoter c kt ni vo mng LAN thng qua cng Ethernet 10Mbps. Loi Router ny hon ton ph hp vi cc doanh nghip loi trung bnh vi kh nng cung cp y cc tnh nng Routing, QoS v Security. Cisco 2600 Series Multiservice Platforms

Cisco 2600 Series Multiservice Platform l loi modular multiservice access router cung cp cc cu hnh LAN & WAN a dng, nhiu chn la v an ton bo mt v c tc x l cao. Loi Router ny c hn 70 loi modules v giao din mng khc nhau cng vi cu trc module to nn mt dng sn phm d dng nng cp khi c nhu cu m rng mng. Model mi nht ca dng sn phm ny l Cisco 2600XM models v Cisco 2691 Multiservice Platform. Nhng models mi ny c kh nng x l nhanh hn, nhiu kt ni hn v kh nng bo mt cao hn p ng nhu cu pht trin ca cc chi nhnh v doanh nghip nh. Cisco 3600 Series Multiservice Platforms

Cisco 3600 Series l dng sn phm dng modular, multiservice access platforms cho cc vn phng trung bnh v ln hoc cc ISP loi nh. Vi hn 70 chn la modular interfaces, Cisco 3600 cung cp cc gii php cho data, voice video, hybrid dial access, virtual private networks (VPNs), v multiprotocol data routing. Cisco 3700 Series Multiservice Access Routers

Cisco 3700 Series cho php cc tnh nng v module hon ton mi v mnh m hn, nhiu kt ni hn. Khi s dng module 16- or 36-port EtherSwitch, Cisco 3700 Series tr thnh mt thit b tch hp c routing v lowdensity switching. Bn cnh n c th h tr internal inline power cho cc EtherSwitch ports, to nn mt platform duy nht cho gii php IP telephony v voice gateway. Cisco 7200 Series Routers

L loi Router ln ng dng cho Enterprise v Service Provider. Cc li ch ca Cisco 7200 series routers bao gm: Unparalleled Cisco IOS-based IP/MPLS feature support (QoS, Broadband Agg, Security, Multiservice, MPLS, and more) Broad range of flexible, modular interfaces (from DS0 to OC12) Support for Fast Ethernet, Gigabit Ethernet, Packet Over Sonet and more Fully modular design in a 3RU footprint Full L2TP and PPP termination support Support for up to 16,000 broadband subscriber sessions with the NPE-G1 Service Accelerator using Cisco PXF technology Multi-protocol support Low initial investment Scalability and flexibility; ideal for network re-deployment Cisco 7500 Series Routers

High-performance Cisco 7500 Series Routers l loi Router mnh nht hin nay c kh nng h tr cc dch v LAN/WAN vi kh nng d phng, n nh, tin cy v mnh m. Cisco 7500 s dng Versatile Interface Processors (VIPs) vi kin trc phn tn l cha kho chnh cho kh nng scalability ca Cisco 7500. Mi VIP c b vi x l ring, c kh nng switching IP data packets v cung cp cc dch v mng. Performance ca Cisco 7500 c tng ln khi cn kim sot cc kt ni mng tc cao v nhiu d liu. Route Switch Processor vn l ct li ca Cisco 7500. Bn cnh kh nng packet switching, VIPs cng c kh nng cung cp mt lot cc dch v mng IP phn tn, bao gm: Access control, QoS, v Traffic accounting (NetFlow). Cisco 7600 Series Routers

Cisco 7600 Series Router cung cp cc tnh nng IP/MPLS mnh m cho cc ng dng ca cc ISP v Enterprise MAN/WAN. S a dng v cc Interfaces v cng ngh x l tin tin lm cho Cisco 7600 Series c kh nng cung cp Integrated Ethernet, Private line, v Subscriber aggregation.

II .Switches Cisco

Cc dng sn phm chnh trong loi cc sn phm Switches ca Cisco bao gm: Cisco Catalyst 6500 Cisco Catalyst 4500 Cisco Catalyst 3750 Cisco Catalyst 3560 Cisco Catalyst 3550 Cisco Catalyst 2950 Catalyst 2950 Series

Cisco Catalyst 2950 Series Switch l dng switch c cu hnh c nh trc c kh nng cung cp wire-speed Fast Ethernet v Gigabit Ethernet. Loi switch ny s dng hai loi phn mm, Standard Image Software cung cp cc tnh nng cn bn data, voice, v video. Vi cc mng c yu cu cao v security, Advanced quality of service (QoS), High availability th Enhanced Image Software s p ng y cung cp cc kh nng trn. Models Cisco Catalyst 2955C, 2955S, 2955T 12 Switch Cisco Catalyst 2950 12 and 24 Switch Cisco Catalyst 2950C 24 Switch Cisco Catalyst 2950G 48 EI Switch Catalyst 3550 Series

Cisco Catalyst 3550 Series Switch l dng stackable, multilayer switch c kh nng sn sng cao, cht lng dch v (QoS), v an ton bo mt. Vi mt lot cc cng Fast Ethernet v Gigabit Ethernet, Cisco Catalyst 3550 Series l mt chn la hon ho cho cc ng dng dng Enterprise v Metro access. Khch hng c th khai thc cc tnh nng dch v thng minh nh Advanced QoS, Rate limiting, Cisco security Access Control Lists, Multicast Management, v High-performance IP routing. Models Cisco Catalyst 3550 48 EMI Switch Cisco Catalyst 3550 48 SMI Switch Cisco Catalyst 3550 24 DC SMI Switch Cisco Catalyst 3550 24 EMI Switch Cisco Catalyst 3550 24 FX SMI Switch Cisco Catalyst 3550 24 PWR Switch Cisco Catalyst 3550 24 SMI Switch Catalyst 3560 Series

Cisco Catalyst 3560 Series switches l loi switch c cu hnh c nh, thuc lp enterprise, h tr chun IEEE 802.3af v Cisco prestandard Power over Ethernet (PoE). Cung cp kh nng availability, security, v quality of service (QoS). Catalyst 3560 l loi switch lp Access l tng dnh cho cc small enterprise hoc branch

office m s dng LAN infrastructure cho cc ng dng IP telephones, wireless access points, video surveillance, building management systems, v remote video kiosks. Catalyst 3750 Series

Loi sn phm ny l th h tip theo ca desktop switches vi cc tnh nng Cisco StackWise technology maximum 32-Gbps stack interconnect. Cisco Catalyst 3750 Series Switches for 10/100 and 10/100/1000 Access and Aggregation Cisco Catalyst 3750-24PS and Cisco Catalyst 3750-48PS with IEEE 802.3af Power Cisco Catalyst 3750G-16TD with a 10Gigabit Ethernet XENPAK Uplink i vi cc mid-sized organizations v Enterprise branch offices, Cisco Catalyst 3750 Series tch hp d dng cc ng dng v thun theo nhu cu thay i ca doanh nghip vi cc cu hnh linh hot. Cisco Catalyst 3750 Series cng s dng hai loi phn mm IOS l Standard Multilayer Software Image (SMI) hoc Enhanced Multilayer Software Image (EMI). Catalyst 4500 Series

Cisco Catalyst 4500 Series Switches c thit k cho Enterprise, Branch offices v Layer 3 distribution. Catalyst 4500 Series h tr ba loi Supervisor Engines v mt lot cc line cards bao gm high density, 10/100, 10/100/1000 (c 802.3af Power over Ethernet Options), 100-FX, and 1000BASE-X. Catalyst 4500 series c cc loi chassis: Catalyst 4510R (10-slot), Catalyst 4507R (7-slot), Catalyst 4506 (6slot) v Catalyst 4503 (3-slot). Catalyst 4500 Supervisor Engine V mi nht (WS-X4516) cho php Layer 2/3/4 switching v routing. Ngoi ra cn c Catalyst 4500 Supervisor Engine IV (WS-X4515) cho Enterprise cng h tr layer 2/3/4 switching. Catalyst 4500 Supervisor Engine II-Plus (WS-X4013+) cung cp Layer 2 switching vi Layer 3 Services cn bn cho cc medium Enterprise v small Enterprise branch office. Models Cisco Catalyst 4510R Switch Cisco Catalyst 4507R Switch Cisco Catalyst 4506 Switch Cisco Catalyst 4503 Switch Catalyst 6500 Series

L loi Switch thng minh mnh nht ca Cisco hin nay, Catalyst 6500 Series cho php cc dch v i vi lp Core ca mng, t datacenter ti WAN edge. C kh nng cung cp t 48 ti 576 10/100/1000Mbps hoc ti 1152 10/100Mbps Ethernet ports vi thng lng hng trm triu packets per second (Mpps). Network cores h tr multiple gigabit v 10Gigabit per second trunks. Catalyst 6500 Series cung cp kh nng switching thng minh cho c Enterprise and Service-provider networks. Models Cisco Catalyst 6513 Switch Cisco Catalyst 6509 Switch Cisco Catalyst 6509-NEB Switch Cisco Catalyst 6506 Switch Cisco Catalyst 6503 Switch

Gii Php ng Truyn WAN cho Doanh NghipCc gii php v h thng mng WAN bao gm: cc nh cung cp, c im cc kiu ng truyn, thit b kt ni ... l nhng vn m phn ln ngi qun tr h thng khng nm c chi tit. Mnh xin trnh by mt bi vit c tng hp t nhiu ngun thng tin rt b ch. Hi vng bi vit s gii quyt mi thc mc cho mi ngi.

Cc cu hi thng gp:Ti Vit Nam, hin c nhng gii php (thay th) no tt hn FrameRelay v MegaWan ? Trong s cc gii php , gii php no c chi ph thp nht m cht lng vn m bo ? Theo nh gi, hin nay nh cung cp WAN ti VN no tt nht ? Xem xt da trn cht lng ng truyn n nh, cht lng h tr khch hng tt. Cc dch v mi nh: - FTTH - VSAT/IP v VSAT/PUMA vn hng ra sao ?

Tr Li:Hin nay c rt nhiu gii php kt ni hay thit k h thng mng din rng WAN. Cc nh cung cp dch v mng Wan nh VNPT, FPT, Viettel, EVN u ang chy ua cung cp dch v ti tng khch hng : - LeasedLine (VNPT,Viettel,EVN) - FrameRelay - MPLS (VDC, VTN) - Metro Net (VNPT) ( hay cn gi l Megawan) - E-Metro (FPT).

a s cc dch v l n nh v tc i Internet quc t ng nh cam kt. Tuy nhin cng c nhng trng hp khng n nh do cp, thit b... gy ra. Ngoi ra cn 1 yu t quan trng khi chn ISP l cht lng dch v nh th no. Ty theo nhu cu m chng ta c th chn mt trong cc dch v trn m s dng. i vi cc knh kt ni ca ngn hng th h lun lm 2 kt ni , 1 ng chnh v 1 ng dng d phng backup, lun lun chn s dng 2 nh cung cp dch v khc nhau m s dng. s dng gii php t tn km hn th chng ta s dng MegaWAN v ADSL lm VPN backup. Megwan chng ta nn s dng dch v ca VTN v h trin khai n 64 tnh thnh. MEGAWAN l loi tt nht cn bng gia chi ph v cht lng. Kt ni Megawan lin tnh th lin h vi VTN2 cn ni ht TP.HCM th lin h vi Cty in thoi ng, ni ht cc tnh thnh khc th lin h ti cc bu in tnh thnh . Nhng nu va trin khai Megawan lin tnh v ni ht th yu cu VTN2 trin khai lun. FTTH la dch v internet Fiber optic, hn ch l chng ta phi t lm VPN kt ni cc site li. Ring VSAT

th chi ph cn mc hn c LeasedLine. trin khai h thng Mng cho Ngn hng th ty vo c s h tng cng nh qui m m chn la. Thng thng th s dng knh thu ring Leased Line, v Backup bng MegaWan (c th cu hnh Load-balance). Leased Line n nh, MegaWAN kh nng chu li kh thp nhng chi ph r. Thu knh leased line TDM cam kt vi tc l cc tt. Cn hin ti leased line thng chy qua DSLAM thng qua Card SHDSL nn tc ph thuc vo modem, cht lng cp, uplink ca DSLAM. Leased line tc nh hn 2Mbps ca FPT thc cht l SHDSL, ln hn na th mi c knh ring thc s. SHDSL c c ATM v xDSL.

Cc thng tin thm cn bit chi tit:Nu chng ta c nhu cu kt ni nhiu a im vi nhau chia s ti nguyn, trao i ti liu th c th tham kho dch v VPN/MPLS ca VDC. M t gii php:

M t k thut Cng ngh MPLS VPN c pht trin da trn tng n gin ho qu trnh nh tuyn lu lng truyn trn mng Internet c th da trn nn thit b mng (hardware) so vi dng phn mm nh trc y. iu ny c th lm cho qu trnh nh tuyn v chuyn d liu c nhanh hn nhiu so vi cc cng ngh khc. Cng ngh MPLS tr thnh mt cng ngh l tng cho vic qun l d liu trn mng cng cng v tr thnh mt phn ct li trong mt mng ring o Ti H Ni: - u ni qua mng cp quang (hoc cp ng) MetroNET ca Bu in H Ni ti POP MPLS/VPN ca VDC ti 75 inh Tin Hong Hon Kim H Ni. - Mng MetroNET ca BHN s dng theo tuyn cp ngm ca VNPT, m bo gim thiu cc s c ma, bo, giao thng. Ti H Ch Minh - u ni qua mng cp quang (hoc cp ng) MetroNET ca Bu in H Ch Minh ti POP MPLS/VPN ca VDC ti 125 Hai B Trng - Qun 1, TP.H Ch Minh. - Mng MetroNET ca B TP.HCM s dng theo tuyn cp ngm ca VNPT, m bo gim thiu cc s c ma, bo, giao thng. Ti cc tnh thnh khc trong c nc - u ni qua mng cp quang thng (trong iu kin c th) ti POP MPLS/VPN ca VDC t ti tr s ca cc Bu in tnh. - u ni qua mng Truyn s liu cp ng (Leased Line) ti POP MPLS/VPN ca VDC t ti tr s ca cc Bu in tnh Kt ni MPLS/VPN trong mng li MPLS ca VDC: - Tc kt ni theo yu cu. - MPLS/VPN s thit lp knh truyn ring, c lp cho PVEP trong mng li MPLS bng phng thc gn nhn d liu truyn. - MPLS/VPN trong MPLS core c bo mt nh kh nng che giu a ch mng li ca MPLS v ring bit trong mng MetroNET. Thit b s dng: - S dng cp quang: N b chuyn i quang in (Converter quang) - S dng cp ng: N Modem TSL tc cao (thng bo sau khi kho st) - N Router Cisco 1841 (hoc 26xx, 28xx) Cam kt cht lng k thut - Tc knh truyn: theo tc ng k - n nh knh truyn: 99 % - Cht lng ng truyn: m bo 100% thnh cng d liu truyn qua knh. - kh dng ca mng: > 99 %. - tr: m bo khi ping gi tin 100 byte t im u n im cui khng qu 20ms. Thi gian trin khai: Trong vng 14 ngy k t ngy c kt qu kho st. Kh nng nng cp v m rng mng Nng cp tc : H thng mng cp quang truyn dn qua MetroNET m bo kh nng nng cp tc ln ti nxGbps, d dng, khng cn thay i thit b. M rng mng: VDC trin khai POP cung cp dch v MPLS/VPN trn ton quc. Do vy, VDC m bo

kh nng thm im kt ni mi trn khp 64/64 tnh thnh (nu cn). Mi th tc thm im kt ni mi u rt d dng, nhanh chng v n gin. (Hin ang l li th ca VDC/VNPT v ch duy nht VNPT c mng trn ton quc). Cam kt x l s c Vi h tng c trin khai bng truyn dn cp quang v qua b cng ngm, xc xut s c i vi cp truyn dn l rt t. VDC cam kt thi gian gin on dch v x l s c nh sau: + Tip nhn thng tin s c: 24/24 + Thi gian xc minh s c: < 30 pht + Thi gian khc phc s c: < 4 ting. Bi vit c tng hp t cc thng tin ca cc chuyn gia k thut qun l ISP ti VN

Cng ngh v dch v Wi-fiI.Gii thiu Hin nay cc nhu cu v dch v di ng khng ch dng li dch v thoi truyn thng m cn c s pht trin nhanh v mnh cc nhu cu v dch v s liu di ng c bit l dch v truy cp Internet di ng, khin cho nh sn xut v khai thc mng phi tm kim cc kin trc mng mi trn c s kin trc h tng truyn thng gim gi thnh v n gin ho vic xy dng cc mng a dch v, a phng tin. Cc mng 2G phc v kh tt nhu cu thoi thng thng v mt s ng dng th h 2 nh SMS hay truy nhp Internet bng cng ngh WAP. Nhng khi ngi s dng i hi cc dch v nh in thoi video hay truy cp Internet tc cao th chng hon ton khng th p ng c. Bn cnh , cc h thng thng tin di ng hin nay l cc h thng bng hp ch cung cp c cht lng thng tin hn ch, nht l i vi nhu cu truyn s liu nhng gi cc cao. S pht trin ca cc thit b di ng cng ngh cao nh my tnh xch tay laptop, my tnh b ti palmtop, thit b h tr k thut s c nhn PDAcng thc y nhu cu truyn d liu di ng trong khi mng in thoi di ng th h th ba (3G) vn c coi l gii php ca tng lai cho cc dch v truyn thng a phng tin di ng li cha sn sng nhp cuc. Bi cnh ny dn n vic s dng rng ri mt lp mng di ng khng dy mi. l mng cc b v tuyn WLAN (Wireless Local Area Network). Mng WLAN s p ng kp thi nhu cu v truyn s liu khng dy tc cao vi gi thnh h v linh hot cao, trin khai nhanh chng. Cc cng ngh Wi-fi da trn chun IEEE 802.11b xy dng cho WLAN c l cha kho gip cc nc ang pht trin i tt n u, ui kp cc nc pht trin trong lnh vc cng ngh thng tin. Nhn thc r c s pht trin tt yu ca cng ngh Wi-fi, Vit Nam cng ty VDC ch ng trin khai im nng (hotspot) truy cp dch v Wi-fi ti nhng khu trung tm v sp ti VDC s ng k c c tn trn bn Wi-fi th gii. S kin ny chng t Vit Nam ang thc s ho nhp v pht trin cng vi nhng tin b mang tnh t ph ca nn cng ngh cao th gii. TNG QUAN V WLAN Mng WLAN l mt h thng truyn thng s liu linh hot c thc hin trn s m rng ca mng LAN hu tuyn. Mng WLAN s dng sng v tuyn truyn v nhn d liu, ti thiu ho vic kt ni s dng dy dn, v vy WLAN kt hp c vic kt ni truyn s liu vi tnh di ng ca ngi s dng. S dng bng tn ISM 2,4 GHz. Vng ph sng ca WLAN trong phm vi khun vin trng i hc hoc to nh vn phng. S ra i ca cc cu ni WLAN em li nhiu li ch v kh nng di ng v khai thc mng linh hot. Vi mng WLAN, ngi dng c th truy cp cc thng tin dng chung m khng cn tm ch cm thit b v cc nh qun l mng c th thit lp hoc lm tng thm mng li m khng cn lp t hoc di chuyn h thng dy. WLAN cn cho nng sut lu lng tng, thun tin, li th v chi ph so vi cc h thng mng hu tuyn truyn thng. Mng WLAN c cc u im: - Tnh di ng lm tng hiu qu v dch v - Nhanh chng v n gin trong lp t - Gim gi thnh khi vn hnh - Kh nng nng cp CU HNH MNG WLAN Mng WLAN thng c hai loi cu hnh c bn sau: - Mng WLAN c lp hay cn gi l mng Ad Hoc (hnh 1): cc nt di ng (my tnh laptop) tp trung li trong mt khng gian nh hnh thnh nn kt ni ngang cp (peer-to-peer) gia chng. Cc nt di ng trao i thng tin trc tip vi nhau thng qua cc b bin i v tuyn, khng cn phi qun tr mng. V cc mng

ad-hoc ny c th thc hin nhanh v d dng nn chng thng c thit lp m khng cn mt cng c hay k nng c bit no v vy n rt thch hp s dng trong cc hi ngh thng mi hoc trong cc nhm lm vic tm thi. Tuy nhin chng c th c nhng nhc im v vng ph sng b gii hn, mi ngi s dng u phi nghe c ln nhau. - Mng WLAN c s (hnh 2): bao gm cc im truy nhp AP (Access Point) gn vi mng ng trc hu tuyn v giao tip vi cc thit b di ng trong vng ph sng ca mt cell. AP ng vai tr iu khin cell v iu khin lu lng ti mng. Cc thit b di ng khng giao tip trc tip vi nhau m giao tip vi cc AP.Cc cell c th chng ln ln nhau khong 10-15 % cho php cc trm di ng c th di chuyn m khng b mt kt ni v tuyn v cung cp vng ph sng vi chi ph thp nht. Cc trm di ng s chn AP tt nht kt ni. Mt im truy nhp nm trung tm c th iu khin v phn phi truy nhp cho cc nt tranh chp, cung cp truy nhp ph hp vi mng ng trc, n nh cc a ch v cc mc u tin, gim st lu lng mng, qun l chuyn i cc gi v duy tr theo di cu hnh mng. Tuy nhin giao thc a truy nhp tp trung khng cho php cc nt di ng truyn trc tip ti nt khc nm trong cng vng vi im truy nhp nh trong cu hnh mng WLAN c lp. Trong trng hp ny, mi gi s phi c pht i 2 ln (t nt pht gc v sau l im truy nhp) trc khi n ti nt ch, qu trnh ny s lm gim hiu qu truyn dn v tng tr truyn dn.

Cc tiu chun WLAN Tn s v tuyn c s dng truyn dn l yu t rt quang trng i vi mng WLAN. WLAN c cp pht bng tn ISM trong 3 di tn s khng cn ng k s dng sau: 902 MHz, 2.4 GHz, and 5 GHz. Hin nay c mt s cc tiu chun WLAN ph bin trn th gii s dng 3 di tn s ny nh ch ra trong bng 1.

Tiu chun ph bin nht hin nay l IEEE 802.11b. Tiu chun 802.11b c Hip hi k s in v in t (IEEE) a ra vo thng 9 nm 1999. Mng WLAN IEEE 802.11b tc cao hot ng bng tn 2.4 GHz v c th cung cp tc truyn dn ln ti 11 Mbps. IEE 802.11b ch xc nh hai lp cui ca m hnh tham chiu OSI: lp vt l (PHY) v lp lin kt s liu (phn lp iu khin truy nhp MAC) (Hnh 3).

CC THNH PHN CA MNG IEEE 802.11B Mng IEEE 802.11b bao gm cc thnh phn sau y tng tc vi nhau (hnh 4): - B dch v c s BSS: l khi kin trc c bn nht trong mng WLAN 802.11b. Hnh 4 ch ra 2 BSS, mi BSS c 2 trm STA thnh phn. - H thng phn phi DS: l thnh phn kin trc lin kt gia cc BSS. - im truy nhp AP: l mt trm STA ngoi vic hot ng nh mt trm bnh thng cn cung cp truy nhp ti h thng phn phi DS bng cch cung cp cc dch v h thng phn phi DSS.

- B dch v m rng ESS: l mt b gm nhiu BSS lin kt vi nhau v c th tch hp vi mng LAN di dng mt BSS c lp. LP VT L CA IEEE 802.11b Lp vt l cp n giao din vt l gia cc thit b v vic truyn cc bit th trn knh truyn thng. IEEE 802.11b cung cp 3 loi tc : tc c bn (1 Mbit/s) s dng iu ch chuyn pha nh phn vi sai DBPSK, tc m rng (2 Mbit/s) s dng iu ch chuyn pha cu phng vi sai DQPSK v tc nng cao (5.5 Mbps v 11 Mbit/s) s dng iu ch kho m b sung CCK. Ngoi ra IEEE 802.11b cn nh ngha vic dch chuyn tc t ng, cho php iu chnh t ng tc truyn trong cc iu kin c nhiu, tc l cc thit b s truyn cc tc thp hn (1, 2, 5.5 Mbps) trong iu kin c nhiu v thit b di chuyn sang vng truyn dn tc cao hn th kt ni s t ng nng tc ln.

Lp vt l ca IEEE 802.11b chia thnh 2 phn: giao thc hi t lp vt l (PLCP) v phn lp ph thuc mi trng vt l (PMD). PMD thc hin vic m ho v gii m v tuyn cong PLCP trnh by giao din chung phn lp MAC v cung cp vic cm ng sng mang v n nh knh ri (CCA). PHN LP IU KHIN TRUY NHP MAC CA IEEE 802.11b Phn lp MAC (Medium Access Control) lm chc nng giao din gia lp vt l v thit b lp trn. Phn lp MAC xc nh mt c ch truy nhp c bn (da trn a truy nhp cm ng sng mang CSMA) cho cc nt di ng truy nhp vo mi trng v tuyn. Hai chc nng chnh ca lp MAC l kim tra d li chu trnh CRC v phn mnh gi (Packet Fragmentation). Mi gi tin s c tnh ton v c gn v mt gi tr CRC m bo rng gi tin s khng b sai khi trong qu trnh truyn dn. Vic phn mnh gi s ct cc gi tin ln thnh cc gi nh hn truyn trong khng gian. Vic ny s mang li hai li ch: th nht l gim yu cu pht li v gi cng ln th kh nng gi b sai cng ln, li ch th hai l trong trng hp gi b sai th cc nt

ch cn truyn li mt gi nh, do vic truyn li s nhanh hn. DCH V WIFI@VNN CA VDC Dch v Wifi@VNN ca VDC c trin khai da trn cng ngh v tuyn Wi-Fi theo tiu chun IEEE 802.11b, cung cp cho ngi dng kh nng truy cp Internet tc cao s dng my tnh c nhn laplop c trang b thm card Wi-Fi. Ngi dng c th s dng Wi-Fi ti cc hotspot. Hotspot l cc im truy nhp Internet khng dy ni c lp t cc AP, c th l sn bay, nh ga, khch sn... s dng Wi-Fi cn 3 yu t: - Kt ni bng thng rng t cc nh cung cp dch v Internet (ISP) - Mt im hotspot vi t nht 1 AP c lp t - Mt card Wi-Fi dnh cho my tnh xch tay hoc my tnh bn kt ni vi cc AP Cc c Im ca dch v WiFi@VNN do VDC cung cp Bn knh ph song ca mi Hotspot nh hn 300 m - Tn s s dng: 2.4 GHz (bng tn ISM), rng bng thng l 22 MHz - Cng sut pht nh hn 100 mW - Tc truy cp l 11 Mbit/s (chia s bng thng) - Phng thc bo mt l dng giao thc bo mt tng ng hu tuyn WEP (Wire Equivalent Protocol) - H thng qun l: hot ng theo giao thc RADIUS (AAA) - Phng thc tnh cc: tnh cc theo thi gian, theo dung lng hoc sut cc ng lot (flat rate). Cu hnh h thng Wi-Fi Hnh 5 ch ra cu hnh y h thng Wi-Fi. Vng ph sng ca cc AP to ra mt im nng hotspot, ngi dng vi cc thit b nh laptop c trang b card wi-fi c th truy nhp vo mng thng qua giao tip vi AP. Cc AP ti mt im nng c tp trung v switch v kt ni vi mng thng qua b nh tuyn (router). Cc router c ni vo mng hu tuyn bng mt phng thc truyn dn no tu thuc nh cung cp dch v.

Trong phng n trin khai ca mnh, VDC la chn phng thc truyn dn SHDSL (Single-pair HighSpeed Digital Subscriber Line). Gii php SHDSL s dng truyn d liu cn bng vi tc c th t t 192 Kbit/s ti 2.3 Mbit/s trn mt i cp n. Thm vo , tn hiu SHDSL c kh nng truyn dn xa hn so vi cc kt ni s dng cng ngh ADSL v SDSL, cho php cc nh cung cp dch v tho mn nhu cu cc khch hng xa. S dng cng ngh ny, ti mi im

truy cp hotspot phi c mt b nh tuyn SHDSL, cung cp truyn dn bng thng rng ra Internet. i vi h thng Wi-Fi: mi trng truyn dn l mi trng sng, truyn tin theo chun 802.11b. Thc cht y c th coi l mi trng pht qung b (broadcast), tt c cc my trm (client) ng vo vng ph sng u c th bt c tn hiu, cc AP t c kh nng iu khin c truy nhp. Gii php c a ra l s dng thit b cng thu bao. Thit b ny s ng chn ti ng ra ca cc AP i Internet, mi trng sng s lun c cc AP cung cp cho bt c mt my trm no ng trong mi trng truyn sng. Nhng khi ngi s dng truy nhp vo mi trng sng ca mt AP th ngay lp tc cng thu bao s tin hnh vic nhn thc thu bao. Ngi s dng s c iu khin t ng truy nhp vo mt trang Web nhn thc c xy dng tch hp trn cc cng thu bao. Ti y, username/password (tn ngi s dng/mt khu) s c yu cu nhp vo. Cng thu bao lin lc vi AAA Server tp trung ti trung tm qun l iu hnh mng theo giao thc RADIUS ly thng tin v khch hng trong h thng c s d liu. Nu nhn thc thnh cng th ngi s dng mi c php thng qua Subscriber Gateway i ra Internet, v thng tin tnh cc s c cng thu bao gi v AAA Server. Cng thu bao cn c kh nng iu khin truy nhp theo thi gian thc, cho php cung cp cc loi dch v a dng. Da theo m hnh mng c xy dng v phng n k thut ca h thng RADIUS v tnh cc th yu cu i vi i ch IP u ni ti cc router SHDSL bt buc phi l a ch thuc di IP cng cng (Public_IP) v phi c cp tnh do h thng cc hotspot s c kt ni v trung tm qua Internet do cc a ch ny phi c hiu trn Internet. V cc cng thu bao phi tin hnh trao i thng tin AAA vi RADIUS server t ti trung tm qun l mng nn cc a ch u ni ti cc SHDSL router phi c cp tnh, khng thay i sau mi ln h thng khi ng li. Theo thit k, c 2 trung tm mng l 75 inh Tin Hong, H Ni v 125 Hai B Trng, TP. H Ch Minh. (Trong trng hp cn trin khai nhanh nhng im s dng Wireless Bridge, VDC 292 Ty Sn c th c s dng thnh mt trung tm). Theo k thut u ni SHDSL, ti trung tm s kt ni ti DSLAM bng mt ng Fast Ethernet, kt ni ny c thc hin trn Switch trung tm. Kt ni i Internet c iu khin bi hai cng thu bao chy song song phn ti. Do h thng wireless, c c im l bng thng ln, mi trng a truy nhp nn cn thit phi c phng php bo v hp l trnh cc hnh thc tn cng vo mng VNN. Phng php bo v thch hp nht l s dng bc tng la (firewall) ti hai im trung tm theo m hnh nh trn.

MT S HNG PHT TRIN WI-FI DA TRN C S H TNG HIN C Sau y trnh by 2 hng pht trin ngh cho Wi-Fi, kt hp vi vic tn dng c s h tng hin c: - Thc hin chuyn mng (roaming) gia cc nh cung cp dch v Wi-Fi - Kt hp Wi-Fi v mng GPRS. Roaming gia cc nh cung cp dch v Wi-Fi Dch v roaming cho php khch hng ca mt nh cung cp dch v Wi-Fi c th truy cp cc dch v h ng k thng qua mng ca mt nh cung cp dch v Wi-Fi khc bng cch s dng cc thng tin nhn thc nh mng nh ca h. Dch v roaming c miu t trong hp ng roaming gia cc nh cung cp dch v. Nh cung cp dch v mng nh ca thu bao s tnh cc thu bao, v nh cung cp dch v mng khch s tnh cc nh cung cp dch v mng nh. thc hin roaming, cn thit lp mt mng gia cc nh cung cp dch v. l do my ch Roaming RADIUS mng khch phi c kh nng kt ni vi my ch roaming RADIUS ca mng nh v my ch mng nh lun chu trch nhim nhn thc thu bao cho d thu bao c thc hin roaming hay khng. Trong hnh 7 l ton cnh mng roaming, trong GRX l gii php cho mng gia cc nh cung cp dch v do hip hi GSM (GSMA) ngh.

Hin nay Vit Nam ch c VDC l nh cung cp dch v Wi-fi. Trong tng lai, khi nhu cu truy cp Internet di ng tng ln, cng vi u im v s nhanh chng v n gin trong trin khai, vn u t khng ln, dch v Wi-Fi c tim nng pht trin v s c nhiu nh cung cp dch v cng cung cp dch v ny. Khi vic cung cp roaming s to ra s thun tin rt ln cho khch hng khi ch cn ng k s dng vi mt nh cung cp dch v v c th s dng dch v nhiu khu vc ng thi em li li nhun cho cc nh khai thc. Kt hp Wi-Fi v mng GPRS Trong khi Wi-Fi cung cp dch v s liu tc cao nhng ch trong nhng vng bn knh gii hn th GPRS

cung cp dch v bo mt cao, c tnh di ng trn vng rng m khng th thc hin c vi WLAN. iu ny c ngha l s tch hp Wi-Fi/GPRS l rt cn thit cho php ngi dng truy nhp cc dch v s liu v tuyn mt cch lin tc, tn dng c u im v tc cao ca Wi-Fi nhng ni c dch v v s chuyn sang dng GPRS khi ngi dng di chuyn hoc ang nhng vng khng c ph sng ca Wi-Fi. C hai phng thc chnh tch hp Wi-fi/GPRS nh sau: Kt hp cht Mng Wifi c kt hp cht c minh ho trong hnh 8. Mng kt hp cht s dng cc ti nguyn ca h thng GPRS sn c cho hot ng mng, cung cp chc nng AAA, bo mt v cc chc nng khc, cc chc nng ny c tch hp vo h thng Wifi, ngi dng Wifi s truy nhp c hu ht cc dch v GPRS. Chc nng hot ng tng tc GIF (GPRS Interworking Function) c dng giao tip vi mng Wifi. Tt c lu lng s c nh tuyn qua node h tr GPRS phc v SGSN.

Kt hp lng Hnh 9 l m hnh mng wifi c kt hp lng. C ch kt hp lng s c da trn Mobile IP. i vi mng Wifi ch cn thay i nh vi thnh phn b sung hot ng tnh cc theo tho thun v h tr ln nhau gia Wi-Fi v GPRS. Ngi dng s nhn c ho n tnh cc kt hp ca c hai mng Trong h thng kt hp lng mng Internet ng vai tr l mng ng trc. u im ca m hnh ny l mng Wifi v GPRS c th c thit k c lp.

KT LUN Mng WLAN s p ng kp thi nhu cu truyn s liu khng dy tc cao vi gi thnh h v linh hot cao, trin khai nhanh chng. Vi nhng u im v tc , gi thnh, kh nng nng cp cng nh pht trin trong tng lai, dch v Wi-Fi ha hn s thnh cng trong thi gian ti khi vic s dng cc thit b di ng cng ngh cao tr nn ph bin hn.